'Thinning' a mainspring?

[TNHillbilly]

I've got two 'Paterson' replica pistols with the traditional 'V' springs. Of all my BP pistols, the mainsprings are bears to cock. They slip on the 'L' lugs integral to the grip frame. I'd like to lighten the tension, but not sure whether to try grinding.....or exactly where to grind. or how to proceed. Any help?

 

[Flint62Smoothie]

Paul Val...D...ham (sp?) once had a write-up on this ... he had me grind (keep it COOL!) the "U-bend" area, keeping it smooth. It worked great!

 

[Old Salt]

Whenever I grind a mainspring or a frizzen spring I grind the width of the spring not the thickness.

If you imagine the spring before it is bent you have a long piece of spring steel with a length @ 4", a width @ 3/8" and a thickness @ 1/8". It's that 3/8" that I grind down. Most of the grinding I do on the half of the spring near the bend on the side away from the lock plate.

On a frizzen spring you want to leave the area that contacts the frizzen cam wide enough to contact the entire cam.

Leo

 

[Zonie]

It is safest to reduce the width of the spring leaving the bend about as it was and reducing the width down towards the working end with a taper.

Reducing the width changes the spring rate at a direct 1:1 ratio. That is to say, removing 1/4 of the width will reduce the springs force by 1/4. Removing 1/2 of the springs width will reduce the force by 1/2.

Changing the thickness of a leaf spring works by the cube of the thickness so removing just a little material can change the springs force by a very large amount. It is best not to do this because if one removes just a little too much material the springs force will be greatly weakened.

When reducing the width (or the thickness) ALL WORK MUST BE DONE PARALLEL TO THE LEAF.
NEVER GRIND OR FILE ACROSS THE SPRING PERPENDICULAR TO THE LONG LEAF DIRECTION.

It is also a very good idea to use a wet/dry sandpaper to sand out all grinding or filing marks and this sanding MUST be done in the same parallel direction that the grinding/filing was done.

The smallest cross-ways scratch will become a highly stressed point that will cause the spring to fail.

 

[Stophel]

Remember, it still has to be strong enough to pop the cap. :wink:

 

[paulvallandigham]

It doesn't take more than 10 lbs of tension to fire any cap.

Use a bathroom scale to measure mainspring tension. put the butt of the gun on the scale, note the weight shown- it may not be accurate for such small weights, but the scale will be accurate relative to other weights added to it. Then slowly cock the hammer back to full cock, watching the scale and not the maximum "weight" shown on the scale. Now, subtract the weight of the gun from that maximum weight to get the spring tension. Do this measuring 3 to 5 times, and average your results. Work from there to reduce the tension.

Remember also that if you round the edges of a flat spring, the metal will bend easier. You often can reduce the mainspring tension to something usable by simply rounding the edges with emery cloth backed by a file.

And, before you do anything with that mainspring, First, check both arms to make sure there are no burrs, nor any portion of the spring rubbing against the lockplate. Sometimes, plates are Bent and have to be straightened, for the lock, and tumbler to work properly.

I have seen bent lock plates that I straightened, which freed up the tumbler, as well as the mainspring arms to move freely, reducing the tension on the hammer by more than 75%. You might think you are shooting an entirely different gun, just because you took a bend out of the lock plate. So, start there, and work up to modifying the springs.

 

[Melton Kidd]

I've got two 'Paterson' replica pistols with the traditional 'V' springs. Of all my BP pistols, the mainsprings are bears to cock. They slip on the 'L' lugs integral to the grip frame. I'd like to lighten the tension, but not sure whether to try grinding.....or exactly where to grind. or how to proceed. Any help?

Are these pistols Colt replicas? If so the springs don.t respond like a side lock muzzle loader. If they are replicas of a Colt revolver, I recommend that you take them to a gunsmith familiar with Colt revolvers for any work.

 

[rich pierce]

+1

 

[wulf]

I never grind a spring...I bevel file the sides.
Safer and easier and far better control than I
have by grinding... :idunno: