G76 Canned threading cycle

G76- Canned threading cycle.

G76 P010060 Q0020 R0005 (first G76 sets parameters for threading)
G76 X Z P Q F R (cuts the thread)

No decimal point allowed in P and Q values

The first G76 isn’t needed but is recommended.
– G76 P Q R

P010060 sets 3 things
– first 2 digits is the number of finish passes – 01 Stored in Param 5142

– second 2 digits is the chamfering amount % of the lead or pullout exiting the thread- 00
00 = almost no angle at pullout and 99 = 9.9 leads away start out (param 5130)

– third 2 digits are the angle of tool tip (infeed angle is actually 1/2)
0,29,30,55,60,80 are usable (Use 55 or 60 infeed to reduce burrs)(param 5143)

Q0030 (Q30 =.003″) sets the minimum depth of cut in Radius, omit decimal point
(good for stainless) (stored in Param 5140)

R0010 or R.001 (R10 = .001″) sets the finish pass amount(+, radius)

The second G76 cuts the thread.
-G76 X.1876 Z.3 P0302 Q0100 F.05 (R-.002) FOR 1/4-20

X.1876 =Minor Dia. of thread at start point in front of part

Z.3 or (W) =The ending Z of the thread including chamfer.

P0302(P302) =Height of thread in radius (Maj-Min)/2 (+, radius, omit decimal point)
Metric thread P= .6495 x pitch
Whiteworth P= .6403 x pitch
Unified thread P= .6134 x pitch
Gas thread P= .6403 x pitch

Q0099(Q99) =depth of the first cut in radius. All the rest of the cuts are calculated.
(+, radius, omit decimal point)

F.05 =Feed-rate 20 TPI 1/20=.05

R = R is optional for tapered threading. R is the amount of
difference in X from start to finish in Z.
When cutting OD thread moving Z and X in a positive direction R is a negative value. Decimal allowed

Note: the maximum IPM should be 200 or less. I was able to run at
1400 rpm on a 6 TPI(1400rpm x .16667 ipr = 233 ipm) if I started
2 threads in front of part. Anything over this caused droop of
first threads. 1800 rpm worked on 12 tpi.

If you have very long threads and want to segment the thread:
1. Set chamfer off with M35.
2. Set the pullout % to 10 on the first G76 line second two digits.
Example: Front turn .600″. Thread the first .5″ Turn to z1.1, Start
second G76 one lead back from end of first thread to allow re-cut and
thread to Z1….

Note: Specify P2 for staggered infeed Threading. Must be in FS15 tape

Taper is 1/16 in PT thread =1.79 degrees

If Parameter 3401.0 (DPI) is set to a 1 then Decimals must be used.
If then no decimal is allowed as noted above.

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