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Author Topic: Simple Threading - lathe heads for the hills...  (Read 2210 times)

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Simple Threading - lathe heads for the hills...
« on: December 18, 2015, 05:10:42 PM »
I have Mach 3 V3.043.062 installed on my lathe and need to cut athread.  I input the thread parameters into the DROs and post the code.  The lathe is set up with the tool set to the stock diameter for X and Z=+3mm but tool well to the right of the chuck so it's cutting air for safety.  When I cllick Cycle Start the carriage heads at full chuff toward the chuck, to some very negative Z value that isn't in any of the code that I can see.  I E-stop the system quickly!  I don't think this should be happening, and it didn't happen when I tried threading a year or two back.  Can anyone advise please?

Also, on the "settings" page for the Wizard it asks for the "Splindle Direction" and the default is set to CW.  My lathe is a converted Myford so the usual spindle direction is CCW, just to verify that I should select "CCW", is that correct?  (For a right-hand thread of course.)

Thanks, John.

 

Offline RICH

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Re: Simple Threading - lathe heads for the hills...
« Reply #1 on: December 18, 2015, 08:17:40 PM »
Keep it simple and you will not go wrong. I don't know what your doing from start to finish....Here is what I do:

1. The part / tool setter is probed using the master tool to find the lathe center X and Z = 0 while in machine coordinates.
    Zero World X and Z buttons will set machine coordinates to zero.
2. Next I move away  to a desired home position, which also the tool change position and reference the machine.
3. Now I move back to  the part face / lathe center ( X & Z =0). So the part is just the same distance as the move away from it  for 2. above but negative values. With the controlled point at part face / lathe center I change to part coordinates and Zero the part. That creates a work offset
from home to the part.

All code generated is "always"  based on the part or stock  face / center.

Simplistically Mach needs to know where machine zero is and be referenced, and  then, it needs to know where the part is relative to home.

I have a write up for the generic screen on how to  use it to create a work offset based on manually touching off.

I think you may have a G54 in affect which is causing your problem. Every body works differently and there are a number of ways to do
things.  

Note, I don't use the generic screen ......it leaves something to be desired.

FWIW,

RICH
 

Re: Simple Threading - lathe heads for the hills...
« Reply #2 on: December 19, 2015, 05:43:38 AM »
Thanks Rich.  Looking at the code the wizard produces I see it has a "G00 G53....." in the second line which I see is a move in absolute coordinates.  I guess this is the cause of the problem as I don't home the machine, I always reference the tool to the material.

John.
Re: Simple Threading - lathe heads for the hills...
« Reply #3 on: December 19, 2015, 10:21:41 AM »
Also, on the "settings" page for the Wizard it asks for the "Splindle Direction" and the default is set to CW.  My lathe is a converted Myford so the usual spindle direction is CCW, just to verify that I should select "CCW", is that correct?  (For a right-hand thread of course.
Spindle direction is as seen from the opposite end from the chuck, ie: back side of the headstock.  Not sure why, it corn-fused me....but that's real easy to do.:)
Milton from Tennessee ya'll.
Re: Simple Threading - lathe heads for the hills...
« Reply #4 on: December 21, 2015, 06:25:16 AM »
I suppose it's based on thinking of the lathe like a mill on its side with the head to your left....
Re: Simple Threading - lathe heads for the hills...
« Reply #5 on: December 21, 2015, 08:02:42 AM »
I suppose it's based on thinking of the lathe like a mill on its side with the head to your left....
Never thought of it that way but that makes sense.  I always thought it was just me & my lack of knowledge.
Milton from Tennessee ya'll.