Help! Problem with M&T fit

[Roy Bennett]

:confused: I am building a small cabinet for my granddaughter and am having trouble with the frame and panel doors. When the M&T joints are assembled, the rails stand proud of the stiles by about 1/32" or so.

The mortices are chopped on a mortise machine (with X-Y vise) and I have taken the precaution of running the stiles through both ways in hopes the mortise will be centered.

The tenons are cut on the TS with the dado blade height slowly increased to inch in to proper fit in the mortises. Since the tenons cheeks are both cut at the same blade height, they also should be centered. Final trim with a shoulder plane is minimal, and I try to work each cheek equally.

With all this, I'm still getting the slight mismatch. What am I doing wrong??

[Dan Racette]

do you have an accurate machinist's square to check everything over with? you'll be surprised how many squares are not!

Otherwise Maybe you might want to see if the dado blade is flat?

[Jamie Buxton]

Your procedure should work, but it doesn't. I'd try to debug it a little. For instance, a micrometer would tell you whether the mortise walls are exactly the same thickness. That, in turn, would tell you which machining operation is going wrong. I use a $25 no-name micrometer; you can buy them from any woodworking catalog.

[Mike Cutler]

Roy. I understand the mortise operation. I use the same method.

When you say "1/32 proud" does that mean that you have a gap between the rail and the stile? or that the rail is 1/32" difference from the stile if tthe panel is layed flat on a workbench?

Are your tenons being cut with a tenon jig?, and are you reversing the piece in the tenon jig.

One more possible issue. If you are using a tenon jig, and it is a copy of the Delta. You may notice that the jig has a little "freeplay" in the miter slot. According to Delta this is supposed to allow you to push in towards the blade on the cutting stroke, and then push it away from the blade when you are bringing the material back. Personally, I think it was poor machining and I place a piece of paper on the table and force the tenon jig down into the slot with the paper.

Just some random thoughts, while I'm at work eating lunch.;)

[Lee Schierer]

Most likely when you turn your parts around and try to recut the mortice, the chisel is simply deflecting and following the original hole. Morticing chisels do not do well making partial holes. My suggestion would be to get your original set up for morticing as close to center ans possible, cut your mortices and then with a piece of scrap determine the height settings for cutting the tenons. Be sure and mark the faces so you keep the pieces oriented correctly as you make each cut.

If you aren't using a tenon cutting jig and are using a dado blade, your dado blade will also leave high spots. I like to to do the should er cuts on my TS with th e pieces flat on the table, then use my tenon cutting jig to remove the resot of the material. You get a much flatter tenon that way with less work. A tenon jig will also let you dial in the fit a lot easier. You can shave off a few thounsandths from one side of the tenon if you need to.

[Roy Bennett]

Thanks for the responses.

Lee Shierer - I tried my best to locate the stock to center the mortise. Your suggestion to cut each tenon cheek depth independently to match the mortise holds promise, just a h### of lot more work.

Mike Cutler - The offset is on the faces of the rail and stiles, that is - laying on the bench. The shoulders fit fine. I cut the tenons on the TS using a dado blade only. Looks like I need to invest in a tenon jig to get increased accuracy.

Does anyone have a tenon jig brand they'd recommend or will any of the Asian copies work?

[Mike Cutler]

Roy.

Most of the Tenon jigs on the market are clones of the Delta that I have, and they are probably just as good. However, every now and then, on that internet auction site, you will see for auction a Delta Tenon jig that is "old school". It's big, it's heavy(weighs about 36lbs, and expensive. It also is not made any longer. If you can score one of these, get it and resell the newer type.

A Tenon jig can also be made. Almost all of the books on Jigs and fixtures, or "Tablesaw Tricks" have some sort of variation of a homemade tenon jig. A table mounted router is also just as good at cutting tenons with a jig as the tablesaw. That may be an option for you also.

Tuning the tenon with a jig is simple. I always have a sheet of paper in between the face of the jig, and the stock. I can either add or subtract another layer of paper to fine tune the tenon thickness if required.

Good luck.