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, where I first encountered the design. Another option is to purchase a tapered reamer from Elia Bizzarri at He can also sell you a matching tenon cutter. It might just be the last great woodworking tool bargain!


Anonymous said...

Have you ever tried leaving the teeth on the blade? I believe John mentioned that this was ok.

Thanks for all the sharing,

Mike Hamilton

Peter Galbert said...

I never tried it. Having the 2 equally sharp blades on opposite sides makes sense to me, with a tool where sensitivity is so important. Then again, John's advice on these things is generally well reasoned. Let me know if you give it a try!

Anonymous said...

Mike, Peter
I made a tapered reamer from John's plans several years ago, and left the teeth on. It leaves saw-teeth marks on the side, but the sides are smooth from the other side of the reamer. One problem I experiece is that it is very hard to extract the reamer as the hole becomes tapered. I have to put the seat in a vise and tap (pretty hard) on the end of the reamer to knock it back out. I made another reamer, this time filing the teeth away (like Pete describes) and do not have this problem.

Larry Barrett

Anonymous said...

I see six degrees written on the side of the reamer. Do you use this angle for all the tapered parts of the chair, including for the legs? I see anything from 8-12 degrees for the leg to seat connection. What do you personally use?

Peter Galbert said...

I use a 6 degree reamer on all of my leg and armpost joints. As I understand it, to get a true mechanical lock requires an angle somewhere below 7 degrees. I wrote an article in the American Woodturner spring 2009 issue about tapered joints. It might be worth checking out,
here's a link to back issues of the magazine

Anonymous said...

Thanks for the answer. I have read what Elia Bizzari said about his thoughts but appreciate it coming from more than one authority on the subject.

Mark H said...

Peter= just prepping to turn a reamer and I've got a blank of maple 2"x12"=== just eyeballing yours looks to be about that length. Yes?

Also, about how long is the minimum length the blade should be? Looks like yours is around 6"-7" +/-. Close or not?


Peter Galbert said...

I base the length on the largest width of the tapered blade, and therefore mortise that I will be reaming. I make mine about 1 1/4 wide at the widest and they end up about 9 inches long, but you can make them smaller to suit your needs,