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How to change helicoils?

Printed From: AMT Guns information
Category: Auto Mag Pistol
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Forum Description: Message Board
URL: http://www.amtguns.info/forum_posts.asp?TID=2324
Printed Date: 21 Oct 2018 at 4:33pm
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com


Topic: How to change helicoils?
Posted By: Pantera Mike
Subject: How to change helicoils?
Date Posted: 13 Aug 2018 at 11:52pm
All,

My cocking piece helicoils need to be changed. Bruce Stark was kind enough to gift me a pair of replacements, and I have a friend who is a brilliant machinist who has the necessary tools to install them. But we have questions:

1). How are the old helicoils removed without destroying the cocking piece in the process?

2) How are the new helicoils retained? Blue Loktite or ?

Tips from those who have been there/done that much appreciated!



Replies:
Posted By: jw4570
Date Posted: 15 Aug 2018 at 1:26am
There are two types of helicoils.  Tang where you put it in and break off the tang and then there is tangless.

Read this catalog and it's very informational:

http://helicoil.in/pdf/helicoil%20catalogue.pdf




Posted By: Pantera Mike
Date Posted: 15 Aug 2018 at 7:06am
Wow that’s a great resource! Thanks!

There are far more than just two different types. The important distinction for us is ‘locking’ Vs ‘non-locking’.   I don’t know what the Auto Mag originally came with, but intuitively I would assume the locking style would be superior for our application. They are distinguishable by their red color. The ones in my cocking piece are silver which may explain why the recoil rods keep coming loose.

Apparently the part number of the locking kind of the appropriate length is

3591 3CN380

where the 380 indicates the length of .380 inches, which works out to 2X the diameter. They have 9 1/2 coils. They are available in quantities of 100 from various sources but I was able to get a pack of 25 on EBay, genuine Heli Coil brand, for $6.99 (some Auto Mag parts dealers charge $18.50 each!)

It turns out there is a dedicated Heli Coil removal tool as well. It’s a simple-looking thing that costs almost $40! There’s a cheap Chinese version on EBay for $10 that I will give a try first....


Posted By: Pantera Mike
Date Posted: 25 Sep 2018 at 2:56am
I finally got around to changing my helicoils today. It was a non-trivial exercise. I can see why professionals charge a fair amount for this service. There was a lot of trial and error, and helicoils that failed to go in properly. 

Most vendors sell them in bags, but the source I used on eBay sold them installed on a plastic strip which is BRILLIANT!  Initially I was removing them and trying to install them, which went quite poorly. Eventually I realized the strip is actually an alignment tool, and after that things went much more smoothly:




Subsequent test-firing showed the recoil rods no longer shooting loose, so it was well worth the effort!



Posted By: Pantera Mike
Date Posted: 25 Sep 2018 at 4:44am
bump to move this ahead of the Chinese spammer posts!


Posted By: USA 1776
Date Posted: 26 Sep 2018 at 4:21am
Mike, whats a "Chinese spammer post" ?? I've seen nothing here matching that description.

-------------
'It has been said that politics is the second oldest profession. I have learned that it bears a striking resemblance to the first.' Ronald Reagan


Posted By: Pantera Mike
Date Posted: 26 Sep 2018 at 4:31am
some jerk from China joined the forum, then started creating one new topic after another after another, with both the post title and the extensive text in the post being in Chinese characters. Dozens of them.  They were appearing in every sub forum. I ‘bumped’ the most recent legit topics to get them in front of the spam topics. I contacted Ian via email who was on vacation and hadn’t seen what was going on. He reacted right away, banning the guy, and deleting all his posts. So if yo weren’t paying close attention to the forum the drama came and went before you knew it....


Posted By: USA 1776
Date Posted: 26 Sep 2018 at 4:54am
Must be what happened. I'm on every night, sometimes very late, but just once a day.

Well, thank you and, as always, Ian, for the prompt action!!

-------------
'It has been said that politics is the second oldest profession. I have learned that it bears a striking resemblance to the first.' Ronald Reagan


Posted By: richie_b
Date Posted: 26 Sep 2018 at 3:00pm
Mike, did you Loc-Tite your new Heli-Coils in place???

Did you take pics of the removal with the tool???


Posted By: TRX302
Date Posted: 26 Sep 2018 at 3:26pm
> plastic strip

All the ones I bought came in little plastic boxes or blister packs. But I'll look for the strips next time I buy some!


Posted By: Pantera Mike
Date Posted: 26 Sep 2018 at 9:53pm
No, I’m told Loc Tite and oil are equally bad. I just used locking helicoils. 

The strip was a nice bonus. Here is the link to the eBay auction:

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F292324972168" rel="nofollow - https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F292324972168


Posted By: jw4570
Date Posted: 27 Sep 2018 at 1:30am
So did you use the triangle spade looking thing to remove them?

I guess I should have said I knew there were more than just tang or tangless, but the tang is the most common. I'm figuring that's what you used and broke off the tang?

Jason


Posted By: Pantera Mike
Date Posted: 27 Sep 2018 at 4:06am
I actually made my own removal tool by grinding a tapered knife edge into the sides of a small screwdriver. The tang tools I had ween were intended for flush-mounted helicoils. The tool in my photo above is the installation tool.  It grabs the tang at the bottom of the helicoil, and slightly shrinks the helicoil as it is installing it because it twists it slightly. If you tried to unwind it, it would expand and be next to impossible to turn. 

The helicoil is inserted so that the end is not bottomed out in the cavity in the cocking piece, then the tang is snapped off.


Posted By: jw4570
Date Posted: 29 Sep 2018 at 9:05pm
Did you buy the installation tool? The tang type used to be readily available at auto parts stores like NAPA. It was a kit with a few helicoils and a tang type tool and usually the proper tap (and maybe drill) for repairing common sizes on cars. We don't need all that stuff. My recollection was that the tool was nothing more than a t handle slightly smaller with a slot cut in the bottom.

