[time-nuts] repairing Maser threads

Dave Powers dave.powers at att.net
Tue Apr 13 14:43:08 EDT 2010

Howdy Corby - 

just a couple of thoughts. I grew up in a machine shop and am an aircraft mechanic. 

If you haven't used them before, Helicoils require a larger hole to be drilled and tapped, because you basically install a large threaded spacer into the original location with the right size inside threads for your original screw. It takes a somewhat expensive drill & special tap and insert tool to complete.

Another solution - especially with metric - is to tap the holes ( only bad - or all - so that they all match) to the next larger Metric size - of the same thread pitch as original - so as not to cut across the original threads, but just cut the same thread pitch to the next size, such as from 5mm to 5.5mm or 6mm. Then you only have to buy a standard - not too expesive - metric tap - and some new slightly larger hardware.

You can also consider tapping the original holes to the next larger SAE - probably National Fine thread - but your new threads will cut across the original threads slightly.

It really depends on how much room you have to do the work - and how much strength you need -

Hope this helps

Dave Powers - KA0KCI


From: Corby Dawson <cdelect at juno.com>
To: time-nuts at febo.com
Sent: Tue, April 13, 2010 1:03:55 PM
Subject: [time-nuts] repairing Maser threads


It does not seem Time-Nutty but I need help repairing threads in a
mounting hole.

I recently installed a new ion pump in an EFOS2 Hydrogen maser and two of
the mounting holes (metric M5)

have damaged threads. 

The bolts go in fine but wont tighten and if you wiggle the bolt you can
pull it out.

I've looked at the various locktight and permatex stuff but am unsure
that they will do what I want.

I'm hoping someone has experience with these and can advise me.

What I hope will happen with the right product is that I apply it to the
threads, screw in the bolt until it just contacts the lock washer, wait
until the goop cures, and then 

tighten until the lock washer is compressed and the bolt is tight.

Just don't know what product to try! Want to be able to disassemble
without special tools or heating.

Any help is appreciated!

Corby Dawson
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