I am currently preparing to assemble the Mk3 front isolastic mounting that has been apart for years. However, the adjuster only screws on a couple of turns and locks solid. There is localised thread damage on the tube and have tried cleaning the thread with a fine triangular file, with no effect. Running a die down the thread would likely be the best and quickest option.
Does anybody know what the front isolastic vernier adjuster thread is?
Andy
Isolastics
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HI Philip how are you ? As I…
HI Philip how are you ? As I read it I think he is asking for the ISO thread not the through bolt thread. But I could be wrong. Pete W
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Phil, thanks for the quick…
Phil, thanks for the quick reply, but yes, as Pete mentioned, it is the thread on the isolastic mounting tube for the vernier adjuster that I need to identify.
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Probably BS Cycle 3/4" x…
Probably BS Cycle 3/4" x 20tpi.
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Vernier Tube
I agree with Stan that it is 3/4" x 20tpi.
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It's in these situations...
... that a thread gauge is invaluable. You can get a cheap one which would be fine for occasional use for a fiver or so.
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grub screw
I’m sure you have checked no grub screw getting in the way?
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Jan, no, the thread of the…
Jan, no, the thread of the abutment with the grub screw is fine it is just the opposite adjuster end of the tube that has the damaged thread.
Also, the tapered end of the vernier adjuster itself has been attacked with a coarse file for some reason, taking off enough material to go into what was a countersunk thread. So a new adjuster is now on order from A-N.
i have never had a bike before where quite so much had been damaged or bodged beyond repair - about 70% replacement parts have been needed. I had thought I had found everything, only to now find during assembly that a part as innocuous as the vernier adjuster should also have received ‘treatment’.
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Well I did think that…
Well I did think that knowing the thread size was one thing but finding a tap/die for such an obscure size would be hopeless. Well, wadda ya know, not that obscure after all:
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Found a similar but UK…
Found a similar but UK supplied (though unlikely made) die on eBay for just £12.95 incl, postage. Maybe not best quality for that price, or perhaps not a big seller so being cleared, but it only needs to work once!
Thanks again for the size advice Stan.
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I sorted out one with a spot…
I sorted out one with a spot of grinding paste on the thread, turning back and forth a bit at a time until it went all the way on, clean up and Bob’s your uncle.
Best regards, Al.
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As follows was buried in the Service Notes. May need confirming.
Isolastics 06-3598 NUT UNF 1/2"x20 SELF LOCK