Mortise and Tenon joint

[Dave Lehnert]

I am not new to a Mortise and Tenon joint.

I use a bench top mortise machine (Grizzly) I cut the mortise, flip the stock around ,and cut again just to be sure the mortise is centered.

I then cut the tenon using the Rockler jig.

First question I have is. What blade do you find works best to cut the tenon,Rip blade? Not thinking I used a combo blade and thought the shop was on fire ( Soft maple wood)

My main problem is I make test cuts in stock from the same stick of wood. I get everything set up so the joint fit is perfect. But after I run all my stock I get a mix bag. Some will fit perfect, some too tight, some too lose.
It gets time consuming to get every joint to fit the way it should. I make sure sawdust is not built up on my jigs to throw off measurements.

Any tips or tricks you use to get a perfect fit every time? Use differant tools or another technique? Or is that just the nature of the beast having to fit ever tenon?

[Garrett Ellis]

I don't have a ton of M&T experience but what little I have done, I never got 2 that initially fit the same. A shoulder plane made it easy and relatively quick to fix too tight a fit. Too loose… well, not sure on that. I've used epoxy instead of wood glue to hopefully expand and fill in the space.

[Frank Drew]

Dave,

I prefer to cut tenons with the work flat on the table saw, with dado blades. With an older saw I guided the work with the miter gauge with an extended wood fence; my most recent saw came with a sliding table (:D), and the accuracy of my cuts increased enough that I no longer worried about how much I'd paid for the saw (:eek:).

[harry strasil]

1. make sure all your stock is the same thickness to start with.

2. use a piece of scrap to determine if your mortise is in the center of the piece..

3. use small pieces of blue painters masking tape or a penciled or chalked X to mark which side is the back or inside of your pieces. and make sure it is showing when you cut the mortices, that way all the mortices will be the same distance from the front or show side.

4. When cutting the tenons, do one side first, then using a go/no go gauge, ( a piece of scrap with the width of the mortice cut in it + the thickness of one side, you will be able to tell if the tenon is going to fit tight in the mortice before cutting the other side of the tenon with the same setting.

In Timber framing work, all the tenons and mortices are marked from the outside of the timbers so that the outside will be true for the application of the siding, the inside is of no importance as it will have nothing put on it. And timbers are usually not exactly the same size. But that is all handwork too.

[Rod Sheridan]

One of your errors was flipping the piece around and re-cutting the mortises to center them.

If you do that, and your stock is slightly different in thickness, then your mortise changes size.

It is also a poor practise due to chisel deflection from not being engaged in the wood on opposite sides.

So,

- cut your mortises once only using a chisel of the correct size.

- make sure that your stock is the same size (machined accurately)

- cut the tenons on the table saw using a tenon jig

I don't use the table saw to cut tenons any more, I use the shaper with 2 cutters and a spacer in between, it makes exactly the same size tenon every time, regardless of stock thickness errors. (And I can cut the tenons with the guards in place, something most table saws can't do).

regards, Rod.

P.S. When I cut the cheeks on the table saw using a tenon jig, I used a rip blade since it's a ripping operation.

[Lee Schierer]

I use a tenon jig to cut the tenons I make. I also noted that a cross cut blade tends to create a lot of smoke when cutting tenons, so I switched to my 24 tooth rip blade. The result was faster cuts, no decrease in surface quality and no smoke at all. When I came to that conclusion, I noted that the cheek cut is a rip cut and not a cross cut. The longer shavings that come off on each tooth have some place to go on a rip blade, almost no where to go on a crosscut or combo blade.

I agree with Rod's comments regarding flipping the mortise with a dedicated mortise cutter. Even Norm doesn't do that though he often flips pieces with tongues and grooves to get them perfectly centered.