Years ago Richard Starr and I were making a low work bench with a Windsor understructure. We needed a tapered reamer to make tapered mortises in the bench. We were in a hurry but didn't have a suitable reamer. And indeed, even if we had had time and money a tapered reamer wouldn't have been that easy to obtain. Antique reamers are expensive and hard to locate. Many commercially available reamers have tapers which we felt were too stumpy and didn't always have the bore we needed. Then Richard remembered that woodwind instrument makers use a saw steel blade slipped inside a slot in a wooden conical stock. At Richard's suggestion, I dug out an old compass saw blade that had the right taper and put a scraping edge on its backside while Richard turned a hardwood stock to the same taper. Between us, it took about 1-1/2 hours. I still use this tool. The price is right, the effort minimal, and you can make a reamer of whatever length, bore, and taper you need. First, locate some saw steel. Fortunately, most compass saw blades have a taper angle between 1:10 and 1:12. This is the taper range preferred by Windsor chairmakers Dave Sawyer and Curtis Buchanan. Don't worry if the blade is rusty, as long as the burred edge is not pitted. If your trip to the Flea Market fails, replacement blades for Stanley Compass Saws Nos. 15-212 and 15-443 have good tapers. If you can't find a compass saw blade you can use a larger saw blade. To cut it to size, use a hacksaw, or place the blade on a hardwood board, cold chisel 1/8" outside the perimeter of your layout, and snap off the waste. Wear goggles. Grind and file the blade to shape, taking care not to burn or distemper it. You can make a saw steel tapered reamer of any bore you desire. For the shaving horse bench, I suggest a blade 10" long, tapering from 1-1/4" to 9/16". Now comes the startling part. You can leave the saw teeth on one edge of the tapered blade! While the fastidious may be offended, I have found no effective difference between blades with one edge toothed and blades with raised burrs on both edges. Leaving existing teeth on the blade is quicker and aids in reaming. Make sure the profile of the teeth is straight. View the blade from the heel, and chamfer so that the blade will ream when rotated clockwise. Drawfile the burr edge (or edges) to a 45° chamfer. It is helpful to chamfer the outside board clamping the blade in the vise. While the 45° arris can be cleaned up with a stone, that is not really necessary. Remember that your blade will be scraping end grain—not a pretty task. Thus the presence of saw teeth and a less than exquisite scraping burr do not adversely affect the reamed mortise. Put a drop of oil on the arris and lay it over by progressively burnishing until the burnisher is 10° below horizontal (1). Test the burr.
Now turn the conical stock (2). Use dry straight-grained hardwood. I have used both hard maple and apple. White oak would work as well. Carefully replicate the taper of the saw steel. Leave at least a 2" diameter cylinder on the large end of the taper for a handle. Saw a kerf down the exact center of the cone. The kerf should stop so that when the blade is slipped in the kerf it will project slightly above the surface of the cone (3). NOTE: Though I have never done this, I am told, that instead of using a lathe, the conical stock can be formed by careful drawkniving and spoke shaving. First, shave the stock so that is has 4 equal tapered sides, then 8, 16, 32 and so forth until a relatively smooth conical surface is obtained. This method will be sufficent for making tapered mortises in a shaving horse bench.
The exact length of the kerf is not crucial. If the blade projects too far, lengthen the kerf. If the blade does not project enough, insert and glue a sliver of wood to the bottom of the kerf. Next surprise. There is no need to secure the blade in the kerf. It can be done, of course, but I never have and the reamer still works well. While in use the blade has no place to go. Chisel a 1/4" clearance relief in front of the saw kerf on both sides of the conical stock (4). This allows the reamoids to fall through the mortise.
Bore a 3/4" hole in the stock handle to accept a slightly tapered jam fitting handle. Tapered reamers are tricky to use. Take care to aim the reamer directly along the axis of the pilot hole and keep it there. A tapered reamer with a conical stock seats itself and when correctly started it is more likely than a traditional reamer to follow its path. My experience shows that the saw steel tapered reamer does as good a job as a traditional reamer (5).
Curtis Buchanan and Brian Boggs have been active in the Green Wood Furniture Project in Honduras (6). The Project aims to train Hondurans in low-tech woodworking, thus providing a sustainable forest-based economy. The principal objects made have been post and rung chairs made from green wood.
Curtis recently designed a shaved Windsor chair for the Project, but experienced difficulty with the close tolerances necessary when a cylindrical leg-to-seat tenon was used. Curtis made a saw steel tapered reamer as described above and reports that it travels well, works well, and the price is right (7). And with a tapered mortise-and-tenon, the harder you sit, the tighter the fit.
This web page is based on an article by John Alexander originally published in the magazine WOODWORK No. 52, August 1998.