Noob Lathe question

[within a thou]

I am new to lathe I have always been a mill guy so please bare with me if this is a stupid question.

 

When using full topping inserts is there a formula for min (on external) and Major (on internal) to compensate for the form of my insert.

 

I use Coromat 266 bars and external holders with the 3 sided single point inserts.

 

Usually I trial and error where I set my X offset go to what nominal size should be and keep adding cuts till my guage or pitch mic reads properly. There has to be a easier way to do this.

 

Thanks in advance for any help.

[crazy^millman]

Are you using the threading process in Mastercam? I have always been pretty close using it for years. Never perfect, that is what offset adjustment is for. I normally cut it once check size make my adjustment and go to town. Got a sample file you can share so we can see what your specific issue is?

[within a thou]

Are you using the threading process in Mastercam? I have always been pretty close using it for years. Never perfect, that is what offset adjustment is for. I normally cut it once check size make my adjustment and go to town. Got a sample file you can share so we can see what your specific issue is?

 

I am manually programmking on a 1981 Fanuc 6T control. The only threading cycle I know that works on this is G92. I will attach a proven program I used for a 1.5"-6UNC internal thread. If anyone knows a better way I am all ears.

 

As for what I am about to start now it is a 3"-4NC internal x 4" deep. Yes I know my sfm is way low but the machine is 32 years old and doesn't move very fast if my rapid hits 250ipm I would be surprised.

 

O1020

G28 U0 W0

T1200

G50

M41

G50 S300

G97 S300 M3

G90 G0 T1212 X1.25 Z.25 M8

G1 X1.28 Z.2 F.1667

G92 X1.3 Z-2.25 F.1667

X1.31

X1.322

X1.33

X1.34

X1.35

X1.357

X1.371

X1.385

X1.399

X1.413

X1.427

X1.44

X1.45

X1.458

X1.465

X1.471

X1.477

X1.483

X1.488

X1.493

X1.499

X1.502

X1.506

X1.51

X1.51

X1.51

X1.515

X1.515

X1.52

X1.52

X1.525

X1.525

X1.53

X1.53

X1.535

X1.535

X1.537

X1.537

X1.537

X1.54

X1.54

X1.543

X1.543

X1.547

X1.547

X1.55

X1.55

X1.553

X1.553

X1.553

X1.556

X1.556

X1.56

X1.56

X1.56

X1.564

X1.564

X1.564

X1.564

X1.564

X1.564

X1.564

X.1564

X1.564

X1.564

G0 Z2. M9

G28 U0 W0

M30

[crazy^millman]

Have you tried the G32? Been years since I programmed a T6, but I thought the G76 cycle was available as well on those machines.

 

Here is some sample code from Mastercam a couple different ways.

 

T10504
G98
M29
G97 S300 M03
G0 X2.5294 Z.2459
G76 P010060 Q0 R0.
G76 X3. Z-4. P1353 Q471 R0. E.25
G0 G28 U0. M05

 

Then Longhand:

 

T10504
G98
M29
G97 S300 M03
G0 X2.5294 Z.2459
X2.8342
G99 G32 Z-4. E.25
G0 X2.5294
Z.2307
X2.8893
G32 Z-4. E.25
G0 X2.5294
Z.2189
X2.932
G32 Z-4. E.25
G0 X2.5294
Z.2088
X2.9681
G32 Z-4. E.25
G0 X2.5294
Z.2
X3.
G32 Z-4. E.25
G0 X2.5294
Z.2
X3.
G32 Z-4. E.25
G0 X2.5294
Z.2459
G0 G28 U0. M05

 

I assume the G92 would do the same thing as the G32.

 

HTH

[within a thou]

I will give it a try and let you know thank you. As for trying the other cycles no I have not. there was a sample threading in the control along with notes showing other cycles but all for a Fanuc 11 and I just went with it what was in the control.

[within a thou]

Ron, I chickened out using your code as I only had one bar big enough to hold a 4TPI insert. What scared me was the number of cuts and stalling out the machine. It is taking me 40 passes to cut this thread and my X is set at +.02