CP 8x12 platen adjustment

When the platen is adjusted is the casting bending a small amount? It doesn’t seem there is any play(room…) to allow the platen to shift in the bolt holes. I’m interested in how this is engineered, plus I do not want to break anything.

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Put some WD40 on the screws and nuts to loosen them up. I do not know how you would bend anything. It is a pretty solid piece and heavier that it looks. The screws are threaded on both sides, and actually have a lot of room for “Play”. My platen is currently off for restoration. If you would like a picture, let me know.

The platen bolts on a C&P are designed as follows: A piece of hexagonal bar stock is machined with threads on both ends and a section in the center turned round, another section being left hexagonal. The four lugs on the rocker shaft casting where the platen bolts go through are smooth holes. The four places in the platen where the platen bolts go are threaded to receive one of the threaded ends of the bolts. As you stand at the press, a threaded end of the bolt is facing you with a nut on it. From this point the round part of the bolt passes through the smooth hole in the rocker shaft lug. On the far side of the lug is the portion of the bolt that is still hexagonal. The last, threaded part of the bolt screws into the threaded hole in the platen.

The nut closest to you is for locking the bolt once it is adjusted properly. The hexagonal part of the bolt acts as a bolt head to turn the bolt for adjusting. The shoulder of this bolt head sits against the far side of the rocker shaft lug. In other words, when you loosen the lock nut and turn the bolt head the screw at the platen end of the bolt either moves the platen away from the bed of the press or towards the bed by the action of the screw thread. The bolt itself stays stationary and rotates in the hole in the rocker shaft lug. Once the four bolts are adjusted properly so the platen is parallel with the bed of the press, the locking nuts are tightened so the bolts will stay in that position.

When adjusting the platen bolts you should have two wrenches, one for the locking nut and one for the platen bolt. Often, loosening or tightening the locking nut will cause the bolt itself to turn and lose whatever setting it had. Use one wrench to hold the bolt in place while you loosen or tighten the nut with the other.

Another thing to remember is that when the locking nuts are loose and you turn the platen bolt, very often the bolt slides a little out of its hole in the lug. This is normal but before checking the setting of the platen after you turn the bolts you must tighten the locking nuts each time. This is tedious but necessary. Fortunately once the platen is adjusted accurately you usually don’t have to do it again.

All of the above may sound more complicated than it is. A drawing would have explained it more quickly but I don’t have the means to make one so hopefully my description will be sufficient to understand the construction and concept.


Front Room Press
Milford, NJ

Google “Leveling the Platen.” Fred Williams has an easy to understand guide with pictures.