strengthening a Mainspring

[duca]

Hi all, I have a lock with what I feel is a weak Mainspring. What would be the proper way to bend it a little to make it Stronger? 
Thanks for looking;
Anthony

[albert]

You would have to aneal it first to bend then re heat treat , you could make a little wooden wedge shape to put in between  the two and that might get you by.

[duca]

Ok, First I heat it cherry red and Bend it out a little. Do I heat it up again to cherry red and then submerge in Oil? Do I just Heat the Bend or the hole Spring? After I Quench in oil am I ready to go?
Thanks;
Anthony

[Long Ears]

If you do that it will break! You have to temper it back after you harden it. There are several threads on the board explaining the processes and the pitfalls. One thing leads to another, ask me how I know. Are you sure it's the main spring and not the frizzen, angle of the cock or frizzen spring? The wedge mentioned by Albert might narrow it down. Good luck.

[44-henry]

You might want to contact the company that made the lock, if it is defective there is a good chance they will take care of it for you at no charge.

[Gaeckle]

Make a small wedge from steel or brass and push it into the the "U" portion of the spring as far as it will go. That is adding a stiffener. You could epoxy it to the spring to help keep it in place. This way you don't have to heat it or add potential damage to your spring.

[Dphariss]

Make a small wedge from steel or brass and push it into the the "U" portion of the spring as far as it will go. That is adding a stiffener. You could epoxy it to the spring to help keep it in place. This way you don't have to heat it or add potential damage to your spring.

I have done something similar in the past until I could get a better spring, this was before I read of the rearc trick.
It also creates a stress riser and I would not consider it a long term "fix". The arms of the spring are supposed to flex along their entire length. Having a block in place concentrates the stress.

Dan

[Dphariss]

Hi all, I have a lock with what I feel is a weak Mainspring. What would be the proper way to bend it a little to make it Stronger? 
Thanks for looking;
Anthony

Polish the spring and make sure its oil/grease free.
Clamp the spring in a manner that will not significantly impede bending the lower leg, it need only flex over the last 3/4 or so of its length.
Using a plier or vise grip on the end flex the spring so to increase the spread perhaps 1/4". Not too much.
Now heat to a pretty bright blue and it should maintain the flex when it has cooled somewhat.
This should rearc the spring successfully.
Only other way is to heat, bend, reharden and temper. My second choice.

Dan

[Dphariss]

The entire lower leg must be uniformly heated, propane torch kept moving and long dwell time at the thicker end will work.
When the right temp is reached the spring will relax and little or no pressure will be needed to hold it at its new bend.

Dan

[duca]

Awesome Dan, Gonna give it a try. Thanks all for your input.

Anthony

[Hungry Horse]

Duca;

  Make sure you check the contact area where the spring contacts the tumbler, just to make sure, that when you re-arc the spring, you don't shorten it to the point it could slip off the tumbler. I did that once on a Navy Arms Harpers Ferry, and it busted the stock below the lock, when I when I shot it.

                       Hungry Horse

[duca]

Duca;

  Make sure you check the contact area where the spring contacts the tumbler, just to make sure, that when you re-arc the spring, you don't shorten it to the point it could slip off the tumbler. I did that once on a Navy Arms Harpers Ferry, and it busted the stock below the lock, when I when I shot it.

                       Hungry Horse

Holy S#@T! That sucks. Thanks for the heads up HH

[Dphariss]

Duca;

  Make sure you check the contact area where the spring contacts the tumbler, just to make sure, that when you re-arc the spring, you don't shorten it to the point it could slip off the tumbler. I did that once on a Navy Arms Harpers Ferry, and it busted the stock below the lock, when I when I shot it.

                       Hungry Horse

Once compressed it should be the same length to the tumbler if the curve is maintained properly. Rearching by 1/4" or so with a nice uniform curve will not change the length of the installed spring since it will compress to the same length as the curve if flattened when conpressed. Otherwise when they go flat, and some reproduction locks are made with springs cast from originals that have lost some of their arch, they would then be too long.
Rearching done right simply increases the preload.
If the spring has a sharp bend put in it then it can effect the length to the tumbler since these do not uniformly follow the proper curve.
Springs with a direct bearing on the tumbler can be less forgiving of this in that case plug the index pin hole in the lock plate and set it back slightly 1/16" perhaps. If the index pin is in the wrong place, the lower leg too short or even long then the pin hole was improperly placed by the assembler.
If the spring is heated to incandescence and if the lower leg curve looks good, its best to slightly spread the legs at the bend. Remember that the top leg flexes too though not so much and can be used to preload the lower leg if its "right".
As with all things moderation is the best policy if the spring is properly tempered then the heating to blue and bending will work very well and only 1/4" or so will make a lot of difference.
Often buying a replacement spring will show that the wax for the original was not at "spec" and lacked proper preload. Often the replacement is better. HOWEVER, its a roll of the dice and I prefer to reshape the spring then I know what it is.
Gotta run.
Dan