An insert can result in a stronger fastening since the thread into the
soft metal (ie the outside of the insert) is a larger diameter - hence
more bearing area. Much the same effect as going up a bolt size. Some
fixings use a helicoil or equivalent from new for this very reason.
Neil
On 19/06/2011 18:28, Bob Spidell wrote:
> 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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