# routing 1/4 inch dado



## autoBrad (May 21, 2008)

Hey 

I know this has probably been covered but I can't find it when I search.. 

I am making a large cabinet, like 90 inches high, 30 something deep. Now I am trying to route 1/4 inch dado's in the sides for bottom(not a rabit, 3 inches up from bottom) and in the top for the top piece, etc.. 

So, obviously I am working with material too large for my router table. So, I started out and made a couple of t-square's.. Seemed like a super easy thing to make, tried them on a test piece. Made one for 1/4 inch and one for 1/2 inch. So, next day I go to use them and did a test run first, and it checked square but the dado's i routed weren't straight, it was obvious. I was like a 1/4 inch off over a 30 inch run.. So, I checked the t square and sure enough over a distance it was off when comparing to the plywood I was cutting, which I checked and even re-cut to make sure it was square, checked, again, etc.. So, I made another one, checked it, it was square, etc.. But then I routed one and it turned out off out just towards the end.. I think I'm getting deflection like out that far in the plywood I made the jig with(3/4 inch poplar).. So I thought, okay, t square method is good for shorter pieces but not out at like 30 inches..

Then I proceeded to put the router in the table and route a 3/4 inch slot in a piece of mdf.. So I could setup a jig to use a guide bushing with.. Apparently it wasn't my night.. So, it routed fine, did it in a couple of passes to make the grove, put an end on it.. but I discovered that it's routed a perfectly straight dado with this.. but that at some points the 3/4 inch slot I made is actually like 49/64ths wide(using my caliper) I am thinking my bit may be worn out, etc.. and the dado I routed with it isn't crooked like with the t-square, but it's like wavy if that makes any sense..

My last idea is to do some mdf and attach a straight piece to it, and then you know, route off the excess, so I can just clamp each end of that to the plywood and route it. In my mind the jig with the guide busing should be the best way cause it would prevent user error, that is if I didn't have a 1/64ths of play in it, lol.. 

So my question is this, obviously I have found 3 ways to route a 1/4 inch dado my hand with a router.. which way do you guys use and what have you found to be most successfull?? I hope my explanations make sense, i'm sure everyone has seen or used the methods I described..

Thanks Again

Brad


----------



## woodnthings (Jan 24, 2009)

*If you want to use your hand held router*

Then my suggestion is trap it. Make a 2 sided jig with end rails square to a slot, using the guide bushing as the width of the slot in between two 5" wide pieces of straight mdf. Or cut a dado with the TS to the exact width of the bushing in one 12" piece. This way the router can't shift in the slot and you will end up with a constant width dado. OF Course, the whole jig must be square with the workpiece. Just a question?? Why cant you use the TS, as it's in 3" from each end? OK, you got a long length sticking out to the left but a helper and a work support would manage this. But, either way it should work fine.:thumbsup: bill


----------



## autoBrad (May 21, 2008)

Yeah, so, basically you are saying use a guide bushing and two fences.. seems to me the fences are kinda redundant when already using guide bushings. I think i might re-make the jig, using the table saw, cut two pieces of mdf, clamp one to a bottom guide, then space the other side 3/4(guide bushing width) and secure it.. and of course put a top piece to keep the other end 3/4 apart.

Also, I work alone most of the time, and I'm sorry, putting like a piece of plywood 90 inches long and cutting that accross the tablesaw in my shop is unrealistic, it's too long, too awkward and I don't think it would end up 100% straight, even with a helper. just a bad idea in my opinion.

So, that's one vote for guide bushing...


----------



## cabinetman (Jul 5, 2007)

I made a jig for routing dadoes and rabbets. It is fast and accurate, and easy to make. See it HERE.


----------



## autoBrad (May 21, 2008)

I like that cabinetman.. See I like how it the cutout and is wider, I think that way you won't get deflection at at the end, etc. 

Also, what does, "mica this edge mean?"

Thanks

Brad


----------



## ACP (Jan 24, 2009)

My dado jig is similar to cabinetmans. You can also, if you don't want to mess with a bushing, rip a straight piece of MDF and attach it to some 1/4 in hardboard that is about as wide as your router base plate. Then just use the edge of your router to push up against the mdf rail and it will cut the hardboard off exactly were your bit will run. Then the guide comes from the fence and not the bushing. Also, if you have just a small bit of runout at one point on your dado, I have to ask if you rotated the router at all during your cut. I'm sure you know but will say it anyway that you shouldn't rotate the router during a cut so if there is any run out it is consistent throughout the cut.


