Mortise machine setup?

[Scoly2803]

Bought a Jet mortise machine about 6 months ago but have never used it. Now is the time.
New project is going to require several mortices and I can tell the machine setup is of utmost importance. Mortice will be 3/8wx1.5Lx1d and the stock will be 3/4 wide. My first attempt left one long side of the mortise thinner than the other. Obviously off center so I began to fiddle. One way then the other. Got it very close but never perfect.
Is there a shortcut to get it exact? What methods work for you?
Thanks
Steve

[smorris]

This works for me, YMMV.

I marked the mortice and the centerline of the mortice. I left the drill sticking out of the chisel slightly and adjusted the fence until the point was on the centerline, that got me close. Then recessed the bit and checked that the chisel was on the setup lines for the mortise, adjust as necessary but it shouldn't be much.

[doncook7]

To get a perfectly centered mortice, set the fence so the mortice chisel is just slightly past the center line of your mortice width. (doesn't matter which side) Make your mortice cuts. Now flip wood end to end and mortice the same mortice again. It will be centered every time.

Doing this does make the mortice a bit larger than the size of the chisel used, so tenons have to be matched to mortice, which is easily done with a few test cuts on scrap wood.

[LCHIEN]

first, get the chisel faces square and parallel to the fence. Run the fence up to the chisel and adjust the chisel rotation until the side against the fence is flush. THen lock the chisel retaingin screw.

Now you have a 3/8" chisel... I don't see how one end of the mortise can be dkinnier than the other??? the 3/8" sets that.

Anyway, you can set the offset like SMORRIS said, or I do mine this way: since you have 3/4" material and a 3/8" mortise, to center it you have 3/8" left to divide between the two sides - 3/16" on each side If your material is exactly 3/4" then use a 3/16" setup bar and place that between the fence and the chisel and close the fence until there's no slop left and you can just slide the setup bar out.

I always layout the mortise in pencil on at least the first item I do, you can then check that the chisel falls in the right places as you test lower the chisel w/o cutting. Thereafter just mark the ends on successive pieces.

The chiesel has a hole in the side for the cuttings to exit. It's best if you place this hole and advance your direction so that the cuttings fall into the mortise where its already cut so the cuttings don't get jammed. Of course the first cut will have to be made with more frequent rasings of the bit to clear the cuttings.
I will also cut both ends and then cut the middle. Probably beause I'm more careful on the first part than the last, when you can just sort of slip into autopilot while doing the main part of the mortise in a straight line.

[Scoly2803]

Ya'll make it so simple. Knew there was an easier way.
Thanks!!!
Lchien
Meant the mortice walls. One side thicker than the other. Leave it to me to make it confusing. Sorry.
Had planned on 3/8 wide mortice but if I go with flipping the board as doncook describes should I go with 1/4 figuring it will be a bit wider with this method?
I'll be doing some experimenting this pm.
Thanks again.
Steve

[LCHIEN]

Meant the mortice walls. One side thicker than the other. Leave it to me to make it confusing. Sorry.
...
Steve

Oh, you mean, not centered.

[Scoly2803]

Yeah! Not centered.
Got home last night and had to many little things that had to be done. Didn't get to try anything but the hope is I'll get off a bit early today and have the time.
Really excited about getting started.
Thanks again.
Steve

[scmhogg]

Steve,

I've found very few sharp tools that are good to go, right out of the box. I flatten the outsides of the chisel on glass plate and use the conical diamond tool from Rockler to complete the sharpening. It makes a BIG difference.

Steve