Monday, February 18, 2013

Pull-Up Bar

This project was mainly inspired by Raku (and the fact that I found a perfectly sized steel tube in the MITERS stock pile). Though getting more exercise has been a thought of mine for a while. During robot season in High School, I wouldn't really play sports or exercise on a daily bases. Now at MIT, it's constantly "robot season" with MITERS and all. Having access to a convenient pull-up bar may help with my lack of exercise (Broomball helps a bit too :).

More on the building process after the break:

I needed to drill an inch sized hole; however, the inch sized drill bits require a half inch chuck. I wasn't able to find any half inch chuck drills around MITERS or in ToolComm at East Campus (only 3/8). The other option was to use a spade bit, but I couldn't find any of those either. So, I tried making an adapter using the milling chuck. 

I found a bolt with the same threads as the threads on the milling chuck. I cut off the bolt head using the parting tool on the lathe. Then, I faced it down to a diameter slightly smaller than 3/8".

The threads tightened into the milling chuck, which could hold the 1" drill bit, and the drill tightened on the adapter piece. I learned later that this is a bad idea. The size of the drill bit and its corresponding chuck size give a sense for how big the drill should be (how much torque is required to use the specific drill bit most efficiently). Using a small drill with an over-sized drill bit can lead to big problems.

Longest drill I have ever seen. Quite ridiculous :P

After a lot of noise and some bad smells, I got a hole through the left 4 x 4 and a hole half way through the right 4 x 4. 

Now for securing the pull-up pipe once in the hole.

I used the end mill to machine an aluminum rectangle to screw into the side of the 4 x 4 piece of wood. This will keep the pull up bar tight against the partially drilled hole in the opposite 4 x 4. 

Conveniently, I found some rubber stoppers on the workbench at MITERS. I threaded them on to the bolt so they can keep a tight seal on the pull-up pipe (when I tighten the bolt to the machine aluminum rectangle). 

Here is the complete mini-assembly for keeping the pull-up pipe in place and from rotating. 

All it took was screwing in the stopper assembly to the left 4 x 4. 

Ready to exercise. 

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