Sometimes a job that seems super easy isn’t, but it can still be rewarding! Check out MAAP’s intern Jack Gavin, and his personal experience with a challenging task.
I started to work in the machine shop in the basement of the engineering building recently. I have been looking for cool projects that excite my automotive passion as well. When testing the motor assembly for the electric sunroof on our Super 90 restoration in the shop, we soon found an issue. The gear connects the motor to the transmission that controls the cables to pull and push the sunroof opened and closed had an issue. The gear had sat in one place long enough to have half of the threads rust away and cause a dead spot in the actuation of the motor. This was something that needed to be fixed. Once the damaged part was identified we needed a way to re-create one. Our original plan was to take it to the local machine shop, but I snagged the project thinking it was going be an easy job on a lathe with only a couple of operations, boy was I wrong.
I started to grind the tip of the chamfer tool to give me the geometry that I needed in order to form the threads. The more and more I looked at the threads, they looked different than I was expected. It turns out they were not threads but after much research and time in front of an optical comparator machine. We determined that it was a modified ACME 10 thread. In addition to this, the hardest part to understand was why the major and minor dimeter of the thread was different than we were expecting for the ACME threading standards. Then it came to us, DUH, it’s metric and that’s what they had in front of them to make it. This meant that half of the thread geometry was metric and half was standard. This makes sense now because back when the system was designed, there were no machining standards, and we were fixated on the notion that this part must follow conventional machining standards, but those simply didn’t exist yet.
With this in mind we were able to find the correct tool insert that we needed and after some time, we had the first one in out hand. Dimensionally the part checked all the boxes, but I wanted to take the project to the next level. The machine shop at school just got a fancy new CNC lathe, and I have been dying to look for the right project to use it on.
Now, I don’t have any experience programming CNC machines so there was a huge learning curve. I spent many days trying to figure out the correct toolpaths, work and tool offsets, and speeds and feeds. All while trying to prevent a 6-figure explosion of a spinning chucks and tooling inside our new lathe. I felt really comfortable doing it on the manual lathe, but now trying to get the programming software to tell the machine what and how to do it was more complicated than I thought. It took about 6 tries to get the result we wanted, but after a lot of time and learning moments, we had a part in hand that we were happy with. This was a really fun project and taught me a lot about CNC machining and general machine as well.