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Jul 28th, 2025
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Joined: Jul 2005
Posts: 293
Sidelock
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OP
Sidelock
Joined: Jul 2005
Posts: 293 |
Hello Gentlemen
My question is I would like to know what I need and how to do it to check the tension of a coil spring for the proper strength. This is my dilemma have just ordered a pair of firing pin springs for a gun I use for bird season. I suspect that one of the springs is weak which is unusual but never the less I am going to try that first. What I want to know is the compression strength of the new spring and then try to bring the old one up to that strength, buy heating it red then putting it in hot lead and holding it then quenching it in oil. I know how to do it with flat springs to put them in a vice and close the vice to see if it springs backs or breaks but I don't know how to test a coil spring. The only thing I can figure is that the thickness of the steel to make the spring decides the strength of that spring. What are your thoughts on this. Any help is greatly appreciated.
Pete
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Joined: Jan 2002
Posts: 474
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 474 |
Coil spring rate is determined by turn pitch, coil diameter, wire dia., and metallurgical condition of the wire itself. It seems to me your only practical test is to compare the two springs in compression. A good spring will allow compression to solid without taking a set. It should be fairly simple to compress each spring to solid on a platform scale and compare the readings.
OB
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Joined: Feb 2004
Posts: 13,883 Likes: 19
Sidelock
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Sidelock
Joined: Feb 2004
Posts: 13,883 Likes: 19 |
My understanding of the strength of the spring is sort of along the lines of what OB said. However, as long as the steel spring is operating in the elastic region (not taking a permanent set), spring rate should not be affected by hardeness of the steel (making the steel harder won't make the spring stronger).
Peters, a modern coil spring is most commonly made from 1095 cold workhardened "musicwire". The process to make the wire aligns grain in a longitudinal direction. This wire is then cold wrapped on a mandrel to form the coil. So, IMO, if you heat the coil spring and quench it, it will allow grain reformation and not the in the longitudinal alignment of the original, therefore the spring will never perform to the level of it's original condition and not have the resistance to breaking of the original workhardened condition.
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Joined: Feb 2004
Posts: 13,883 Likes: 19
Sidelock
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Sidelock
Joined: Feb 2004
Posts: 13,883 Likes: 19 |
Sorry for going off track of the original question. Coil spring testers measure force at specific height/length. The tester shown in this link to ebay is typical of how coil springs are tested. http://cgi.ebay.com/ebaymotors/Rimac-VAL...sspagenameZWDVW
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Joined: Jan 2002
Posts: 5,983
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 5,983 |
Don't know what happened to my reply to this thread. Maybe I didn't properly submit it. I'll try again: Keep it simple. Place two compression springs end to end(slipping them on a rod, similar in size to the spring I.D. might be a help). Push them against each other. The one that collapses most is the weaker one. Ditto for extension springs. Hook them eye to eye and pull. The one that stretches most is the weaker.
> Jim Legg <
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Joined: May 2005
Posts: 207
Member
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Member
Joined: May 2005
Posts: 207 |
I would be inclined to take the lazy man's way out. Locally we have a spring shop that appears to cater primarily to the automotive industry. They also however carry a large selection of small coil springs. Just take a set of dial calipers with you to the local equivalent shop and buy a spring with a little thickner diameter wire and of course with inside and outside dimensions that will still fit in the space alloted.
Referring back to your original problem, I find myself wondering if your problem is not spring strength but friction and if something is binding; bent firing pin for example or simply crud in the hole.
cheers Doug
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Joined: Aug 2004
Posts: 411
Sidelock
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Sidelock
Joined: Aug 2004
Posts: 411 |
Although I have never had any problems with the M-21 coil mainsprings and they are always under some compression and many have been that way for 60 years,I have problems with newer springs. The Citori and 680 series Berettas,if fired in competition (15,000 shots per year) shorten 3/16" after two years (mainsprings)and with a simple replacement,function as new.The older guns have large diameter wire and ,if they lose strength, still have enough power.While the newer guns use smaller diameter wire and take a noticeable set in a much shorter time.
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