Repair or redoing of sight-block screw threads?

token_kiwi

New member
I have an older Hoyt riser which has been well-used, to the point that the screw threads in the mounting holes for the sight-block are no longer holding as they should. Does anyone have any experience with options for what to so I can keep using this? I had tried to use PTFE tape on the screws for the sight block, but that didn't hold any better beyond the first arrow. Not sure whether my next step is to try a thread-sealer like one of the Loctite products (and if so, which!), or to see about getting new holes drilled and tapped (is there anyone who does this sort of work as a repair, or do I talk to a friend with a drill-press...?).

Thoughts welcome, information of solutions that have been tried (whether they worked or not) moreso!
 

token_kiwi

New member
Its an Avalon Plus, so I presume its machined aluminium. Would you generally use a helicoil with loctite or similar, or just on its own?
 

dvd8n

Supporter
Supporter
I would not try loctite, it's not really intended for reforming threads. There are products on the market that claim to be able to do so, like jb weld or molecular metal (really just high strength fillers). I don't know if they would be strong enough to take the vibration though. I'd suspect not, but it could be worth a shot.

Beyond that you are into proper engineering solutions, which need tools and skill.

The proper way to fix it as nigel says would be a helicoil. If you cannot fit one yourself any small engineering shop would do it. If you don't know one ask at a local garage. The only problem would be that the shop would probably only stock the larger sizes so you may end up financing their purchase of smaller kit.

If you can cut threads yourself then you have three options. You can (if there is enough meat on the riser) drill and tap the holes deeper and use longer bolts. Or, drill the holes and tap them for larger (thicker) bolts. But you'd need to drill the sight block larger too. Or, again if the riser design allows it, remake the holes a few mm away from their current position. Careful positioning would mean that the holes would stay hidden behind the block.

A more low tech solution would be to drill the holes through and add a nut in the sight window. It sounds extreme but you can neaten it up a lot by using a countersunk barrel nut (colloquially known as Chicago screws or sex bolts :) ) in the window. This has the advantage that you can do it with just a hand drill, and would be really strong.

I'd advise not letting a machine shop weld and remake the holes. While it would work it would risk warping the riser and would ruin the finish.
 
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ThomVis

Member
My first thought is to drill through the riser and use countersink bolts from the inside and nuts on the mounting block side. Not the most elegant solution, but engineering wise the strongest.
 

Nigel Hewitt

New member
The proper way to fix it as nigel says would be a helicoil. If you cannot fit one yourself any small engineering shop would do it. If you don't know one ask at a local garage. The only problem would be that
The problem is, being archery equipment, it's probably a UNF thread and most of the world is only tooled up for metric these days.
 

Libris

Supporter
Supporter
The problem is, being archery equipment, it's probably a UNF thread and most of the world is only tooled up for metric these days.
I'd just re-tap the holes to a slightly bigger size and do the same with the sight mount. You could use metric taps and bolts and most model suppliers have either carbon or stainless steel bolts in huge ranges of sizes (including UNC and UNF).
 

dvd8n

Supporter
Supporter
I would not try loctite, it's not really intended for reforming threads. There are products on the market that claim to be able to do so, like jb weld or molecular metal (really just high strength fillers). I don't know if they would be strong enough to take the vibration though. I'd suspect not, but it could be worth a shot.

Beyond that you are into proper engineering solutions, which need tools and skill.

The proper way to fix it as nigel says would be a helicoil. If you cannot fit one yourself any small engineering shop would do it. If you don't know one ask at a local garage. The only problem would be that the shop would probably only stock the larger sizes so you may end up financing their purchase of smaller kit.

If you can cut threads yourself then you have three options. You can (if there is enough meat on the riser) drill and tap the holes deeper and use longer bolts. Or, drill the holes and tap them for larger (thicker) bolts. But you'd need to drill the sight block larger too. Or, again if the riser design allows it, remake the holes a few mm away from their current position. Careful positioning would mean that the holes would stay hidden behind the block.

A more low tech solution would be to drill the holes through and add a nut in the sight window. It sounds extreme but you can neaten it up a lot by using a countersunk barrel nut (colloquially known as Chicago screws or sex bolts :) ) in the window. This has the advantage that you can do it with just a hand drill, and would be really strong.

I'd advise not letting a machine shop weld and remake the holes. While it would work it would risk warping the riser and would ruin the finish.
I forgot to mention - holes don't strip their threads just to be bloody minded. A bit of thought will stop it happening again. Possible reasons are:

Too much force used to tighten the screw - small screws don't need to be horsed up with all your strength - they will strip. If they vibrate loose it's a job for loctite.

Too long a screw used in a blind hole - this is a classic recipe for stripping threads. If you are screwing something up and it gets stiff, then stop and have a think about what might be wrong.

Wrong sized screw used, typically metric in a UNF hole or vice versa. In a lot of these cases the screw seems to fit but tightens up after a few turns as the threads go out of mesh. But by that time you've decided that you have the right screw and you plough on leading to disaster. Again, if you are screwing something up and it gets stiff, then stop and have a think about what might be wrong.

A manufacturing issue (porous casting or badly cut threads in the factory) - not a lot that you can do here, but if it is a dodgy casting then that may affect how (or even if) you choose to effect a repair.
 

snowman

Member
Have used 5 minute araldite as a temporary fix on a 20# club bow before now. Found that bolt can be removed later if careful and leaves thread in epoxy resin. Doesn't last too long if you keep undoing bolts though. Fill hole and hold bolt in position till set. On an old bow of my own I have drilled and retapped hole through riser and just used longer bolts and loctite.
 
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