[Power_user_EX]

Hello guys I m building a CNC for the first time and have some basic questions. I plan to use 10mm or 12mm diameter Lead screw.

1. Whats the pitch (in mm) or TPI generally used for hobby CNCs? After some research I see many ppl using 10 TPI (0.1" / 2.54mm pitch) lead screws... am I correct ? Does Higher TPI or Pitch decrease the accuracy ?

2. What sort of bearings can I use to hold the lead screw in place at both ends? Will 12mm ID bearing (rotary) work perfect ?

3. As per Nema 23 standard the shaft diameter is 1/4" or 6.35mm in metric. What kind of coupler can I use to couple the 6.35mm shaft to 12mm Lead Screw?

Can some one list the standard sizes in Imperial and Metric system for lead screws and bearings which are used for CNCs ?

[louieatienza]

1 - Typically, one would have a design done first and an idea of the weight of each moving part and the cutting forces involved with the materials plaaned to be cut, at the speed it needs to be cut. That would determine the leadscrew pitch and motor choice. You have to do more research here and elsewhere to get an idea of what's needed, as there are no hard-and-fast rules.

2 - Again it depends on the application. For light duty wood or foam cutting it is probably fine. Maybe not so for metals, though there is a mill in the metalworking section that uses radial ball bearings with success. The cutting spindle and tooling however is small.

3 - There are NEMA23 motors with 8mm and 3/8" shafts as well. Again, research is needed. You would want a coupling that's rated a bit higher than the torque rating of your motors.