# Adding Sacrificial Straight Surface to Table Saw Fence: What and How?



## Mad (Dec 9, 2017)

High up on this weekend's *suckat* list (_things I suck at doing_) is adding some sacrificial straight and flat surfaces to my extruded aluminum table saw fence that has T slots already in it for doing just that.

The previous owner to my fence already added a sacrificial surface, but I find it deficient in three ways:

1. He put the mounting bolt precisely where the big bold instruction label still in tact on this 30 year old fence stated NOT to put a bolt... directly in the path of the saw blade. Automatic fail. Must be changed.

2. He used CDX plywood. Not exactly the smoothest surface to run boards along.

3. He only mounted a surface on one side of the fence. I want a surface on both sides of the fence.

4. He didn't make the sacrificial fence long enough to cover the base fence, which creates a catch point when introducing sheet material to the table. It also reduces the ability of the fence to keep the material aligned prior to being cut.

So this means a redo, and rather than limit myself to just correcting his mistakes, I thought to put post my intent on this wonderful board of woodworking talkers, in order to seek some advice to help me avoid making mistakes of my own. So please post your experiences, thoughts, recommendations, and past mistakes that you would do differently next time, on adding sacrificial surfaces to fences.

The first question I had was regarding materials.... UHW plastic, vs Baltic Birch Plywood, vs MDF, vs Yellow Pine, vs Melamine... I've read a smattering of recommendations for each, only to be faced with lack of local availablity of the most preferred materials. I still seek advice on the pros and cons of each type of material, but in the meantime, I'm going to make a practice run at this with MDF as an interim improvement over the CDX and nothing that I have now.

The second question I had was regarding elevation... how much higher than the original fence should the sacrificial fence extend above the factory fence?

Third question: Fence float... should the sacrificial fence extend no lower than the factory fence, in order to float easily across the table? Or should the factory fence extend a millimeter or two below the factory fence to practically an interference interface with the table, in order to prevent slivers from sliding underneath the fence?

The fourth question is hardware orientation. With T slots in the aluminum extrusion, should I slide square nuts into the extrusion slots, and mount bolts through the sacrificial fence surface, with the bolt heads recessed? Or should I slide the heads of short square headed bolts into the extrusion slots, and capture the sacrificial fence surface with nuts recessed into the material? Pros/cons of each? Is there yet another, better way to make the attachment? Different type of hardware altogether?

The final question is one that I haven't and cannot ask, because I don't know enough to think of it. But you might, so please ask and answer those unknown questions with regard to mounting sacrificial surfaces onto extruded aluminum fences.

It shouldn't much matter, but I happen to have an Exact-I-Rip fence with one T slot per side on the vertical surfaces of the fence, and two T slots on the top surface of the fence.

Thanks in advance for your assistance!


.


----------



## TomCT2 (May 16, 2014)

I have used MDF for decades as fence/sacrificial/sled type stuff - subject to the caveat that after cutting/building/construction/gluing/whatevering you put on a sealing coat of polyurethane. 

MDF swells & warps with moisture - including humidity - but one coat of poly, heavy on the raw edges, prevents that. given the edge voids/etc in plywood, the MDF seals better imho - and drips/runs are rarely an issue as it sucks up the poly near instantly.

it stays straight & flat & smooth - it's inexpensive so if I need to chop/hack into it I don't hesitate or regret. other thoughts come to mind when considering sacrificing a nice chunk of 3/4 birch.....

as the need requires I use brads/nails/screws for stops/etc - a sharp chisel removes any bumps to the flat surface when you are done.

if you want something 'slicker' aka less friction look at the ready-made shelving. plastic coated for smoothness - but I still poly coat the edges to prevent any swelling with humidity. I use that for fencing on the router table where slick is good. here you can see the coating is torn a bit where a sharp edge caught - it's also cheap - about $1.50 for the piece so I'm not upset when it needs replacing . . .


----------



## GeorgeC (Jul 30, 2008)

I have three or four of those sacrificial fences. Not sure how I wound up with that many, but guess they serve their needs. Maybe one day Iwanted one and could not find what I had so just made another. Only takes a few minutes to make. One has a T track in it so that I can put feather boards on it. One is made of plywood and the other solid wood. Nothing special about any of them. Just whatever wood I had on hand when I wanted to make one.



Do not have any idea of a bolt you are talking about on yours. Mine have two bolts, one about 1/4 was in from each end. tThe nuts on the bolts are captured by the T track in the fence. The heads of the bolts are countersunk into the wood. They are bolted so that they just barely clear the top of the table. 



Simple little items with minimal construction hassle. I have no need of a sacrificial board on the side away from the blade. Why would you want one?


George


----------



## Jim Frye (Aug 24, 2016)

My table saw also has has an extruded aluminum rip fence with T-slots on all three exposed faces of the rip fence (as well as the miter fence), and I have made several jigs and fixtures that utilize the slots. I made a tall fence add on that has faces on both sides of the fence and has small guides that slide in the side T-slots. The top of the tall fence has threaded inserts in it so that a pair of 1/4x20 bolts can be run down to bear on the top slot. The fence slides onto the rip fence and is so snug, I've never needed the bolts to secure it. This tall fence is made from hard maple scraps and also has threaded inserts in the faces to attach things like sacrificial faces. It was made double sided to use for panel raising. My saw is a right tilt saw, so I do panel raising with the fence on the left side of the blade. Normally the fence is positioned to the right of the blade for sawing and dadoing. I also have a tenoning guide that slides on the rip fence guided the the T-slots. It is made from some 3/4" quality plywood. I also made a router table fence that mounts on the top T-slot with some flat head bolts with fender washers that fit into the T-slot to secure it to the rip fence. The router fence is constructed from plywood also. All of these jigs were stained and varnished to help keep them fresh. The following articles have .pdf files attached that give the details of construction. I hope this gives you some answers to your questions. Apologies for the poor photography in these old articles. I didn't have access to Photoshop to clean them up back then. 



