Popular Woodworking 2001-08 № 123, страница 32
The secret to cleaning out the bottom of your mortise is to go back over your work once you've cut the shape of the entire mortise. I repeatedly raise and lower the head of the mortiser about /2" while moving the workpiece in small increments side-to-side. Use Your Mortiser Right One of the most common problems for mortiser users is that the mortised part and the tenoned part don't line up correctly. As a result, your project is out of square or you need to do a lot of sanding and planing to flush up your joints. Several things can cause this problem: your bit's not cutting in the center of the stock, your stock isn't all the same thickness or you're not being consistent in the way you are cutting your mortises. Fortunately, there are easy ways to prevent these problems. First, cut all your mortises with the face side against the fence. Second, make sure your bit is cutting in the center of the stock. Some people make the mistake of marking a centerline down the wood and lining that up with the tip of the auger bit. It's an easy mistake to make. The tip of the auger bit is supposed to be in the middle, but this is rarely the case. Instead, mark on your test piece of wood where the shoulder of the tenon will go. For example, if you're mortising into 3/4"-thick stock, you should use a 3/s" chisel bit. (As a rule of thumb, tenons should be one-half the thickness of the wood.) That means you should have a shoulder on either side of the mortise. Mark a line on either side of the wood 3/l6" in and line up the chisel bit between these marks. Make a test cut, then measure the resulting shoulder using a dial caliper. Adjust the fence until these two measurements are equal. Now you're in the center of your stock. Even when your mortise isn't supposed to go in the center, use the calipers to determine exactly where your mortise should go. Another common mistake that pros and amateurs make is to cut the first hole with their mortiser, and then to cut the next hole adjacent to the first. This a serious mistake. Here's why: When you cut an adjacent hole, the bit has one side that is against wood, and one side that's against nothing. The bit tends to bend toward the unsupported side. Do this enough times and your chisel will bend or break. Finally, after you've cut a few mortises, your machine will probably change its tune, from a thrumming to a noise that sounds like a kicked cat. Turn off the machine for a minute and get out some canning wax (you can buy it at your grocery store; sometimes it's called paraffin). Rub it against the auger bit through the slot in the chisel bit. The heat of the bit continued on page xx
sharpen the underside of the cutting lip, not the top cutting lip When you sharpen the cutting spur, try not to touch the cutting lip (left).When you sharpen the cutting lip, stroke the file upwards into the bit and try not to change the cutting angle. Conical sharpening stones can be used to touch up the inside edges of your chisel bit.This should create a burr on the outside of the bit that you can remove with a stroke or two on a fine-grit sharpening stone. |
