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11th Oct 2021, 02:55 PM #1New Member
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Damaged Threaded Shaft - Rethreading?
I have a threaded shaft with damage meaning the corresponding nut won't engage. I think it is just the top and one-two starting threads that are damaged.
Pics below.
It's about 14mm across (might be imperial) and most die sets I can find stop at M12. Never tried cutting new thread before and am a bit reluctant to have a first go at something I can't easily find a replacement for.
I've called a few engineering shops I can find and some might be able to assist by machining new thread.
Does it looks like something I could DIY with something I'm missing, or do a need a new one machined?
IMG_20211011_101008.jpgIMG_20211011_100942.jpgIMG_20211011_100911.jpgIMG_20211011_100846.jpg
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11th Oct 2021, 04:37 PM #2Member: Blue and white apron brigade
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If you have access to a belt sander or finisher I would try carefully grind a bevel on the end of the treaded shaft that grinds away the damaged threads.
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11th Oct 2021, 05:05 PM #3Golden Member
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This is the type of job where a Thread File is invaluable,
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11th Oct 2021, 05:06 PM #4Senior Member
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I did a very similar repair using a thread file. A slight deformation on the lead in made it impossible to start a die with any confidence.
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11th Oct 2021, 05:07 PM #5New Member
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Yes Bob - Do have a standard GMC belt/disk sander.
Right, could just slowly bring the very tip to the side of the belt and try to grind away just the 1st/2nd thread and try not to hit the next
Yes - Had seen a thread file, but thought the damage might have been too much. Or difficult if it is imperial
Tried the smallest triangle file I had, felt I still might have been hitting the thread below. Could be technique
Hmm, not a lot of thread there to practice on!
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11th Oct 2021, 05:10 PM #6Most Valued Member
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A small triangle file and half a beers worth of filing will guarantee you dont hit the next thread...
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11th Oct 2021, 06:10 PM #7Member: Blue and white apron brigade
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It doesn't matter if you hit the next thread or even 2 with the sander or the file.
When I cut bolts with a thin kerf cut off saw,. if I remember I put a nut on below the cut, then when it's cut I take the burr off by removing the nut.
BUT
I usually forget to put the nut on before cutting so then I use the Linisher with a fine grit paper and round over the end. My cut off wheel and Linisher are on the same grinder so I literally move it from one to the other.
For awkward situations where its difficult to get the nut started I sometimes grind a 2-4 thread long taper on the end of the bolt to help the nut find the tip of the bolt. I've never had a problem with cross threading doing this.
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11th Oct 2021, 06:13 PM #8
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11th Oct 2021, 06:25 PM #9Golden Member
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The problem with butchered shafts like this is that it is not only the Major diameter of the thread that is "mushroomed" slightly, but also the minor diameter, so cleaning up the O/D may not be enough to get the nut started.
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11th Oct 2021, 07:50 PM #10Senior Member
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What is the diameter of the thicker section of the shaft?
If it is less than 26mm (the spindle hole size of my operational lathe) and you can wait until we are let out of detention in metro Melbourne (hopefully only a few weeks away), I would be happy to see how well it would clean up on the lathe by picking up on the good part of the thread.
That should also clean up any minor diameter issues mentioned by Techo1.
Ray
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11th Oct 2021, 08:18 PM #11Senior Member
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I would first try using a split die if i had one of the correct thread.
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11th Oct 2021, 09:07 PM #12Golden Member
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I am in Mount Waverley and I can help if you are not too far from me? Maybe it is better off to put on highest speed then spin the chuck by hand.
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13th Oct 2021, 08:26 PM #13
Hi FlaminGunz
If you are having difficulty in identifying that your thread is metric or imperial, the best way might be to take it to a dedicated fastener supplier. By dedicated , I mean that nuts and and bolts are their main product/s.They often carry single dies- I don't know about the die nuts.Probably a enginneering tools shop might be the best place to look for them
They have tools to measure thread pitch and diameter and will happily identify your mystery thread and sell you a die nut or even a die if it comes to that.
Apart from the problem of getting there- lockdown?? there is are other snags in this plan.
A die nut is a hex shape and is used to repair damaged thread -not to cut a new thread from a bare steel shaft. You can use a shifter to turn it.
However,there is also a round die nut , sometimes referred to as a thread chaser and has to be held in a decently strong die wrench, so that is an extra expense. Note that it has no split in it unlike the threading dies in your set. Pics below of both types.
You may think you might buy the same die diameter as your existing set. While the die may fit the circular aperture of the smaller wrench ,the wrench may be too small across the handles to have effective leverage. Some of these die wrench handles are made from die cast zinc and are not very robust.
I take it that the shaft is not too heavy to carry around. You could take the nut instead. I am pretty sure they should be able to ID that .
If you can get it to one of the fastener shops they at least can tell you what the thread is, even if the don't have a die to sell you.
The lads here can advise you on a local engineering tool shop once you get a id on the thread.
Does this help?
Grahame
Die nut hex.com.jpg Round die nut com.jpg
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18th Oct 2021, 09:19 PM #14Diamond Member
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There are also square ones:
IMG_2050.jpg
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20th Oct 2021, 10:55 AM #15New Member
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Just an update - success!
Pics - https://imgur.com/a/mW8HmYN
I ended up taking BobL's advice as it was the simplest with the tools I have available.
Now just need to sort out putting the tablesaw back together
Thanks all for the tips and offers of assistance, will keep in mind next time I am inevitably stuck.
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