Archive for August 19th, 2013
The discussion following that post on getting feature coordinates from an existing part reminded me of an old project that I’d written up for Digital Machinist: making repair parts for the half-century old storm doors on our house. Here’s the whole latch, with a replacement drawbar and cam:
The other side of the drawbar and cam:
An early version of the drawbar that engages the latch strike and gets pulled by cam:
Three iterations on a cam; the messed-up one in the center, IIRC, helped track down an EMC2 bug:
Now that I look at it again, there’s nowhere near enough meat around that square hole for a 3D printed plastic part… so the notion of printing the complex part of the cam and adding wear bars along those ears just isn’t going to work.
I made a fixture for the Sherline CNC mill to hold the drawbar for inside milling:
Then a block screwed down in the middle clamps the drawbar in the same place for outside milling:
The square post in the left rear corner holds the cam:
Note that I had to file the square hole before milling the cam shape, which meant that if the CNC process screwed up, all that handwork went into the show-n-tell bin… which I’m not going to show you.
I used an early version of the grid-overlay technique to map out the drawbar coordinates; this was an illustration for the column: