Gunsmithing Helicoil action lugs to increase torque?

[Thunderskunk]

Afternoon gents,

Anyone ever heard of boring and helicoiling an action just to get some more torque on the mounting screws? Something in "The Bolt Action Vol. 2" made mention of there being benefits to A) having a tighter grasp on the action and B) being sure the bolt holes are as close to on center as possible. We use helicoils in aluminum parts that the designer was worried would strip out, so we purposely manufacture the parts with helicoils.

Just an idea.

 

[chevy_man]

Are you using an aluminum action?

If I was that worried, I'd machine the holes and use a thread mill to cut them a size up.

Helicoil won't give you any more torque. Bigger threads will.


If the action is bedded properly into the stock there is zero reason to need it. The recoil lug should be holding recoil. Action screws are just keeping it from falling out of the stock.

 

[Supersubes]

What he said ^

 

[...]

Afternoon gents,

Anyone ever heard of boring and helicoiling an action just to get some more torque on the mounting screws? Something in "The Bolt Action Vol. 2" made mention of there being benefits to A) having a tighter grasp on the action and B) being sure the bolt holes are as close to on center as possible. We use helicoils in aluminum parts that the designer was worried would strip out, so we purposely manufacture the parts with helicoils.

Just an idea.

helicoils arent installed to prevent aluminum threads from stripping out due to torque....

they are installed for wear resistance in threads that are expected to be screwed and unscrewed frequently, a steel screw will slowly erode the aluminum threads, hence the steel helicoil inserts.

you have to remember that even though the helicoil is steel, its still threading into aluminum, so while you may see a slight increase in torque it can handle due to larger diameter, the aluminum is still going to be the failure point.

 

[Thunderskunk]

I might have confused some applications when it comes to helicoils... to my credit, I just made parts, I didn't design the product.

The engineer who explained it to me at the time did mention torque, and I do believe him because he mentioned a test bench where helicoiled parts were expected to strip at a higher torque than normal threads. This was an oddball part though: laser cut aluminum plate for aerospace control stand use. There was some sort of safety factor involved where the likelyhood of failure was decreased by the installation of a helicoil. It might have had more to do with contact surface area.

I'm curious enough that I might test it. I know it sounds silly and obvious, but the only thing I'm missing in the shop is a grade of steel for receivers. Don't take me as saying anyone is wrong though.

 

[Supersubes]

I might have confused some applications when it comes to helicoils... to my credit, I just made parts, I didn't design the product.

The engineer who explained it to me at the time did mention torque, and I do believe him because he mentioned a test bench where helicoiled parts were expected to strip at a higher torque than normal threads. This was an oddball part though: laser cut aluminum plate for aerospace control stand use. There was some sort of safety factor involved where the likelyhood of failure was decreased by the installation of a helicoil. It might have had more to do with contact surface area.

I'm curious enough that I might test it. I know it sounds silly and obvious, but the only thing I'm missing in the shop is a grade of steel for receivers. Don't take me as saying anyone is wrong though.

On a rifle receiver, this is a solution searching for a problem. Nobody is breaking receivers out of stocks because screws threads were insufficient.

 

[357Max]

^^^^ yes solution looking for a problem in this case, but nothing wrong with learning.

Generally speaking since no specifics were given I think it would be a bad idea.
To qualify that I'm speaking of modern actions that are very hard 42-53 Rockwell C & what is being clamped between action screws & receiver (aluminum usually). There would be more benefit making sure your chassis/bedding blocks are at least 7075 T6 to handle the clamp force applied.

A properly installed Helicoil will increase torque load capability if base metal is inferior to fastener alloy. Ex. Grade 5 - 6061 T6 or Grade 8 - cast iron.
The above is why I avoid scope rings/bases that are not 7075. Also why I prefer 7075 chassis.
The bigger limitation with actions (not that there is an actual problem) would be thread depth engagement. 1-1/2 x diameter is required & I have a few that are shy of this. A Helicoil also needs 1-1/2 x engagement albeit a larger diameter. The required depth is not going to be available for properly helicoiling a receiver.

 

[DAVETOOLEY]

"The bigger limitation with actions (not that there is an actual problem) would be thread depth engagement. 1-1/2 x diameter is required & I have a few that are shy of this. A Helicoil also needs 1-1/2 x engagement albeit a larger diameter. The required depth is not going to be available for properly helicoiling a receiver. "

Exactly
I'll add more is not always better.

