Spring Tempering

[ggggr]

CapitalBee sent me a spring to try in a Webley Junior pistol.. It was easy to cock but was down in power, and after 15 shots when I checked it had shortened a lot. I've been told that airgun springs are over stressed compared to most springs---and I wonder if this spring could be retempered or is it down to the quality of the wire?
I'm quite happy with the normal springs for the pistol and as I only tend to have the over on on Christmas Day and New Years Day, cannot see my throwing it in the over for quite a while!

[ccdjg]

CapitalBee sent me a spring to try in a Webley Junior pistol.. It was easy to cock but was down in power, and after 15 shots when I checked it had shortened a lot. I've been told that airgun springs are over stressed compared to most springs---and I wonder if this spring could be retempered or is it down to the quality of the wire?
I'm quite happy with the normal springs for the pistol and as I only tend to have the over on on Christmas Day and New Years Day, cannot see my throwing it in the over for quite a while!

Guy, If a spring shortens after compression then this is down to the fact that it has been tempered too soft (that is, it has been tempered at too high a temperature.) As long as the spring has no obvious cracks or other defects, it could be completely softened and returned to its original length, then completely hardened to almost glass brittleness, and then tempered back to a proper spring flexibility.

Cheers,
John

[ggggr]

Guy, If a spring shortens after compression then this is down to the fact that it has been tempered too soft (that is, it has been tempered at too high a temperature.) As long as the spring has no obvious cracks or other defects, it could be completely softened and returned to its original length, then completely hardened to almost glass brittleness, and then tempered back to a proper spring flexibility.

Cheers,
John

Thanks John. I wont bother with it as I'm happy with the normal Junior springs. It would cost me more in Leccy to do it! Could it not just be thrown in the oven to retemper? I'm sure someone on here straightens old springs and puts them in the oven for half an our then turn the oven off?

[ccdjg]

Could it not just be thrown in the oven to retemper? I'm sure someone on here straightens old springs and puts them in the oven for half an our then turn the oven off?

No, you can't retemper a spring that is too soft just by heating it, but you can retemper a spring that is too brittle and make it softer if you heat it to a temperature higher that in was originally tempered at.

The trouble is you only find out that a spring is too brittle after it has snapped!

The heat treatment sequence for making a spring is to first heat it to a red heat and quickly quench. That makes it extremely hard and brittle. Then you remove the brittleness by tempering, which means heating it again, but to a much lower temperature and letting it cool naturally. The higher the tempering temperature the softer the result. The trick is to get the correct temperature for tempering, as a good spring has very specific requirements.

[ggggr]

No, you can't retemper a spring that is too soft just by heating it, but you can retemper a spring that is too brittle and make it softer if you heat it to a temperature higher that in was originally tempered at.

The trouble is you only find out that a spring is too brittle after it has snapped!

The heat treatment sequence for making a spring is to first heat it to a red heat and quickly quench. That makes it extremely hard and brittle. Then you remove the brittleness by tempering, which means heating it again, but to a much lower temperature and letting it cool naturally. The higher the tempering temperature the softer the result. The trick is to get the correct temperature for tempering, as a good spring has very specific requirements.

Cheers John. Nice to know even though I've no intention of doing this one.

[TonyL]

Fascinating stuff; thanks, chaps.