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.
Yes you can set up a spindle motor as Step/Dir, you just asign the pins for Spindle in Ports and Pins, Motor Outputs and then once you have that enabled you can then tune it as you would an axis. You need to calculate the Velocity as revs per second rather than per minute.
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.
I am not sure how well the axis is controlled with the parallel port when threading, there were reports that it was slowing the Z if the spindle slowed down but how well it tracks I dont know. I cant test for two reasons, firstly I use the SmoothStepper and dont have a parallel port on the Pico motherboard and secondly even if I did my spindle has far too much power to let a mere threading tool slow it down
I can however confirm that the SmoothStepper controls the Z axis well when threading as a recent sheared key in the headstock saw my lathe slowing from 1000rpm at the start of each pass down to around 200rpm by the end and this was the same for each of the 10 passes and the thread was perfect, so might be worth considering?
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.
Threading has been improved but the basic way of threading is the same as it always was, its the way Mach deals with things internally that have changed.
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.
You dont actually need Mach controlling the spindle at all to be able to do threading, all you need is an index pulse but possibly your present motor is not capable of holding a reasonable speed under load.
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.
Think you may be pushing a sherline trying to do m16 threads, in steel especially, make sure you do plenty passes
Hood
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