----------



## cabinetman (Jul 5, 2007)

autoBrad said:


> I like that cabinetman.. See I like how it the cutout and is wider, I think that way you won't get deflection at at the end, etc.
> 
> Also, what does, "mica this edge mean?"
> 
> ...



The edge that the router base rides against get's laminated with "Formica" or a similar laminate to allow smooth movement.


----------



## woodnthings (Jan 24, 2009)

*Same as cabinetman's but I use the guide bushing*



woodnthings said:


> Then my suggestion is trap it. Make a 2 sided jig with end rails square to a *slot,* *using the guide bushing as the width of the slot in between two 5" wide* pieces of straight mdf making it a long as you will ever need for dado. Or cut a dado with the TS to the *exact width of the* *bushing in one 12" piece.* This way the router can't shift in the slot and you will end up with a constant width dado....."
> 
> This requires only one layer of wood/mdf for the jig not 2 and it's easier to make and less wide all in all. With the side fences referencing off the base plate, if you rotate the base as mentioned above your dado width will grow or diminish. By using the guide bushing there is less probablitiy for this type of error.:blink: bill


----------



## autoBrad (May 21, 2008)

Yeah, when using the t square, I did experience it rotating as I slid it, but then again I didn't laminate what I was pushing it up against. Also, when I did i couple more passes it became obvious that it got easier to do with practice... Skill and experience do matter sometimes.

So, basically it's kinda a tie so far between guide bushing style and a better designed t square.. Oh yeah and the idea of using mdf and a fence, sorry like a circular saw guide. 

One thing I am glad is that all my books I have seen and tried all but circular saw guide method. Maybe I should create a thread type vote... so people can vote on their favorite way..


----------



## autoBrad (May 21, 2008)

when I say better designed t square, I am referring to cabinetman's design..


----------



## GeorgeC (Jul 30, 2008)

cabinetman said:


> I made a jig for routing dadoes and rabbets. It is fast and accurate, and easy to make. See it HERE.


That is almost exactly like one I made for multiple passes many years ago. I was outfitting my new store with cabinets and had a lot of passes to make.

Works very sweet.

George


----------



## rrich (Jun 24, 2009)

*Another way?*

Brad,
When I have to do something like you are describing I'll use a dado blade in my table saw. My table saw has all the supporting structures to allow for an accurate operation.

HOWEVER

If you don't have a dado blade and must use your router, the following should help.

It is an accepted fact that the router bit is not centered in the base plate of the router. (Never has and never will be) I have used a router with a flat side on the router base plate to solve similar problems. You could make a base plate with one flat side to solve your problem. Just make the base plate with ONLY ONE straight edge.

Another issue is getting a straight dado across the 30" that you are describing. Does the dado need to be perfectly square? Not really PROVIDED that the dado is routed using from the same reference edge on both sides of the cabinet. (e.g. Use the front edge on both sides of the cabinet.) 

When I have to do something like this I'll use one of those clamping guides. (They come in various lengths from 24" up to 96+".) Using your cabinet as an example, I would draw a mark 3 inches plus half the diameter of the router base plate minus half the diameter of the router bit from the bottom along front and back edges of the cabinet. Then use the clamp guide as a fence or guide for the router to make your dado. It is rather easy to align the clamp guide to the marks on both the front and back edges of the cabinet side. This technique is particularly useful for cutting stopped dados.


----------



## autoBrad (May 21, 2008)

Thanks for the input. I am using a plunge router with one base that's flat for the operation, I should have said the earlier.. Yeah, the straight edge is a good idea.. I just like having a t square or something so that I don't have to do that measurement everytime.. repeatability and accuracy. 

I have a stacked dado, I do not have a table, etc built up around my table saw, keep in mind 2 car garage everything on wheels.. I realize it was just trying to be helpful but I want to get good at this operation with a router.. 

Thanks Again 

Brad


----------



## supershingler (Apr 28, 2009)

a spiral cutting bit help also

i have found with a standard cutter sometime the sawdust will get behind the bit and force the router away from the fence.

with spiral bit you lift the sawdust out of the way

it made my dados a lot beter

kendall


----------



## autoBrad (May 21, 2008)

You know what, I think that's a good idea. My 1/4 inch bit i think is dull and now when I route with it, it like has tearout on the sides of a dado, like little fibres sticking up.. So, since it's time for a new bit or to have it sharpened.. 

So, would I need and upcut or downcut bit? Or would it matter if I am using it as a handheld router or a router table??

