# Idiot Proof Squaring Table Saw Fence, Blade, and Mitre Guage



## Show Soogie Bam (Jan 3, 2019)

Hello long time lurker first time poster.

As the topic says, I need to square a fence, blade, and mitre guage. I have read some forum posts and watched howtos but after trying a bunch of things, I still have some questions.

This shouldn't be so hard but some things may be complicating it for me:

1) I'm new to this
2) I'm using a DEWALT DWE7491RS - most of the edges are beveled which is making me second guess my readings and very hard to square using T slots. Just straight measuring from a slot edge to the blade flat or a tooth seems to be off the table. 
3) I watched a video that said not all squares you buy in the stores these days are actually square. I only have one and I've been using it to try to figure things out but now I'm wondering if it's not even square. I lined it up against some bulky factory-made square things and it actually seems like it might be slightly off. I'm guessing I should invest in a square I have more confidence in.
4) the mitre guage is an Incra 1000SE. The face plate is actually grooved, which doesn't make it easy to measure/see gaps.

Under those circumstances, how should a fool like me go about a precise, triple square job?

So far I've tried: a) using square at both ends of blade flat pressed against fence and the same again using 1 tooth method. It's off but is it my square or the blade/fence?
b) measuring from edge or T slot. That bevel and shadows make it hard to be certain but it seems slightly off. Per a HowTo video, I measured from slot to 1 tooth, then rotated that tooth and measured again, but this didn't feel at all precise to me. 

Very grateful for advice on what rabbit hole I should try next!


----------



## Maylar (Sep 3, 2013)

You need a combination square.

Set blade to miter slot first. Blade all the way up. Mark one tooth on the blade with a marker. Put a straightedge in one of the slots, held up against the slot's wall (it helps if you can jam something in there to keep the straightedge vertical). Using a combination square set the base of it against the straightedge and adjust the length such that the ruler just touches the marked blade tooth. Then rotate the blade 180-ish degrees and move your square along the straightedge and verify that that same tooth is the same distance from the slot as before. Adjust trunion (or whatever your saw has for adjustment) until this is true. You're adjusting the blade mechanism laterally until that one tooth is the same distance from the miter slot at the front and rear of the blade rotation.

Adjust rip fence to be parallel to the miter slot. Loosen the fence screws and slide the fence against your straightedge. Hold it there while you tighten the fence screws.

Miter gauge is the only thing that your square needs to be square for. I don't have an Incra but typically I set my gauges by squaring the front face to the bar that rides in the slot. Or, square it to your (now parallel) rip fence.


----------



## Steve Neul (Sep 2, 2011)

I think you would be safe with a framing square. I've got 4 or 5 of them and all were square at one time. One I had an employee tie a string onto one and use it to throw up to someone on a ladder which didn't catch it every time. It's out of square now but the rest are good. 

The best way I've found to square a miter gauge is to put a board in the miter slot and put a framing square between the board and the miter gauge. A fence if you have a good one should be able to set it up where you don't have to be concerned with it being straight with the blade. On poorer fences you can always measure the distance between the fence at the front and back of the fence to the miter slot. Powermatic used to make a fence with two lock down levers for this purpose.


----------



## FrankC (Aug 24, 2012)

You don't need a square to set a miter gauge, cut a board, that you know is the same width at both ends, in half using the gauge, flip one half over and push ends together, lay them against the fence, if they fit without a gap the gauge is square, if not make an adjustment until they do.


----------



## TomCT2 (May 16, 2014)

he beauty of a framing square:
you can measure, and using a^2+b^2=c^2, you can 'prove' it is / is not square


I'm partial to using a tape measure in millimeters. you can read a whole number, or estimate to a half millimeter. way easier / more accurate than using fractions.


a millimeter is 1/25.4 th of an inch. so you need to measure to a 1/32 in inches to have the same degree of accuracy.


I use a dial indicator to check the blade parallel to the slots, and the fence parallel to the slots.
some people think that's too complicated, but when I watch videos of the 8 armed/handed octopus carpenter checking with a combination square, steel rule and feeler gauges, I get to thinking these folks have inhaled way too much saw dust.


----------



## FrankC (Aug 24, 2012)

Whatever method you use it will only be as precise as the touch of the person doing the adjustments, in hockey they talk of players having soft hands, that goes for machines as well.


