This past fall and winter Pete Galbert and I collaborated in designing a tapered reamer for making round tapered mortise and tenon joints. It can be used for other things, but my primary use for this tool is in creating the joints used in windsor chairmaking. Since we made the tool available my workshop has switched over from primarily a chair shop to primarily a reamer shop. I'm very pleased with the reamers, and I continue to minutely refine both the reamers and the processes I use to make them.
I recently finished a batch of eight reamers and thought that I would share the techniques I use to sharpen the blades before I send the tools out. The short description is that I use an angled block clamped to a granite plate with 600 grit wet/dry sandpaper adhered to it. It is important to maintain the 6 degree flat taper along the length of the blade so that it continues to perform well in the reamer body. The combination of the angled block and the sandpaper on granite makes maintaining these blades fast and simple.
The blades are ground to a 70 degree bevel, so I cut my angled block at 75 degrees. This produces a five degree microbevel which takes me straight to the edge and brings up a burr in 5-10 strokes. My granite plate is a 3" wide strip cut from a 12"x12" granite tile. The 600 grit sandpaper is attached with spray adhesive. The dimensions of the angled block aren't the least bit critical. It should be as long as your stone, wide enough to clamp securely, and have an angle that produces a slight microbevel. Nothing fancy. Mine is a scrap of spruce lumber that I made in five minutes.
As I slide the blade against the angled block I also apply downward pressure to the blade. This produces a burr quickly. Once I have a burr the clamps come off and I lay the face of the blade against the stone to polish that portion and to begin to remove the burr. When polishing the faces of the blade I use my thumbs to apply downward pressure and I walk them up the blade making about ten back and forth motions with my thumbs in each position as they move down the blade. It is important to keep the downward pressure from your thumbs directly above the edge you are trying to polish.
Polish both faces and then return to the angled block for a few more light passes. Alternate light passes on the faces of the blade and the bevel until there is no longer evidence of a burr. When the burr is gone insert the blade back into the reamer body and ream away.
For more information about this reamer check out Pete Galbert's blog here.