Thursday, October 3, 2019

Making a Tapered Reamer

This has been on my to-do list for quite a while.  I've made some small, four-legged stools in the past and they've had round tenons glued and wedged in round holes.  But I know it would be better to have tapered tenons in tapered holes.  That way, every time the stool gets sat on or stood on, the joints only get tighter.

I wanted approximately a 6° angle on the taper (3° either side of an imaginary center line) and calculated that over 8 1/2" length of taper I'd need 3/8" diameter at the small end and 1 1/4" diameter at the large end.  So I glued up some oak, octagonized a 1 3/4" square blank and put it on the bungee lathe.
Checking the taper for straightness
So far, I'm a fairly horrible turner and I had some trouble getting the taper to be straight along its entire length.  But it's close enough.  For anyone interested, there's about 1/4" allowed for the transition from taper to octagonal section and the octagonal section is about another 3 3/4" long.  I later bored a hole through the octagonal section for a handle.

To guide my sawing a kerf lengthwise through the tapered section, I marked some lines carefully along the length of the taper.  Having marked crosshairs on both ends before turning helped to get the lines 180° opposed to one another.

For the blade of this tapered reamer, I'm using a really crappy and cheap garage sale saw that I've been cannibalizing for scratch stock blanks.
Blade marked out
But before I cut out the reamer's blade from the saw plate, I used the saw to make the kerf that the blade will fit into.
I had hammered most of the set out of the teeth to get a kerf that will match the blade's thickness
I also did a quick sharpening of the teeth before cutting out the blade and fitting it to the taper.
The blade cut out and the edge filed to match the taper of the reamer
Bladed installed in the reamer: the saw's teeth are just barely showing
On the other side, the edge is proud of the taper by about 1/32"
I bored a through hole in some pine and made the first test taper.

The first cut
The tapered hole showing the reamer's teeth marks
This is good enough for a prototype and proof of concept.  Next I'll write about making the other part of the equation: the tapered tenon-cutter.


  1. Way cheaper than the prices I've seen for a tapered reamer.

    1. Yeah, it cost me just a bit of time to make. I doubt mine will be as good as one from Elia Bizzarri or Peter Galbert, but at least it'll give me a start.

  2. Matt,

    You are the man. Your reamed hole looks good, thing is the angles just have to match. Degrees make no never mind. I've one more project for MsBubba before I can make the next chair or stool but soon.


    1. Thanks, Ken. My next post will include details on getting the angle on the tenon to match the one in the hole. It wasn't too tough, but it definitely wasn't as easy as I'd hoped.

  3. How did you cut out the blade? I've been using a triangular file to score the line and then putting it in a vise to break it off - sort of like cutting glass. Is there a better way that doesn't require an angle grinder?

    1. Hi Paul. I started with a dremel tool with a cutting disc, but the dremel stopped working and I can't figure out what's wrong with it. So I used a (dull) hack saw. It took a while, but worked OK. I've since gotten new blades that work a bit better.

      I'm interested in that method you mentioned about scoring the metal and breaking it off. I'll have to try that sometime.

  4. Way cool, you just keep adding to my To-Do pile. Thanks, I think? :-)

    Bob, swamped in block planes

    1. Sorry about that, Bob. But it's all in good fun, right?

      Now I've got to spend some time with your new post on block planes ...