strong spring SOLVED

[T*O*F]

This had never occurred to me before.  I've got a Davis Golcher percussion lock that is a bear to cock.  I've got mechanic's fingers and I can't squeeze the limbs at all.  If the spring is tempered too hard, will it make it harder to bend; ie, softer spring more give.

[rich pierce]

This had never occurred to me before.  I've got a Davis Golcher percussion lock that is a bear to cock.  I've got mechanic's fingers and I can't squeeze the limbs at all.  If the spring is tempered too hard, will it make it harder to bend; ie, softer spring more give.

Word in the shop is that it’s not the temper (hardness), it’s the thickness and width that determine force needed to compress a leaf V spring. Temper determines if it takes a set (too soft), works safely without a set (spring temper) or snaps (too hard)

[T*O*F]

Word in the shop is that it’s not the temper (hardness), it’s the thickness and width that determine force needed to compress a leaf V spring.

Two rifles, identical locks, identical springs.  The other lock doesn't have the problem.

[flinchrocket]

If the springs are cast they would have to be the same material to end up with the same strength.

[Hungry Horse]

Maybe its not the strength of the spring, but something interfering with the travel. If the spring is not flexing where it is suppose to, it will act exactly as you describe.

Hungry Horse

[T*O*F]

HH
We hold this truth to be self evident

[kutter]

Word in the shop is that it’s not the temper (hardness), it’s the thickness and width that determine force needed to compress a leaf V spring.

Two rifles, identical locks, identical springs.  The other lock doesn't have the problem.

Take the problem spring and place it in the 'The other lock' that you have.
Then see if the problem spring still shows the same issues, or if they magicly go away.

If the issues with the problem spring dissappear when placed into the second  lock mechanism,,then the first lock is slightly different in geometry and leverage or something is interfering with the parts.

If the issues continue with the spring when placed in the second lock, then that spring is slightly heavier in mass through the arm(s) IMO.
Trim it down some and reshape it to a more pleasing V spring shape. I think most of them could use it anyway.

There's no telling where the springs are sourced from and what mould they are cast from. There has to be more than 1 mould and there's likely  differences in  dimensions however slight .

[James Wilson Everett]

Guys,

The temper of a spring has nothing whatsoever to do with it's load/deflection.  Identical springs will act the same if tempered at 600 - 700 - 800.  To change the strength of a spring you must change it's shape or thickness.

 Here is a quote from people who know:

The Iron Age Volume 89 May 9, 1912, page 1151

The stiffness of a piece of steel cannot be increased by alloying nor by heat treatment.  By this I mean that provided the elastic limit is not exceeded, the amount of deflection for a given load cannot be decreased.  However, heat treatment will raise the elastic limit so that a much greater load can be carried without causing a permanent set.  Until the elastic limit is reached all steels, no matter how treated or of what nature, will deflect the same amount under the same load.  However, the poorer grade steel or the un-heattreated one will reach its elastic limit first and will then deflect much more and retain a permanent set.

[Bob Roller]

i have almost zero knowledge of cast main springs and never wanted my reputation to be dependent on the indifferent quality control in a foundry.I learned how to make springs by watching an old gunsmith who allowed me to watch him and when I was able to obtain a good quality of spring steel that was consistent in quality it shortened the "Cut and try"learning process probably by years.I tested all my mainsprings after they cooled down by installing them in the lock and then holding the sear up I rocked it back and forth about a dozen times and if if had the "oily feel" it should have I then finished it by beveling the edges and polishing.A STIFF spring in any lock as described here can if it breaks at full cock can knock the bottom out of the lock mortise and I got calls from people who had that happen and ask me to make new springs and I told them I didn't  repair any locks unless it was one I made.Wes Kindig asked me to make replacement springs for production locks and I turned him down.My methods and techniques rank right up there with the stone axe but they work and apparently still do.I have a lot of flintlocks "out there"that I can no longer get frizzens for and the moulds that produced them are in limbo because the owner passed away after a long run with adult dementia.The locks are the Shoults,Ketland and Maslin.The Ketland I made in no way resembles those now made by Chambers and Kibler and the Shoults was sorta/kinda copied on the early Dixie squirrel rifle and the Maslin by CVA(maybe).Lock making is now 3 years into my past but I have forgotten nothing.There is more to making a mainspring than making something that looks like one and I learned a lot from owning and studying locks made by masters in England and borrowing samples of these from Lynton Mckenzie and Tom Dawson.I got a GOOD comparison of locks by looking at original Hawken and the fine Brazier lock on my own Whitworth long range rifle.The Brits were over the top and a challenge to try to copy but I enjoyed the challenge and perhaps came close on some of these.OK,long,boring rant over.
Bob Roller
The springs that broke and wrecked stocks were broken close to the tumbler when the lock was fully cocked.If they had cracked or broken in the bend there would have been no damaged wood.