----------



## woodnthings (Jan 24, 2009)

*the board needs to be 5/8" thick and fit snugly*



Steve Neul said:


> .....
> The best way I've found to square a miter gauge is to put a *board* in the miter slot and put a framing square between the *board* and the miter gauge. A fence if you have a good one should be able to set it up where you don't have to be concerned with it being straight with the blade. On poorer fences you can always measure the distance between the fence at the front and back of the fence to the miter slot. Powermatic used to make a fence with two lock down levers for this purpose.



Adjusting the fence is the easy part. Use your thumb nail to check for parallelism to the miter slot.


Adjusting the miter gauge is also easy. Use a known square against the miter gauge face and the miter gauge slot. It needs to be 90 degrees or square. You can use a 5/8" thick scrap inserted snugly into the miter slot, as Steve suggests.


Adjusting the blade to be parallel to the miter slot, can be complicated or not, but tedious for sure. The trunnions, those are what holds the arbor assembly, need to be shifted by loosening 3 of the 4 bolts and pivoting on bolt no. 4 in the desired direction, either CW or CCW. A pry bar or lever will shift/pivot it in very small increments until a measurement at the front and at the rear of the blade is identical. It's best to measure from the same marked tooth each time by rotating it around back and forth as you go.


:vs_cool:


----------



## DesertRatTom (Aug 14, 2012)

A good combination square is a basic tool you use the rest of your life, and then pass it on. A cheap one may not be perfectly square, however, nor the 45 degree be accurate. A tiny error is enough to spoil a serious project. The only way to know you have an accurate square is to purchase an engineer's square, which arrives exactly at 90 degrees, and check out your combination square. Half a degree off will make it impossible to glue up parts. After you get an accurate combination square (it will be expensive), use the square in the miter slot to check the blade, mark one tooth and slide the square up to that tooth. Rotate the blade til that tooth is at the back of the opening and see if the combination square's rule touches it exactly the same way.

My combination square is very old, very accurate. A gift from a carpenter friend of the family way back in my childhood. Had it almost 60 years, recently cleaned it up and used a machinist's square and found it was still dead on. Starret is the brand that comes to mind for a top notch tool. Here's a review: https://wiki.ezvid.com/best-combination-squares (Pix 3 below)


With an accurate combination square, you can check to see if your miter gauge is exactly 90 to the blade. Many miter gauges that come with tools are NOT accurate. That's where the cut test comes in. It isn't set to 90 until the gap disapears. 

I also have a Rockler draftsman's square that's about 1/4 inch thick that is very accurate. I used it to calibrate my crosscut jig's back fence, and once that was set, it allowed me to set my fence just right, out very slightly at the outfeed end.

Because I'm fussy about saw setup, I popped for the Woodpecker dial gauge to set blade and fence. Overpriced, only used occasionally, but it's so pretty. (pix 1). second picture is of a Wixey digital angle gauge, $30 and use it every time you change the blade angle. Could not do without it.


----------



## Show Soogie Bam (Jan 3, 2019)

Thank you for all this great advice. I think I might need several sittings to process it all, which is great.



Maylar said:


> Using a combination square set the base of it against the straightedge and adjust the length such that the ruler just touches the marked blade tooth.


Contact can be made all over the tooth. Is it okay for me to assume that the teeth are always precise and it doesn't matter where on the tooth my ruler/whatever makes contact? 

I've got a chunky straightedge that won't fit in the slot, but I can see already this is going to end with me picking up more tools >


----------



## FrankC (Aug 24, 2012)

Show Soogie Bam said:


> Thank you for all this great advice. I think I might need several sittings to process it all, which is great.
> 
> 
> 
> ...


Measure from the same spot on the tooth, this is not nearly as difficult as some will make it, you don't need a bunch of precision tools for this. 
Generally the more precise the measuring tool the longer you spend chasing your tail. :smile2:


----------



## Show Soogie Bam (Jan 3, 2019)

Update:

Picked up a framing square and a combination square. As suspected, the square I was using was actually not square. Empire brand steel engineer's square from Home Depot = scrap metal.

Tomorrow going to try again using tools that actually work and then use FrankC's no-tool-only-cut method to verify.

Thanks again. Learned some new stuff, confirmed some stuff I thought I knew.


----------



## FrankC (Aug 24, 2012)

Show Soogie Bam said:


> Update:
> 
> Picked up a framing square and a combination square. As suspected, the square I was using was actually not square. Empire brand steel engineer's square from Home Depot = scrap metal.
> 
> ...


