Modified another of my creedmore molds using the very cool method JLouis provided in the post below. The roll pin spring hold down works so well I went out and bought a bag of pins for additional conversions.
thanks
kw

Has anyone tried the powdered graphite one buys for locks?

Graphite under sprue plate works fine. Its maintaining the uniform plate tension on some molds that is the challenge. The roll pin finger assists in that.

kw

I think JLouis hit the nail on the head regarding lapping the sprue plate flat and this does help the sprue plate hole to have a sharper edge which does a better job of cuttting the sprue. I think this problem is kind of common on factory not custom molds. I have an ancient cast iron surface plate I bought for $20 bucks over 40 years ago. And I use silicon carbide paper to flatten the underside of the sprue plate. Magic markers make good layout tools for seeing how things are progressing. But some of the sprue plate holes are so poorly cut that they would be hard pressed to cut a wet noodle. So I use a 60 degree center drill and recut the cutting edge. Once that is done a few more passes with the silicon carbide paper to get the burrs caused by redrilling the hole.. Saeco-Redding usually has good flat sprue plates and sharp cutting edges. The surface plate has never been tested to see how flat it actually is but have a stainless steel rule and no light shines through when last I checked it. The owner used to buy out old machine shops when they shut down. He had a 20' shipping container full of them. Frank.