[frogwalking]

I have seen a number of guns damaged as you described, but did not know how it came about.  Thanks Bob.

[Bob Roller]

As I said earlier,I have no real knowledge of cast mainsprings but the PREloading of a forged spring will determine the performance and speed of the lock and the length of the lower limb will set most of that tension.The high quality locks seen on British rifles and shot guns
will resist the initial pull on the hammer and as it rotates to full cock it relaxes.The lock TOF described should not have got out of the shop and whoever assembled it knew little or nothing about the function of a gun lock and it should have been set aside.
Bob Roller

[Bob Roller]

As I said earlier,I have no real knowledge of cast mainsprings but the PREloading of a forged spring will determine the performance and speed of the lock and the length of the lower limb will set most of that tension.The high quality locks seen on British rifles and shot guns
will resist the initial pull on the hammer and as it rotates to full cock it relaxes.The lock TOF described should not have got out of the shop and whoever assembled it knew little or nothing about the function of a gun lock and it should have been set aside.

One thing that we did not mention is the movement of the link that hooks the spring to the tumbler.It should be free to go back to the shaft that holds the hammer..
Bob Roller

[T*O*F]

Disclaimer:
1.  My LED overhead was burnt out and I was working on my desk with a 40w lamp.
2.  I just had cataract surgery and my glasses aren't suitable for my new vision.

The spring was "in the gray."  When I took it into the shop to start working on it, I noticed a small nubbin of slag.  Tried to knock it out, but it was part of the casting.  Looked at it under the scope and it goes down a bit and doesn't allow the spring to compress like it should.  I have nothing thin enough to remove it except a Dremel with a thin cut-off wheel.  Will try to polish it out with that.

[Bob Roller]

Polish it real bright and it will be a really good looking spring.I like the shape and I have made a bunch of them.
Bob Roller

[PIKELAKE]

I had  a situation very similar to yours a way back when. I think I doubled up or used three Dremel cut of wheels ; I don't know if that would help you remove the slag.  JZ

[helwood]

Greetings,
I have used the Handpiece in the past but a number of years ago I believe it was Bev Decman told me about a trick she used from working stained glass.   You can cut your old Diamond Band Saw  Blade and mount it in your Jewler's Saw  and it is very accurate.   I have used it for this exact casting problem several times.   It's  a very thin blade and you can take that nub out of there very nicely.  Sorry the pic is upside down.        Hank
                     

[Not English]

Hank, that's a heck of a good idea. Thanks for putting it out there.

[smylee grouch]

Where are those neat sanding blades sold?

[WadePatton]

Dave I'm glad it was a simple fix, for a fully-sighted man with good lighting. 

Bob, thanks for your rants and raves. I read 'em all.

[helwood]

I'm pleased to share the information.   Inland is a big company supplying tools and supplies to the folks doing Stained Glass.  I included the packing sheet with the Stock Number--90005   at the top so folks could find it easily.  I  had a Glass Band Saw and not sure if I had ordered it from Internet or from my Instructor.   They are really  a Saw Blade.   They are pretty easy to find after you know they exist.

[smylee grouch]

Thanks for that info and posting helwood. This tool looks like it has more than one use.

[Jakob]

Thanks for that info and posting helwood. This tool looks like it has more than one use.

Yeah, that's just a plain old handy idea.