When you use the flip to fit method be aware that any variance will actually show double what the actual difference is, so make adjustment half of what you see.


----------



## Tool Agnostic (Aug 13, 2017)

Someone started a thread here about "favorite tool" and my response was my Starrett combination square. A combination square is a highly versatile, essential tool for a woodworker. My first combination square was very very cheap, so I should not have been so shocked when I tested it and found that it was badly out of square. 

At that moment, then and there, I decided to buy the best combination square I could find. I bought a Starrett, although other less expensive brands may be equally good for less money. Just verify that it is well made and absolutely accurate.

Nobody seems to have mentioned the easy "flip test" for combination squares: 

* Find a table, desk, or counter with a perfectly straight edge. 
* Check the edge to make sure it is perfectly straight. Use a metal ruler, for example. Verify that your straightedge is straight, too. Flip it around and check again, for example. ;-)
* Lay a sheet of paper down on the table surface next to the edge.
* Place the combination square against the edge with the blade (ruler) perpendicular to it. 
* Use the combination square to draw a long fine line on the paper. 
* Flip the combination square over and draw a second line very close to the first line. 
-> The two lines should be perfectly parallel. Perfect. Really perfect. Not close; perfect.
@Show Soogie Bam did not say how he was testing his table saw alignment work. 

Nobody seems to have mentioned the five cut test to check a table saw for square. There are many different sources and examples on the web. Some seem specific to crosscut sleds, but the general principle is the same. Do a web search for "Five Cut Table Saw Test" to get you started.


----------



## Mycrossover (May 18, 2018)

Show Soogie Bam said:


> Hello long time lurker first time poster.
> 
> 
> 
> ...


Checking a square is easy. Hook it on the edge of a clean straight edge of wood or mdf or whatever and draw a line Now flip the square over and see if it is still square to the line.

Sent from my SM-G900V using Tapatalk


----------



## Tool Agnostic (Aug 13, 2017)

Tool Agnostic said:


> [...]
> Nobody seems to have mentioned the easy "flip test" for combination squares:
> 
> * Find a table, desk, or counter with a perfectly straight edge.
> ...





Mycrossover said:


> Checking a square is easy. Hook it on the edge of a clean straight edge of wood or mdf or whatever and draw a line Now flip the square over and see if it is still square to the line.


ECHO ... Echo ... echo ...


----------



## woodnthings (Jan 24, 2009)

*After verifying your squares ....*

With known "square" squares, it's time to cut some wood. Rip a 1 X 6 so the edges are parallel. Set your miter gauge face to 90 degrees from the blade using your combination square OR "0" on the degree scale. Now, cross cut the 1 X 6, flip it over onto the opposite side and but the cut edges together. The edges of both pieces should till from a straight line! If not, something ain't right. Make adjustments to the miter gauge until you get one continuous straight line and that will be exactly a 90 degree cut on the ends.


For a 45 degree miter, do the same adjustment as above but to 45 degrees, and make a miter cut. Now butt the cut edges together and see if the assembly forms a 90 degree angle. You can test it with your verified framing square or the combination square. Another test method is to use the miter slot and the front edge of the table saw top. These are factory milled to be at 90 degrees to each other. If you slip a 5/8" thick board in the miter slot so it sticks up an inch or so it can be used as a reference "fence". Now you can compare the mitered assembly to the front edge of the saw table. Adjust the angle on the miter gauge face until your cuts form a perfect 90 degree angle.


The cuts are the final proof that the settings are correct, after all a even a verified combination square can not cut wood.... just sayin' :vs_cool:


----------



## Show Soogie Bam (Jan 3, 2019)

Tool Agnostic said:


> Someone started a thread here about "favorite tool" and my response was my Starrett combination square. A combination square is a highly versatile, essential tool for a woodworker. My first combination square was very very cheap, so I should not have been so shocked when I tested it and found that it was badly out of square.
> 
> At that moment, then and there, I decided to buy the best combination square I could find. I bought a Starrett, although other less expensive brands may be equally good for less money. Just verify that it is well made and absolutely accurate.


I followed some early advice from DesertRatTom and did pick up a Starrett combination square (and a framing square too). I found one in great condition on Ebay for 40 bucks. I couldn't pay 200+ for a new one, though I'm sure it would be worth it. I went with a seller that offered "free returns" in case the square wasn't actually square.

It was perfect. More than that, the quality is obvious. It's one of those tools you almost want to find an excuse to use.

+1 for Starett


----------

