[Shop-talk] stripped screw hole in carb

[Bob Spidell]

re: "... the repaired threads are actually stronger than the originals, especially in soft metals like carb bodies ..."

I like thread inserts, but I've given this a lot of thought because I sometimes use them in critical applications (shock 
mounts where the Armstrong shock is actually the upper suspension arm).  While a steel thread is stronger than soft 
metal threads, the joint itself can only be as strong as the weakest part; i.e. at some load the screw/bolt will pull 
the insert out of the brass or other soft metal.

Anyway, I think what you meant is the threads themselves are stronger--i.e. less likely to strip--which should be the case.

BTW, I used the Locktite product to 'fabricate' new threads for a clutch slave cylinder mount on an aluminum housing, 
and with a little trial-and-error was able to get pretty good torque on the bolts.  I will, however, install inserts 
next time the gearbox is out of the car (an Austin-Healey 3000).

Bob


On 6/19/2011 9:37 AM, Randall wrote:
>> 2. us JB weld with soap on the bolt.  Once the epoxy has cured,
>> unscrew the screw.
> Although I've not tried that on a carb, I have in other places where the
> loading was light.  The JB Weld is still too weak to take threads, IMO.
> Loctite makes a similar product specifically for repairing threads:
> http://media.midwayusa.com/pdf/instructions/Loctite_stripped_threads.pdf
> which comes with a chart of allowable torque values for the 'repaired'
> thread.  23 INCH pounds for a 1/4" bolt isn't much!
>
> So if you can find a Helicoil in the appropriate size, that would be my
> suggestion.  They aren't cheap, but the repaired threads are actually
> stronger than the originals, especially in soft metals like carb bodies.
>
> -- Randall
>
>


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Bob Spidell           San Jose, CA            bspidell at comcast.net

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