Thanks


----------



## woodnthings (Jan 24, 2009)

*Upcut bit*



supershingler said:


> a spiral cutting bit help also
> 
> i have found with a standard cutter sometime the sawdust will get behind the bit and force the router away from the fence.
> 
> ...


He said* lift* the sawdust out of the way, for a hand held, upcut. For a table mounted, downcut since that's where the dust is trying to go.
bill


----------



## rrich (Jun 24, 2009)

autoBrad said:


> Yeah, the straight edge is a good idea.. I just like having a t square or something so that I don't have to do that measurement everytime.. repeatability and accuracy.


Brad,

I only measure once, regardless of the number of times that I have to do the lay out. I take a piece of scrap and cut it to length, usually using the table saw fence measurement. Then I hold the scrap against the edge and mark the appropriate mark. It's similar to the system that you would use to install drawer slides, etc.


----------



## cabinetman (Jul 5, 2007)

Doing rabbets or dadoes on the table saw or a table router especially on long wide sheet stock as in this application is more easily done with a hand router. Controlling an entire sheet when machining close to the edge, no matter how much support is provided is extremely difficult.

There is a philosophy I usually follow that when the piece is small you take it to the tool. When the piece is large, you bring the tool to the piece. There are disadvantages to doing dadoes on the table saw. Granted there are in some procedures featherboards that can be incorporated and hold downs. But, invariably, holding down the sheet, and maintaining a straight continuous cut is very difficult. Viewing the machining isn't possible.

While it is possible in some cases that the base outside circumference may not be concentric to the router shaft, using the router with a "T" square or even a straightedge of some sort can be successfully done with repetitious perfection in developing a simple habit in how the router is held. I make it a habit of holding the handles in the same orientation to the guide edge, once the spacing has been marked.


----------



## autoBrad (May 21, 2008)

Thanks for all the advise. I totally understand what you are saying cabinetman. That's exactly Why I didn't even attempt this on the router table or the tablesaw. I completed my dado's last night using the t-square and had good success. I think I might stick with that method for 1/4 inch dado's. One side of my router base is flat, and with some practice like you said, just playing with how to hold and guide it, I have gotten pretty good with it.. 

My t-square is a hair out of square.. and I tried to get it good when I made it, my square is square I checked it. I think I need to use a larger square when making another one.. When I say out, like out at 34 inches, I am about 1/16ths out..

I also bought an upcut bit.. In hind sight, using a t square I should have used a downcut bit, so it wouldn't tearout on the surface.. 

Thanks for all the advise. I'll upload some pics of this monster when I am done with it. 

Thanks

Brad


----------



## RIGOOD (Feb 7, 2009)

Would it be an upcut spiral for either the hand held or the table. Unless I am wrong (a real possibility, just ask my wife) an upcut pulls the chips away from the material while a downcut pushes the chips towards the material. Please correct me if I am wrong.


----------



## woodnthings (Jan 24, 2009)

*U R Right*

The upcut will get the chips out of the narrow groove, but may cause a little tearout. Try the painters tape trick to reduce tearout.
The downcut bit should work on the table mounted router since the groove is facing down, not up. Such a narrow groove/dado is prone to clogging no matter what, that's why I asked about the TS. But it just occured to me you could sandwich two circ saw blades together with a cardboard or other spacer to get 1/4" groove with an exact fit. No problem with the chips, but might have some tearout, depending on the blades. You could still use the same jig for either circ saw or router if it's a simple fence or clamp bar.:yes: bill


----------



## autoBrad (May 21, 2008)

Yeah, I don't think it matters how it's mounted. An upcut bit, is more likely to create surface tearout.. a downcut is more likely to not.. Table mounted or handheld in my mind it shouldn't matter, a bit still works the same as it would regardless.

Also if you have a shop vac or some sort of dust collection on the router, i would think the downcut wouldn't rreally clog if it can suck the stuff out of the way.


----------



## rrich (Jun 24, 2009)

As Brad said...

An Up cut spiral bit brings the chips TOWARD the router motor.

A Down cut spiral bit brings the chips AWAY FROM the router motor.

The Up cut is for faster operation and is normally used when the dado is more of a mortise application. i.e. The part going into the dado has shoulders. The up cut has a tendency to produce some chip out.

The down cut has a tendency to fill the dado with chips however makes a cut with very little chip out. When the down cut is used for a deep dado or mortise operation must be done in steps. The down cut does not hog out material as well as an up cut.


----------

