Thursday, February 26, 2009
The Tapered Reamer
This post coincides with an article the I've written for the Spring 09 issue of American Woodturner Magazine about tapered mortise and tenons.
Making a tapered reamer to suit your needs is a relatively simple and rewarding project. This reamer works with a scraping action.
The two edges of the blade, which is easily made from an old compass saw, are ground to the desired angle, then the edges are ground at 45 degrees and honed. Next a small burr is turned opposite the grind to create the cutting edge. Take care not to "roll" the burr too far, you're really just trying to point it in the right direction.
Once the blade is made, turn a long cylinder with a diameter the same size as the largest width of the blade. It’s important to use a dry hardwood for a stable and long wearing tool.
Then turn a taper to match the blade. Once this is done, it's time to cut a kerf down the middle of the taper for the blade.
I mark the kerf by clamping the body of the reamer to my bench top, check to make sure that the centers at both ends are the same height off the table. Then cutting a block of wood that raises a pencil to the height of the center of the turning. Finally, I run the pencil and block down both sides of the taper to mark the line. Cutting the kerf is one of the trickier parts, so take your time!
If you find that the kerf is not wide enough to let the blade slide in easily, use sandpaper around a thinner card scraper to even and widen it. Then carve out a couple of “gutters” for the shavings to fill and drill a 5/8ths inch hole for the handle.
Its important that the blade extend a hair beyond the wooden body of the reamer. It need not be too tight in the slot, so that it can self center in the body while reaming. If the blade is not protruding enough, simply slip a shaving in the bottom of the slot to expose more of the cutter.
This tool cuts relatively slowly, and requires that you remove the blade from the body often to clear jammed shavings, but I find that the control that it offers during reaming and the ease of making it are just right for my needs. More instructions on making this reamer can also be found on John Alexander’s www.greenwoodworking.com, where I first encountered the design. Another option is to purchase a tapered reamer from Elia Bizzarri at handtoolwoodworking.com. He can also sell you a matching tenon cutter. It might just be the last great woodworking tool bargain!