# Dado cuts - how wide?



## Rekster (Feb 9, 2011)

I'm relatively new to woodworking and I recently acquired a Ridgid R4510 table saw so my first project is to build myself a workbench.

The plans I have ask for 3.5 inch dado/rabbet cuts to support the frame built out of 2x4.

My question is, how wide of a dado cut is even possible? I have yet to purchase a dado set, the the manufacturer says the saw will take a 6" dado set which does not seem to be as common, but I can't imagine making a 3.5" dado cut it just seems far too wide of a cut. Does this require multiple passes with the dado set to achieve the 3.5" width? What's the maximum width these even support?

Any words of wisdom would be greatly appreciated. Thanks!



Edit - I should have done some searching first, I guess I need to make multiple passes to achieve this after all. I'm still wondering the max width of a dado cut though, and how to make it extremely accurate other than just measuring and cutting very precisely.


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## duncsuss (Aug 21, 2009)

I'd approach it by building up the dado stack to whatever its maximum width may be -- an inch perhaps?

Add a sacrificial extension fence to your miter and push it across the dado cutter. With a square and a marking tool of some kind (knife or pencil), extend the sides of the cut out up the fence. Now you can register each end of the cutters to layout marks that you make on your workpiece.

Lining up the marks, I'd cut one end of the desired dado, then line up the marks at the other end of the dado and make that cut; when both ends are cut precisely, it's easy to just nibble away the waste in between.


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## Starkey (Mar 1, 2011)

Just do your dado cuts gradually. If you have lots of patience you don't need a dado bit, just keep adjusting the fence.


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## woodnthings (Jan 24, 2009)

*Dado or half laps?*

You said:

The plans I have ask for 3.5 inch* dado/rabbet* cuts to support the frame built out of 2x4.
I wouldn't call a 3 1/2" wide cut a rabbet, rather a lap joint, but that's just me. 
As far as how to do it, it doesn't really matter, the technique is the same...nibble,....nibble,...nibble until your cut is the desired width. I personally wouldn't use the full stack for this since it won't get you there in one pass anyway. I'd go with 5/8" or so since it easier to control. I would cut at either ends of the mark as precisely as possible, then nibble out the material in between.  bill


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## Rekster (Feb 9, 2011)

Thanks guys, appreciate all the good advice! I think I'll do some practice cuts on scrap first to see what I'm up against.


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## SteveEl (Sep 7, 2010)

Since I'm a rookie, I look for ways to try to eliminate layout error and here's two ideas.

If the dado needs to line up on different pieces of equal length, try to lay them out with the pieces clamped (to eliminate too-high/too-low error on one piece)

Then to eliminate errors in laying out the width, I do this:

Use a sled (or an extended fence on the miter guage) with a kerf for the current blade setup in the fence

Place the first piece of stock so that whatever layout mark is farthest to the right lines up with the L side of the kerf in your fence 

Place scrap of the intersecting piece to the R of your stock and then anchor the stop block to the R of the scrap.

Remove scrap

By eye, slide the stock over so your mark is now on the R of the kerf, and cut the first pass.

Gradually repeat while sliding the stock ever closer to the stop block.

When you're done (and if I described it correctly) it should be a perfect fit.

Before I had a table saw I used my circ and a speed square to do this.

Tedious, like I said.


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## Tony B (Jul 30, 2008)

*Dado and Lap Joints*

My workbench is a combination of lap joints and dados.
The way I make my lap joints are to stack my dado to ¾” wide cut or 13/16” if your blade bolt can handle it. Some saws wont stack more than ¾” wide. 
Next thing is to set the height of your cut. This is done by measuring which will get you close, but no cigar. The thing to do in your case would be to have some scrap 2x4’s handy. Make sure that they are the same thickness as the ones for your workbench. Then go ahead and make cuts on one end of both scraps. The length of the cut is not important at this point. After the 2 ends are cut, flip one over and place one on top of the other and see how flush they are to each other. Then make adjustments in height of cut accordingly. 
Now that you have the height set, move your fence out so that the left side of the dado is exactly 3 ½” from the fence – see attached sketch.
Make your first cut using approx. half the dado width. This will give you a nice size removal without over burdening your saw or your dado blade. Continue doing this ½ dado width at a time. Eventually the end of the 2X4 will slide along the side of the fence which will act as a stop for your final cut. This is a fairly safe way of doing it because the dado blade is not trapped inside the wood – the right side is always open. 
Use a similar technique for the dado slot which will be trapped inside the wood. This is a little hairier because the blade is surrounded by wood but not to worry. You already have some experience at this point. Start by marking off the area that the dado cut will be made. *Without* the fence, using the miter gage, make your first cut approx. ¼ “ in from the right end of the cut. You will have to use the full width and full height required on this cut. Not hard to do, just have a good grip on the 2X4 and make a slow and steady cut as the saw will allow. 
After you have done all of your pieces this way, move your fence into position so as to make your next cut where the right side of the dado blade will make the cut on the right side line you drew. The fence will act as your stop. *IMPORTANT !!! *Before you actually make this cut, move the miter gage to the slot on the right side of the blade. You will have much better control of the 2x4 this way. Then go ahead and make this cut on all of your pieces. 
Next, move your fence again to act as a stop for the left side of your intended dado slot. Then proceed like in the lap joint portion in that you will chew away wood using ½ dado blade width at a time. This time the miter gage can be used in either right or left side of your blade depending on what you are most comfortable with. When making these cuts, the right half of the dado blade is not cutting wood. It is in ‘free’ space. 
This is actually easier to do than to explain.


