Making the Tools. Part I: The Tapered Reamer

Previously, I linked to an article by Jennie Alexander about making a tapered reamer using just a piece of dry hardwood and a compass saw blade. The tools described in that article are a bit rough, but apparently work just fine.

Other chairmakers have taken that basic concept and elevated it to a new level. Tim Manney probably makes the best tapered reamers available that include several refinements beyond the original design. First, the top of the reamer is gently tapered to a point to aid in sighting down the reamer in use; the upper portion is turned to a perfect cylinder to allow it to be used as a reference surface for accurate measurement; finally, the tool includes a set screw to allow for a fine adjustment of the blade projection. I chose to copy this more refined design for my own tapered reamer.

I started by picking up a $10 compass saw from Lowe’s. I also picked out a nice piece of osage-orange. It probably doesn’t make too much difference what kind of hardwood you use, as long as it’s straight-grained and not too soft. It doesn’t get much harder than osage, and it certainly is eye-catching!

The raw materials: a compass saw blade and osage-orange.

The first step is to grind the teeth off the saw blade. Yes, in Alexander’s article they leave the teeth on, but all of the top chairmakers these days seem to use un-toothed reamers, and I’m not interested in taking shortcuts. A wide, shop-made tool rest was a huge help in doing this accurately.

After grinding the teeth off completely, I measured the blade with a protractor and found that it tapered at 5° rather than the desired 6°. This may seem like a small detail, but I decided to go ahead and grind the blade down to the right angle.

With the blade ground properly, I used a cold chisel on my “anvil” (a short section of railroad track) to score it and snap it to length. The narrow end is about 3/8″ wide.

I filed the faces completely smooth with a long single-cut bastard file, then I did the same to the edges. You can see on the right edge a dimple from where the teeth were over-set in the factory. I would have preferred a vintage blade, which likely wouldn’t have had this problem, but the modern blade was quicker to find.

Once I finally had a properly shaped blade, it was time to start on the wooden parts. I didn’t completely remove the dimples from oversetting, because I figure the opposite side of the blade will do the work if I ever ream this deeply!

It may seem like overkill, but I created a Sketchup drawing of the wooden body using photos as a reference. Armed with this, I cut out a 1 3/8″ square blank, 16″ long, and headed for the lathe.

I started by turning a cylinder a bit proud of 1 1/4″. Next I used a parting tool to take the end of the reamer down to 3/8″. I marked out a length of 8 3/8″ from the end, then carefully turned the taper. As I closed in on the final sizing, I checked frequently by sighting down the blank with my blade. I use my toolrest as a guide to ensure that the taper is straight.

I was able to get it pretty straight with the skew chisel, but backlighting with a straightedge revealed that it was imperfect.

To get a perfectly straight edge, I use a clever trick that I can’t even remember where I picked up: I use a long, single-cut bastard file and hold it firmly against the wood as the lathe is spinning. I would have taken a picture of this, but unfortunately this is a two-handed technique! The tail of the file goes towards the tailstock, and you just keep it rubbing until you get a consistent polish from the file, then it’s done! You can see it this picture that I have a bit more work to do: there are still some chatter marks visible from the skew work.

After turning the taper and the cylinder to perfection, the last bit of turning is to do the rounded taper at the top of the reamer. Use the skew to cut a couple of notches that define the three parts. Having not used a skew chisel in 8 years, I was pleased to be able to achieve a nicely polished surface with it. The rest of the reamer is finished straight off the file, which also leaves a pleasant surface. Before you part off the ends, use the indexing head of your lathe to mark out the saw cuts on opposite sides of your reamer, and also mark out where the handle is going to go. (I forgot to do this, and it made the layout that much harder!)

If it seems like near-perfection is required in every step of this tool, that’s because it is! I used a Ryoba and slowly, carefully cut the slot for the blade. I followed the Ryoba with a panel saw to widen the kerf, and finished up the slot with some 180-grit sandpaper on a card scraper.

One step I didn’t photograph: chiseling out 1/4″ space for the chips to collect on the clockwise side of your blade. Next, bore a 5/8″ hole for the handle (best to bore from both sides and meet in the middle) and turn a snugly-fitting handle to match.

Finally, I added a setscrew to fine-tune the depth of the blade. I carved the pocket with a gouge and a chisel and drilled the hole, aiming for the center of the top of the blade. The screw is just a machine screw.

It took a bit of fiddling with the setscrew, but the finished reamer looks pretty slick and created a lovely taper in this scrap of sassafras.

Up next: using the tapered reamer to make your rounding plane.