The fret wire I have bought usually came pre-radiused. The radius didn't match my fingerboard radius, but it deformed enough to match while being pressed into place. However, the fretboard wood doesn't always have enough bite to keep the fret from lifting (it wants to return to it's original radius before being pressed in), as I found out with using cherry for a fingerboard. So I decided to do it the right way and bend the fret wire to match the fingerboard radius.
There are a bunch of fret wire bender DIY's out there, but none of them impressed me as much as the ones available from Stew-Mac or Luthiers Mercantile International Inc. Thus, I decided to build one as close to those as I could figure based on their pictures and videos. All the parts came from McMaster and the local home center. It cost me about $45 (a little more than half what it would cost to buy one) and only took about an hour to make. I could have made one for 10-$15 using a bunch of parts from the home center, but, I'm only going to make one of these, so I'm going to make the best one I can. McMaster part numbers are provided in (parenthesis).
Here is what I'm starting with...
drill bits: 1/4", 5/16" and 3/8" diameters, crank handle with 5/16-18 thread (6129K1), rubber tubing 1/4" inside diameter x 3/4" outside diameter x 1" long (9697K31), 5/16" shaft collar with set screw (9414T7), 5/16" washers (local store), 5/16" hex bolt x 2 1/2" long (local store), thumb screws 10-24 thread (95150A150), bearings 1/4" inside diameter x 1" outside diameter (6383K22), 1/4" washers (local store), 1/4" should screws (91259A540) and a piece of 5/16"x3"x12" aluminum (8975K891).
fretwire bender template
Tape the template to the aluminum and center-punch the hole locations.
Drill the holes. I use a glue syringe to apply the cutting fluid.
Holes drilled. After some useage, I made the two bottom-most holes 3/8" to allow for greater adjustability. The template (above) has been revised accordingly.
The rubber tubing has a 1/4" inside diameter, but the handle shaft is 5/16". To make sure the hole is located perfectly, put the 1/4" drill bit into the tubing, then into the drill press chuck, then clamp in place.
Remove the 1/4" drill bit, chuck the 5/16" bit and drill the hole.
Install the bearings and set the calipers to their centerline. This is to locate the fret tang slot into the rubber tubing.
Slide the rubber tubing on to the 5/16"x2 1/2" bolt and chuck it into the drill press and transfer that distance to the rubber tubing by scoring a line as it spins.
Use a fret slot saw to cut the slot for the fret tang. Be concentious of the rotation direction, you want the saw to be pulling away from you, not throwing towards you.
Cut off the extra tubing, install the shaft collar on the bolt, then the rubber tubing, a couple of washers and finally the handle. Use the calipers to measure how much of the bolt needs to be cut off.
Take it apart and transfer the distance to the bolt.
Cut the bolt to length. I had previously cut off some of the threaded portion so that only smooth shaft would remain when fully threaded into the handle.
File a flat spot for the shaft collar set screw.
Feed the wire...
...turn the crank and watch in amazement as bent fret wire comes out the other end!
Be happy with your successful project.
WOW. I snagged the parts to build one recently, but this makes me want to grab some fresh stuff for much of it, and start over
Did you not make it radius adjustable? I know its not super critical, but I have to nitpick something! It looks from the holes youve drilled that you did, (one side of the bearings has a much larger hole than the other), but I cant see any actual method to change it.