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Software and Information for Machinists |
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Belt Drive for the Industrial Hobbies/Rong Fu Mill
Part 2: Construction Planning
Spindle Drive Adapter
The critical and most difficult part to fabricate for the IH belt drive is the Spindle Drive Adapter. This piece has to fit over the top splined part of the spindle to drive it. It must do so tightly, while transferring the full power, and it must be supported in bearings so as not to allow the tension on the belts to transfer lateral force onto the spindle itself.
Here are the dimensions for the Industrial Hobbies mill spline:
Rather than broaching the splined piece, I plan to just mill out an approximate shape, something like this:
This path can be milled out via CNC using a 3/16" endmill. I want this part of the adapter to be 1" thick so it is solidly clamped to the spindle. That's apt to be a chattery business to cut more than 5x deeper than the endmill diameter, so I plan to drill 6 holes and then interpolate the center hole (or perhaps bore it in the lathe) before I attempt to profile the complex curve. The spline width of 0.232 is a touchy business too, since it is smaller than 1/4" and much larger than 3/16", finding an appropriate endmill diameter is problematic. If I can use a 6mm diameter endmill, that gets me with an oversize of 0.004". Worth a try to see if it works very well being that much oversize.
I'll machine a test piece that consists strictly of this part to trial fit it to the spindle shaft before I attempt to make the overall adapter. I want to make sure it all comes off well!
CNC Codes
Note: These codes are for a test piece, and not the actual adapter!
Spline Holes: Drill 6 holes with a 0.236" twist drill bit ("A" drill).
Center Hole: Interpolate the center hole with a 1/2" 2 flute endmill.
Final Profile: Cut the final profile with a 3/16" (0.1875") endmill.