How to choose correct tool to re-thread stripped bolt?


Trying to assist a friend with the repair of a piece of exercise equipment. Someone stripped a threaded part. See the post sticking straight up from the cylindrical part in the picture?
http://i27.photobucket.com/albums/c197/ancientangler/PivotTube.jpg?t 53112064
Exactly what's the name of the re-tapping tool I need to look for, and how to do choose the right size? I can determine the original thread size by removing the non-stripped one from the other side of the machine. What's next? Are these tools designated in the same size as the stripped bolts or nuts?
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wrote:

You want a "die." Take the non-stripped one with you to the hardware store and the "helpful hardware man" can measure the piece and help you select the right sized die. And yes, the tools are designated in the same size as the stripped bolt or nut, e.g., 7/16 x 20. A die can clean up the threading on a stripped bolt but it can't add material back.
Tom Young
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wrote:

You want a "die." Take the non-stripped one with you to the hardware store and the "helpful hardware man" can measure the piece and help you select the right sized die. And yes, the tools are designated in the same size as the stripped bolt or nut, e.g., 7/16 x 20. A die can clean up the threading on a stripped bolt but it can't add material back.
Tom Young ================ Thanks, Tom.
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wrote:

There are a couple ways to fix this thing.
First, you need to determine the screw size & pitch (threads per inch) and also determine if its imperial or metric.
If you dont have thread pitch gage and a means to measure the screw diameter (to the nearest 1/16)
(http://www.opentip.com/Tools-Auto-Industrial/Thread-Pitch-Gage-Set - p-527516.html)
you can take the undamaged unit to the hardware store & try differnet nuts on it until you find one that fits.
I'm guessing that (if its imperial) the size & ptich is going to be one of the following
5/16 - 18 3/8 - 16 1/2 - 13
or if metric 8mm, 10mm or 12mm
next you'll need a thread cutting or thread chasing die (the tool that can cut or clean up thread) the easiest type to use would be one that has a an external hex shape (so oyu can use a socket or wrench & avoid having ot buy a die handle)
One of the drawback of a die, is that you can only get "kinda close" to the handle on a threaded stud situation.
Also if the threaded are completely buggered up, then there may not be enough material to resurrect the threads :(
If the threads need to be good all the way to handle & they're still kinda ok there....you can use a thread file to clean them up
If all of this fails..........
and this thing is just a "keeper screw & handle" you might be able to find a stock palstic knob with a threaded stud
or
cut off the stud, drill it out, tape the hole (with a tap) the correct size & loctite (red) in a new stud (cut off bolt)
cheers Bob
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*A die would work, but I have something that has worked on bolts and rods if only a few threads are partially damaged. It is called a thread restoring file. I think that I got it from McMaster-Carr years ago.
There are thread gauges that you can insert into the grooves to determine the thread count.
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You want what is called a thread restorer They are available at Sears, auto parts stores, etc. It also obviously depends on how mangled the thread are. Unless they are real bad, it should work.
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wrote:

A Die *might* work but a better tool is a thread file. Most come with many different sizes all on one tool.
http://commons.wikimedia.org/wiki/File:Thread_file.JPG
You just find a good spot on the stud and work your way around following the existing good threads and cleaning up the bad threads.
Works great lasts long time.
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JoeSpareBedroom wrote:

I have often just used just a nut to fix threads. Put the bolt in a vice and start the nut. Use plenty of oil and a big wrench and thread the nut on, screw it all the way down and back several times. Be careful not to cross thread it or you will wreak the threads worse.
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Van Chocstraw wrote:

Cut some slots across the threads of the nut and it will work better. It does for me.
TDD
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wrote:

You may have more trouble than you know. Make sure the nut isnt stripped too. You will probably need a bottom tap to repair that.
Jimmie
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wrote:

Call the manufacturer and find out how much a new part would cost. They might even give it to you for free.
If the threads were truly stripped, they'll just be more likely to fail again even if you "clean them up". You might be able to make them look better, but don't think that you're really fixing or restoring anything.
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wrote:

Call the manufacturer and find out how much a new part would cost. They might even give it to you for free.
If the threads were truly stripped, they'll just be more likely to fail again even if you "clean them up". You might be able to make them look better, but don't think that you're really fixing or restoring anything.
================== The manufacturer sucks - Horizon Fitness. Five voice mail messages and two e-mails & still no response. The part is no longer available at one site which sells parts for exercise equipment. But that's OK. I mentioned this to my excellent auto mechanic, who said "Why buy the die or some other tool? Bring the part when you come for your oil change next week." These guys love the occasional non-automotive challenge. Try that with Jiffy-Lube. :-)
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