There are two companies I know of that supply powerhammer springs. Triangle Auto Spring in Pennsylvania. Their springs are not tapered and sized for a Yoder K90 or similar machines with a high reciprocating mass. They are cheap and can be softened by removing a leaf or grinding some taper into the leaves. Triangle part number 1270A95. I have not bought any in years but they should still have the prints and they build to order anyway.
The other is Detroit Eaton Spring. He does exact replacement springs for a 2M Pettingell. They have full forge tapered leaves, done on their flat belt powered 1910 spring leaf tapering machine. These springs are for a lighter mass but are much more expensive than the Triangle pieces. Not sure that Mike Eaton is still involved in day to day operations anymore but the current crew would know where to find him to locate the prints for these obscure parts.
For reference "tuning" the spring is important to the hammmer's function. It's rate needs to be matched up with the dynamic mass it needs to support. In a Pettingell it is 50% of the bobbins / links, the belting, upper die holder and upper die, wedge / shims. The belting tension plays a key roll in setting the rate as well. Don't freak that you have to get it sweet right to the pound, it is not that fussy but you need to be aware it needs design attention. Too light and the die will shake / chatter too tight and the die will "club" the panel.
Rick
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Rick Mammel
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