How much threads are needed on the bolts?

Mostly Printed CNC - MPCNC Advice
1

I’m sourcing my hardware as I’m printing the parts for the mpcnc and saw that in the kit from V1 the M8x40mm bolts are not threaded all the way?

Is it OK if they are threaded all the way?

How much threading is needed?

Would these work for instance (less threading than in the kit it looks like)?

2

Partial or full threading are both fine. There was some debate on another topic about whether partial was better for the bearings, but machines are getting built with both kinds and are working just fine. I just examined my machine in terms threads length. I did not find any place where 15mm of threads wouldn’t work, and you might be able to go down as low as 12mm. The bolts in your link are galvanized. Personally I don’t recommend galvanized bolds for your machine. It has been my personal experience that the coatings can sometimes increase the diameter of bolts, and tolerances in the printed parts are tight.

3

Thanks a lot! Yeah I was just looking at the galvanized ones since they were a lot cheaper :blush: But then I’ll pick something else.

Thanks again!

4

A common type of bolt is ‘BZP’ for bright zinc plated - i.e. galvanized but shinny. It’s not as thick a layer as the hot-dipped galvanizing that you’d see on, say a gate hinge or boat anchor, and should be good for the MPCNC. It’s enough protection to stop them going rusty if your workshop is occasionally humid but they have a nice finish.