Did the screwdriver tool work ok and bite into the helicoil? it was heard enough? I keep old screwdrivers around for that purpose too. I have a few "custom" ones.

I actually have a tangless tool in the correct size, never used it. I also have a few "prewinders" for Helicoils too (but I think they are automotive sizes as they are in the garage).

I have a love hate relationship with helicoils…….They are great when you need one, the trick is not to need one if it's not necessary.


Posted By: Pantera Mike
Date Posted: 29 Sep 2018 at 9:25pm
Originally posted by jw4570 jw4570 wrote:

Did you buy the installation tool? The tang type used to be readily available at auto parts stores like NAPA. It was a kit with a few helicoils and a tang type tool and usually the proper tap (and maybe drill) for repairing common sizes on cars. We don't need all that stuff. My recollection was that the tool was nothing more than a t handle slightly smaller with a slot cut in the bottom.

Did the screwdriver tool work ok and bite into the helicoil? it was heard enough? I keep old screwdrivers around for that purpose too. I have a few "custom" ones.

I actually have a tangless tool in the correct size, never used it. I also have a few "prewinders" for Helicoils too (but I think they are automotive sizes as they are in the garage).

I have a love hate relationship with helicoils…….They are great when you need one, the trick is not to need one if it's not necessary.

Yes, I bought an installation kit consisting of a flat-bottomed tap, installation tool and some helicoils of the non-locking variety which I set aside. The removal tool wouldn’t have worked (and wasn’t included) because the top of the helicoils weren’t  flush with the top of the holes. A good quality Craftsman screwdriver sacrificed its life in the name of the project. It was narrowed just enough to be smaller than the size of the threaded openings in the cocking piece, but wider than the inside diameter of the helicoils. Then the edges were ground to a knife edge. With the cocking piece supported in a vice (with an old automotive serpentine belt used to pad the vice) a few light raps with a small hammer was enough to get the tool to bite into the inside of the helicoils and then they could carefully be wound out. It often took several attempts as it would come out 2-3 revolutions then the tool would slip. But once we got the hang of it (I was working with a machinist friend at his shop) it wasn’t too difficult.

You would never want to install a new helicoil that way.  The proper tang tool did the trick just fine.

I had some difficulty with one hole installing the replacement, and after destroying a number of them we ran the tap to clean up the threads and got a bunch of debris out. Once that was done the next helicoil went in fine. 

We probably destroyed 12-15 helicoils in the process. The learning curve was pretty steep. Many would get just about installed but the last coil would choose to flip out and not follow the rest, and then we would have to dig it out and start over. 

It was a fun project I hope not to have to do again anytime soon!


Posted By: John Nada
Date Posted: 10 Oct 2018 at 2:36am
Originally posted by Pantera Mike Pantera Mike wrote:

No, I’m told Loc Tite and oil are equally bad. I just used locking helicoils. 

The strip was a nice bonus. Here is the link to the eBay auction:

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F292324972168" rel="nofollow - https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F292324972168


This is the exact Helicoil needed for original replacement?
(Do you have 25 of them in this auction? )


Posted By: Pantera Mike
Date Posted: 10 Oct 2018 at 6:00am
uh...I can’t guarantee that is how the guy is still selling them. All I can tell you is that I bought mine from that seller, and they came on a strip. 

Nor can I tell you for sure that they are ‘right’. They are the proper size to fit, and their length matches the length of the threads on the recoil rods.  But I don’t know for sure what the guns originally came with.


Posted By: TankMan
Date Posted: 10 Oct 2018 at 1:26pm
I have to ask a dumb question: Why are threaded inserts required on an Automag? was there an
issue with direct threading of the part involved? Apologies if the answer is obvious. I'm not unfamiliar with machine work however I've yet to use a helical  type thread insert ...

See I told you it was dumb.

Jerry
http://tanks.linite.com" rel="nofollow - http://tanks.linite.com


Posted By: TRX302
Date Posted: 10 Oct 2018 at 4:22pm
Taps wear, and the holes wear when the rods are screwed in and out, and if the fit isn't perfect, the holes get wallowed out from the offset load across the recoil rods.

You can get a more consistent thread fit and finish with the Helicoils than with a simple tapped hole. And if the hole wears, you just replace the Helicoil.

The Auto Mag doesn't *have* to have the Helicoils, but they were a good design decision that probably cut down on manufacturing rejects and failures in the field, and made repair of the cocking pieces practical instead of replacement.


Posted By: Travis Morgan
Date Posted: 10 Oct 2018 at 5:02pm
Originally posted by TankMan TankMan wrote:

Why are threaded inserts required on an Automag?  Apologies if the answer is obvious.
Jerry
http://tanks.linite.com" rel="nofollow - http://tanks.linite.com

I would imagine the decision to use what is literally heat treated spring steel, was to prevent thread wear on what otherwise would have been cast stainless. 
Especially critical for a thread that is required for take-down disassembly; keeping in mind it would be cheaper to replace rods if needed.

So why does it make any sense to use helicoils on on an AutoMag?  ...... "It just does"






Posted By: TankMan
Date Posted: 10 Oct 2018 at 10:37pm
Thanks for the replies, the responses given make sense. Better to replace a basically sacrificial parts than the entire cast part.

As part of my main hobby I do foundry work in aluminum, bronze and small grey iron castings; for me if a part goes south I can make a new one.

I would not want to recast some of my more complex parts in case something went wrong with a threaded section so I can see the utility of a helical thread insert.

Jerry
http://tanks.linite.com" rel="nofollow - http://tanks.linite.com



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