Jun 26, 2015

Brass Pen

Because I want to knurl something. And look at knurls.
Knurling = My current obsession.

First machining project of the summer is to create an everyday-use brass pen. 

I trade in some crufted steel rod for MITERS brass stock and start turning stuff to size. I went for a desired 3/8" diameter after finding a size that felt good in my hand. 

The ink cartridges I'm using were cannibalized from my favorite pens, Uni-ball's 0.38mm Signo pens. I adore these, so I opted to build the pen around these cartridges instead of using a more standard sizing. This involved a ton of caliper measurements and test fitting, but I enjoy that sort of thing.

After roughly sizing the brass, I bandsawed the rod in two and started shaping the front half. I started with a 20° taper but ended up going with something closer to 10°. I then rotated my tool to near-parallel and did a finish pass.

The knurling itself was glorious, but not quite as clean as the flashlight handle from 2.670. Knurls here serve several functions: grip surface, AESTHETICS, and hiding any differences in diameter between my front and back halves.

But 99% aesthetics.

I then face off the tip and drill a hole through the front, just large enough to admit the tip of the pen.  

Then, the pen gets flipped around (chuck grabs a collar of extra material on the back to avoid clamping on the knurls!) and a series of drills go through the back to match the rest of the ink cartridge dimensions.

And... I broke it. Time to go to bed; try again tomorrow :(

Take Two has slightly worse surface finish, but doesn't break the pen. After completing the front, I turn down the back to the same diameter.

My pieces mate with a 5/16"-18 thread. I discovered experimentally that cutting external threads with a die should always happen before drilling the interior cartridge hole. I know that's common sense, but I need to remind myself every so often when teaching other people to use machine tools.

I made a pen! And it writes!

I ended up needing a longer back-piece than I had originally anticipated, so part of my clamping-scrap ended up in the final pen. I hid the toolmarks with more knurls and some artistic tapers. In addition, the first thing I did with this pen was get a screw stuck in the barrel. The second thing I did with this pen was drill a hole through the back to poke the screw out.

that unfortunate screw hole
before/after comparison

The third thing I did with this pen was send a picture to my mother, who reminded me that my grandfather loves shiny pens... so below is an in-progress photo of the next one!