Rookie Mistake

[Double Play]

Originally Posted by edgarspencer

Making the material bend 180 degrees, even when heated cherry red, opens up edges on the outside of the radius. The best springers will carefully grind and polish the springs after bending, and tempering. Lesser quality springs probably don't get this skilled attention.

Edgar,
I agree with everything you said but it dose not explain why this spring broke in the location that it did.

[edgarspencer]

The kinetic energy is stored along the entire spring. From the bend, to the stirrup hook, they are tapered, so that the energy is progressive. (High Performance springs in competition cars are called Progressive Springs) Any minute defect (As John stated, called a stress riser) along the surface can cause a failure when the spring is compressed.
It is blasphemy to say this, but visually compare the lock springs of our beloved Parkers to the spring in a "Best Grade" English gun, and it will be immediately evident the attention paid (or not) to these little bits. 'Theirs' look they're polished to a fairthewell compared to 'ours'.

[Eldon Goddard]

Is this true even for a high grade parker hammer? Do you think an A grade hammer gun would have polished springs? I have heard this from someone before so I am holding out hope that at least the high grade parkers stood up to the English best.

[edgarspencer]

Eldon, my highest grade hammer is a grade 3, and it's springs aren't polished very much. Brad Bachelder needs to ring in on this as he is messing with these for our dedicated hammer gun guys on a regular basis.

[Richard Flanders]

I don't know about the rest of you guys but when Edgar opines on metallurgy, I listen carefully and believe what he says. I'd love to put a wire into each of his ears and "download" his knowledge base on the subject. I never use Simple Green in my sonic cleaner. The ammonia in it is obnoxious and can not be good for any metal. I can't even stand to use that stuff on the sink with a sponge. The fumes play hell with my sinuses. I've permanently shelved what I have in stock in favor of pine oil cleaners.

I made a similar screwup recently with another cleaner and a gun part. I machined out an 80% AR lower of 7075 T6 aluminum. I always soak them in hot water with Dawn dish soap to get the oil off but added some Oxi-clean to this last soak, which was a mistake. Oxi-clean is a peroxide compound thus an oxidizer. 7075 is alloyed with something (Zn?-can't remember right now) and the O-clean darkened the entire lower slightly and caused some black spots where there were larger accumulations of the alloyed metal, which is clearly more subject to oxidation than the aluminum. No real damage to the lower but it's clearly microscopically etched. Won't make that mistake on the next one I can tell you. All in all this spring thing is a good lesson to us all on using sonic cleaners to clean gun parts.

[B. Dudley]

The fit and finish on high grade Parker guns was very good. I have seen cross hatching on Hammerless hammers as low as grade 3 guns. And I have seen high polish on even the trigger springs in BH grade guns. The last high grade hammer gun I was into was a very early $225 or $250 grade and everything had a very good finish on it.

[edgarspencer]

Thanks Richard. My wife agrees I should have a wire inserted in each ear, but I'm not sure she's as much interested in downloading stuff, as she is offing me.
I am far from any wizard on this stuff, but I think these broken springs are a result of a 'perfect storm' of events; still under compression, not to mention being cocked, harmonics possibly, but I'm not so convinced on this, and an aggressive cleaner. The mere fact the springs appear black, as opposed to a near chrome-like finished of highly polished springs is damning in itself.

BTW, I like Dawn for a lot of applications other than doing dishes.

[edgarspencer]

Dean, I would agree that the heat didn't play a part in this from a metallurgical point, as it would need to get above about 900 degrees F, the lower critical temperature for alloy steel, but I think if the case can be made that the cleaning agent played a part, the heating of that agent would most likely intensify the etching effect.

[10 bore]

BTW, I like Dawn for a lot of applications other than doing dishes.[/QUOTE]

I use it to wash and help degrease ducks that i mount,
i couldn't tell you how it works on dishes but think it's used for that too.
scott

[wayne goerres]

I find it strange that the main spring for the bottom lock in the photo appears to be broken in two places and that the brake at the middle of the spring looks oxidized like it has had a crack for a while.