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Best way to fix an aluminum stripped bolt hole

M

Markks

New User
What is the best procedure to repair a stripped out bolt hole on an aluminum housing??
I am considering going back with a self tapping bolt. What has everybody with more experience done?? Thanks...
 
If you try to tap aluminum, go very slow, liberally use a lubricant for the purpose. Helicoil highly recommended.
 
The "best" procedure is to have the hole welded up and retapped. A heli coil or similar threaded insert would probably be the second best procedure. Dave
 
Used to fix pulled studs in VW blocks all the time with a treaded insert a bit bigger that a Helicoil. Gave a lot more diameter to bite into.
 
I know it is not "proper", but I have had success with retapping the bolt hole to fit a somewhat larger bolt.
 
The proper fix would be to purchase a helicoil repair kit. Also available is material called Devcon. It comes in several types, including aluminum. Once it becomes hard, it can be drilled and tapped.
 
Dave, I question the idea that a welded and retapped hole is better than a helicoil repair. A lot of the mil-spec stuff I used to work on had helicoils installed at the factory, because helicoils make for stronger threads that are resistant to cross-threading. Also, welding and ACCURATELY machining a new hole requires skills and equipment that most of us don't have, while any dummy can install a helicoil and get it right the first time.
 
like these.
I think timeserts are bit better than helicoil but
I never had trouble with helicoil either.
http://www.timesert.com/
 
He asked for the best procedure. I've seen people bugger up heli-coils too. It depends a lot on the particular part that needs to be repaired. Sometimes with welding, you can add extra material for more strength. Dave
 
I've seen too many Helicoils fail and make a bigger mess than the original problem, especially in something that is taken apart frequently. I only use Permaserts or Keenserts to repair threads that cannot be tapped to the next larger size. The inserts typically need no special tools to install and are way stronger than the substrate metal.
 
The best stuff to use is Devcon. It was designed for aircraft repair of aluminium. We use it on flap tracks all the time and it has never failed. As long as it hardens for 24 hours the stuff is harder than the aluminium around it.
 
99.9 percent of the time, a helicoil or other insert IS the best procedure for the shade-tree mechanic. The other 0.1 percent of the time, the part needs to be repaired by someone who knows what they're doing and has the equipment to do it. Depending on the circumstances, this might require major disassembly. Helicoils can usually be installed on-site without disassembly by a person with minimal skills. With welding, you're introducing a whole bunch of unknowns: Is the alloy even weldable? Is it heat treated, and if so what's the process to bring the welded part back to its original strength? Can the new hole be accurately drilled and tapped at its original position?

There's a place for welded repairs, but for simple repair to a stripped-out threaded hole the helicoil does the job cheaply with very little risk of creating additional damage.
 
Nothing wrong with Heli Coils.I have used them a lot of times and had no problems.There are different kinds.If you put them in right they will stay in.Some have locks that hold them in.Those are probably better for something that has to be taken apart a lot.
 
I disagree. Just about every threaded hole I've seen in aluminum at work (aerospace co) has either a helicoil or keensert. I can't imagine anywhere that you would simply use a tapped hole unless the fastener was used only for alignment while an assembly was brazed.
 
That might depend on what it's used for and how bad it is now...
I'd probably try retapping it first to the same size and see how it looked. If not I'd probably use a heli-coil or possibly drill it larger and tap to another size. Again... it depends on the application.

Rod
 
Inserts do work good but it depends a lot on the application. I'm around motorcycles a lot and heli-coils are used sometimes and other times it's best to weld it and re tap it because there isn't a lot of extra material around the hole. Most aluminum with threaded holes is cast aluminum which is a softer variety(4043 filler metal). Sometimes the holes are welded up with a harder/stronger aluminum alloy(5356). Inserts are easier for the DIYers but again it depends on what it is. Dave
 
I agree with you. Decades ago picked up a stock Chevy aluminum L-88 427 intake manifold that had a stripped carb mounting hole. I've had success with Helicoils since, but that was my first experience when a friend looked at it and said "Helicoil will fix that", and he took it and botched it. I took it to another friend at a machine shop that welded it closed, then retapped it to size, and decked the mounting flange surface .005. Helicoils are good if done right, but not first choice in my book either.

Mark
 
I agree.

If the directions are followed properly, the heli coil repair will always be stronger than the original design.

Dean
 
If you have access to a lathe, even a 9x12, find a bolt a little larger than the one you stripped. Metric tend to halve the gaps between SAE stuff and vice versa,so look into those. Cut the head off the bolt, chuck it in the lathe and center drill it for the tap size of your stripped one. Cut it off to the correct length.

Now tap the part to the bolt you just drilled. Install with Loc-tite and you're done. No special drill or tap, which is usually out of stock when you need it. Since it's a solid piece of metal, it's lots stronger than a helicoil. I've been doing it this way for over 20 years and never had one fail or unwind like a helicoil is prone to do.
 
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