 

[308pirate]

Putting helicoils in a steel receiver, into which you're going to insert steel screws that you remove very infrequently if ever, is a complete waste of time and money.

 

[Wannashootit]

Never seen a discussion, much less an argument, as to why "more" torque would be beneficial/desirable?
Recoil forces are straight to the rear. The lug, properly seated firmly against the chassis/stock/bedding, absorbs these forces.
So the action can't move to the rear, or sides when properly bedded. There may be some slight upward and rotational forces but I don't see how they could be significant.

As long as there is sufficient torque to prevent the screws from loosening under vibration I don't see how "more" would be better.
Quite aware of how action screw torque can affect accuracy on "factory" rifles where the action isn't bedded, or there is improper fit in a chassis.
If an action is perfectly fitted, and stress-free, how could it be affected by even large variations in action screw torque?

What am I missing, that supposedly makes action screw torque critical? Never has been in my personal experience; same as barrel torque to the receiver; 50-60 ft lbs to make sure it won't vibrate loose, no need to go gorilla on it.

 

[Thunderskunk]

So... I really hope folks aren’t taking this personally. Maybe I’ve got the wrong vibe, but it’s just a question, with a lot of good answers by the way.

The exact reason I bring it up is from a paragraph I read in “The Bolt Action” about a particular action which Stuart Otteson believed could have been more accurate if said action could be torqued tighter to the stock. I don’t have an exact reference as both volumes have been a bedside reader for some time. I’m not saying all actions suffer from this problem, but at some point one has. At least in his opinion. He prefaced the books with the point that he’s not really an expert, but he’s had the privilege to talk with many who were.

The end state of whether helicoiling an action would tighten a shot group is more than likely a “no.” I’m not confident enough to say that adding helicoils to an already hard material will or will not enable higher torque values before stripping. I’m also curious what it does for alignment given there’s no pins between the stock and the action. It’s a fun experiment. Don’t let me ruin your day.

 

[DAVETOOLEY]

I have Stuart's book somewhere. I've done many things over the years that in the moment I could yell " Holy Shit I've discovered the secret to the universe" only to find out it wasn't repeatable. There are certain basic things in the accuracy world that matter.

 

[LRI]

If you take a minute to evaluate the linear tensile load on a 1/4-28 fastener snugged up to around 40-50 inchlbs, it works out to around 1500psi worth of linear compression.

In a nutshell, park Miss Piggy on your junk and pull the trigger.

It's attached pretty well. . .

 

[chevy_man]

So... I really hope folks aren’t taking this personally. Maybe I’ve got the wrong vibe, but it’s just a question, with a lot of good answers by the way.

The exact reason I bring it up is from a paragraph I read in “The Bolt Action” about a particular action which Stuart Otteson believed could have been more accurate if said action could be torqued tighter to the stock. I don’t have an exact reference as both volumes have been a bedside reader for some time. I’m not saying all actions suffer from this problem, but at some point one has. At least in his opinion. He prefaced the books with the point that he’s not really an expert, but he’s had the privilege to talk with many who were.

The end state of whether helicoiling an action would tighten a shot group is more than likely a “no.” I’m not confident enough to say that adding helicoils to an already hard material will or will not enable higher torque values before stripping. I’m also curious what it does for alignment given there’s no pins between the stock and the action. It’s a fun experiment. Don’t let me ruin your day.

Very simple. He was basing his observation on an improperly bedded or even inletted stock to reciever relationship.


We have marine Tex and accra -glass now. Zero reason to play with vudoo when you can simply eliminate it from the start.

 

[308pirate]

The exact reason I bring it up is from a paragraph I read in “The Bolt Action” about a particular action which Stuart Otteson believed could have been more accurate if said action could be torqued tighter to the stock. I don’t have an exact reference as both volumes have been a bedside reader for some time. I’m not saying all actions suffer from this problem, but at some point one has. At least in his opinion. He prefaced the books with the point that he’s not really an expert, but he’s had the privilege to talk with many who were.

So basically he's a layman offering opinions. No different than probably 90% of gun "experts" out there with zero data to prove what they claim.

In my profession guys like that are dismissed out of hand.

 

[Thunderskunk]

So basically he's a layman offering opinions. No different than probably 90% of gun "experts" out there with zero data to prove what they claim.

