Looking for tips on three wire thread measuring

B

Boyd Allen

Active member
Preliminary to doing my own work I decided to get set up to measure tenon threads. Looking around on Ebay, I picked up a 1"-2" mic. and some thread wires. After they arrived I pulled a barrel out of the drawer, cleaned the Permatex anti-seize off the threads with some brake parts cleaner, and set about measuring. After dropping wires multiple times, I rigged them up with some tape at their ends, and managed to take a measurement. What I am looking for are tips as to how to do this more easily. Talk about awkward. It felt like doing a four handed operation with two hands.

One little sidelight. When I got the 1-2" mic. it came with a 1" standard. Measurement showed a .0004 discrepancy, so used the tool that came in the wood box, and adjusted the mic. till it read right on the money. Later I got to thinking about it, and pulled out my 1" mic, and measured the standard. It measured at about the same error as the 1-2" mic. had. ( and for that matter my dial caliper, which I found easier to ignore)Perhaps the standard is not standard. Now I need to have it checked. It never ends.
 
Get a copy of Machinerys Handbook for a good read on this.

Measuring over wires gives a better read than thread mikes.

Hint-use 2 rubber bands.
 
You are probably right Jerry. I use either a thread mic or I have threaded inserts that I use most of the time. When the Bat, Stiller, or Kelbly inserts screw on with the feel that I like, I call it good.
Butch
 
I went through the same troubles when I first got wires. Jackie offered a tip to use a dab of grease in the thread on each side and just set the wires in the grease. Works great and so simple.
 
easy to do

This is very easy to do , just set two wires into the top of the threads and leave one thread between the two wires. Then set the adjustable end (anvil) of the mic gently down on them level and make sure it is set close to the dia. then just run the third wire tip down the thread from the right wire down to the anvil on bottom while holding pressure on the two top ones, then just run it into the thread between the anvil and thread while adjusting down on the mic. Takes a little practice but is easy to learn. I usually put a shop towel or paper towel under the wires just in case I drop one.
good luck
 
Also...you might get a one-inch gage block from MSC. They have weekly specials, and you could probably get one for less than $25.00.
 
When you set your mic. or caliper to a standard, pull a piece of clean white paper through the contact points. Also do this with the contact points on the standard. In the machinery handbook you will find this Formula, M=D-( 1.5155 X P)+(3XW)
M= measurement over wires
D= maj. dia.
W = wire dia.
Some simple figures to write down
1 divided by no. of threads = pitch
pitch x .65 = depth of of thread
pitch x .75= depth of cut with compound @ 29.5 degrees.
minor dia. = maj. - 2 depths of thread
pitch dia. = maj.- 1 depth of thread
These are from some old notes I had.
 
When looking in the machinery handbook, they will tell you the three wires should be within
.00002 to hold a thread to .0001. We are not into guage making here, plus a set of wires to that tolerance will give you a real taste of sticker shock. There is a book by Martin Cleeve called screw cutting in the lathe. I feel this is the best source of information I have found.
 
Thanks fellows. This is all good stuff. George, I will have to get some modeling clay. I have some somewhere, but it may be faster to just go out and buy some more. As to wires, mine are cheap and off by a couple of tenths, but that gave me the idea of looking at the geometry with an eye to developing a formula for using any wire diameter that is consistent and close. That should knock some rust loose. I know that the way barrels are fitted that worrying about a couple of tenths is a waste of time. I just want to see if I can do it, work out the formula that is.
Boyd
 
Boyd,
Order an action insert from Stiller and Kelbly if you are doing Stiller, Kelbly, or Bat receivers. Use them as your go gauge. Hell of a lot easier than wires or a thread mic.
Butch
 
Someday I'll figure out why people don't just get a good set of thread mics and forget those things...
 
4Mesh said:
Someday I'll figure out why people don't just get a good set of thread mics and forget those things...
Click to expand...

+1

A good set of thread mics does not take a lot of magic to use. Then the threads are consistent to size from barrel to barrel to barrel-like using thread wires only easier.
 
I can also recomend thread mics. I have a 0-1" and a 1-2" in the same brand so that I only need one set of anvils. I have GO gages for the common receiver threads.
 
A thread mike is a piece of compared to wire's. You really need to go back to manual training 101.
 
I can read thread wires, I can read a thread mic. Why should I go back to what you call manual training 101 because I use a Kelbly thread insert to check the thread on a Panda thread tenon? Get real.
Butch
 
Butch...I didn't know BAT offered inserts that match their action threads?



Eddie in Texas
 
Eddie,
Both of my Bats measure with the dasterdly thread mikes are the same as the Panda. I use a Panda thread insert on them. The Stillers are very consistant, but I use a Stiller insert on them.
Butch
 
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