Wondering if any of you gents have ever taken a weak Vee spring, and re-heat treated to include tempering - to get the strength back? I can fit a new Vee spring that's slightly oversize, but would much prefer using the original one. Any experiences would be appreciated. Thanks in adavance. Silvers

Frank,
a spring gets it's strength from the fact that its steel and, more important to this conversation, its shape.

Simply re-heat treating a spring won't make it have more spring force in the throw/travel you are using it in. You need to reshape it to gain more force or make a stronger spring if it exceeds the limits of the spring.

If the spring used to have adequate force and it now doesn't, it probably yielded (took a set/bent) and needs to be re-formed to it's original shape. That may require annealing, re-forming, then heat treating to proper hardness, then tempering.

Hi Silvers:

I must disagree with Chuck on this question.

There used to be a place called Standen Spring on McLeod Trail in Calgary that specialised in the re tempering springs for autos. It was done as an inexpensive way to get springs working again after they lost their tension. My buddy had to do it to his 70 240Z. It was an inexpensive way to get working springs for rare classic cars.

I remember doing this in a Hot Metals class that I took as an undergraduate. I think that the spring was brought up to a certain temperature and quenched when a certain colour was achieved. If done correctly, the spring was returned to its original state.

Of course,YMMV!

Try tempering the spring again with help from a heat treating company that specialises in this type of work.

Good luck,

Franchi

Here is a generic formula for heat treating simple carbon steel springs. First, you will need a little can a vermiculite or hard wood ash, a can of oil for the quench ( olive, peanut, transmission fluid).

The spring needs to be annealed first, heat it to a very dull red in a dark room, imediately put it in the vermiculite /ash. It will help alot of you can heat a larger bar of steel to go in with it. The keey is to cool to room temp SLOWLY. Do this three times. This refines the grain of the steel and greatly enhances the toughness. Polish, make sure there are no deep scratches anywhere

Next, using a magnet to check for proper temperature, heat the spring EVENLY until the magnet has no attraction to it. Quench it in the oil until room temp. Clean it off, polish it again and put it in the oven at 500 degrees for two hours, let it cool, temper it again, same temp for two hours. It should be a bright blue color.

I've made litteraly thousands of springs. The most important step is the anneal prior to hardening. You can't skip this step as it puts the steel in a known state ( dead soft with as fine a grain structure as you will achieve). The fine grain structure will more than double the toughness and flexability of the spring over "normal" grain.

If you have access to a digital furnace, even better. The temps are 1350 for the anneal, simply leave it in the furnace and turn off the furnace to cool. Heat to 1450, quench and temper at 500.

I don't think you can compare car springs to gun springs. Just re-hardening it without knowing the proper temperature will result in spring either breaking or not working, and the only one that would know would be a good gunsmith, a good one.

There is a certain temperature for all hardened parts and a certain temperature for annealing them. This work must be done in an oven and not with a torch, as the temperature is achieved too fast.

If you have a replalcement, some are oversize and I suggest you measure the old one and grind the new one to shape, keeping a dish of water so as to not over-heat during grinding.
Keep the old one for a copy.
Most likely, the other spring was not of the right temperature to begin with.
There are some guns that I have that are over 120 years and the springs in the locks and top lever are still strong.

I think Franchi's anology to a car spring is not without merit. Both are springs and both made from steel. The part that was not mentioned about the coil springs of a Datsun 240Z was what happened inside the shop where the springs were reworked.

I've had springs from cars and even a couple airplane landing gear legs reworked. In all cases, the springs were re-formed to their original shape by being stretched in the cases for coil springs, or re-arced in the case for leaf springs and the set of airplane cantilever spring gear. A sagged coil spring has been compressed and has taken a shorter set height. It must be stretched back to original shape so it can give the original pressure and height. Simply re-heat treating won't restore coil spring height nor a gun's "hat pin spring" pressure.

Thee is annealing, hardening and tempering. Three distinct processes. Yes, anneal the spring first. The re-shape it to whre you want it.

Then harden it by heating it to the proper temp and quenching it. Now it is "file-hard" but very brittle.

So you must now temper it by placing it at a known temp for a certain length of time.

The problem is, you don't know the spring alloy so you don't know if it is oil, water or air-hardening (I would guess it's oil)

And since you don't know the alloy you don't know the tempering requirements but you can do this by color rather easily if you have an electric oven.

When you watch someone experienced do it the process looks simple but in reality takes a lot of skill.

Thanks everyone for your replies. I should have added more words in my post. Yes, I was planning to reshape the Vee spring after annealing and before re-heat treating. My question was more around: has anyone here done this, did you recover the spring's strength, and is the spring holding up? Silvers

I have not done it but I know that you can conrol the temper and therefore the "springiness" or "strength" of a spring. The stiffer the spring the more force but also the more prone to breakage.

I watched my father do this on a wee little vee spring (holds up cocking rod in Cashmore SLE) a couple of months ago. After reading Bailey's post above, I can see it was an amateurish job, but is working well so far. He used a propane torch and judging by color, annealed, opened and bent ends to reshape cold, hardened and tempered. First try he tempered to far (when tested with pliers spring lacked spring), so rehardened and retempered. In fairness to William Cashmore, I have a vague memory of making said spring under my father's guidance 35 years ago after fiddling with and breaking the original.
Inspired, last week I made a new top lever spring for my project gun out of a hacksaw blade. I shaped the spring hot. Took three tries, but it seems to be working.
I say go for it.

I've done this successfully. The information aboveis pretty accurate. There is a high probability that the spring steel is 1095 plain carbon and works at the colors/temperatures stated. Be sure to check for a crack asthis is frequently a cause for weakening. Otherwise, it should be quite repairable.

Note for those interested in working steel. The hardening process adds little to the stiffness of the spring. What hardening does is to allow the spring to be compressed past the point where an unhardened piece of steel of the same dimensions would be permanently deformed (plastic deformation). Tempering extends the amount a hardened steel spring can be deflected without breaking (brittleness). A properly designed, made, hardened,and tempered spring can be fully compressed without damage. Consider the number of times an engine valve spring is cycled without loss of performance. And, this after being left compressed for long times.