On the 1st day of Cruftmas, Chetan received... 7 tuning forks.
Every year, Putz does Cruftmas, a secret santa where you're not allowed to spend any money on gifts. While on the lookout for possible presents, I rescued a few old-fashioned finger clamps from a box in the Stata loading docks. Since they kinda looked like tuning forks and kinda sounded like tuning forks, I decided to turn them into (surprise!) tuning forks.
I got assigned to Chetan, who usually leads our hall in singing happy birthday, so I figured he would appreciate an instrument to play while singing. Happy birthday is apparently supposed to be sung in G major, so I figured I would tune the forks to that scale. I made a slight mistake and wrote down the frequencies for F major while trying to decide if I should pitch it down for easier singing, and ended up tuning the forks to the those frequencies instead.
I started by cleaning up the two outside sides of each fork, hopefully making the thickness of the tines more consistent and the tuning easier.
According to Wikipedia, the frequency that a tuning fork produces is inversely proportional to the square of the length, and directly proportional to the cross-sectional area. I figured that I could mill off some amount of the tines, measure the frequency, and repeat until I figured out the relationship between tine length and frequency, given a certain thickness. In practice, this meant somewhat arbitrarily using the horizontal bandsaw to cut off somewhere between 0.1 and 0.2 inches more than the final amount of tine removed for the previous fork. I was then able to take it to the mill in order to creep up on the target frequency.
I overshot on the bandsaw cuts for a few of the forks, so I had to make the tines thinner in order to increase their resonant frequency. This made a couple of the higher pitched forks longer than the lower ones, which is kinda unfortunate aesthetically, but otherwise ok.
Later, I faced the other end of the forks, drilled, and tapped some M5s in preparation for mounting. The forks were held upright in the mill vice, using a 1-2-3 block as a reference for perpendicularity. This wasn't the most ideal workholding solution due to lack of rigidity, so I torqued down the vice to compensate. The tuning forks were then bolted to a length of 2x2, orbital sanded, aluminum square tubing.
Each note was labeled, the entire thing was wrapped in 3.091 goodie bags, and it was truly the season for shitty music.
Festive spirit aside, Cruftmas caused some casualties as well. My T-motor U12 fell off the top of our "tree" and seized up, so I guess I'm gonna have to rebuild it.