https://www.sawdustzone.org/articles/jigs-fixtures/824887-high-fence-for-dado-and-panel-raising
https://www.sawdustzone.org/article...6-construction-notes-for-the-bt3000-tenon-jig
https://www.sawdustzone.org/article...-ryobi-bt3000-router-fence-construction-notes


----------



## woodnthings (Jan 24, 2009)

*The shelving is Melamine*

Melamine is nasty to work with because it's razor sharp. Other than that it's really slick and good for sliding contact from wood workpieces.
This is a miter gauge with T tracks and a sacrificial fence and would be similar to yours









There are other ways to attach your sacrificial fence like this:


----------



## Mad (Dec 9, 2017)

woodnthings said:


> There are other ways to attach your sacrificial fence like this:



I was visualizing never removing the sacrificial surfaces (at least the vertical ones) and thus wanted to avoid using the clamp on jigs in your photo of the oak on the Align-A-Rip fence.


I was going to set my Zero markers on the fence to index to the surface of the sacrificial pieces that would be remain bolted to the fence permanently, much like what a Biesemeyer looks like (which appears as if built with a box beam of melamine laminated baltic birch plywood I assume, but do not know).


----------



## Mad (Dec 9, 2017)

GeorgeC said:


> I have no need of a sacrificial board on the side away from the blade. Why would you want one?



Not sure... but my 30/24 fence has measured demarcations on both sides of the blade, and the fence has a continuous track that extends equidistantly away from either side of the blade, which indicates that it was designed to be used on either side of the blade, so why not protect it on either side of the blade?


----------



## Mad (Dec 9, 2017)

Jim, I made a file folder in my computer with your name on it, and downloaded all three of your very detailed and helpful pdfs to it, and reviewed them. When I say review I mean that loosely... it was more like how a preschooler might review a PhD dissertation, recognizing a few words like "at" and "the", but not quite ready to grasp the concepts being conveyed. Even while recognizing the relationship of your three projects with what I'm trying to do, and readily seeing the advanced utility of the tooling you fabricated... all of that is going to have get added to my suckat list for a later time, after I've learned to walk.


----------



## woodnthings (Jan 24, 2009)

*make a slip on fence*



Mad said:


> I was visualizing never removing the sacrificial surfaces (at least the vertical ones) and thus wanted to avoid using the clamp on jigs in your photo of the oak on the Align-A-Rip fence.
> 
> 
> I was going to set my Zero markers on the fence to index to the surface of the sacrificial pieces that would be remain bolted to the fence permanently, much like what a Biesemeyer looks like (which appears as if built with a box beam of melamine laminated baltic birch plywood I assume, but do not know).


You need not attach your auxilary fence to your permanent fence, merely make it a snug fit so it comes off easily so you can turn it around if needed. This one has a higher side for certain operations:


----------



## Mad (Dec 9, 2017)

woodnthings said:


> You need not attach your auxilary fence to your permanent fence, merely make it a snug fit so it comes off easily so you can turn it around if needed. This one has a higher side for certain operations:












But that's just it... I'm not trying to build the removable auxiliary fence (the wooden component in the photo above)... I'm trying to make and attach permanently mounted sacrificial sidewalls to my metal box beam fence (like the _*white walls*_ attached to the metal box fence in the photo above).

Those white walls appear as if made with Delrin or UHW or some type of plastic... sacrificial, in that the white walls are replaceable less expensively than the metal box beam that makes up the spine of the fence itself.

Similarly, my metal box beam is an aluminum extrusion with T slots. As far as I'm concerned, it is made with unobtainium, since it is the spine to a fence that is forty years old and is not readily replaceable. I had to buy an entire saw just to get this fence. So I want to make sidewalls to protect the metal, exactly like the white walls shown in the photo above.

Then later on, I can graduate to building that drop on, reversible, instantly removable, truly sacrificial wooden fence that is shown hovering in mid air in the photo above, as well as the much fancier versions of the same as outlined in the pdfs of Jim Frye.


----------



## GeorgeC (Jul 30, 2008)

Mad said:


> Not sure... but my 30/24 fence has measured demarcations on both sides of the blade, and the fence has a continuous track that extends equidistantly away from either side of the blade, which indicates that it was designed to be used on either side of the blade, so why not protect it on either side of the blade?



Why complicate a simple problem?


George


----------



## GeorgeC (Jul 30, 2008)

woodnthings said:


> You need not attach your auxilary fence to your permanent fence, merely make it a snug fit so it comes off easily so you can turn it around if needed. This one has a higher side for certain operations:



What keeps it in position when the cutting blades are biting into it. 



George


----------



## woodnthings (Jan 24, 2009)

*I donno?*



GeorgeC said:


> What keeps it in position when the cutting blades are biting into it.
> George



Friction?:surprise2:


----------



## Jim Frye (Aug 24, 2016)

Mad: I purchased my table saw in 1993 and made those jigs within the first few years of ownership. I've always treated jigs and fixtures as regular woodworking projects. They are learning tools and that's why I fully finish them too. Well constructed jigs will last for decades and enhance your woodworking quality. The tall fence proved so useful that it has been permanently on the saw for the last 20 years. The router fence is mounted on a second rip fence for use with the table wing mounted router on the saw.


