Tempering a New Cast Mainspring and Frizzen Spring

Loyer

Loyer

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SW Ontario
I bought an old flintlock without a mainspring or frizzen spring. I purchased one from the internet knowing
I had to fit it and temper it.

It is now fitted but I am unsure of the best way to temper it.

Does temper also mean harden first and then temper ?
What is the preferred method for a novice ?

ThANKS FOR ANY HELP YOU CAN GIVE ME.
 
You will need to heat the springs evenly to red heat, then quench in oil. Red, not orange. A file should skate on the surface.
Then the temper needs to be drawn. One method is to submerge the springs in melted lead.
Or, place the spring on its side in a little steel pan with some oil. Heat the pan until the oil burns. Keep the spring wet with burning oil, so that the temperature of the steel is uniform.
The first time you try the spring, you will know if it is correct.
 
Sounds like I would need to know what I am doing or else the parts would be junk.
Any shops out there that do tempering ? My local gun shop won't do them.
 
Would a salt bath work as well? I have a salt bath annealer with a PID controller that allows me to set the temperature precisely. Lead melts at 371C; I can set my salt bath anywhere from 142C to 590C. Is a simple dip enough or does it need to stay at the tempering temperature for a certain amount of time?
 
google "jack rowe spring" or "larry potterfield spring"

Both will have youtube videos (almost too many) but I managed to make a hammer spring for a Miroku O/U by watching their videos.
 
tiriaq said:
You will need to heat the springs evenly to red heat, then quench in oil. Red, not orange. A file should skate on the surface.
Then the temper needs to be drawn. One method is to submerge the springs in melted lead.
Or, place the spring on its side in a little steel pan with some oil. Heat the pan until the oil burns. Keep the spring wet with burning oil, so that the temperature of the steel is uniform.
The first time you try the spring, you will know if it is correct.
Click to expand...

When I draw the temper using molten lead, I use a high temperature thermometer and keep the lead at 720 D to 740 F and keep it immersed for 3 minutes by the clock. Amazing how long 3 minutes takes. If you are using an electric lead pot you will probably have to immerse each end separately because it is fairly difficult to keep the top end immersed

cheers Mooncoon
 
Like other said you need to heat red hot, quench in oil (depending on the properties you want) and then temper it.
Funny thing is we manufacture ovens for stress relieving and tempering springs in Quebec we ship those to manufacturers in the USA, Europe and Asia.
If you have more info on the material type, hardness you're trying to achieve etc...
Tempering depending on the material could be done in your kitchen oven since it is quite low temperature generally speaking.

Lead would not be recommended since it has no benefit other than shorter quench time. Oil will give the same properties but need to be quenched for longer (approx 6 min depending on geometry).
Oil is less of a challenge as well as being more safe for a beginner, the parts and health.
In my 6 years visiting various plants for springs and automotive parts I have never seen Lead quench.
 
Last edited:
denydart said:
google "jack rowe spring" or "larry potterfield spring"

Both will have youtube videos (almost too many) but I managed to make a hammer spring for a Miroku O/U by watching their videos.
Click to expand...

I found a similar article and re-hardened and tempered a spring. It did fail eventually, but in all honesty was is poor shape to begin with.

As mentioned, when heated to the Curie point, metal will lose it's magnetic property, app 1200 for spring steel. I found this to be a very red color for my spring. Heat slowly and evenly. I then quenched in oil.

To temper I immersed the spring in molten lead, pure lead melts at 621° F. Therefore if you keep the lead just above melting temp, you will have the correct temperature for the tempering step. Pure lead also solidifies at the same temperature, no slushy stage.

Obviously a DYI with minimal tools method. No specialty thermometers, no skills.

If you are into the old skills, Foxfire 5 is one heck of a book.

As is mentioned in the Larry video, the spring should be polished, to avoid stress points.

Spring steel and the carbon steel for swords and knives is similar. Swords are sometimes tempered to spring temper to reduce breakage. (Wiki)
 
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