I Need A CNC Threading for Dummies Book

That sounds like a canned cycle , although threading used to be G76 . That's inflation for ya . ;)
 
MontanaAardvark said:
Edit to add: I think the answer is yes.

In the sense that Mach3 has a "threading wizard" that writes a GCode snippet that cuts the thread using a G84 canned cycle. It doesn't do something like let me say, "4-40 external threads 0.150 long", but I enter starting and stopping diameters, thread pitch, end point, and a few other things.
Click to expand...
Excellent, this is pretty much what most conversational controls do, this is a Bridgeport control from the 90's.
Easy as could be, fill in the blanks.
It has a good deal of safeguards that will not allow certain moves in conversational mode but will do whatever you program in G code manually.
Anyone that knows how to run a manual lathe could be running this machine in hours.
 
P . To me , that looks confusing . I used a Funuc 6mb ( conversational programming ) on a Makino Count 15 back in the 90s . My codes were something like this .

G76 P1020060 X Z F
G76 P Q U W R

Been a long while ago , so I know this is not perfect :grin:

I miss that lathe . :frown:
 
G76 P1020060 X Z F
G76 P Q U W R

What could be less confusing then that (-:
1=External thread
2= Internal thread
Lead/TPI
Thread height/Full depth of finished cut
First pass DOC
Following passes DOC
Finish pass DOC
Spring cuts, just as one does on a manual machine, same finish diameter just dusting it off.
Withdraw is the distance that the tool will retract in order to clear chips
Engage Angle is like using the compound on a manual lathe, in the case of this thread it is a 1 1/4-4 Acme thread or 29 Deg. included
Start Z (.200") from the beginning of the part, same as a manual machine
End Z (13 3/8") from zero, same as a manual machine
Start diameter and end diameter are the same unless you are making a tapered thread, same as a manual machine

Anyone with a small amount of experience with a manual machine can run this.

It is fill in the blanks, no code and no math.
Simple manual operation done for you simply by filling in the empty text fields.
If one can not operate a keypad all bets are off
 
Yep , similar to the Fanuc , just fill in the blanks . :encourage:
 
If I can ask, then, what puzzles me is that my cuts look worse the closer I get to the chuck. I'm trying to figure out how to fix that.

It's not like they're the wrong pitch, it's like sometimes the cutter ends up in the wrong place. Look at the left end of this picture.

Long-10-32.JPG

(the bad focus will hurt your eyes if you look to the right - sorry)
See how there appears to be two different cuts? There's like a wrong number of peaks and they're shaped wrong. This is about a 3/4" long piece of 10-32 thread. It gets about the first half of the threads right, but the farther it advances to the left, the worse it does. I did this after I fixed the backlash but before I adjusted the G00 rapid moves to go faster

This seems like it could only be that it's calculating really wrong values for Z. I can't see how it could be the index pulse because they don't booger up the threads on the right and if they were wrong by a half or a quarter turn, I'd guess they'd mess up those threads but it would stay the same end to end.

Any ideas of what to look for?
 
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Have you tried cutting a larger thread , say a 1/2-13 or so ? If so , same results ? I would put an undercut in the back btw . I think I said it in an above post also , sometimes these small threads can be a PITA and end up looking like a plowed field . You get down to where the material can't support itself and trouble arises . 10s ? Should be no problem , but I did have to use dieheads on alot of projects just because of problems like this .

Try that 1/2" with an undercut and see what you come up with . :)
 
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mmcmdl said:
Have you tried cutting a larger thread , say a 1/2-13 or so ? If so , same results ? I would put an undercut in the back btw .
Click to expand...

I haven't cut a 1/2-13, but I've cut 1/4-20. Not as long, just half an inch. I think it would have showed up though.

First_qtr-20-12-19-18.JPG

I can try the 1/2-13 tomorrow morning.
 
The 1/4 looks better than the 10 . You have alot of excess stock sticking out of that chuck which multiplies your problems .
 
MontanaAardvark said:
If I can ask, then, what puzzles me is that my cuts look worse the closer I get to the chuck. I'm trying to figure out how to fix that.

It's not like they're the wrong pitch, it's like sometimes the cutter ends up in the wrong place. Look at the left end of this picture.

View attachment 283133

(the bad focus will hurt your eyes if you look to the right - sorry)
See how there appears to be two different cuts? There's like a wrong number of peaks and they're shaped wrong. This is about a 3/4" long piece of 10-32 thread. It gets about the first half of the threads right, but the farther it advances to the left, the worse it does. I did this after I fixed the backlash but before I adjusted the G00 rapid moves to go faster

This seems like it could only be that it's calculating really wrong values for Z. I can't see how it could be the index pulse because they don't booger up the threads on the right and if they were wrong by a half or a quarter turn, I'd guess they'd mess up those threads but it would stay the same end to end.

Any ideas of what to look for?
Click to expand...
I can only make some observations on this.
Whenever a machining process develops a change over a short distance such as above there are machine issues at play, otherwise the thread would be awful the entire length and not just at one position, speed an feed must remain constant in order to single point thread as opposed to facing a large part without CSS, the cut speed changes drastically in this case.
That being said there may well be a problem near the chuck where most of the work has been done in the past.
 
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