Threads not deep enough

rronald said:
Amazon brought me some thread wires today. It still amazes me that I can buy something that is incredibly specialized (like thread wires) and get them in a day (or even less if I were willing to pay $3.99 to get it by 8AM).

So, I used one of the online calculators for the three wire method and it said to use the ,032" wires and that the measured thickness of bolt and wires should be .5743".

I measured .5732 (the last digit is definitely a guess). I call being just over a thousandth off as a great victory. Especially given that my only measuring tool was a nut. And that nut happened to be the one holding down the QCTP....so each time I trial fitted it, I had to remove it from the QCTP, attempt to spin it onto the bolt I was cutting, and then return it to the QCTP without changing the position of the tool-post.

I had a lot of trouble the first time I measured with the wires. The bolt being measured was handheld, so I had to hold the bolt, the wires, and the micrometer.

I repeated the measurement a second time and (IMHO) made several improvements.
  1. Don't be a knucklehead and hold the threaded part being tested in your hands! I stuck it back into the collet on the lathe.
  2. All the pics I see for the three wire method show the two wires under the thread being measured and the single wire on top. Seems silly to me. You can see the harder side of the problem if the double wires are on top of the thread.
  3. found it far easier to install the two wires on top and close the micrometer on them w/o worrying about the third wire. Don't even pick that one up until the two side-by-side wires are (lightly) clamped in place by the micrometer.
  4. It's then easy to loosen the micrometer a tiny bit-just enough to slide in the single wire.
Thanks to all for the help! While I was able to cut a thread before, it was mostly due to luck and lot's of trial and occasional error. Now, I think that I'm armed with enough information to cut external threads reliably.
Click to expand...
You can use a small rubber band to hold the wires in place Or some modeling clay (just don’t get it between the wires and the threads).
 
You might want to take a look @ Joe Pie's thread measuring system. Beats the hell out of trying to use 3 wires!
 
Actually, modeling clay or grease on the threads is a great way to stick those wires in place! The pressure will smooth right through the clay.

They make little rubber bridges that snap onto your mic and hold the wires. Very nice

Sent from my SM-S911U using Tapatalk
 
ChazzC said:
Or new tool: thread mic with interchangeable anvils.
Click to expand...
Joe Pie's 1 wire method does work and it's a lot less fiddly than 3 wires. Different math though. I made a spreadsheet to come up with the desired readings.

Thread mics are a wonderful thing and a whole lot easier to use though. I have a 0-1" Shars thread mic.

Over 1" I use Joe Pie's method. Some day I'll get a 1-2" thread mic, but will still use the single wire method for the bigger stuff. Really can't justify the cost for the larger mics.
 
WobblyHand said:
Joe Pie's 1 wire method does work and it's a lot less fiddly than 3 wires. Different math though. I made a spreadsheet to come up with the desired readings.

Thread mics are a wonderful thing and a whole lot easier to use though. I have a 0-1" Shars thread mic.

Over 1" I use Joe Pie's method. Some day I'll get a 1-2" thread mic, but will still use the single wire method for the bigger stuff. Really can't justify the cost for the larger mics.
Click to expand...

Wait, can’t justify the cost of a tool? The only tools I’ve ever been able to justify were those few needed to fix something my wife wanted fixed (or to help with a school project).
 
WobblyHand said:
Thread mics are a wonderful thing and a whole lot easier to use though. I have a 0-1" Shars thread mic.
Click to expand...
I have that size from Shars, but in metric. I plan on getting the next size up as well, but will probably use wires for anything larger. Looks like i need to replace my mill spindle bearings, so that will need to wait a bit longer.
 
I have 0-1" and 1"-2" (Shars) thread mics, but find myself using wires more often - they often seem more convenient to me for a one-off. I keep my mics set up for a couple of common threads (that I don't seem to cut so often anymore...), but changing them over seems like more of a hassle than using wires. YMMV, of course.

GsT
 
rronald said:
Amazon brought me some thread wires today. It still amazes me that I can buy something that is incredibly specialized (like thread wires) and get them in a day (or even less if I were willing to pay $3.99 to get it by 8AM).

So, I used one of the online calculators for the three wire method and it said to use the ,032" wires and that the measured thickness of bolt and wires should be .5743".

I measured .5732 (the last digit is definitely a guess). I call being just over a thousandth off as a great victory. Especially given that my only measuring tool was a nut. And that nut happened to be the one holding down the QCTP....so each time I trial fitted it, I had to remove it from the QCTP, attempt to spin it onto the bolt I was cutting, and then return it to the QCTP without changing the position of the tool-post.

I had a lot of trouble the first time I measured with the wires. The bolt being measured was handheld, so I had to hold the bolt, the wires, and the micrometer.

I repeated the measurement a second time and (IMHO) made several improvements.
  1. Don't be a knucklehead and hold the threaded part being tested in your hands! I stuck it back into the collet on the lathe.
  2. All the pics I see for the three wire method show the two wires under the thread being measured and the single wire on top. Seems silly to me. You can see the harder side of the problem if the double wires are on top of the thread.
  3. found it far easier to install the two wires on top and close the micrometer on them w/o worrying about the third wire. Don't even pick that one up until the two side-by-side wires are (lightly) clamped in place by the micrometer.
  4. It's then easy to loosen the micrometer a tiny bit-just enough to slide in the single wire.
Thanks to all for the help! While I was able to cut a thread before, it was mostly due to luck and lot's of trial and occasional error. Now, I think that I'm armed with enough information to cut external threads reliably.
Click to expand...
A few thread ring gages in commonly used sizes would help too.
 
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