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How to make female BSPT

Question asked by Foad Sojoodi Farimani on Jul 11, 2017
Latest reply on Jul 12, 2017 by Casey Bergman
  • There are tones of posts about making BSPT threads but:
    1. Most of them show how to make the male part (external thread)
    2. They do not include any tolerances
    3. They do not include the  taper internal thread (female)  Rc ISO 7


  • Why is it important for me? I have a 3D printed part from ABS which is fragile and prefer to have the threads 3D printed not machined. and I want to have the female tapered so the 3D printing inaccuracies will be compensated.
  • My questions:
    1. how to draw the profile? should it be aligned to the coordinate system or the tapered cone? in the picture below I have drawn both. should it be like (a) or (b)? BSPT.png
    2. how much the α needs to be? according to some sources it is 1 inch over 16 inches but I have no idea what that mean? is it like α=atan(1/8)? and other sources say it is just  1 degree and 47 minutes equal to 1.78333 degrees
    3. what does clockwise and counterclockwise means? so if I look from top to the hole I want to thread, the helix should go clockwise or counterclockwise?
    4. what should be the pitch diameter of the female considering the tolerances?


I have drawn the BSPT 1/8 inch in SolidWorks including the parameters and common equations. you may see it in the attachment.