No. His literature is on the same level if not higher than "Hatcher's Notebook" which he even references in said books. My point in bringing up his humility is that he came at the subject with an open mind. He wasn't a gun expert who decided to bless us with his opinion, he's a guy who picked up a bolt action rifle at a store and decided to ask some questions. By continuing to ask questions, he became an expert and still believed he could learn more, specifically by talking with the designers, tool makers, and managers of said firearms manufacturers directly. On the physical side, he grabbed an action, a set of calipers, and a pencil. His graphics aren't engineering prints, but they're understandable, and that's key.

My quote there doesn't do him justice; obviously I got the wrong point across. The books aren't about how to make the perfect bolt action, it's just an extremely in-depth analysis to the history of each and the pros/cons of their geometry. One of his talking points is the "look" of the action. Obviously this is opinionated, but it had a direct effect on sales, which effects production numbers, and therefore is a great point to bring up. There's a reason you can't find these books for less than $100 a piece.

I wouldn't dismiss someone for saying they aren't an expert. Quite the opposite really; The people I want working for me are the ones who admit they don't know everything but are willing to learn, and the self-proclaimed experts I tend to dismiss. Experts let their product or reputation speak for itself .

 

[308pirate]

No. His literature is on the same level if not higher than "Hatcher's Notebook" which he even references in said books. My point in bringing up his humility is that he came at the subject with an open mind. He wasn't a gun expert who decided to bless us with his opinion, he's a guy who picked up a bolt action rifle at a store and decided to ask some questions. By continuing to ask questions, he became an expert and still believed he could learn more, specifically by talking with the designers, tool makers, and managers of said firearms manufacturers directly. On the physical side, he grabbed an action, a set of calipers, and a pencil. His graphics aren't engineering prints, but they're understandable, and that's key.

My quote there doesn't do him justice; obviously I got the wrong point across. The books aren't about how to make the perfect bolt action, it's just an extremely in-depth analysis to the history of each and the pros/cons of their geometry. One of his talking points is the "look" of the action. Obviously this is opinionated, but it had a direct effect on sales, which effects production numbers, and therefore is a great point to bring up. There's a reason you can't find these books for less than $100 a piece.

I wouldn't dismiss someone for saying they aren't an expert. Quite the opposite really; The people I want working for me are the ones who admit they don't know everything but are willing to learn, and the self-proclaimed experts I tend to dismiss. Experts let their product or reputation speak for itself .

If the adjectives in your first quote about him are indeed correct (he believes, he's of the opinion, etc) then I have no use for him.

I believe in data and credible, reproducible data at that. When engineers present their findings, they can back it up with solid research and empirical, reproducible observations.

What is this Otteson's character's professional qualifications? Is he an engineer? Physicist? Metallurgist? Who has ever hired him to design a rifle?

He sounds to me like one of the many self-appointed "experts" in the gun world who never actually did anything other than write a book.

 

[Thunderskunk]

If the adjectives in your first quote about him are indeed correct (he believes, he's of the opinion, etc) then I have no use for him.

I believe in data and credible, reproducible data at that. When engineers present their findings, they can back it up with solid research and empirical, reproducible observations.

What is this Otteson's character's professional qualifications? Is he an engineer? Physicist? Metallurgist? Who has ever hired him to design a rifle?

He sounds to me like one of the many self-appointed "experts" in the gun world who never actually did anything other than write a book.

Hey man, your loss. They're great books for understanding bolt action rifle design and development.

 

[308pirate]

They're great books for understanding bolt action rifle design and development.

From a guy who NEVER DESIGNED ONE.

Great fucking reference material................

 

[Thunderskunk]

From a guy who NEVER DESIGNED ONE.

Great fucking reference material................

Dude... you OK? I'm not trying to spite you or anything. Nothing I said was meant to be malicious.

I honestly don't know if the guy ever designed a firearm or not. I think he worked for Hornady at some point, but I don't have his biography. I'm not even sure if he's still alive.

 

[DAVETOOLEY]

From a guy who NEVER DESIGNED ONE.

Great fucking reference material................

From a guy who averages 12.6 posts a day and probably wear's Depends.

 

[308pirate]

From a guy who averages 12.6 posts a day and probably wear's Depends.

And yet I still manage to see my work fly all around the world.

As for the diapers, I bet you'll be in them long before me.