Dado cutting recommendations

[Anthony Scott]

Are there any real guidelines for when to use a router as opposed to the table saw for cutting dados? I have a relatively cheap set of dado blades for my table saw. It actually does OK for some cuts. Sometimes though there is significant chip out. This combined with the fact that it is a pain in the butt to set up makes me want to favor the router.
I haven't really used the router for this purpose yet. But I am looking to find an easier and cleaner method for dados.

Thanks

[Joe Scharle]

I haven't seen any creditable guidelines and I think it's more of a personal preference. I used dado stacks until I discovered spiral router bits and now I can't remember the last time I fiddled with chippers and shims. With the proper jig, I don't even measure the dado width. I just rout to match the other part.

[Lee Schierer]

Are there any real guidelines for when to use a router as opposed to the table saw for cutting dados? I have a relatively cheap set of dado blades for my table saw. It actually does OK for some cuts. Sometimes though there is significant chip out. This combined with the fact that it is a pain in the butt to set up makes me want to favor the router.
I haven't really used the router for this purpose yet. But I am looking to find an easier and cleaner method for dados.

Thanks

I've never seen any guidelines either. I generally do what seems easiest at the time. You can limit tear out on your TS by using a zero clearance insert for your dado blade. You can also run a wide strip of masking tape along the area where the dado will be cut and peeling off what's left after the cut is made by pulling it toward the cut. I use the regular masking tape not the blue or purple painters tapes as they don't stick very well.

With the router you are limited to the size f your cutters or making several passes. Most Dado sets can be adjusted to get exact widths, but you do have to make test cuts in scrap to get it right.

[Anthony Scott]

Thanks. I should have mentioned, I do have a ZCI but I get tear out on the ends of the cuts where the blades exit the cut.
I will try the masking tape.

[Bill Huber]

Woodline has one, its called the DadoMax.

I have never used it but it looks like it should would very well and is made well.

http://www.woodline.com/p-2373-dadomax.aspx

[Ellen Benkin]

Both methods work for through dados and it is a matter of preference. Stopped dados can best be safely done with the router. Build a jig to keep the router on line and you'll find it works well and you get a flat bottomed dado.

[Lee Schierer]

Thanks. I should have mentioned, I do have a ZCI but I get tear out on the ends of the cuts where the blades exit the cut.
I will try the masking tape.

To prevent tear out at the end, the tape will help, but a piece of scrap held tightly against the primary board will totally eliminate tear out with either a router or a TS. This piece can be attached with double sided tape or you can make a trim cut along the edge after teh dado is cut to size the board and cut off any tear out.


Stopped dados can best be safely done with the router. Build a jig to keep the router on line and you'll find it works well and you get a flat bottomed dado.

You can do stopped dados on a TS, but always raise the blade into the work, never ever lower the work onto or lift it off a moving blade. Let the saw stop before removing the piece.

[Brian Tymchak]

With the proper jig, I don't even measure the dado width. I just rout to match the other part.

Hi Joe,

I've been thinking about building a jig like for a little while. Would you be willing to post pictures of yours? Or can you refer me to plans or a publication with plans?

Thanks, Brian

[Chris Tsutsui]

The only guideline i'd follow is don't make your dado cut too deep and don't remove too much material the router and bit can't handle. heh

I only have basic dado bits and straight bits for 1/2" and 3/4" dados but i'm really wanting to try spiral bits. They are just a bit on the pricey side...

I'm assuming a spiral down cut bit is what to use for clean dados?

BTW, would anyone recommend a compression spiral dado bit or is that for CNC use only?

[Joe Scharle]

Hi Joe,

I've been thinking about building a jig like for a little while. Would you be willing to post pictures of yours? Or can you refer me to plans or a publication with plans?

Thanks, Brian

This a jig from Shopnotes # 76. They even have a little video on the site. Depending upon skill sets and tools available it can be made in as little as 4 hours, but a weekend would be usual. I've held jig workshops on this jig and the self-clamping foot seems to be the most problematic piece of the construction. From experience, plan on making it twice, as the measurements ARE critical. However, if built exactly as shown it's a piece of cake.

For dado's, I use a down-cut spiral as it gives a clean shoulder.
For slots, I use a compression bit as I leaves both sides clean. But it's not a cheap bit, so I only use it sparingly...as needed.
For mortising in the middle of wide panels, I use up-cut spirals as the tenon shoulders will the slight tear-out.
For rabbets, you'll have to determine the 'visible' edge and setup accordingly.
Incidently, I've built 3 (1/8 bit, 3/8 bit and 1/2 bit) and if you do build this jig, you may just want to build the 3/8 unit as it covers dado's from 3/8 to well over an inch. But the 1/2" jig is a great sliding dovetail guide.
BTW, a friend and I had a race on a pair of small shelf units a couple of years ago. I had mine in the clamps before he had his stack setup! Here's a pic.

http://www.ncwoodworker.net/pp/data/194/Dado_Jig.JPG

[Brian Tymchak]

This a jig from Shopnotes # 76. They even have a little video on the site......


Joe, this is great info! Thanks for sharing. I think I know what I'll be doing in the shop next weekend..

Brian

[Joe Scharle]

Brian, don't hesitate to PM if you have questions.
And make sure the threaded rod is straight. Roll some on the floor and pick a good 'un.

[Anthony Scott]

I found part of the problem. My dado set cuts nice along the grain. However, cross grain cuts are very poor. I guess you get what you pay for....

[Rod Sheridan]

I found part of the problem. My dado set cuts nice along the grain. However, cross grain cuts are very poor. I guess you get what you pay for....

Yes you do.

The issue with cross grain cuts is that a dado would need to look like a cross cut tooth, it would need some bevel on the outside teeth to score the wood fibres befor they are hogged out.

The more steep the bevel, the cleaner the cut, however now you have "bat ears" on each side of your dado.

The compromise is less bevel, more teeth, slower feed rate, or go to a dado that looks like a shaper cutter with scoring and hogging teeth. Those provide the cleanest cuts and flattest grooves.

regards, Rod.