Metrology/Calibration Technician

I am not familiar with the 2 wire method. I am familiar with 3 wire. Am I missing something?

Have a read through this little link!

As stated, it is a three wire, not two wire way of measuring the pitch diameter of a thread!

That's the way it's done. Nothing fancy. Of course a thread mic also works very well. I have been responsible for calibration of plug gages of many sizes and types and have found it to be quite straightforward.

cr3

Any idea what the "n" in the formula for calculating best size wire is?

2. PITCH

-This is the distance from a point on the screw thread to a corresponding point on the next

thread measured parallel to the axis of the thread. It is represented by the letter p. (p=1/n).

p=1/n

you know the pitch 'p', so n=1/p

Now I'm confused, (not hard to do ). p=1/n ≠ n=1/p

After reviewing this formula some more, I'm thinking n=threads per inch, (TPI)

Plug in the numbers for 18 TPI

p=1/18 p=.0555 (the machinist hand book has it at .0555)

So to calculate best size wires where G=wire size and .57735 is the constant for 60 deg thrd.

G=.57735/18 = Ø.032 wire. (Machinist hand book has pitch line at .0321)

I might have answered my own question but it doesn't discount that people say that I'm just a very confused person!

That's what it looks like to me too! I prefer the ovee gauges, easier to hold, don't have to mess around looking for 3 bits of wire the same size and of a specific diameter, it's all there in one handy spring like gauge!

I'm a thread mic guy although I have not used the Ovee.

The 3 wire can get a bit tricky - the math is straight but the diameters are not.

3wires and a mic can be tough on small or large threads.