9x20 Lathe Sacrifical 80 tooth gear

This gear should work on numerous 9x20 lathes available from Grizzly, Central machinery (Harbor Freight), Jet, and many others. This is an 80 tooth "sacrifical" gear - so called because the idea is that in the event of a head crash or similar unfortunate lathe incident, this plastic gear will be destroyed rather than more expensive components. This is the 80 tooth gear which is driven by the lathe spindle. This is not a "change gear" although it has similar specifications; in typical lathe operations this gear is not removed.

I have included in the photos the hear specifications used to make the gear. Some of these specifications have been adjusted from the factory specs to allow for 3D printing variances.

The OnShape 3D CAD file for this are available here:

https://cad.onshape.com/documents/6972fa915e8bec8931a466e6/w/2222457e43a805ed2991d955/e/8b9b741fa5a6ed931efc812a

Print instructions

I printed the gear in PLA and it seems to work OK (although I have only used it briefly so far). PETG might be a better choice. IF I find that PLA does not hold up well with extended use, I will update this entry (if I remember!).

Easiest way to print the gear is to use the 3mf file. However, here are some important setting:

• infill 60% rectilinear
• top/bottom fill = concentric
• perimeters = 6
• seam position = random
• top/bottom layers = 5
• external perimeters first = checked