Handy clamp seems good for mainsprings

[rich pierce]

I bought a small lot of machinist tools and a couple of these were in the lot. Seems to work well as a mainspring clamp.





They go for about $20. Nice thing is the smooth, fast clamping action.
https://www.lapeermanufacturing.com/knu-vise/squeeze/pliers/fgp-400.html

[P.W.Berkuta]

Looks a might bit big and clumsy  - I am familiar with those clamps and they are smooth acting . The pads look a bit big to get onto some of the legs of the springs .  Just my two cents worth.  

[Jim Kibler]

I think it's important that a clamp applies pressure in a similar manner that the spring sees in operation.  A clamp point at the top and another point near the hook.  If you squeeze and apply pressure further back on the lower limb, it can result in excess stress and potentially cause problems.  So in practice always extend the clamp such that it applies pressure out as far as possible near the hook.  Pliars or clamps like those shown don't do this. 

Now, some springs are robust enough to not mind the extra stress, but others may be more sensitive. 

Jim

[rich pierce]

Good points