making a better tenon.... - Woodworking Talk

Dvoigt · 04-17-2009, 11:49 AM

So I've pretty much completed my first coffee table, just have to install the hinges for the lid and do the finish. I didn't use an fasteners and went with my first go at mortise and tenon joinery. It was harder then it looks on TV...

I did the mortises with my plunge router and edge guide... and sometimes something would move, so I would end up with a crooked mortise. I could never see anything move, it was weird. But that wasn't a big deal since I cut the mortise in 2 passes and never drifted too far before I caught it.

I did the tenons on my table saw with my dado blade and I was not happy with how they turned out. After spending about an hour dialing in the height of the blade so that I would end up with the correct thickness on the tenon, I would run the board through with my miter gauge and then flip the piece and run it though again. The length of the tenon on each side was almost never the same, off by a 1/16 or so of an inch. See the exaggerated sketch for a better explanation. So therefore I didn't end up with a nice flush fit joint. It was "ok" but not at all what I had hoped for. Oh and then there was cutting the little section off at the top and bottom of the tenon, which I did by a hand saw, and even less accurate by hand!

How could I have done this better? To avoid measuring each cut I clamped a short block to my fence, set my fence to the correct dimension with the block. Placed my work piece against the block and then ran it though with my miter gauge, the fence wasn't involved in the cut just there for measure purposes, the work piece was only in contact with the block on the fence for a few inches. The only thing that I can think of is that when I would contact the dado blade there felt like there was a tendency to pull the piece into the blade. Maybe there was a few times that I wasn't holding the piece tight enough to the gauge in it moved in towards the blade? Other then that I'm at a loss.

I see these joints and think what a waste of wood, my wife see it and says "Awesome you made a table!"

Thanks,
Derek

Rob · 04-17-2009, 12:13 PM

I'll have to look through my magazines, but I'm pretty sure the plans were in the latest edition of Shop Notes.
Though I'm pretty fair at cutting M&T's, this simple (probably 1/2 hour construction time) jig makes cutting tenons a whole lot easier and I'll make the jig next time I cut M&T's.
It's a small sled that uses the TS and dado blades. There is a stop block to the right of the stock. A small nail or brad is set into the fence at a height where it will meet the end of the tenon when both the cheek and shoulder cuts are made. This allows for the same distance from the blade regardless of what cut you are making. You don't have to worry about the fence or other stop block being exactly 90* to the table.

Tom5151 · 04-17-2009, 05:24 PM

I cut M&T using your method and have had fairly decent results so far. Was the end of your workpeice a perfect 90? I found that if the end of the stock i am cutting the tenon on was not exactly 90 degrees, I would have a very similar result to what you pictured above. The slightest fraction of a degree that my stock was from a perfect 90 caused the shoulders to be off and thus resulted in a gap when the apron or stretcher was attached to the table leg.

Webster · 04-17-2009, 09:01 PM

A few things that come to my mind....
as Tom mentions, the importance 90 degrees
some self adhesive backed sandpaper on the miter gauge
do the cheek cut with a single blade and clear out the rest with a dado
multiple cuts with a single blade and clean it up with a chisel
Rick

Tony B · 04-17-2009, 09:54 PM

Quote:

Originally Posted by Dvoigt

............................
I did the tenons on my table saw with my dado blade and I was not happy with how they turned out. After spending about an hour dialing in the height of the blade This should only take a few tries and a few minutes. Just inch your way up on your dado and keep testing for fit. Measuring and calculating will really screw you up. ...... Oh and then there was cutting the little section off at the top and bottom of the tenon, which I did by a hand saw, and even less accurate by hand! This too should have been done with the Dado blade. It would require a different height setting, still using the 'inch your way up' technique.

How could I have done this better? To avoid measuring each cut I clamped a short block to my fence, set my fence to the correct dimension with the block. Placed my work piece against the block and then ran it though with my miter gauge, the fence wasn't involved in the cut just there for measure purposes, the work piece was only in contact with the block on the fence for a few inches. The only thing that I can think of is that when I would contact the dado blade there felt like there was a tendency to pull the piece into the blade. Maybe there was a few times that I wasn't holding the piece tight enough to the gauge in it moved in towards the blade? Other then that I'm at a loss. The block is your problem. It is safe to use the fence if you start chewing up the tenon with the dado starting at the end of the proposed tenon and slowly making a few cuts working your way to the fence at which point you should be at the correct distance for the tenon. The only time it would be dangerous would be if your start the dado cut inside the wood as opposed to at the end. The way you will end up is with the end of the tenon flat against the miter gage and the fence at the same time. This will let you know your are exactly at 90 degrees.

I see these joints and think what a waste of wood, my wife see it and says "Awesome you made a table!"

Thanks,
Derek

Whenever you are making anything that requires joinery, ALWAYS cut a few extra pieces (After planing) for 'test' cuts and height adjustments. When I had students and apprentices I always stressed the point of not being cheap with your wood when you buy it. When you calculate and buy 'closely' you stand a good chance of having to make another trip to the hardwood lumber yard for more wood and more money. In the long run it will cost you more.

I hope this helped

gregL · 04-17-2009, 11:05 PM

I have been using this Incra miter gague to make table saw tenons and it does an very accurate job because of the stop that keeps your workpiece from moving. I am currently trying to come up with a design to add to my other miter gague that came with the table saw that would use a hold down clamp in addition to a flip stop. The key to a successful tenon is no movement in any direction.

johnv51 · 04-18-2009, 08:50 PM

Tony is right. Use the fence to set the tenon length, not a spacer between the piece and the fence.

Dvoigt · 04-19-2009, 12:43 AM

Thanks everyone for the advice. My pieces were too long to just use a miter gauge and a block, so that is why I used the fence. I always thought that it was a no-no to use the miter gauge at the same time as the fence. That is used the block.

I'll have to keep all this in mind for the next time....

Tony B · 04-19-2009, 01:23 AM

Quote:

Originally Posted by Dvoigt

........ I always thought that it was a no-no to use the miter gauge at the same time as the fence.....
I'll have to keep all this in mind for the next time....

That is true if you had the the end piece dropping off where it could be trapped between the fence and the blade. When you are chewing the end off of a tenon with a dado and working toward the fence there is only sawdust falling off and the wood is never trapped. When making tenons with a 3/4" dado, I use about 2/3 of the blade per pass (about 1/2" per pass), so if my tenon will be 1 1/2" long, it will take me 3 passes until the end touches the fence. Sometimes I will take off less depending on how the saw is reacting to the wood, but never more. Just cut slow and steady, the saw will tell you if you are taking off too much.