Introduction: Cookie Tin Banjo Part 1: Make a Tuning Peg Hole Reamer From Scissors

By www.mit.edu/people/robot
About: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of www.zcorp.com, manufacturers of "3D Printer" output devices. His detailed drawings of traditional Pacific I…

Here's a great sounding banjo you can build in a few hours.
It's a lot lighter and a little quieter than a regular banjo.

It's based on the traditional folk instruments seen in "Foxfire Volume Three".

First step: Make a tuning peg hole reamer from a pair of scissors.
The reamer is a tool for making tapered holes. First you drill the hole then you ream it out to enlarge and taper it. The taper of the reamer matches the taper of the tuning pegs that will be plugged into the holes.
The smoother, straighter, and better matched to the pegs the holes are, the better your tuning pegs will work.

You can skip this step if you want, either by buying a commercial peg hole reamer, or by tapering your peg holes with a rat-tail file.

Commercial peg hole reamers cost from $26 on up.
They can be obtained from:
http://www.internationalviolin.com/item_detail.aspx?ItemCode=T410
http://www.internationalluthiers.com/tools.php
http://www.stewmac.com/shop/Tools/Reamers/Peghole_Reamers.html

Step 1: What Taper?

I made my reamer with a 25:1 taper, which is what older violin tuning pegs used.

I've learned from experience that pegs that taper too much are hard to use. You have to loosen, turn, and force them back.
Pegs that don't taper much need to be made from very hard wood and need a hard headstock hole. Otherwise the peg enlarges the hole from use and bottoms out at the knob end of the peg.

I've got an old violin that needs that kind of pegs, so I can kill a few extra birds with this project.
I plan to buy violin pegs for my banjos in the future when I get lazy.
Modern violins use a 30:1 taper.

Here's the scissor jaw with the grinding guide lines marked on it.

The wide end at the base is .34" wide.
The narrow tip, 3" from that is .22" wide.

Step 2: Grind

Here I am grinding down to the lines on a big grinding wheel.
If you don't have one of those, a file or body grinder would be fine.
Use whatever you've got.

Don't overheat it.
Dip it in water repeatedly before the steel ever changes color.

WARNINGS:
I used a grinding wheel once with the guide plate too far from it. My finger got pulled into the slot and ground down. I couldn't pull it back out until it was a lot thinner and bloody. Don't do that. Make sure the guide is nice and close to the wheel.
Grinders are great at spraying hot sparks into your eyes. Also if the wheel fractures it can fling sharp rocks at your eyes and head. Wear lots of safety equipment. Don't get hurt.

Step 3: Quench

Quench it in water every few seconds. If the steel ever turns yellow, brown, or blue from heat you've softened the temper.
A beltsander with a wet belt is probably the best thing for this type of work.

Actually you could make a reamer from pretty soft metal and it would be okay, you're not going to be doing mass production of peg holes.

Step 4: Finished Reamer

Here's the finished tool along with one of the tuning pegs it will make holes to match.

Want to make a peg shaver to make your tuning pegs fit perfectly?
continue to Part 2, Make a Tuning Peg Shaver!