8 replies to this topic

[L400RAS]

Hi,

Just putting my thermostat back together, and one of the threads is damamged. It appears the first 1/2 threads have crushed. I know the thread is 5/16th UNC - is it worth trying to re-tap this to clean it up? (i have a brand new good stud to put back - it nearly starts to go in, but i don't dare wind it in). If this method does not work, could someone confirm the next size to tap to? Metric M6? (and also confirm the clearence hole to drill first please! (Martin /MRA I hope you read this...)

Edit: If i do go larger thread, what should I use - threded bar as a stud, rather than a bolt? - as the bolt would have to be exact length... anyone got any experience doing this?

kind regards mini fans,
Ryan.

Edited by L400RAS, 11 October 2010 - 05:18 AM.

[Cooperman]

You can try to clean out the thread with a tap. If this does not work you need to fir a thread wire insert (Helicoil). You just buy a 5/16" UNC Helicoil kit from someone like Namrick (buy on line from them - their kits are called 'Re-coil', but are the same as Helicoil). The kit comes complete with drill, taps, wire inserts and an insert fitting tool. When done it's as good as new.

[L400RAS]

You can try to clean out the thread with a tap. If this does not work you need to fir a thread wire insert (Helicoil). You just buy a 5/16" UNC Helicoil kit from someone like Namrick (buy on line from them - their kits are called 'Re-coil', but are the same as Helicoil). The kit comes complete with drill, taps, wire inserts and an insert fitting tool. When done it's as good as new.

Hi Cooperman,

thanks for the advice. Do you know what size drill to use with the 5/16 UNC? - as i don't think a drill bit comes in the kit. Also - are you positive there is snough space in the head to go that big - ie not to hit a waterway etc....

Ryan

[Ethel]

As it's a stud, you could probably get away with glueing it in with thread lock.

Stainless studs are a good idea by the way.

[Cooperman]

You can try to clean out the thread with a tap. If this does not work you need to fir a thread wire insert (Helicoil). You just buy a 5/16" UNC Helicoil kit from someone like Namrick (buy on line from them - their kits are called 'Re-coil', but are the same as Helicoil). The kit comes complete with drill, taps, wire inserts and an insert fitting tool. When done it's as good as new.

Hi Cooperman,

thanks for the advice. Do you know what size drill to use with the 5/16 UNC? - as i don't think a drill bit comes in the kit. Also - are you positive there is snough space in the head to go that big - ie not to hit a waterway etc....

Ryan

The drill comes with the kit.
Yes, you can always Helicoil without fear of breaking into a waterway.
Namrick are the best source of the kits IMHO.

[L400RAS]

thanks for the help guys

I will try to chase the threads with a 5/16 first, then go for a recoil if necessary. Will let you know how it goes - probably attempting it this weekend.
Ryan

[dklawson]

I agree that you should try to chase the threads first to clean them up. Loctite on the stud will hold it in place well if more than 50% of the thread remains. As Ethel said, stainless studs are a good idea.

For future reference, you can determine the tap drill size for bolts easily at home without a table, however, you do have to know the pitch of the threads. In the case of 5/16 UNC, the bolt/stud is threaded 18 threads per inch. The tap drill will be the major thread diameter minus the pitch. For 5/16-UNC this means 5/16" - 1/18" = 0.257" The closest common drill will be 1/4" diameter or roughly 6.5mm.

[L400RAS]

Thanks for the info Doug, really appreciate it. I'll let you know how i get on

[L400RAS]

mate came down, retapped to 5/16 UNC, worked a treat. thanks guys