taper pipe threads on lathe

[cherokeechief79]

i have to cut taper pipe thds 3/8 and 1/4 both 18 pitch on a hyundai lathe with a siemens 840 control.i never was able to get mc to post properly to this machine but it is very easy to do what we need to do on the conversational siemens control.is there a chart or something somewhere that gives the taper in dimensions for these 2 threads?if not im sure i can find something in the machinery handbook.

thank you

mark

[elbro]

Taper is 1 deg 47 minutes per side of all american tapered pipe threads.

[cherokeechief79]

thanks im still a little confused about how much "flat to leave on the thred tops"does anyone have the "start dimensions for 1/4 and 3/8? thank you mark.

 

 

i did find this but im still a little confused web page

[Carl Vallance]

OSBORN PRODUCTS INC.

.............DATA FOR PIPE THREADS.............

 

................. 3/8-18 NPT ..................

 

Outside diameter of pipe....................... 0.6750

Threads per inch............................... 18.0

Decimal lead................................... 0.05556

P.D. at beginning of external thread (E0)...... 0.61201

Length of handtight engagement (L1)............ 0.2400

Number of threads engaged...................... 4.32

P.D. at length of handtight engagement and at

gaging notch or large end of internal thread(E1) 0.62701

Effective thread length of external thread (L2) 0.4078

Number of threads in effective thread length... 7.34

P.D. at effective thread length, external (E2). 0.63750

Length from handtight engagement to effective

thread length.................................. 0.1678

Number of threads from handtight engagement to

effective thread length........................ 3.02

Wrench makeup length for internal thread (L3).. 0.1667

No. of threads in makeup length for int. thd... 3

P.D. at makeup length for internal thread (E3). 0.60159

Vanish thread length........................... 0.1928

No. of threads in vanish thread length......... 3.47

Overall length of external thread.............. 0.6006

Nominal complete external thread length (L5)... 0.2967

P.D. at nominal complete ext. thread length(E5) 0.63055

Height of thread............................... 0.04444

Increase in diameter per thread advance........ 0.00347

Width of flat is...................from 0.0021 to 0.0057

Run date is 06-27-07

 

 

OSBORN PRODUCTS INC.

.............DATA FOR PIPE THREADS.............

 

................. 1/4-18 NPT ..................

 

Outside diameter of pipe....................... 0.5400

Threads per inch............................... 18.0

Decimal lead................................... 0.05556

P.D. at beginning of external thread (E0)...... 0.47739

Length of handtight engagement (L1)............ 0.2278

Number of threads engaged...................... 4.10

P.D. at length of handtight engagement and at

gaging notch or large end of internal thread(E1) 0.49163

Effective thread length of external thread (L2) 0.4018

Number of threads in effective thread length... 7.23

P.D. at effective thread length, external (E2). 0.50250

Length from handtight engagement to effective

thread length.................................. 0.1740

Number of threads from handtight engagement to

effective thread length........................ 3.13

Wrench makeup length for internal thread (L3).. 0.1667

No. of threads in makeup length for int. thd... 3

P.D. at makeup length for internal thread (E3). 0.46697

Vanish thread length........................... 0.1928

No. of threads in vanish thread length......... 3.47

Overall length of external thread.............. 0.5946

Nominal complete external thread length (L5)... 0.2907

P.D. at nominal complete ext. thread length(E5) 0.49556

Height of thread............................... 0.04444

Increase in diameter per thread advance........ 0.00347

Width of flat is...................from 0.0021 to 0.0057

Run date is 06-27-07