Uneven Tenon Shoulders

[Leo Vogel]

Since Sarge answer another question so well today, I thought I would ask another.

I do all of my tenons on the table saw. In the past, I have used a dado blade (changing to a box joint blade). I cut all four sides of the tenon on the saw, with the miter gauge and the fence as a stop block. Sometimes, two of the shoulders are a bit taller than the other two. Probably no more than 1/16, but noticeable to me. Has anyone else experienced this? What can I do to make all the shoulders of the tenon the same height, flat, and even? Thanks

[Wes Grass]

Is the end of the piece square to begin with? If not, then the high spot riding on the fence may disappear after the first cut or 3 making the last cut 'deeper' than the others. Making the end cut on all 4 before going to the shoulders should fix that.

[Peter Quinn]

Either the wood is not square, the miter gauge is not square, or the fence is not square, or some combination of the above. The error will be doubled as it is added to one shoulder and subtracted from the other if the wood is not square. It should not effect the edges of the tenon or the corresponding shoulder so much because the width acting as your reference is not as great.

If the miter gauge or fence are not square the shoulders on the width should be different than the shoulders on the width of the board, but faces on opposite sides of the board should be similar.

Should be easy to verify which is the problem using a good square and some carefully tracked test pieces.

[Tony Bilello]

Maybe your wood is not perfectly flat?

Or.....If you have a Delta Contractors Saw, they are notorious for not being able to hold a 'height' adjustment.

I think the most probable cause is as the others have stated about your settings and adjustments. That is where I would start.

[Paul Ryan]

Leo,

I just cut 52 tendons on my saw with the same method you are talking about and I had the same problem on about the 1st half. The problem was my mitre guage had some slop when in the miter slot. That little bit of slop will cause those problems. I fixed the problem buy making sure I held the miter guage tight against one side of the slot when pushing it through. You either have that problem or problems with your fence. Joint that and it should sove your problem, if it is the fence. Other wise it is your stock that is the problem.

I have about another 120 to do in a few weeks. I will invest in a tendoning jig before then.

[Rick Fisher]

If you have a router table, try using that to cut the tennons. I find it way more accurate.
If its chippy wood, like fir, I cut the flats with a normal tablesaw blade and clean the rest off with a straight cutter on a router table.

Its a bit slower but I find it super accurate.

[John Thompson]

I agree with all that you must have a square end on the stock. Then you have to be sure before you final clamp it to the fence that the stock is flat on the table. Then I am going to agree with Paul that it very well could be caused by slop in the miter gauge.

I used to have that happen even though I though-fully always tried to keep the gauge pressured against the side of miter groove toward the blade. How I solved it was to purchase an Incra V 27 miter guage which can be adjusted so there is no slop what-so-ever. It changed my whole attitude about miter guages.

I was so impressed... I purchased a second one to add a long fence too with a short on the original.

Good luck...

Sarge..

[Leo Vogel]

Rick - what bit are you using in your router for the tenons?

[Rick Fisher]

I just use a plain old straight cutter.

My router table has a t-slot, so I use a miter guage. I set the bit at the height that will remove the right amount of material.

I doubt its kosher.. set the fence the depth of the tennon.

To avoid chipping, I will climb cut a touch before clearing away the material.
I find the router bit leaves a perfectly flat, smooth tennon.

I know there is some safety thing about routers, miter guages and fences, but when removing such a small amount of material, its more than safe..

[Mats Bengtsson]

I just use a plain old straight cutter.

My router table has a t-slot, so I use a miter guage. I set the bit at the height that will remove the right amount of material.

I doubt its kosher.. set the fence the depth of the tennon.

To avoid chipping, I will climb cut a touch before clearing away the material.
I find the router bit leaves a perfectly flat, smooth tennon.

I know there is some safety thing about routers, miter guages and fences, but when removing such a small amount of material, its more than safe..

I use same technique. As long as the bit has diameter enough to remove all the material needed for the tennon in one go, then it works fine.

--- Mats ---

[Joe Scharle]

If you have a router table, try using that to cut the tennons. I find it way more accurate.
If its chippy wood, like fir, I cut the flats with a normal tablesaw blade and clean the rest off with a straight cutter on a router table.

Its a bit slower but I find it super accurate.

I made this jig after I discovered what great tenons a router bit could make. One thing I do on fuzzy woods is to climb cut lightly, then full cut the shoulder. The long shoulders are cut in front of the fence as shown and the short shoulders are cut behind the fence. Short shoulders that need a haunch are simply stepped onto a pad of 1/4" hardboard. For more info, American Woodworker printed this jig a few months ago.

http://www.ncwoodworker.net/pp/data/194/thumbs/RT_Tenon_Jig_1_.jpg (http://www.ncwoodworker.net/pp/showphoto.php?photo=11393)

[Leo Vogel]

Well, I double checked everything again. Miter slot alignment, miter gauge, fence, etc. All were perfect. I then looked at the table top blade insert. Could the insert be a hair high somewhere? I dropped it well below the table top, and all my problems went away. Perfect tenons with all the shoulders nice and flat. This has been driving me nuts for months. I am so happy to have the problem solved. If there is a way to screw something up, I can find the way. Thanks for all the help.

[John Thompson]

Glad you got it resolved as it turned out to be a simple fix.. It's also difficult to set blade height with an insert higher or lower than the table surface. Sometimes simple can turn into complex with the most minute of details out of kilter.

Sarge..