Helicoil for mount threads?

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Morgan
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Helicoil for mount threads?

Post by Morgan » Tue Aug 19, 2014 9:26 pm

Thinking about a .22lr design that has aluminum threads for attaching to the barrel. Anybody used a helicoil in the mount threads? Purpose is to reduce parts count, it would only be three parts total! Concerned about slop in the threads and longevity. The aluminum part is the monocore and made of 7075.

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john.t.little1
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Re: Helicoil for mount threads?

Post by john.t.little1 » Tue Aug 19, 2014 10:32 pm

Are you making the monocore out of bar stock and using a hand drill for everything? If you are using a lathe why not thread it? Aluminum? Press in a steel plug that's threaded.. We use helicoils on aircraft they brake a lot. You'd just have to replace the helicoil from time to time and I'm not sure how that would effect the way it mounts up but to many factors in that for me.
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Morgan
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Re: Helicoil for mount threads?

Post by Morgan » Tue Aug 19, 2014 10:46 pm

The monocore would be threaded in the lathe after drilling. Just concerned about the threads wearing out, would be easier to helicoil it up front rather than down the road.

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Re: Helicoil for mount threads?

Post by BinaryAndy » Wed Aug 20, 2014 6:37 am

A helicoil will hold up a lot better than aluminum threads, though I don't know that I'd trust it to align accurately. In any case, good luck finding a 1/2-28 helicoil.

I wouldn't worry too much about the threads holding up in 7075, especially if you get it hard coat anodized (which you should). If it did worry me, I would make what amounts to a thread adapter: make a bigger thread in the aluminum (5/8-24 or something), then thread the outside of a piece of stainless to match and make your 1/2-28 internal threads in the same setup.
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Re: Helicoil for mount threads?

Post by mx201er » Sun Aug 24, 2014 7:55 pm

I think it would be better than aluminum threads, but make sure a face of the can tightens against a face om the barrel so that you aren't relying on helicoil to keep you aligned..
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Re: Helicoil for mount threads?

Post by wp6529 » Sun Aug 24, 2014 10:40 pm

I was going to suggest solid thread inserts rather than the heli-coil type, but a quick search on McMaster seems to indicate that none of them are available with 1/2-28 as the inside threads.

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Re: Helicoil for mount threads?

Post by BinaryAndy » Mon Aug 25, 2014 9:06 am

wp6529 wrote:I was going to suggest solid thread inserts rather than the heli-coil type, but a quick search on McMaster seems to indicate that none of them are available with 1/2-28 as the inside threads.
Yeah, and I don't think you'll find 1/2-28 Helicoils either. It's an extra-fine thread, nobody outside of the firearms industry seems to use those.
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Re: Helicoil for mount threads?

Post by Historian » Mon Aug 25, 2014 10:36 am

Perhaps, as usual, I might be misreading what you are asking ...
but why let that stop one. :)

Starting with an Aluminum bar stock, bored out to desired O.D. & I.D.,
wanting a robust and secure way to thread say 1/2" x 28 TPI barrel hole one
could consider taping a .685"-40 thread* in the Ally. Then take
a SS rod; turn to .685" O.D. and thread 40 TPI; and then bore/tap a 1/2" x 28 TPI hole
in the SS 'plug'..

Then use loctite to complete the steel/aluminum coupling.

Bypass single point threading if one is uncomfortable doing such with
Brownells tap & die ... which has many possibly many uses in the future.

Idea inspired by "How Its Made ... Super Cars" on their sleeving SS
cylinder wall in aluminum engine.


* Brownells: 080-598-685WB .685"-40 thread tap
080-598-686WB .685"-40 Die

<< http://www.brownells.com/gunsmith-tools ... 41914.aspx >>
<< http://www.brownells.com/gunsmith-tools ... 41914.aspx >>

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Re: Helicoil for mount threads?

Post by Historian » Mon Aug 25, 2014 10:41 am

Above die & tap set was a must-have for a DIE-hard tool junkie to have. :)

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Re: Helicoil for mount threads?

Post by curtistactical » Mon Aug 25, 2014 11:55 am

Keensert makes a solid plug which would have threads on the O.D and be solid, so once you installed it you could chuck it back up in the lathe and put the 1/2-28 thread in it so everything is nice and true. I would never recommend using a tap for the end cap, no matter what you do it is way to easy to get it screwed up. The keenserts have two broaches built into them so once you screw it in you drive the two broaches in which lock the insert in place.

catalog.alcoafasteners.com/category/keenserts-reg-
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Re: Helicoil for mount threads?

Post by Historian » Mon Aug 25, 2014 7:44 pm

curtistactical wrote:Keensert makes a solid plug which would have threads on the O.D and be solid, so once you installed it you could chuck it back up in the lathe and put the 1/2-28 thread in it so everything is nice and true. I would never recommend using a tap for the end cap, no matter what you do it is way to easy to get it screwed up. The keenserts have two broaches built into them so once you screw it in you drive the two broaches in which lock the insert in place.

catalog.alcoafasteners.com/category/keenserts-reg-
+1!

Sloppily expressed above: idea was to suggest a way to make a SS plug for
Ally end cap. Then drill ==>> bore ==>> single-point thread
1/2" x 28 hole on lathe.

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