----------



## Mad (Dec 9, 2017)

GeorgeC said:


> Why complicate a simple problem?



I just want my fence to look and function like the white fence in the photo above, where wood blade friendly materials are on both sides of the metal spine of the fence.

Since there are a variety of blade friendly materials that can be used, and an infinite number of heights above the fence spine that these materials could be ripped to, and a variety of ways the hardware can be oriented to accomplish the attachment... I thought it would be good to ask the opinions of those with more experience than I have in modifying or enhancing a fence.

It may be a simple problem for you, and that is great. For you. 

For me, since I have not done this before, some questions occurred to me, such as those that I outlined in the original post. Questions like hardware, because if I use MDF, and I have to clearance a port for the hardware well deep enough so that the hardware recesses below the surface of the fence wall, then the strength and integrity of the material remaining beneath the point of attachment is naturally much weaker, and could potentially lead to rapid tearout when subjected to rapid forces transferring from a blade bind acting on the material being cut that is trapped against the sacrificial fence surface. So that possibility, about which I do not have the experience to estimate the probability of, led me to question either the choice of material, or the choice of hardware, or the orientation of the hardware, to reduce the risk, if the risk exists.

Yes, that does "complicate" the problem, but I'd rather ask and learn, than be soured into silence by criticism for asking the questions.


.


----------



## TomCT2 (May 16, 2014)

methinks you are over thinking the problem.


first - there should never be any blade biting. the sacrificial fence idea is to allow the blade to go past the vertical line of the (metal) fence. when you're going to be doing that you position the fence and gently raise the saw to cut a clear "pocket" first. 



trapping a work piece between the blade and fence is not common except for really short (cross) cuts. if you are pushing a board thru on a rip cut and it binds up you need to immediately stop and figure out why. that is not normal and the danger is the harder you push the more apt you are to slip and rip something other than the wood - like your hand/fingers.


the fence should not just 'sit' unconstrained over the original fence. there should be something that pinches or grips or tightens to keep the sacrificial fence in place. the detail depends on your design.



using 3/4 thickness the remaining material under a 1/4-20 flat head bolt - or carriage bolt - or hex head bolt is more than adequate to not 'rip out'


----------



## woodnthings (Jan 24, 2009)

*Attaching a sacrificial fence ....*

Your stock fence has T slots, so T nuts seem a logical way to attach any separate side panels or integral fence slip over design.... if needed.
In the automotive design field, we would speak about having bumpers on your bumpers ala 1960 Cadillac front nose cones. This reminds me somewhat of that since I am understanding you want to have side panels and then possibly and additional slip over piece?

I would simplify it to one or the other. UHMW plastic is not cheap:
https://www.ebay.com/itm/UHMW-Polye...208262?hash=item545b408686:g:fDQAAOSwNvxa6IvE

Melamine is cheap and readily available. Hardwood is also cheap and available. Baltic Birch seem like a waste of good plywood, but it would look great and be flat. You can use flat head screws set below the surface, out of the way of the saw kerf, into T nuts in your existing fence. That's as complicated as I would get.
I personally like the slip over design with a friction fit, easy on easy of to flip around, but that's just my simple mind at work. :nerd2:


----------



## Mad (Dec 9, 2017)

I have not been able to find any sort of "T Nut" that will fit. 

The throat width to these T slots will just fit a 1/4" diameter bolt, and the throat depth will just barely accommodate the head of a normal 1/4 x 20 bolt, or the thickness of a 1/4 x 20 nut.

On the other hand, 1/4 x 20 T nuts designed for T slots have a require a wider width through the throat of the T slot, and a deeper depth in the channel of the T slot.

Most searches for T nuts yield the kind of T nuts that are round with tines for placement into wood, so you better believe I searched out machine tooling websites and looked at the dimensional specs for true T nuts before arriving at the conclusion that they may not be available for T slots this small.


----------



## Mad (Dec 9, 2017)

TomCT2 said:


> the sacrificial fence idea is to allow the blade to go past the vertical line of the (metal) fence. when you're going to be doing that you position the fence and gently raise the saw to cut a clear "pocket" first.



What type of cuts or operations benefit from a blade pocket scarfed into a sacrificial fence?


Jim Frye's Cadillac bumper on top of a bumper secondary sacrificial fence also has a blade pocket (second photo in his high fence article/design).


What is the purpose of this type of fence where the blade is nested inside of it?


.


----------



## Mad (Dec 9, 2017)

Jim Frye said:


> Mad: I purchased my table saw in 1993 and made those jigs within the first few years of ownership. I've always treated jigs and fixtures as regular woodworking projects. They are learning tools and that's why I fully finish them too. Well constructed jigs will last for decades and enhance your woodworking quality. The tall fence proved so useful that it has been permanently on the saw for the last 20 years. The router fence is mounted on a second rip fence for use with the table wing mounted router on the saw.



I'm not dismissing your design and ideas. I was just admitting that it was going to take me a while to understand them. But I'm working on that understanding with every re-read. I see why you interjected... if I use the T slots on the vertical wall to bolt on a semi permanent side surface, then I lose out on the opportunity that you capitalized on, which is to use those T slots as retention guides for a slip on fence instead. Only rather than slipping on via downward application, your design slips on from the rear end of the fence in a reverse telescoping motion.

Once I bolt a semi permanent smooth faced semi permanently mounted sacrifical surface to the vertical sides of my metal fence spine, then I lose the use of those T slots as guidance rails. Yes, I'm starting to understand now. But I never claimed to be quick witted. If intelligence is a prerequisite for posting questions on this forum, then I am woefully underqualified. So I do appreciate everyone's patience as I try to catch up and learn something here.


