Tips for cutting tongue and groove on Tablesaw

[Dave Dionne]

I am sure there is some folks here that have done this before, I need to cut a bunch of tongue and groove in white cedar for a couple of projects. Wife is out of work with no pay after surgery so no money to buy new router bits.

Any tips to help make these boards come out right the first time?

i have a freud dial a dado and will be using that on my Jet cabinet saw.

Thanks for any help or insight provided

Dave

[Brian W Evans]

I did this pretty recently with some ash and it came out very well. I would suggest cutting the grooves first by running each face against the fence (essentially cutting the groove twice), this guarantees that the groove is exactly centered. Next, measure the groove with dial calipers and cut the tongues to fit. As I said, this worked out fine for the most part, but I did use a rabbeting plane (could use a shoulder plane or file or sandpaper) to make a few spots fit - wood must've moved on me between milling and cutting the T&G.

I also cut a small chamfer along the edge of each board. IMO, this looks better and will also cover up small misalignments.

Good luck.

[Lee Schierer]

Adding to what Brian said. You'll need a sacrificial fence to cut the tounges. Make the tongues just a bit shorter than the depth of the grooves. Use feather boards to hold your stock tight to the fence for all cuts. Two passes on each side of each board should give you T&G lumber.

[glenn bradley]

I do what Brian does. You'll know after a test cut but crosscuts on ceder (and others) can leave a fuzzy edge even with a sharp cutter. I run a knife down the line to score the fibers. I'm not glutton for punishment, I don't do this as a rule; I only do this if the wood is uncooperative.

[Dave Dionne]

Thanks gentlemen

I knew somebody would step up with the info I needed

Brian where abouts are you in Vermont?

Thanks Again

Dave

[Rod Sheridan]

Hi Dave, you've received some good advice above.

One thing that's often done on commercial T&G is to cut the bottom cheek of the groove a few thou narrower than the top to maintain zero gap at the the top surface.

Regards, Rod.

[Jim Becker]

Cut the groove first. Then, using scrap, make your blade height adjustments to zero in on the tongue fit.

[Peter Quinn]

You can minimize that chip out on the tongues with a ZCI in the throat and a fresh backer on the miter or sled. A slightly scarier option is to make a very shallow climbed kerf cut, just like using a scoring blade, then go back and dado the tongues as normal.

[Brian W Evans]

Dave,

I'm in Williamstown, near Barre/Montpelier.

[Bob Feeser]

I think all of the suggestions here are great ones. When I think of doing this task, I don't even think of dadoe blades. I use a Forrest WWII, which is exactly 1/8th of an inch thick is an alternating bevel, which has the scoring tips to help prevent tear out.
My thinking is that with a 3/4" board, I would be looking to take 1/4" inch out of the center to make the groove first. Using a piece of scrap, long enough to be safe on a table saw, I would be moving the fence to create a cut 1/4" off of the fence. You could err on the side of a 1/32nd more. That would create a slightly narrower groove by only 1/16th overall, but eliminate the possibility of leaving a sliver in the center. Make the usual double pass to guarantee that your groove is exactly centered. It could be 1/4" to 3/16ths wide.
For the tongue, use a regular blade also. Measure your tongue opening to try and get the proper fit, but use a scrap piece to make trial cuts until you get a snug fit. Run your piece on both sides. With a single blade you will be cutting without be very close to the outside of the board, which will enable you to use featherboards on the outside edge, giving you a guaranteed even cut. After running all of the boards to the proper depth, which allows for a small amount of breathing room at the bottom of the tongue. (You don't want to be in a position of having the tongue bottom out anywhere, leaving a wider gap along the seam.) You are making passes on both sides of course to create the tongue. Then you are going to readjust the blade to the proper height, and set your fence to the proper width, laying your board flat on the saw top, to make the final pass to finish your tongue pass. Personally I like to set the depth of the tongue a hair shy, and make up the difference to the full depth of the cut with the final pass using the board flat on the table.
As was already mentioned, chamfering all seam edges that show will give you a better look. Without it, you are winding up with what looks like one piece of wood joined in some areas, and sharp edge gaps in others, where the wood moved. Chamfering is important. You can do it with a router in a table which is my preferred method, or you could even do it with a sanding block, or a small hand plane if you have the knack with it. The router bit, with a final touch with sandpaper to touch up.
I've done a lot of tongue and grooving for cedar walls, and even an addition that has stood up to the elements. I actually used Home Depot 5/4 decking cedar, planed to 7/8ths. It all works the same at that size as well. I actually built this addition on my own home, dug and poured the footers down 42", built the block wall, capped it with Mohave stone, framed and finished the walls, roof etc. Mounted the windows, hung the door, whatever needed to be done. That is Sikkens finishes on it, which is the only thing that holds up to the weather. It looks that good today 5 years later.





This next shot is another one of the cedar addition that I built. The piece of 1/4" ply over the door was temporary, a piece of glass fills that spot now.




This is the basement fitness room that I have been working on. I created a wall to seal it off from the shop.

[Walt Caza]

Hi Dave,
All good answers so far, but I would certainly recommend using
a featherboard to keep the stock tight to the fence with no
wandering at all. It is like a helper standing there quietly just pushing
the stock toward the fence! I used to use a homemade one, which worked fine.
Then I used a bench dog Feather-Loc, which was nicer but still used a miter guage slot.
Now I use the rare earth magnet one from LV, which
works great, without the limits of reach from the slot.
Just another suggestion to avoid trouble...
be well,
Walt

[J. Z. Guest]

Nice work Bob!

I'd like to reinforce what Jim said: When cutting the tongues with a dado, the depth of cut is absolutely critical, because any error is multiplied by two. After you cut the grooves you're going to use, do a bunch of practice cuts with scrap to get the tongue exactly right.

If you have the time, the router table with a regular old straight bit will make cleaner cuts (which will form better glue joints) than the dado set. It will just take more passes and more time.