Thumb Roller Hook for Dial Caliper
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Published on October 15, 2011
This thing was Featured on October 16, 2011
Description
This is a replacement part for the thumb roller hook that broke on one of my dial calipers. I made the part by injection molding polypropylene. I included the model files used to make the aluminum mold.
I don't know how often these things break but I couldn't find a direct replacement for mine. I did see some company selling a similar part that might have worked for ~$8. I think I bought the caliper for about $15.
Additional information about my injection molding process can be found at home.comcast.net/~sskroch/Injection_molding/injection_molding.html
I don't know how often these things break but I couldn't find a direct replacement for mine. I did see some company selling a similar part that might have worked for ~$8. I think I bought the caliper for about $15.
Additional information about my injection molding process can be found at home.comcast.net/~sskroch/Injection_molding/injection_molding.html
Instructions
I used a CNC mill to make aluminum molds and injection molded polypropylene to make this part. The model is designed so that the mold can be milled with a 1/16 end mill. I used a Dremel 1/16 carbide grout removal bit for the bottom half mold because my standard length 1/16 end mill was not long enough. I used a 1/16 ball end mill on the top side to make it look nicer. The models for the molds do not include the gates for injecting the plastic. I milled the gates in manually after the main section of the mold was made.
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Nice work, always wanted my own injection molder, not got around to it yet :)
Polyurethane (e.g. from Smooth-On) can be done nicely on a budget - I shoot the liquid pre-polymer in to the mould with a syringe (cut the threaded shell portion off the luer lock and mill the gate to fit the luer tightly) and it works well.