----------



## AlWood (Apr 18, 2010)

woodnthings said:


> Friction?:surprise2:


Bill, for such a strong proponent of using physics (and safety) in the shop as you are, your assumption that the friction is enough for an auxiliary fence to stay in place is a bit inconsistent, to say the least. The auxiliary fence, if not fixed to the main fence by some kind of a clamp, may be easily pulled along with the work-piece and make a lot of trouble (speaking from experience). This is especially true if one puts a lot of side pressure on the work-piece by trying to keep it snugly to the fence. BTW, it is always the case when one uses a strong (steel) splitter (even if you use a dado-set). It can be even worse than using a wrong spelling (just saying... :wink


----------



## AlWood (Apr 18, 2010)

woodnthings said:


> Friction?:surprise2:


Bill, for such a strong proponent of using physics (and safety) in the shop as you are, your assumption that the friction is enough for an auxiliary fence to stay in place is a bit inconsistent, to say the least. The auxiliary fence, if not fixed to the main fence by some kind of a clamp, may be easily pulled along with the work-piece and make a lot of trouble (speaking from experience). This is especially true if one puts a lot of side pressure on the work-piece by trying to keep it snugly to the fence. BTW, it is always the case when one uses a strong (steel) splitter (even if you use a dado-set). It can be even worse than using a wrong spelling (just saying... :wink)


----------



## GeorgeC (Jul 30, 2008)

woodnthings said:


> Friction?:surprise2:



Nope!!


George


----------



## GeorgeC (Jul 30, 2008)

Mad said:


> I have not been able to find any sort of "T Nut" that will fit.
> 
> The throat width to these T slots will just fit a 1/4" diameter bolt, and the throat depth will just barely accommodate the head of a normal 1/4 x 20 bolt, or the thickness of a 1/4 x 20 nut.
> 
> ...


'
You do not need any type of "T nut" for this job. You have a T track. The standard nut that goes on the end of any bolt (correct size of course) does the job. You are over thinking the problem.


George


----------



## GeorgeC (Jul 30, 2008)

This thread is sure a whole lot of words for a very simple function/build. Regardless of whether the sacrificial fence is of the slip over type or the bolt on using the t track type. 



George


----------



## Terry Q (Jul 28, 2016)

Personally, I use the fence without sacrificial faces unless I need to bury a dado blade into the fence, then I just use whatever stock is handy since I’m going to take a chunk out of it anyway.

The bolts aren’t a problem. You need to find nuts like these (they also come in 10-32 thread). You can get short screws or grind them shorter if you need so they won’t bottom out in the track. 

I just recess the screws in the sacrificial fence.

https://www.amazon.com/Woodhaven-5760-4-20-Oval-Nuts/dp/B002TWBJSE


In woodworking there is always more then one way to accomplish something.


----------



## woodnthings (Jan 24, 2009)

*For all you naysayers ....*



AlWood said:


> Bill, for such a strong proponent of using physics (and safety) in the shop as you are, your assumption that the friction is enough for an auxiliary fence to stay in place is a bit inconsistent, to say the least. The auxiliary fence, if not fixed to the main fence by some kind of a clamp, may be easily pulled along with the work-piece and make a lot of trouble (speaking from experience). This is especially true if one puts a lot of side pressure on the work-piece by trying to keep it snugly to the fence. BTW, it is always the case when one uses a strong (steel) splitter (even if you use a dado-set). It can be even worse than using a wrong spelling (just saying... :wink)


I promise you all that I can make a friction fit slip over fence that will NOT slide on the stock fence, whether Mad can, is a 'nother issue. All you would need for added "insurace" against slipping is a bolt on the off blade or right side of the stock fence in a T nut as a stop. There's always more than one way to solve a problem in woodworking....
or so says a member here. :vs_cool:

Like this one:
https://youtu.be/U3a1hqTLjg4?t=202


----------



## Jim Frye (Aug 24, 2016)

Most properly constructed jigs don't need a lot of physical securing. 1/4 turn past snug is likely more than necessary. The aluminum flanges on the OP's rip fence are likely pretty thin anyway (they are on mine), so a lot of torque is really not necessary. What you really want to do is clamp the jig to the face of the fence and use surface area to give the needed friction. If you have a sliding jig, you can tighten it up by wiping on coats of wiping varnish (50/50 mix) until you get the fit required. As for a bolt head being a bit thick to fit, a file or grinder can remedy that quickly. Nuts can be thinned by putting two on a matching bolt and using the second nut as a jam nut while you file/grind the other one to the correct thinness. T-nut flanges can be filed to fit the T-slot easily. Toilet flange bolts are often used by folks making jigs for T-slots. Flat headed machine screws can be fitted with a washer to hold in a T-slot. I used a cone shaped grinding stone in an electric drill to shape the washer hole to fit the flat head of the screw and then secured it with some two part epoxy. These are used to mount the router fence to the top of the rip fence and have been in use for over twenty years. Also, since I don't know the make of the OP's rip fence, it's possible it may be sized for metric fasteners. Just a thought.


----------



## Tool Agnostic (Aug 13, 2017)

I have a Bosch REAXX table saw. It has the blade safety feature where the blade retracts if you touch it, like SawStop, only different.

The aluminum fence has T-slots on both sides and the top. All three sides are covered with snap-in plastic panels, which protect against triggering the blade safety retraction if you make electrical contact between the blade and the fence. (I am not sure how that could happen exactly, but the plastic panels are there.)

If you want to install a sacrificial fence, the Bosch REAXX manual says to remove the plastic panel and use "Three (3) 1/4 x 20 x 3/4” long hex. head machine screws, Three (3) 1/4” Washers, and Three (3) 1/4 x 20 machine nuts." They also recommend a 3/4 inch board for the sacrificial fence. 

*To answer @Mad's fourth question:* 
Bosch's instructions have you insert the bolts in the T-slots on the fence. The washers and nuts go in the wood sacrificial fence itself. The instructions say to drill 9/32” through holes, then counter-sink each hole (down 3/8 inch) using a 3/4 inch drill bit.

The oval shape T-bolts that they sell at woodworking stores will also work in the T-slots, I believe. 

_I don't do any of that_. Instead, I use the Rockler Universal Fence Clamps. They are fast and easy, and I don't have to bother with removing the plastic guards, or dealing with the bolts. I also use them to clamp quick and dirty miter fences to my miter gauge. The universal clamps fit into 3/8 inch holes. (FYI: They are on sale through 5 July 2018. Normally $20, now $10.)

http://www.rockler.com/universal-fence-clamps

The only issue with the universal fence clamp design is that they limit the height of the sacrificial fence to the height of your existing fence. One solution is to attach a second tall fence to the lower sacrificial fence that you clamp to the table saw aluminum fence, I suppose.

A different design uses dovetail grooves, which allow for any height sacrificial fence. I like the idea, but it isn't nearly as convenient as drilling two holes. You need a router and dovetail bit to cut dovetail slots in the back of your sacrificial fence. It is interesting to note that they no longer show the product being used to hold a sacrificial fence. 

https://www.microjig.com/products/matchfit

*Answering Mad's first question:*

I use 3/4 inch Baltic Birch plywood for my sacrificial fences. I keep a small supply of Baltic Birch plywood on hand. It costs a little more, but it is reliably flat and I don't have the space to store many types of flat sheet goods. 

*Answering Mad's third question:*

I cut a ~ 1/16 x 1/16 inch rabbet on the bottom blade side of my sacrificial fences as a relief to help prevent sawdust from interfering with the cuts. Of course we keep our saw tables clean, but we don't want any sawdust to get pinched between the fence and the workpiece, so the relief gives any remaining or newly created sawdust a place to go, out of the way.

*Answering Mad's final question that was not asked:*

Sometimes I use the universal fence clamps to sandwich two boards in place for a sacrificial fence, mostly when I use a wide dado (say, 3/4 inch). One is there as the sacrificial fence, closest to the blade. The other board is there as insurance, just in case I mess up and position the fence incorrectly before I raise the blade - better wood than raising it into the real metal fence.


----------



## TomCT2 (May 16, 2014)

Mad - over the years I've used a lot of the "white plastics" for rub rails / etc on machinery and conveying equipment. I would not recommend using the material primarily because it frequently curls / warps over time. it's not that expensive from an industrial supplier - from a 'hobby house' it can be very expensive. 



if you have T-slots I'd recommend bolt head in slot with washer&nut countersunk on the outside. T-nuts would have to have a larger diameter, that you grind two flats on, otherwise there's nothing to prevent spinning in the slot - presuming you flatten/cut off the spurs.


I use the 1/4-20 sized T-track. it's useful to file off any numbers/marks from the head, polish it smooth. also check the 'underside' of the head for burrs and sharp edges. the heads are stamped, so they can have little points/burrs than don't help with smooth sliding. 



check the hardware section for "jam nuts" - these are thinner than regular dimension. 

you'll want to use a dab of removable thread lock (purple Loc-Tite) on jam nuts to ensure they don't loosen and fall off into the blade. being thin they don't have the full thread length to engage.


----------



## Mad (Dec 9, 2017)

Much appreciation extended to @*TomCT2*, @*Tool Agnostic*, @*Jim F*rye, @*Terry Q*, for your _incredibly *informative*_ comments that you all contributed today.

While I had already finished my first attempt at lining my fence with sacrificial surfaces yesterday, without having the benefit of today's deliciously detailed suggestions, the second attempt I build (to correct all the mistakes I made with the "prototype") will be further improved by a synthesis of all of your ideas.

And thank you especially for snapping the focus back to answering the questions, rather than deriding all these words. Your words are valued, and helped me learn something today. I'm quite certain that your words will help future searchers learn something also. This is no doubt the very best use of a discussion forum. To discuss ideas, not to dismiss them. Thanks for not dismissing my quest to learn.


.


----------



## Mad (Dec 9, 2017)

*VERSION 1 - PRACTICE:*













The original idea I had in mind was to make my fence bar look and feel and function like a Biesemeyer fence beam... with smooth slabs of melamine gracing both sides of the fence, making a massive unbendable box beam. This is my first attempt from yesterday, using MDF, which is .662", not .750". I had planned to use melamine shelving material from a big box store, ripped into strips approximating the height of the blade from the table when fully raised, and finished off with iron on edging strips trimmed flush. But then I saw these pre painted MDF strips already ripped to the correct height in the trim isle, and decided to give that a shot first, following the path of least resistance.


*HARDWARE:*











That .088" reduction of thickness difference with MDF trim versus the 3/4" thickness of most other materials previously considered made a difference when it came to hardware selection, which itself was limited to the somewhat generic and standardized hardware typically available locally at the usual suspects. There are those days when you can find 1/2" long, and 1" long, but not 3/4" long. Yesterday was one of those days.


I didn't know that ovalized long flag nuts existed until today (thanks Terry Q), so I selected 1/4x20 square nuts to slide into the T track, since the corner points to the square, being further apart from the center axis of the thread circle, will resist rotation within the channel wall sooner than the corner points to a hexagon, which are closer together, point to point, than that of a square.



