Get a longer screw, drill a hole threw the extra, tighten with a reasonable loctite and run a wire threw the hole and twist it secure like they do on airplanes.

Jas

Attachment 13218


this might work

Jason,
Maybe, but the issue isn't the screw backing out...its the registration between the point of the fastener and the shaft. Some "grub" screws have a flat bullet point, others sharp, others knurled. The issue is getting a flat to flat connection on a round shaft - thus the reason why so many have ground an additional flat side to the motor shaft for 2 points of contact with the pinion.

A flat mill file or a carefully handled grinder does the trick quickly!

Fix the problem with a spring pin. I and someone else on this forum mentioned that already but some seem to think that this would make changing a motor or pinion in the future harder to do. I have been using this method for many years now and I have never really found it that hard to change something later. Just remove the pin and redrill. Also this is extremely precise and stays that way. I just finished engraving 4000 1'' square lamacoid plastic tags with consecutive numbers from 1 to 4000 with not a hitch. Now that is a lot of lines of code.

Just my 2 cents worth.:D

Ok,so if the grub screw is tightened and it still shows marks on the project when cutting where does one look.The one thing I never thought to look at is the shaft that comes out of the gearbox.One of my gearboxes are F... How I found out?I had power on the motors and wiggled the pinion gear and the whole shaft moved there is a lot of backlash.It was the one x-axis motor.Moral of the whole story don`t let the spring pull the motor through the rack.I will take the gearbox apart and see what it looks like inside.Will get new pinions for my Motion king motors and fit them.

Sorry for post to old thread. But has anyone tried doing keyed shaft and spur gear? This way the set/grub screw is just to hold from falling off, not from keeping registration with the shaft.

Jack, there really isn't much "meat" on the 20 or 24 teeth spur gear left for a key way. Hence, grub screw.
you might have more space in 34 or larger spur gear.
But than again, grub screw is a good hack.

Instead of using a grub screw, then use a pin. It will not come loose and it will not fall out. On the 24 tooth pinion it works great.

I'm too lazy to drill precision pin holes... Grub screw suits lazy me very well.