Topics

1

General Mach Discussion / Questions on Threading With Turn on Sherline - From Yahoo SherlineCNC Group

« on: January 19, 2009, 10:32:16 PM »

This is an attempt to move some discussions from the SherlineCNC group over here, where I hope to find some information I need.  Over the last several days, we had a long discussion on what it takes to thread successfully on a CNC lathe. 

I have tried threading several times with Mach3 on my Sherline CNC Lathe.  It has almost never worked (I did get one usable 8-32 screw).  Guys on the SherlineCNC list recommended a few things.  First off, stronger steppers than the 70 in-oz motors I'm currently using.  No problem. 

Here's where the Mach questions start: can Mach3 drive a stepper at a fixed RPM to replace the Sherline spindle motor?  I don't see a specific place where I can set this up. 

Next question: I currently have an opto-coupled feedback sensor that appears to give me stable RPM numbers.  They might even be correct.    But Mach3 doesn't seem to use that information to adjust the Z axis.  Am I missing a configuration issue?  I have just read other folks saying they're sure it does use it, but I'm not sure it works with parallel port drive. 

Is threading addressed in an article or app note or something?  I see the Turn pdf book is the same one I have that goes back many versions.  I've read threading was recently improved, and I have the R3.042.020 Lockdown version, so that won't be documented in that pdf file.   

If Turn can control a stepper on the spindle, I will order 3 new higher torque motors and the spindle stepper mount.  If not, I'll just get 2.  So far, one usable brass 8-32 screw (for $1200) isn't terribly worthwhile.  I'd like to set up my lathe to be more useful.  I am probably more interested in finer pitches, but recently had to cut a 2mm pitch M16 screw in steel (manual cranking the lathe) so I'd like to be ready for anything.


Thanks,
Bob