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HelioCoil HELP...

Mycool

Well Known Member
Hi gang,

I'm having a problem finding a heliocoil, I need to change from 1/2"X20 and reduce to 5/16"X24 thread.

can anyone point me in the right direction to source
 
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Pretty sure that don't make helicoils that fat. They are made to drill out just past the thread major diameter then re-tap, netting the same thread as original. You can probably find or make an insert to reduce like that, but not sure I would trust if for such a critical attach point, as you won't have a lot of meat to support the internal threads (.311 on the inside and around .435 on the outside, netting only a .060 wall where the threads intersect). That said. most of the stress is taken by the pin and not much on the bolt as it's job is just to hold the gear on the pin and keep it flat. I would want an engineer to weigh in as it doesn't seem to be enough in my mind.
 
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Hi gang,

I'm having a problem finding a heliocoil for a crankshaft I need to change from 1/2"X20 and reduce to 5/16"X24 thread.

can anyone point me in the right direction to source this?

its for the crankshaft gear, I want to avoid enlarging the crankshaft gear hole.

Never heard of using a helicoil to reduce size/change thread pitch.
 
OH manual

I am a total rookie to building motors but here is what I found in the OH manual.
 

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There is absolutely no way I would be messing around with trying to do anything to the crankshaft gear bolt threads. That thing is the equivalent of a Jesus nut on a helicopter!

Send it in and let the professionals deal with it.

Likely not what you want to hear but some things are not worth the risk!
 
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Helicoils can't change thread pitch which is why you are not finding one for that.

You can use a thread-sert. (several brands) This will change pitch. Some manufactured items are made to have these especially on aluminum, so they can be stronger than just threading directly.

I can't speak to if your application is correct for it, but that is the name of item you are looking for.
 
Hi gang,

I'm having a problem finding a heliocoil for a crankshaft I need to change from 1/2"X20 and reduce to 5/16"X24 thread.

can anyone point me in the right direction to source this?

its for the crankshaft gear, I want to avoid enlarging the crankshaft gear hole.

I've never heard of putting an insert into a crank shaft, but sounds like you are looking for threaded insert (aka Keensert). Google MS51831 and you will find the mil spec for these inserts.

Part number MS51831-203 is 5/16 x 24 internal thread with a 1/2"x 13 external threads. Are you sure you need 1/2"x20 external? If the mil-spec does not provide the internal/external thread combination you need, you may have to go custom - assuming this is the path to follow.

Good luck,
 
After reading this again along with the replies, why is the crankshaft hole larger than the 5/16 bolt normally called for? Has the crank been drilled and tapped for a larger bolt? As already stated, this bolt holds the gear that drives all of the accessories on the back of the engine. Pretty disastrous if the gear comes loose!
 
Sounds like you have a single-drive Dual-Mag crankshaft which came with a 1/2-20 threaded hole. Why not use the mating Dual-Mag crank gear? That way you can use the proper bolt arrangement without modification.

Another way around this is to chuck your non-Dual-Mag gear (with the 5/16" hole) into a lathe and bore the hole to 1/2". That would be much better than trying to modify the hole in the crank.

If you try to modify your crank gear, make sure you check for gear alignment to the other accessory gears. Not sure if the Dual-Mag crank has the same dimension fore-aft on its mounting flange compared to the standard crank.

Part numbers below. IO or O engines doesn't matter as to the crank gears.

crank 1.JPG crank 2.JPG
 
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It is winter and the ice is pretty thin as of yet.
I think you are heading for the middle of the pond.
Never heard of this application of heli-coils But I've only been a mechanic for 55 years and installed plenty of them.
Art
 
the original engine is a 0-360-A1F6 "D" I sent case to divco to change out to a A1F6, in other words switching from a single dual mag to 2 single mags. the crank is original and was yellow tagged by aircraft specialties, the original crank has a 1/2-20 thread for the original gear hence my dilema. I didn't realize the bolt issue until after assembly.
 
the original engine is a 0-360-A1F6 "D" I sent case to divco to change out to a A1F6, in other words switching from a single dual mag to 2 single mags. the crank is original and was yellow tagged by aircraft specialties, the original crank has a 1/2-20 thread for the original gear hence my dilemma. I didn't realize the bolt issue until after assembly.

Okay, so can you use your original "D" crank gear with your new A1F6 configuration? Or not?

If the original "D" gear will fit with the new accessory gears, then that solves your problem...
 
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no. but original crankshaft can accept both gears, with the exception of the bolt.
 
A phone call to Aircraft Specialties in Tulsa will connect you up with experts who can tell you what is possible, what parts will fit what, and most importantly, what is safe. I visited them a couple of months ago, and was pretty impressed with their capabilities (and parts department) - and their stack of red tagged cranks. When I asked what they do with them, they said that most were recycled, but some that fail aircraft standards go to Florida for air boats…..
 
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Hi Paul thats good advice and will call them Monday, however my only question was options on finding a fitting to change from 1/2”-20 to 5/16-24 . I appreciate all who offered solutions. Still looking for good fix…
 
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