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Author: Subject: Thread repair
joneh

posted on 28/3/19 at 10:06 AM Reply With Quote
Thread repair

Morning all,

I have a stripped engine mount thread on a crossflow block. Only noticed it after finishing the rebuild - rookie mistake.

Whats the best method of fixing this, being cast iron? I'm thinking an m8 tap as its slightly bigger than 5/16 UNC? The bolt spins freely so I assume I can't use an original size tap. If that doesn't work can I helicoil it by hand?

Jon

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rusty nuts

posted on 28/3/19 at 10:47 AM Reply With Quote
Personally I would get a Helicoil repair kit and do a proper job. You never know , you may need it again . Failing that find someone with one? Iíve lost count of the times incorrect fittings have caused me problems.
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joneh

posted on 28/3/19 at 11:10 AM Reply With Quote
quote:
Originally posted by rusty nuts
Personally I would get a Helicoil repair kit and do a proper job. You never know , you may need it again . Failing that find someone with one? Iíve lost count of the times incorrect fittings have caused me problems.


Sounds the right approach. Is that easy to do by hand into cast iron?

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MikeRJ

posted on 28/3/19 at 12:22 PM Reply With Quote
quote:
Originally posted by joneh
quote:
Originally posted by rusty nuts
Personally I would get a Helicoil repair kit and do a proper job. You never know , you may need it again . Failing that find someone with one? Iíve lost count of the times incorrect fittings have caused me problems.


Sounds the right approach. Is that easy to do by hand into cast iron?


If you can drill a hole straight and start a tap straight then it's a piece of cake.

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rusty nuts

posted on 28/3/19 at 01:08 PM Reply With Quote
As Mike says really, only thing I would add is use plenty of lube when drilling and tapping. Drilling and tapping fluid from Toolstation is cheap
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steve m

posted on 28/3/19 at 04:26 PM Reply With Quote
I helicoiled all my crossflow mounts to 8mm, as the old 5/16th threads were manky

helicoil kits are easy to use, and once bought, used them loads of times

steve





Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at




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907

posted on 28/3/19 at 07:54 PM Reply With Quote
I would drill it out to 8.5 mm and tap M10. Drill the mount 10.5 mm





Member of the Suttol Owners Club, the MX5 Owners Club and the BMMC

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joneh

posted on 28/3/19 at 10:02 PM Reply With Quote
Thanks all, the hole is pretty beat up, so might have to go to 3/8 unc or m10. Will take a look tomorrow.

Jon

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