Hello,

I'm curious what others are doing for accurate design profiles for threads, internal and external. I know some use the SW thread tool, I'm not asking about this, I'm aware of it and know how to modify the profiles and use it, not what I'm after.

How are you dimensioning the thread sketch profile using the data form a calculator or Machineries Handbook? I get the form is simple, it's a truncated triangle or a triangle with a radius, but it really depends on the tool making the threads. Assume machined thread with root radius for the moment. There are several ways to 'define' the sketch using the values provided in the book or from the calculators. 

• dimensioning the pitch diameter + root radius
• dimensioning to the root radius + tangent of the root radius to be the Minor diameter?
• dimensioning to height of the profile or width of root, truncation of triangle...etc. etc.

It seems the 'proper' way to measure the threads is based on the pitch diameter over wires. But the machinist only knows the tip of his tool position and it's radius. So is the 'proper' way to dimension the sketch to the tangent of the root radius with the root radius specified?

If anyone has a sketch or nut + bolt thread assembly they could share containing proper design profiles using values from a published source, I would really appreciate it.

Here's an example of an M28x1 thread I'm working on. Calculator is METhreadPal. The sketch shows the full root radius 0.144*P and the Minor Diameter (max) used to define the thread with a driven dimension showing the Pitch Diameter to ensure it falls in the range specified.

Would you do this differently?