While it would have been easier to mount the sacrificial fence surface if the bolt heads were in the track, with the threaded bolt shafts sticking out, especially when trying to align 5 fasteners simultaneously when installing the surface (rather than loose nuts sliding around in the track)... it was ultimately the limitations in immediately available tooling and hardware that led me to reverse the fastener direction and use Pan Head machine bolts with heads out.


Even though the width of a standard 1/4x20 machine nut is the same at 7/16" flat to flat, the thickness of the nut can vary with special features like toothed wheels, serrated flanges, or nylok inserts... anti rotation features that are all too thick to slide into the slot. But a featureless nut is somewhat thinner than the depth of the T slot, such that when the outward face of the nut is drawn up tight against the arm pits of the T slot, there is some space available between the underface of the nut and the bottom valley of the T slot. I wanted to take advantage of that tiny bit of space. I needed to, since I was working with MDF, which is thinner than 3/4" ply, and since I was using 1" long bolts (the lesser of two evils... as 1/2 was not enough thread engagement, and 3/4 was not available in 1/4x20 locally). 



If the bolt heads were drawn up against the armpits of the T slot, the overall length of the fastener assembly stickout would be longer than if the nuts were inside the T slot, and the bolt length extended through and beyond the slotted nut into that tiny bit of space between the nut and the valley of the T slot that is realized once the fastener is torqued. I hope that made sense. The next version will likely incorporate more elegant hardware ordered online, such as those ovalized long flag nuts Terry linked.


*COUNTERSINKING:*












Perhaps the most challenging issue I faced was countersinking the hardware wells to a consistent depth from hole to hole, as well as determining a depth that would recess the hardware stack enough to clear the sliding surface of the fence, while not recessing it so much as to cause the bolt to bottom out into the valley of the fence before the clamping torque was achieved between fastner and the fence. I wanted to avoid a problem with the bolt being tight, but the fence surface rattling around back and forth between the bolt head and the T slots, if the bolt bottomed out before the bolt head and washer stack had frictionally engaged the bottom of the well I was countersinking with this bit and brace.


Next time, I'd probably use a forstner bit chucked into a hammer drill set to the rotary drill (non hammering) action while using the depth bar as a stop along with a piece of guide tape on the body of the forstner. Or I might use drill press having a quill travel lock. But all of those tools of mine were unavailable (two hours drive away from the table saw location), so I broke out my decades long held standbys that I manage to keep on hand at every location I own (what if there is no power?). Old tools still work just as good today as they did before all the grid reliant gizmos came along. But do keep in mind the irony... I'm fixing up a saw that relies on 220V!


What was difficult to estimate was how much MDF might deflect under the compression of clamped hardware. I tried to account for this ahead of time, but I did not test and measure. I just ball parked it. If I change materials for Version 2, and say, use Melamine that has a particle board substrate, then I will do a compression deflection test to first before determining the depth of counter sink. If I use Baltic Birch, or solid wood, or plastic, then I wouldn't bother. But from working with this material, it is something to consider, especially when clearances are tight.


In this specific case, I added a split lock washer under each pan head bolt flange, not only to resist the bolt backing out, but to also make up for the compression of the MDF when the bolt was tightened. The crown of the pan heads lays not more than 1/16" beneath the skin of the sacrificial surface. Enough to clear, but not so much as to thin out the meat of the MDF being compressed under the fastener. The lock washer is backed by a flat washer that split tine can dig into, rather than the soft MDF. Also, I beveled the rims of the countersunk holes, to reduce any catch points from paint chip tear out.



*OTHER CONSIDERATIONS:*


By asking the questions in the original post, and hearing your answers, I learned that I need to anticipate the entire gamut of uses for a fence prior to making version 2. Specifically, I need to consider what kind of jigs, retainers, feather boards, sliding features... any ancillary system that relies on the fence for either guidance, retention, or support... all of these systems, what they do, how they do it, and how they mount, need to be considered in advance of making an optimal semi permanent fence surface. I simply wasn't ready for those classes yet, and wanted to simply use my fence for ripping, without marring the metal spine of this new to me fence that I was so happy to have compared to the original fence fitted to my Craftsman saw.


Yet, before investing more time, and more expensive materials for Version 2 of a sacrificial fence surface, I see that I need to first learn more about various designs of jigs and fixtures that involve a fence. The more I can utilize the T slots already built into the fence, the better I'll feel... rather than having awkward gargantuan L clamps hanging off the fence for lack of a better way to grip an accessory. That being said, I'm definitely going to pick up a few of those clamps Tool Agnostic pointed to while they are on sale! I will never rely on friction alone to retain anything near a saw blade. (even though clamping, by definition, is friction). Some type of positive stop or locking engagement that resists movement is what I would always prefer. 



Now that you have seen what I've done thus far, I widely welcome any and all suggestions for improvements, so that the next version will be better executed and more functional in ways that I cannot yet anticipate for lack of experience. Thanks!


----------



## woodnthings (Jan 24, 2009)

*I give my advice using carefully chosen words ....*

My advice is based on many years of experience using several types of tablesaws and fences, from junk Craftsman, to the Biesemeyer and Unifence. My present fence collection includes 2 Biesemeyers, and 3 Unifences. 
The reason I have 3 Unifences on the Sawzillia is simple, they each do different things better than the other. One is the stock Unifence and is adjustable fore and aft as well as capable of having a tall side or a low side. A high or tall fence is useful for ripping material that extends above the normal height fence. The low fence allow more room between the blade for push blocks and fingers when necessary. Both features are great to have, improving operation and safety.

