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Author Topic: G76 giving bad threads  (Read 5272 times)

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G76 giving bad threads
« on: August 13, 2009, 03:40:15 PM »
OK I have my licensed copy of mach on a very tight lathe (no unauthorized movement in any axis) I have my tool ( a new, sharp, 60 degree threading tool) perpendicular to, and in the center of, the 1" diameter 6061 tubing .25" thick workpiece riding 3" from the chuck. I run the program with 2 cleanup passes and taking .005 each pass (just to make sure) up to .050 depth at 86 rpm. My .05 pitch threads are all U shaped and the tops are cut off.

Any guesses?

« Last Edit: August 13, 2009, 03:43:45 PM by kdoney »

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Re: G76 giving bad threads
« Reply #1 on: August 13, 2009, 03:47:51 PM »
whats the infeed angle?

Hood
Re: G76 giving bad threads
« Reply #2 on: August 13, 2009, 04:02:05 PM »
I thought g76 always went at 29 degrees but I didn't see any evidence of it. The cross slide angle was the 29 just in case.

G0 G40 G18 G80 G50 G90
T101M6
G00  X1.025
G00 Z0
G00 X1
M03 S86
M08
G76 X0.95 Z-1 Q2 P0.05 J0.006 L45 H0.005 I29 C0.025 B0.0001 T0
M9
M5
M30

« Last Edit: August 13, 2009, 04:05:44 PM by kdoney »
Re: G76 giving bad threads
« Reply #3 on: August 13, 2009, 04:25:12 PM »
some photos

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Re: G76 giving bad threads
« Reply #4 on: August 13, 2009, 04:35:41 PM »
Yes it is set to 29 degrees, you can see that by the value for I in your G76  Just for kicks try setting that to 15 and see if it makes any difference, you can either just edit the code or you can click on the settings button in the wizard to set all the default parameters.

Hood
 
Re: G76 giving bad threads
« Reply #5 on: August 13, 2009, 05:34:14 PM »
I changed to 15 degrees and I can see no difference. Here's the photo

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Re: G76 giving bad threads
« Reply #6 on: August 13, 2009, 05:42:26 PM »
Afraid I dont have a clue, only time I have had problems with threading is when I set up the new computer and the sync wasnt enabled. That produces a very distinctive step on the trailing edge of the thread which doesnt show on yours so it doesnt seem to be that.

Can you try a piece of steel?

Also if you look in the m1076.m1s macro and alter the Test line to read true then it will output your code as G32 and see if it works fine with that. You will find the macro in the main Mach3 folder.
Hood
Re: G76 giving bad threads
« Reply #7 on: August 13, 2009, 06:43:34 PM »
I found it. Your test gave me the clue when it said RAD MODE. Looking in my Machinery handbook I found the minor DIAMETER for .05 pitch on 1" tube should have been .05. When I knocked the depth down to .025 it worked fine. Sorry again. I really do try to solve these things myself.

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Re: G76 giving bad threads
« Reply #8 on: August 13, 2009, 06:53:11 PM »
 I should have twigged that, even remember seeing you had Rad mode set when I looked at your xml the last day, only problem is I just remembered when you said it just now :D
 Dont worry about it, I wont tell you how many things I did to try and solve my step face issues on the threads, good thing is if it ever happens again I will know exactly what the issue is and I have already helped someone out when I saw a pic of their threads. Yours will also be noted mentaly and if someone has issues similar then the info will be there :)

Hood