Machining Adventures: Part 2!

Hey guys!  This semester in the machine shop has been even more interesting because as our skillset grows, we can make more complicated projects with less oversight. We’ve even been choosing our own projects and designing our own blueprints in the last few months.

First up in January was the bolt project, which tested our ability to cut external threads and use an indexing head.

Our blueprint

Although the threads were tricky at first, once we got a hang of it, it wasn’t that bad, especially because we were going for a coarse fit (and therefore more a forgiving tolerance).

The newly cut threads—you can still see rough stock where the bolt head should go.

Next was the head. We set up a direct indexer on a milling machine, divided 360 over 6 (for each face) to get 60, and turned the head 60 degrees every time we wanted to take a new cut. This was the final product below.

Finished bolt

Our next project was self-selected. I decided to go with the hammer because there’s just something powerful about saying “I made a hammer!” (I made my second grade music teacher crazy for adding extra lyrics to the “If I had a hammer,” song we were learning, and I was reminiscing.) The first part to tackle was the handle, which was turned, tapered, and knurled on a lathe. This was my first time knurling and I was a bit nervous, but it came out great! It was also nice that we were only knurling aluminum—the tougher the material, the harder it is to manipulate.

Knurl finished

Done with taper

Final product

Next came the hammer faces, which I made out of brass because I wanted this to be a softer mallet for precision work. These were very simple—turn to size, drill and tap. What was interesting for me was the polishing process because the brass changed color slightly.

Halfway through (left) vs. finish polish (right)

Finally was the main hammer head that connected all the parts together. This was a little tricky because it involved both lathe and milling work, the latter of which required a round part to be held in a square vise. Luckily it cut smoothly without incident.

The round stock I started with.

Diameter cut to size


After hacking some bolts to the correct size, I began the assembly work and my hammer came together!

Now I Have a Hammer!

Next up—a countersink handle. This was one of my trickiest projects yet because I made it out of stainless steel. If you’ve never worked with stainless steel, it is incredibly hard—literally. I felt like I was trying to cut through a diamond. There was a lot of smoke and nasty screeching until I got the coolant system and feed rate calibrated just right. (Pro tip—deep cuts work the best with stainless steel because the lighter cuts tend to just rub and generate heat and stainless steel work hardens the more you heat it—you don’t want it to get even hotter!)

Freshly knurled part

Because knurling isn’t a cutting operation—it’s just force into or squeeze the material and hope it moves—this was much more difficult to knurl. Even with the coolant blasting and my feed rate slower than a snail, there was still a LOT of heat generated. Luckily it didn’t heat my part enough for it to become too hard for later operations to cut through.

Next came another unusual operation—cutting the radius on both ends. We used a huge scythe looking cutter that swiveled around the part to create a cool looking radius on both ends.

Finished countersink handle

Lastly was more “round part in a square vise” milling work but it was just a small tapped hole and didn’t create enough pressure to shake the setup.

So now we only have a few more weeks of class, just enough to eke out one more project. I finally badgered the professor into letting me try out a long-time curiosity of mine—gears! He had warned me that gears might be difficult, but I had no idea how to cut gears and I wanted to know, so it felt wrong to not even try. Per usual, the professor was right—gears were very difficult. Who knew so much math could go into such a simple shape? Especially since instead of starting with a blueprint and finding the cutting tools to match, I began with a limited number of cutting tools and had to design a blueprint that these would work for. Cutting gears up to industry standard is an incredibly precise operation so this might take a while, but I hope to update you once they’re finished!

Posted in: Gap Year Blogs