127T change gear to fit to 100T change gear

thingiverse

This is a more refined version of my previous design, specifically tailored for machining metric threads on Harrison L5 lathes. To see more variations on lathe gears, check out my other designs here: http://www.thingiverse.com/nglasson/designs The gear I remixed from took a long time to print, so it occurred to me that designing a gear with 127T on the outside and 100T on the inside would be a simple way to mount an existing steel 100T gear. Either the 100T or the 127T is normally mounted at the lead screw drive end, making it unnecessary to use both gears simultaneously. This part is made in four segments to accommodate printers with smaller beds, such as those measuring 150mm square. I deliberately varied the segment sizes to prevent misassembly and to facilitate nesting if desired. All four pieces can easily fit on a 200mm square bed. I recommend using the complete 127T gear for convenience when switching between metric and imperial threadcutting, but this option of adding a plug to your existing 100T gear might be more suitable if you primarily work with one or the other. Printer Settings Printer Brand: RepRap Printer: Steelfence Rafts: No Supports: No Post-Printing I suggest printing small test samples initially, only a few mm high, to verify the jigsaw fit and ensure proper alignment on the 100T gear. If the fit is too tight or too loose, you can adjust two variables in the OpenSCAD file to fine-tune the fit: 'SF' scales the internal size of the 100T gear and 'kerf' adjusts the gap in the jigsaw fit. If the join fit is loose, secure the parts together with glue and/or cable ties through the 6mm holes adjacent to the joins. The other four holes are designed for cable tying the 127T gear to the 100T gear (if your 100T gear has spokes). Alternatively, you can use two longer cable tie loops through each pair of adjacent holes to prevent slippage. My print was a bit tight on the 100T gear, so I had to spend five minutes using a thin file to dress the teeth slightly. It's still a bit tight and likely won't require any additional support. How I Designed This I used my customizable change wheel design as the base STLs and the excellent puzzlecut code to divide the parts into segments. With OpenSCAD, you can modify the code to suit your printer and then compile each segment individually by commenting out the other three segments. Alternatively, you can save all four segments at once and post-process them separately.