Popular Woodworking 2004-04 № 140, страница 49

To locate the mortise, put the tenon across the edge of the stile where you want your mortise to go. Use a sharp pencil to mark the tenon's location on the edge. Bingo.You've just laid out the mortise's location.

tenon. If something doesn't fit when you know it's supposed to, try making a second pass over the dado stack and push down a little harder during the cut.

Using this setup, mill all the face cheeks on all your tenoned pieces. When that's complete, raise the arbor to ³/s" and use the same routine to cut the edge shoulders on all your boards. Your tenons are now complete.

Use Your Tenons Like a Ruler

One of the major pains in laying out the mortise is figuring out exactly where you should bore your hole. You end up adding weirdo measurements and subtracting the measurements of edge shoulders. If you lay out mortise locations using math only, you will make a mistake someday.

Troy Sexton, one of our contributing editors, showed me this trick one day and I've never done it any other way since. Say you are joining a door rail to a stile -quite a common operation. Simply lay the tenoned rail onto the edge of the stile and line up the edges of both pieces so they're flush. Take a sharp pencil and - using

the tenon like a ruler - mark where the tenon begins and ends on the stile. That's it; you've just marked everything you need to know to make your mortise.

If you are placing a rail in the middle of a stile, there is one more step. You'll need to mark on the stile where the edges of the rail should go. Then line up the edge of the rail with that mark and fire away. There's still no addition or subtraction. With all your mortises laid out, you can then get your hollow-chisel mortiser going.

A Finicky Machine

I've used a lot of hollow-chisel mortisers and find them fussy to adjust. Along with our review of the machines, we published a complete tutorial on the topic in our August 2001 issue. In a nutshell, here are some of the important adjustments not covered by some manuals:

• Make sure the chisel is at a perfect 90° angle to the machine's table. I've set up a dozen of these machines and only one has ever been perfect. The solution is to use masking tape to shim between the table and the machine's base.

• Set the proper clearance between the auger bit and the hollow chisel that surrounds it. Some people use the thickness of a dime to set the distance between the tooling. Some people measure. Either way is fine. If the clearance is too little, the machine will jam and the tooling can burn. Too much distance makes a sloppy-bottomed mortise.

• Square the chisel to the fence. The square holes made by the chisel should line up perfectly. If the edges aren't perfectly straight, your chisel isn't square to the fence. Rotate the chisel in its bushing and make sample cuts until everything is perfect.

• Center the chisel so it's cutting in the middle of your work-piece. There might be a clever trick to do this, but I've found that the most reliable method is to make a test cut and measure the thickness of the mortise's two walls with a dial caliper. When they're the same, your mortise is centered.

Simplify Your Mortising

As you make your mortises, here are a few tips for making things a whole lot easier.

• I like to cut a little wide of the pencil lines that define my mortise. Not much; just ¹/32" or so. This extra wiggle room allows you to square up your assembly easier. It doesn't weaken the joint much - most of its strength is in the tenon's face cheeks.

• As you bore your mortises, don't make your holes simply line up one after the other. Make a hole, skip a distance and then make another hole (see the photo below). Then come back and clean up the waste between the two holes. This will greatly reduce the chance of your chisel bending or breaking.

• Keep your chisel and auger lubricated as they heat up. Listen to the sounds your machine makes. As the auger heats up, it can start to rub the inside of the chisel wall and start to screech. Some dry lubricant or a little canning wax squirted or rubbed on the tooling will keep things working during long mortising sessions.

• Finally, make all your mortises with the outside face of the work against the fence. This ensures your parts will line up perfectly during assembly.

By cutting over your line slightly, you give yourself just enough forgiveness at assembly time.A little wiggle can mean a lot when you are trying to close up the gaps as you clamp up your work.

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