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## woodnthings (Jan 24, 2009)

*Nice effort on the sketch tony*

To add to your technique for a mid length dado or half lap, all the board widths must be the same for the joints to be uniform and tight.
This is the method I use:
Determine the edge of the dado from the right side of the board and mark it.
Using the miter gauge , make your first pass, turn off the saw leaving the blade in the kerf.
Set the fence to the right end of the board using a stop block clamped to the left side of the fence, to avoid a pinch between the fence and blades.
Using a sample piece, mark the left side of the kerf for reference.
Nibble away material right up to the line, fit the crosspiece and continue to take very small, 1/64" cuts until it fits exactly. DON"T MOVE IT.
Move the fence and stop block to the left until it bumps the piece you have held in place.
Make all the remaining cuts using the stop block as a reference for the left edge of the lap/dado.


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## cabinetman (Jul 5, 2007)

Dadoes can be any width. Another method would be to leave a single blade as the cutting blade, make left and right cuts the depth of the recess desired. Then do a series of cuts across the area (like ¼" apart), and just use a chisel and chisel off the sections. The bottom may need to be flattened or not. 












 







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## Rekster (Feb 9, 2011)

Beautiful job with the sketch and the photos guys - that really helps a lot!! I'm still waiting for the dado insert for my saw to arrive (any day now) and then I'll be able to try some dado cuts out! I come from the IT world where people are often arrogant and condescending on forums, nice to see woodworking folks are much more friendly and helpful! :yes:


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## Rekster (Feb 9, 2011)

Hey guys, I finally got my insert and a 6" stacking Dado set! I have another question regarding setup if anyone can help. I'm extremely cautious regarding safety as this is all new for me. I'm trying to follow the instructions for set up which say that I need to 'make sure the teeth of the chippers are in the gullets of the outside blades. This isn't a problem for the first blade beside the arbor but the last blade always shifts when I lock down the locknut. I can't get it to stay in the gullet no matter how many times I try it always shifts as I tighten. I'd use the collar first after the outer blade but the arbor isn't long enough so the locknut has to go directly against the blade. Is this something i need to be concerned about? The outer blade always ends up in the gullet of the next chipper instead of the other way around. I'll attach photos if it helps explain.


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## Rekster (Feb 9, 2011)

Ok I apologize for the amount of questions here, one last question regarding Dado's I promise.

I went ahead and did some test cuts and I'm finding the surface is far from smooth and very uneven. Is this normal? Should I be sanding it lightly afterwards to smooth it out?


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## H. A. S. (Sep 23, 2010)

Chippers don't have to be EXACTly centered, and your surface finish roughness may be caused by feeding too fast?


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## Rekster (Feb 9, 2011)

Perhaps I was feeding too fast, I'll try again and see how it goes. I best wait until tomorrow now though it's getting late, I'm sure my neighbours are wishing I chose a different hobby. :laughing:


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## timmybgood (Jan 11, 2011)

is that cut in a 2x4? if so, it doesn't look too bad for that soft pine. when i dado hardwoods the bottoms are almost completely smooth, but when i use some softwoods i get small scoring similar to yours, it also looks like that when i dado a plywood.

it looks like you may have fed slightly too fast, just keep at it. practice makes perfect(sometimes!)


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## Rekster (Feb 9, 2011)

Yup it's in a spruce 2x4. I just did another practice run and went especially slow this time when passing through the blade - no change. I can accept the scoring but I'm finding the cuts are not evenly across though. It's almost as if the cutters aren't at the exact same depth as the saw blades (unless I'm mistaken). If this is normal then so be it but I just want to make sure things are as perfect as they can be. This is only for a workbench I'm building so no biggy but down the line I'm going to be working on furniture and I'm going to be especially picky then! Is this normal?


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## woodnthings (Jan 24, 2009)

*Take this the right way..*

I think your problem is that it's a "cheap" dado set and there is a variation in the cutters vs the blades. I donno? If you want a better finish, and I certainly would, see if you can upgrade the set to a better one. ....or return it entirely. They last for ever so there's no point in having one that you are not satisfied with.  bill
BTW I have a set of these in 8" but a 6" will do most everything you'll ever need.
http://www.holbren.com/oshlun/?&catid=892

If you end up choosing the Oshlun, I'd suggest getting it from Holbren.com (10% discount with "SCM10" code, free s/h over $75, great supplier)


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## Webster (Mar 6, 2009)

woodnthings said:


> I think your problem is that it's a "cheap" dado set


That is what I'm thinking also....that's if it 'is' a lower price set.
A higher end (more $$$) set will always give you a smoother finish.

Try a sample going with the grain or on a different kind of material and see what you get.

Rick


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## cabinetman (Jul 5, 2007)

It's unlikely that any stack dado set will give you an absolutely smooth bottom. You can still get an effective glue joint with a slightly rough surface. You could smooth out the cut with a block sander, like these shop made block sanders.

They are made with belts from a handheld belt sander. Those belts come in varied grits in 3"x18", 3"x21", 3"x24", and 4"x24". The block that is cut to fit tight can be any substrate in 5/8" or 3/4". Those are the common sizes. When the 3" are used, they are easier to hold than the 4".












 







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## Rekster (Feb 9, 2011)

Nice, that Oshlun set has full body chippers instead of the wing style chippers. I think I will see about returning the one I just got and get that one instead. In the meantime I'll make the cuts I need and sand to smooth them out. Thanks for all the info, I'm glad I found these forums I think I'll be reading through them often.


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