Repairing threads in aluminium

[Phil Russell]

Over the years I have had to repair several threads in aluminium and steel parts on air guns. Sometimes there has been very little choice as to what to do ... some threads have been mangled by e.g. a previous owner screwing a self tapping screw in and I saw the only solution was to retap the hole a size larger and use a screw to fit, reprofiling the head as well as possible to be aesthetically acceptable.
But a more recent stripped thread in aluminium was repaired (sharp intake of breath) with a helicoil insert. It was the first time I had removed the screw and I suspect that the previous owner had stripped the thread and sealed the screw in using a loctite or similar. I say this because there was no sign of any thread remnants but there was evidence of a thread lock compound. The helicoil worked well ... I could not see an opportunity to re-tap to a larger size in this instance.
However, while pondering it again I was wondering if anyone has tried filling a stripped hole with something like JB Weld, letting it set and then re-tapping to the original size? Certainly not as fast as using a helicoil; but would it work?

Cheers, Phil
PS In case you wonder, I am not equipped to weld the hole up and start again.

[bighit]

Over the years I have had to repair several threads in aluminium and steel parts on air guns. Sometimes there has been very little choice as to what to do ... some threads have been mangled by e.g. a previous owner screwing a self tapping screw in and I saw the only solution was to retap the hole a size larger and use a screw to fit, reprofiling the head as well as possible to be aesthetically acceptable.
But a more recent stripped thread in aluminium was repaired (sharp intake of breath) with a helicoil insert. It was the first time I had removed the screw and I suspect that the previous owner had stripped the thread and sealed the screw in using a loctite or similar. I say this because there was no sign of any thread remnants but there was evidence of a thread lock compound. The helicoil worked well ... I could not see an opportunity to re-tap to a larger size in this instance.
However, while pondering it again I was wondering if anyone has tried filling a stripped hole with something like JB Weld, letting it set and then re-tapping to the original size? Certainly not as fast as using a helicoil; but would it work?

Cheers, Phil
PS In case you wonder, I am not equipped to weld the hole up and start again.

If you have the space ,a Timesert is better than the helicoil as helicoils can and often doo come out with the bolt or screw. .

The Timesert is a more permanent fix as it looks into the material its inserted into.

Timeserts cost a lot more than Helicoils though,so unless you are doing a lot of repairs it may be worth seeing if a local garage or engineering place will do it for you or hire out the Timesert kit.

We saw some jobs in that people tried to fix with J B weld or other two part repair options. Often they did not last and had to be repaired again and we only used Timeserts. We had Helicoil kits but they were very old and no inserts left.

[WebleyWombler]

Over the years I have had to repair several threads in aluminium and steel parts on air guns. Sometimes there has been very little choice as to what to do ... some threads have been mangled by e.g. a previous owner screwing a self tapping screw in and I saw the only solution was to retap the hole a size larger and use a screw to fit, reprofiling the head as well as possible to be aesthetically acceptable.
But a more recent stripped thread in aluminium was repaired (sharp intake of breath) with a helicoil insert. It was the first time I had removed the screw and I suspect that the previous owner had stripped the thread and sealed the screw in using a loctite or similar. I say this because there was no sign of any thread remnants but there was evidence of a thread lock compound. The helicoil worked well ... I could not see an opportunity to re-tap to a larger size in this instance.
However, while pondering it again I was wondering if anyone has tried filling a stripped hole with something like JB Weld, letting it set and then re-tapping to the original size? Certainly not as fast as using a helicoil; but would it work?

Cheers, Phil
PS In case you wonder, I am not equipped to weld the hole up and start again.

I use helicoils if I can but JB weld or Lumiweld can be just as effective (Lumiweld needs a heat source though) . I have used JB weld in greatly stressed situations such as Motorcycle cylinder heads and crankcases. If repairing threads, the coarser the pitch, the better but it still provides a 'parent metal' strength in most circumstances. highly recommended by me if the bits are thoroughly cleaned before the repair is carried out

[Black Beard]

You can also also add gas welding aluminium solder and then screw in a steel bolt, which the aluminium will mould around. I haven't done it and it will take practice and a solid chunk of metal to solder into.

[trajectory]

Other than mechanical inserts or metal building processes I have found two part epoxies to be sufficient in many instances. All processes need to executed properly but perhaps there is a possibility that epoxies appear simple but in fact are sensitive to divergence from what's needed to get the maximum properties attainable. Cleaning & degreasing are very important, in fact propper pre treatment is essential as is mixing the components properly & in the correct ratio. Curing fully is paramount & some epoxies need heat to cure fully & ensure cross linking. Some epoxies are metal filled... not entirely sure in my own mind if that is a true benefit for thread building, but I consider a high modulus formulation to be of benefit.