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mainshaft thread pattern

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Old Oct 12, 2007 | 07:05 PM
  #1  
pdaly13's Avatar
pdaly13
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Default mainshaft thread pattern

Hello.1980 4-speed tranny.I messed up the threads on the mainshaft under the clutch hub nut. Looking to get a die to clean them up. I'm guessing 3/4 inch, 18 threads per inch, left-hand thread. But, I don't really know how to tell for certain. Can anyone help me get the info for ordering the Right one?
Thanks,
Pat
 
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Old Oct 12, 2007 | 07:50 PM
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1flhtk4me
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Default RE: mainshaft thread pattern

I dont know the size but you can measure it.
Measure the OD of the thread with a dial caliper or mic.Then measure the thread pitch with a pitch gage.
Or get yourself a set of jewelers files.You need to use one that is angled enough to to file the sides of the threads.
Or just replace.
 
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Old Oct 12, 2007 | 09:56 PM
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Default RE: mainshaft thread pattern

I've done that. I got confused reading an old machinists book which described "pitch" as the number of threads in the length of the circumfrence, i.e. wrap a paper around the bolt, mark it, then count the threads in that distance...
theOD of the threadsmic'd out, if I remember, at 0.72 or 0.73 inches diameter. pitch gage reads 18.
I'd file it, but it was a twelve point socket that some bonehead jammed on it, so there are a number of places. It's not bad enought to replace, though.the tranny is good.
Thanks. let me know if something(s) I said here don't seem reasonable, and I'll get the die.
 
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Old Oct 13, 2007 | 07:35 AM
  #4  
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1flhtk4me
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From: Billings,Mt.
Default RE: mainshaft thread pattern

.720/.730" dia sounds small.The size should be .7486/.7399". for a 3/4-18UNS externalthread according to the Machinist's handbook.
To double check,you can measure the ID of the nut.The minor dia. of the nut(ID) should be .690/.703".
You could also verify by checking the nut with a 3/4-18 bolt before you buy a die.
The pitch is the number of threads in 1 inch,has nothing to do with circumfrence.
I would try to file the thread to see if it is soft.If the shaft has been hardened then the die may not cut it.
 
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Old Oct 15, 2007 | 10:49 AM
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Default RE: mainshaft thread pattern

I'll recheck the size after I get home/back--I think you have it right. I'd check with a regular bolt except for the left-hand thread.
Pat
 
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Old Oct 18, 2007 | 07:48 AM
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Default RE: mainshaft thread pattern

Go to a hardware store or an auto parts store and ask for a thread restoration file. It has a square shape and a different thread pitch per side. Be sure the file you buy has a thread pitch that matches the pitch you want to restore. Stroke the damaged threads as you go around the shaft untill the threads clean up enough to install the nut.
 
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Old Oct 18, 2007 | 11:51 AM
  #7  
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Default RE: mainshaft thread pattern

Ah, a thread restoration file. Never heard of the animal, but I like it. Thanks.
 
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Old Oct 19, 2007 | 07:54 AM
  #8  
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ajayrk
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Default RE: mainshaft thread pattern

View the tool here:

http://buy1.snapon.com/catalog/item....mp;dir=catalog


 
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