Hello all,
I've been browsing this forum for a year or so now and finally decided to join up. I look forward to picking your brains and maybe helping out some myself.
I currently am having an issue with thread milling. I'm running some smaller parts out of Nitronic 60 and after lots of frustration breaking taps while tapping from the back spindle , I decided to switch over to thread milling. This particular tapped hole is also a zero chamfer hole, so I know that was a bit of my problem. I know there's probably a few different ways on this machine to do so (I do have the live 30-tooling option).
Currently I'm using this approach for a 1/4-28 thread mill with a .180 diameter.
[Live tooling on=2847RPM]
G0 X0.0
G1 Z.350 F10.0 [IPM]
G1 X[.036*2] F1.0 (FEED INTO shoulder for .251 major diameter)
W[-[.03571*2]] H[-[360*2]] F1966.0
G0X0.0
Z-.1
It's working, but the tool life isn't what I've been expecting. I actually added a roughing pass instead of just going full depth for my pass, but every once in a while the mill will snap. It will do so right before it completes it's first full 360-degree rotation.
I've seen someone mention using G32, but I'm a bit reluctant to do so primarily because I envision it stressing the tip of the tool and deflecting off-center as it tries to feed straight in. Also, I'm not sure that my spindle will let me program a 4-5RPM rotation.
I have some smaller shanked mills coming in tomorrow and I believe my next attempt will be similar to:
G0 X0.0
G1 Z.350 F10.0 [IPM]
X[.036*2]W-.03571H-360.0 ~F1000.0
W[-[.03571*2]] H[-[360*2]] F1966.0
G0X0.0
Z-.1
I assume that giving it a full lead to shoulder into the part may help it seat a bit better.
In any case, does anyone have any tips or tricks to thread milling with the back spindle? Would G32 or G92 be of any use at all? I know that G12.1 programming is an option, but I have used very little G12.1 programming, although I did manage to write an ellipse sub program to mill an adjustable ellipse on the back side of a part. I wish I could just do a true helix into the shoulder as I would on a mill but I'm hesitant to try it until I understand the G12.1 programming a bit more. If it's as simple as throwing the code in, and spitting out mill-style G2/G3's then I'm all for it. I just worry because my X is in Diameter and I'm not sure how that affects anything.
Thanks in advance. I have another issue regarding interpolation I'll address in a seperate thread tomorrow when I have more time.