The middle Unifence has been replaced by a Peachtree UHWM sided extrusion with "T" tracks top and on the side, which is my main fence. When I need a low fence I just slide the left side fence over an away I go.

The right side fence uses only the Unifence head and not the bar which has been replace by a 1" X 2 1/2" tall X 36" long Oak section. This is my sacrificial fence for making rabbets. I have zero issues with raising the dado blades into that piece of Oak as can easily and cheaply be replaced. 

So, based on those different capabilities, I choose the fence that will do the operation best. The reason I suggest using a slip over fence is that it allows a tall side or a short side without have 2 fences. It can have a sacrificial side which may cause youR work to hang up in the cut occasionally as well as a unmolested, smooth side for most typical operations. If you go to some trouble making your perfectly flat and smooth surfaced side panels with holes and recessed bolts for T nuts, you may not want to cut into that nice piece of material sacrificially.... just sayin'. There are unintended consequences to some decisions.

Advice is just that, not hard or fast rules, just one guy's opinion based on his experience. I never fully explained the rationale for the slip on fence so I did that above, take it or leave it. If only had one fence and was a rectangular section, I would most certainly make a slip on fence, maybe more than one. :vs_cool:
Referencing the jigs and fixtures that can be attached to the fence, I have never felt the need to use the "T" tracks in the one fence that has them. I did drill one of the Biesemyer fences for pressure feed rollers, years ago, but removed them soon after since they were more in the way than useful. A stop can be a small block clamped to the fence or just a pencil mark. I rarely need a stop block in a ripping operation. Crosscutting to a spacer block to allow of the off fall is something I rarely need because my miter gauge fence is extended and pushes the off fall beyond the blade. I don't make a practice of reaching between the spinning blade and the fence to retrieve a cut off, too much can go wrong..


----------



## TomCT2 (May 16, 2014)

"Specifically, I need to consider what kind of jigs, retainers, feather boards, sliding features..."

the answers to that question occupy several large tomes. 

what you need depends on the kinds of things you do - and that varies by project. to sit down and in advance design something that will meet every need for every kind of jig/fixture or cut or bevel or dado or cheek cut or tenon making or . . . not going to go real well.

your 'prototype' looks entirely serviceable. so just get going with whatever projects you have in mind and make what you need when you need it.

as for clamping, many ways - here's another
View attachment 362153


----------



## Tool Agnostic (Aug 13, 2017)

Tool Agnostic said:


> [...]
> 
> _I don't do any of that_. Instead, I use the Rockler Universal Fence Clamps. They are fast and easy, and I don't have to bother with removing the plastic guards, or dealing with the bolts. I also use them to clamp quick and dirty miter fences to my miter gauge. The universal clamps fit into 3/8 inch holes. (FYI: They are on sale through 5 July 2018. Normally $20, now $10.)
> 
> ...


I was mistaken about the height limitation of the universal fence clamps. A friend told me about how you can use the universal fence clamps to hold a high single-board auxiliary fence in place. First, drill out large holes to make room for the fence clamps. Inside those large holes, drill the 3/8 holes needed for the fence clamps. (On observation, it might be tricky to drill those 3/8 inch holes. I suppose they don't have to be perfectly vertical, but they should be close. Personally, I would drill them "upward" from the bottom of the fence.)

Scroll down partway on this web page to see an example: 

http://www.rockler.com/how-to/woodworker-shares-a-few-new-uses-for-the-universal-fence-clamp/


----------



## woodnthings (Jan 24, 2009)

*I posted this back on 02-07-2013*

What's your table saw fence like was the title:
I have both Biesemeyers and Delta Unifences.........

The difference in performance between the two is minimal EXCEPT for this. The Unifence bar is removable and is capable of a high and low fence height. The low height, about 1/2" allows your hand/fingers to get down closer to the table, in between the blade and fence. Sounds dangerous, but it's not really in my opinion.
Narrow strips can be better managed with a push shoe or your hands and you have greater control. When the fence is tall like a Biesemeyer, you *must* use a push shoe to move the workpiece forward, OR use another sacrificial scrap to back against the work.

You can make your own "low" profile fence (which can be clamped on any rectangular section fence like the OP's) with 2 pieces of straight parallel edge scrap, one being wider than the other. Screw them together making a "L" which you can clamp to the Biesemeyer fence: 
Attached Thumbnails  
I don't recommend doing this by the way!

 
This is somewhat safer because the splitter is on the saw and will keep the workpiece registered to the fence both during and after the cut.

 

 




Notice how easy it is to use the low fence when ripping thin and narrow strip, whether you use your hands or a push stick between the blade and the fence.


----------



## Mad (Dec 9, 2017)

Bill, I do see your point about the benefits of a low height fence, as far as manipulating a skinny piece of material between the blade and the fence.


However, I hope to never find a need to use my fingers for pushing material that close to the blade. It could very well be my inexperience with woodworking (as opposed to rough carpentry) in making this assessment, but I would always try to use a push stick of some sort instead. I have yet to learn why fingers would need to be used that close to the blade instead of some sort of jig or pushstick, so any for examples where fingers are preferred might help me visualize merits to what otherwise appears like a bad idea.


