leveling the platen on a 8 X 12 C&P old style

After much testing I have found that the lower left hand corner of the platen is low. I know the four big bolts under the platen are used to even out impression. Can any one tell me how the adjustment is made and how much of a turn adjusts how much impression? Any help will be appreciated, Thank You..

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Loosen the center nut first. Next loosen the four nuts at the bottom of the bolts. Turning the bolt clockwise brings the platen up towards the bed of the press. Each nut face is .010
After you have brought up the corner that is low tighten the nuts, watching to make sure the bolt doesn’t turn as you tighten (you might need two wrenches). Tighten the center bolt last.

There is no center bolt on an OS C&P 8x12. Here’s the process I sent recently on Letpress:

“Adjusting the platen … is fairly straightforward. Lock up 4 large Cap H or M (48 point or larger) of some sans serif metal type into the 4 corners of the chase; I find nice square letters work best for me. Pack the press with your normal packing (tympan, press board and a couple of sheets of paper) and print a test on a text weight sheet.

Adjust the impression screw under the corner(s) not printing well. Use small turns. 1/8th of turn on the impression bolt is plenty to start and use less as you close in on an even impression. As you increase one you may find you need to decrease another. Don’t try to rush it; this may take a bit of time. You’re aiming for a kiss impression on all 4 corners with even inking.”

you should always look first at adjusting two screws at a time. i have seen many simply “crank one up” to pressure which could be “pulling up” on another. this is not good. preferably you want the pressure balanced on all adjustment screws. therefore, if you need to raise one corner, fine, then, look at lowering the diagonally opposite corner, or in your case the upper right hand corner. leveling a platen is a delicate job. go slowly. imagine a table on 4 legs. would you just keep making each one longer? keep in mind the pressure setting you need, as this will determine if you need to raise one stud or lower another stud. if you loosen a nut on a given stud, the stud should not raise up. that would indicate an imbalance.

Thank you to all above, I was able to make the adjustment to near perfection. Thank you all for making the adjustment so much less formidable.

very cool! have fun! stay safe!