Threading math question….

[Stephen S]

Hmm, haven’t tried the foam method.

In some of the shops I have worked in have called out what is referred to as bastard threads. At the time the only way I had to measure was thread wires.

 

[mmcmdl]

Like I said . A set is under $15 and will cover the gamet of sizes . They're simple to use also .

 

[OTmachine]

I find my thread wires in my chip pan . They are a bit of a PITA
Since I have 7 fingers, I struggle even more than most trying to use thread wires.
Once I learned how to use these thread mics, I find measuring thread depth much easier. This set covers 0-2” diameter and all the popular threads per inch.

This Shars set was not too bad $$$.

If you use these, as I do also at times, you need to verify / calibrate them before each different thread pitch range. Usually, I will just match a good section of the threaded part that I am replacing’s major diameter & pitch diameter, so that I know it will work.

 

[MrWhoopee]

Hmm, haven’t tried the foam method.

A lump of modeling clay also works.

 

[mac1911]

Regardless of what you dial in , you're after the pitch diameter . Thread wire sets are $15 , invest in a set to save all the hassles .

Its on the list. In operating basically on a -0 budget .
I figured for the amount if threading I will do I can put those off and purchase more needed items. Right now fun money is depleted to negative territory , lol.

 

[mmcmdl]

Right now fun money is depleted to negative territory , lol.

And it always will be in this trade/hobby , but at least we have fun while being broke .

 

[RJSakowski]

For those who have trouble managing three wires and a micrometer, pitch diameter can be measured with a single wire.

There is a less cumbersome way to measure pitch diameter that is only slightly less accurate. It involves using a single wire. First measure the major diameter of the thread. It doesn't have to be geometrically correct but it should be uniform across the thread. Then insert one wire and measure across the thread and the wire. The M value in the Pee Dee chart is equal to 2 x the second measurement minus the first measurement.

This value is the same one that you would measure with three pitch wires (labeled M in the Pee Dee chart and Machinery's Handbook). You still have to go back to the table that is furnished with the pitch wires or to Machinery's Handbook to determine the actual pitch diameter based on the thread pitch, the value of M and the diameter of the wire.

 

[f350ca]

A small dap of light grease will stick the wires in place. There may be a slight error due to the grease film thickness but it seams negligible.

Greg

 

[Janderso]

For those who have trouble managing three wires and a micrometer, pitch diameter can be measured with a single wire.

There is a less cumbersome way to measure pitch diameter that is only slightly less accurate. It involves using a single wire. First measure the major diameter of the thread. It doesn't have to be geometrically correct but it should be uniform across the thread. Then insert one wire and measure across the thread and the wire. The M value in the Pee Dee chart is equal to 2 x the second measurement minus the first measurement.

This value is the same one that you would measure with three pitch wires (labeled M in the Pee Dee chart and Machinery's Handbook). You still have to go back to the table that is furnished with the pitch wires or to Machinery's Handbook to determine the actual pitch diameter based on the thread pitch, the value of M and the diameter of the wire.

Great idea.
See, always one of the smartest guys in the room

 

[benmychree]

I have wires and thread mikes, but usually just use a nut to check size; we are not making rockets to the moon here. I do, however run a tap through the nut before using it for gaging. Sometimes I may make a gage from round stoch, knurled on the OD to ensure a good fit, using a new sharp tap.