Threading question

[PBMW]

I'm going to ask a stupid question. But what the heck
I'm threading some parts. This looks like a wood screw. Sort of.
Dia at nose is .12
Dia at big end is .375. Threads are 1.4 long
This is a tapered thread.
This is what I got in Mastercam:

(TOOL - 7 OFFSET - 7)
(COPY (SLOT #4) OF OD THREAD RIGHT INSERT - NONE)
G0 T0707
G97 S200 M03
M8
G0 G54 X.575 Z.2119
G76 P010029 Q0. R0.
G76 X.0484 Z-1.4 P350 Q138 R-.1467 F.05556
M9
G28 U0. W0. M05
T0700


This didn't work.
Am I supposed to have the small dia on the G54 line and the .375 on the second G76 line?
Not sure about the R value being -.1467 either.

Never done any tapered threads before. So this is just a little new to me.

[Geof]

I would need to stand up and pull a manual of the shelf to be sure, (I am sitting doen drinking a latte ) but I think in G76 your R value is the radial difference between the small diameter and the large diameter on a tapered thread, and the X on the G76 line is the small diameter; in your case X0.12 which gives R0.1275.

Maybe I should stand up and get the manual; this disagrees totally with your code.

Mind my experience is on Haas, which machine are you programming for?

EDIT: Too lazy to get up, look in your own manual

[PBMW]

Not too lazy Geof
Too confused. It's a Fanuc
I cured it though by using G32's. That worked out just fine...

[SeymourDumore]

Your first G76 line has a Q0. That is a min. DOC value.
I know if you omit it completely, the default from parameters takes over. In this case though you specify it to be 0. Not sure!?!

The R in the second line specifies the taper amount in radius value, and is used to calculate the large diameter at the end. It is a little unintuitive though. It is in fact a negative value for a typical OD thread, and positive for a typical ID thread. It signifies the signed distance from the (calculated) end diameter to the starting diameter.
In your case the starting diameter is X.0484, which is the minor diameter at Z.2119.
Your minor diameter at Z-1.4 will be (according to the code posted)
(.1467 x 2)+.0484=.3418 diameter.

I would think that your posted code should work with the Q changed to something like 30 or so. About the only change I'd suggest is to make the starting diameter before the G76 calls to be smaller, perhaps .06 or so in this case, provided the taper is already turned onto the stock.

This should work:

G54
G00 G97 T0707 S200 M03
G00 X.06 Z.2119
M08
G76 P010029 Q30 R0
G76 X.0484 Z-1.4 P350 Q138 R-.1467 F.05556
M09
G28 U0. W0. M05