Threading With Pictures

[Cadillac STS]

Measure the PD over wires, a thread wire set will be the cheapest tool that you will EVER BUY. The book that has all of the thread dimensions will cost way more.
The Pitch Diameter is the most important dimension, measure it.

You mean like this?

 

[Wreck™Wreck]

Exactly, however I would not use a caliper for this so I use a micrometer which tends to keep the wires out of the soup. Also put something across the ways under the part to catch the wires when you drop them because you will drop them. I use a plastic bin.

 

[T Bredehoft]

You can't drop the pins if you first stick them into a piece of styrofoam..... not my idea, but I'll never use thread wires again without it.

 

[chevydyl]

A note on spring, I recently turned an 1.5-8 thread Gage and I probably made 3-5 spring passes after every compound adjustment because of the large course thread, at that size .001 is ALOT of stress and force.
One thing that may help you determine when your "there" is to cut a relief on the nose or the back of the thread that is the same as the minor diameter, when the tool makes a scratch in it, it should fit or almost fit, you may need to do a couple spring passes.

Also the is different classes of fit, 1,2,and 3, the latter being closest tolerance, the nuts from the hardware store may be a 2, while the thread your cutting is a 3 and won't fit based on you threads cut are the size you intended them to be.

 

[British Steel]

You can't drop the pins if you first stick them into a piece of styrofoam..... not my idea, but I'll never use thread wires again without it.

I prefer a wine cork, grips the wires better, and a good excuse to open a bottle

 

[Wreck™Wreck]

I prefer a wine cork, grips the wires better, and a good excuse to open a bottle

1 15/16-12 thread, to big for a cork but I like your thinking. If I have to measure a lot of large threads I tape 2 wires together loosely with masking tape to a piece of string which is then taped to the third wire, works a charm.

Also opening a bottle of wine at work would probably get me fired (-:

 

[Cadillac STS]

A note on spring, I recently turned an 1.5-8 thread Gage and I probably made 3-5 spring passes after every compound adjustment because of the large course thread, at that size .001 is ALOT of stress and force.
One thing that may help you determine when your "there" is to cut a relief on the nose or the back of the thread that is the same as the minor diameter, when the tool makes a scratch in it, it should fit or almost fit, you may need to do a couple spring passes.

Also the is different classes of fit, 1,2,and 3, the latter being closest tolerance, the nuts from the hardware store may be a 2, while the thread your cutting is a 3 and won't fit based on you threads cut are the size you intended them to be.

That is a great idea! You would cut a relief anyway so the thread can cut into air at the end so why not cut it at the minor diameter?!