Bolt Action Metal Scribe
I watch a lot of YouTube channels that involve custom tool making, and when I'm in my garage working these things weigh on me. As I continue to expand my own tool library I'm starting to see more clearly the psychological benefits of using tools that you yourself have created. It provides an extreme satisfaction to be able to use something you made to help you make another-- And that satisfaction can help build up and maintain the creative momentum needed to complete some of these self imposed labors.
Aside from that, I am also EXTREMELY picky, and want things to be just so, and that applies to my tools as well. Who wants lame tools when you can have artisan tools?
Sure you can buy a metal scribe for five dollars, but why get that when you can spend over a hundred dollars in time, labor, and parts for something slightly cooler? OK, maybe it's just me... but it's my time so it's free, right? (No)
So let's get to it. If you don't like reading, this process is condensed into a video for your viewing pleasure. This post, however, will be more in depth than the video will be.
One limiting factor in my home shop right now is the lack of a lathe. I could borrow one of them at the day job, but huge metal lathes are a little out of my comfort zone (especially after one of our machinists ripped some fingers off in one, and he was lucky at that). So we're going to work around that with a drill press. It's a little more time consuming, but we'll live.
There's four main components to this build, the Outer Barrel, the Inner Assembly, the Tip, and the Clip.
The Outer Barrel was made from a length of Ø3/8" 316 stainless steel tube. It was cut to length then loaded into the large mill to cut out the slot for the bolt to ride in. The original idea was to include a 45° angle at the end of the slot to force the bolt to twist and lock when pressed in.
The Inner Assembly is composed of the Press Barrel, the Spring, and the Scribe. The Scribe used is a replacement tungsten carbide scribe tip for generic metal scribes. I wanted to use these in case I ever dulled the point enough warrant changing them out. The spring is just a click pen spring (a slightly larger than average one).
The Press Barrel was made from a Ø1/4" brass rod. Normally this part would get turned in a lathe for the step down and center hole for the scribe. Since we are going lathe-less, we'll pretend the drill press is a lathe. (Check out this video for a better tutorial on this) Loading a drill bit upside-down in the drill press chuck allows you to position your vice and clamp to the opposite flute end of the bit. Tighten everything down good and tight. Now you loosen the drill bit from the chuck, and you have a quasi vertical lathe setup, with the vise and drill bit functioning as a tail stock of sorts. Mount the bar stock in the chuck and very slowly lower it onto the drill bit. The drill will naturally try to center itself as it cuts into the rotating material. Once it's cutting smoothly, drill as usual.
For cutting the step to hold the spring I kept the rod in the drill press, then used a file to shave down the outer diameter. This took a very long time, but a lot of that was figuring out a good rhythm and pressure. Once I had that figured out it filed down pretty quickly. I also used the file method to chamfer the ends. After all that, I drilled and tapped a hole for the clip's mounting screw to fit in.
The Tip started with Ø3/8" brass rod, and was shaped with the same method as the Press Barrel. Drill a center hole in the press, file down a step. For the angle I tried filing, but realized I couldn't keep the file straight enough. So I chucked the brass in my drill and ran it against a belt sander, which worked surprisingly well.
Finally the Clip was made with aluminum stock in my Nomad 880 CNC mill. The first pass was straightforward with a surfacing and silhouette operation. Flipping the part over was a little nerve wracking, as there was only 1/16" material clamped by the vise jaws, and the ball mill barely dodging the vise top with 0.020" clearance. Everything ran fine though, and the part was sanded and ready to go. The original plan was to have a gold plated clip, but to gold plate aluminum it must first be zinc plated, then copper plated, then gold plated. Therefore it's an aluminum finish.
Time to put it all together! My original plan was to press fit the scribe tip and the brass tip into their respective barrels, but I ended up gluing the pen tip, and taping the scribe tip. It really doesn't change the function in any way, it just wasn't ideal. Oh well.
But honestly, the final scribe is awesome by the way, and turned out way better than I thought it would. I thought the lack of a lathe would really hamper on the final quality, and it did to a small extent, but with enough patience and love I was able to work through it. (However, I won't do something like this again until I have a lathe)
Thanks for reading!