----------



## woodnthings (Jan 24, 2009)

*You are completely right to be concerned!*

That's why I posted the comments under the photos..... safety first!
The rule is "Do as I say, not as I do" .... after 50 years of doing this, I know my comfort zone and limitations, so I may not always adhere to my own rules. :surprise2:


There is another rule, "Never post a photo of the wrong way to do something, newbies won't get it and will attempt a bad practice. Even with posted warnings against it, some goof ball may attempt it.... not my problem. :|

Finally, the last rule of woodworking states "If you don't feel comfortable doing an operation or a procedure, DON'T DO IT!"
Funny thing is, There is an entire thread devoted to blood, gore and stitched up fingers where the most asked quest is "How did it happen?" ... wait, I'll show you.... photo to follow. :vs_OMG:


----------



## Mad (Dec 9, 2017)

Yes, I am usually one of the first to ask "how did you do it" whenever someone reports cutting off their finger. Usually, I am disappointed with the lack of detail in their response, but naturally, out of respect for their loss and suffering, I don't push it, and only ask once. If they say, "I was being careless", then I don't feel right badgering them back into a horrible memory by following up with "Yes, but HOW were you being careless? What SPECIFICALLY were you doing"... yet that really is what I want to ask them, because, in addition to empathizing with their misfortune, I want to learn from their mistake.


----------



## Mad (Dec 9, 2017)

Here is an interesting innovation...


Spring loaded, lever action "fingers" with ratcheting, canted roller bearings for "fingertips" that not only press skinny materials down against the table and laterally against the fence... they also only roll one way, preventing kick back.












If I had interest in this device, then that interest would dictate how high I make my next version of smooth fence sides... either flush with, or higher than, the top surface of my already T slotted tubular metal fence spine... depending on the thickness of the cleats of this device that lock into the T slot. If the cleats are wider than the outboard lips of the top T slots in my native fence, then I'd make the fence high enough to also recess a horizontal board flat across the top of the fence in between the two smooth sides, that would be thick enough to screw in and secure the bolt on T slot provided with this device. Alternatively, I could make the new smooth sides low enough to meet flush with the top of the native fence spine, and any outboard portion of the cleats could partially rest on top of the smooth side while locked into the native top T slot.


Hard to visualize what I'm describing without a closer photo, but I've never seen this device before, and have no idea how wide the mounting cleats are, and so I cannot judge whether or not I'd be better served with the add on T slot they provide, or with the native T slots that are biased toward the outboard edges that already exist on the top of my fence. But this is what I mean about at least giving some thought to possible accessories of interest prior to making another version of fence surfaces.


----------



## Tool Agnostic (Aug 13, 2017)

I am truly grateful for @woodnthings presence here at Woodworking Talk. He has shared a lot of helpful hints and great ideas. Unfortunately, the "don't do this" hint above, with the fingers close to the blade, is scary for me, too. I am glad that woodnthings has the experience to avoid injury, but I would not recommend doing it his way. In fact, woodnthings recommends not doing it his way, too.

For cutting thin pieces close to the blade, I use GRR-Ripper push blocks:

https://www.microjig.com/products/grr-ripper

It takes time to remove/replace the blade guard, riving knife, and anti-kickback pawls on my table saw so I can use the GRR-Ripper push blocks, but it is worth the time and effort to me.

I have a set of standard "Bench Dog" push blocks with the rubber/foam bottom, which I also use. I have the usual assortment of push sticks. Despite those other safety tools, the GRR-Ripper push blocks are my preferred solution for certain types of cuts.


----------



## bargoon (Apr 20, 2016)

Mad said:


> What type of cuts or operations benefit from a blade pocket scarfed into a sacrificial fence?
> 
> I use this method to cut dados. I over-stack my dado set and get an exact measurement with part of the dado set under the pocket. This ensures you don't run the blades into the fence.


----------



## Tool Agnostic (Aug 13, 2017)

bargoon said:


> Mad said:
> 
> 
> > What type of cuts or operations benefit from a blade pocket scarfed into a sacrificial fence?
> ...


Same for me, but I think that @bargoon meant "rabbet." By adjusting how much of the dado blade is exposed beyond the sacrificial fence, you can make micro-adjustments to close in on a perfect fitting rabbet. 

A dado is a groove in the middle of the board, a rabbet is on the edge. I don't know why we need two different terms, but it is what it is. Sometimes I say "dado groove" just to be extra clear in my writing.

If you make the perfect dado stack width to cut an exact rabbet, then the blade may rub against the fence, as bargoon points out. Even if you manage to keep the blade from touching the fence, a sacrificial fence adds "insurance" against accidental scratches and cuts. Scrap wood is cheap compared with fences. 

Why do I tuck a wide dado stack into the sacrificial fence instead of making a narrow, but perfect fitting dado stack? Because it is fast and easy. It is fast and easy for me to make a 3/4 inch dado stack with my Freud SD-208 dado set. It requires only blades and chippers, no spacers or shims. It is fast and easy to adjust the fence; much faster and easier than it is to remove the blade stack, add or remove shims, reinstall it, test again, and then repeat it several times. No, thank you.

-----

*Related, but Off Topic: *

You can also "zero in" on a dado groove by using a narrower dado stack (or an ordinary blade) and making multiple cuts to expand the dado to the perfect width. This is useful when you are trying to cut a dado groove to match the edge thickness of another piece of wood that will fit into the dado groove. The problem is that wood dimensions vary. They may be true Imperial or the "metric equivalent" or just "off."

There are a variety of jigs that simplify the setup to make perfect fitting dados with multiple cuts. You can make or buy them. Here is one example. Other companies make similar products or it is simple enough to make your own:

https://www.microjig.com/products/dado-stop

I do not own one, but I have helped a friend who has one. It is simple to use, once you "get the idea" of how it works.

P.S. Some ordinary table saw blades do not make flat bottom cuts. Combination and general purpose table saw blades are often "ATB" (alternate top bevel) type blades. If you use one of these blades to make dado grooves, the bottom may be "good enough", but it may not be as flat as you would get with other types of blades, including dado sets. You can make more cuts to flatten the groove better.


----------

