C&P Rocker is binding as the platen closes

Hi everyone!

I’ve cleaned and relocated a later model C&P 8x12 and am reassembling after cleaning and some refurbishing. The move from NY to KY was not eventful. The press was mostly disassembled as a means of moving it off the truck and downstairs.

The platen rocker assembly follows the internal cam path to rock the platen up and toward the person feeding the press.

There is a bind that occurs as the rocker begins to rotate towards the feed board, please see http://youtu.be/Z1FKpxphLT4

The issue is barely noticeable when the half moon collets are in place but not tightened; you can see this in the video.

As soon as the rocker assembly is cinched down with nuts, the bind is absolute, the press stops. I made this video to help in diagnosing the issue. Note, the press worked fine when it was picked up and when I got it home. It was not until I disassembled the press for cleaning, and reassembled the platen rocker, that this issue was noticed. I need some ideas on what is causing this.

All machined surfaces are clean and properly lubricated, and the internal cam follower is rotating freely on its spindle.

I am tempted to put a small washer under the half moon collets prior to bolting them in place, but am thinking that would mess up the design of how the rocker bearing is lubricated.

Also there is an image attached showing how the cam arm may be just a millimeter or so out of alignment, as you can see light coming through the bearing where there should be none.

I have done this twice before on a C&P but never remember having this issue with binding at this early phase of assembly.

Mike Moore

image: Possible reason for binding, you can see light coming through the cam arm on the rocker assembly.

Possible reason for binding, you can see light coming through the cam arm on the rocker assembly.

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Mike, have you tried switching the “Half Moons” from left to right or visa versa. these parts were line bored in place on the press and cannot switch places. One other idea… the entire structure on the press is bolted together (left and right side frames) if these pieces were unbolted or shifted in your move they could be out of alignment and thereby causing a bind. good luck, Carl.

in the movie its very rough (metallic) sounding. I’ve been printing on mine today so its still in my ears and it nothing like your sounds. Carl above i think is on the right track. Also check the cam follower the only other possibility. love to here how this resolves. to stop the press it must be pretty major. Its running pretty quick!


The collets are oriented correctly, as I had taken an enormous amount of photos while tearing this down. Also the wear marks reveal the only possible orientation, though there is a slim possibility I may have gotten the large washer on backwards. Also, I did not mark the position of the bolts, so I suppose those could be an issue. How interesting that these were machined in place, I did not know.

Even though I did not disassemble the base, I am sure plenty of the bolts were loosened, I had not thought of this and will have a look. Shoring them all up tightly could certainly true up the path that the rocker travels.

There’s a small chance I might have skewed the cam bolt or the rocker arm to a tiny degree. I had forgotten the cam follower bolt is press-fit in place and was trying to remove it through the timing hole in the bull gear… I may have supplied a bit too much persuasion!

Yes, the metal on metal grinding, and corresponding binding, that has to clear up before going any further. At this point she should spin up with very little force, and spin down with nothing but momentum.

Thanks for everything. Ya gotta love these machines because how else could we charge by the sheet? Ha!

Mike Moore
Letterkraft Press


The half moons, as Dad always referred to them, are more accurately known as the right and left rocker boxes. Even though there is nothing box like about them.


image: image.jpg


It seems the rocker journals are not the issue.

The sound corresponds prominently to when the rocker is in the full-up position and not moving.

I’d wager the cam arm or the follower bolt is scraping the gear. I would look closely for witness marks on the cam arm and cam gear.

With any kind of luck, I could get my phonecam up close and personal with that journal and have a look. I bet you are right. If there is evidence of contact with the inside of the bull gear, I’ll try knocking it back into alignment, and a few other things mentioned here.

The only thing I don’t understand is why the issue gets worse when the rocker boxes are cinched to the expected torque — this essentially freezes the rocker. I could get it to move but it’s against my nature to bust up such a fine machine.


have you tried torquing one side at a time to identify if only one side is the problem…

Ericm -

Thank you for your comment, no, I don’t know why I didn’t think of that. I will give that a try. If the problem is the cam arm slightly out of alignment (thus the cam follower), then I would expect tightening on the other side to not cause the binding.

Also, to all - I have to admit to a Homer Simpson moment. First off in the movie I think I recall running the press in the wrong direction. Running in the correct direction, there is binding, but none of that grinding metallic sound. I am so glad there are only three dimensions and the arrow of time is one-way.

Also last night I went down there and looked inside of the bull gear and it was dry as a bone. Apparently I had used a lubricant that was way too lightweight. Trying again tonight.

Thanks to all.

Mike Moore

The track inside the gear is not exactly what you need to lubricate. Rather, the cam follower that runs in it has a lubrication hole that is often overlooked. Clean everything, get oil into the hole of the cam follower until it can turn. Absolutely, do not put grease in there. I have seen cam followers ruined by the application of grease which then caused the cam follower to slide rather than roll, eventually resulting ain a flat spot on the follower.

Thanks for your comments about grease. I aways figured if we were supposed to use grease, these things would have come with grease guns. But I have been tempted.

Got that about the cam follower. I remember my dad pointing out that hole - actually I think there might be two of them diametrically opposed, but I was eleven so didn’t really understand its importance. And more oil there really did seem to help, but still with the grinding noise and binding when bolts are tightened.

Checking that sleeve, this was one of the reasons I took the rocker off its journals, to look at the follower under its sleeve to check for undue wear. There was not any - clean as a whistle. It seems the former owner knew his way around an oil can, and the press is really not that old, early fifties.

AnonyMouse mentioned having a look at tell marks inside the cam path, and there is. About 1/2 centimeter at the top border of the inside cam, on the inside face of the bull gear seems .. not really worn, but just unduly clean. So I think this is the source of the ugly grinding noise in the movie. I’ll try to remember to get a photo of the oil-less track in the cam path that might signify wear in-the-making.

Since the rocker binds up when the half moons are torqued, it probably means the entire cam arm is out of alignment. It sure wouldn’t take much.

So, I have to figure out how to test this theory, that the cam follower or cam arm is chucked slightly out of alignment in the direction of the bull gear teeth (it certainly does not look that way in its currenlty installed state, but I may pull it out of there again and have a look).

Also I thought, what if I got that sleeve on the cam follower the wrong way? Are those machined parallel to the cam walls? it is almost bahaving as if it had an orientation that makes a difference.

Things I have tried:
more oil. and more oil.

Looking at the bolts around the base, making sure the base was not skewed. There was only one bolt on the base assembly that I had to loosen, it was holding the OSHA hand-saver contraption in place. I don’t think the base is skewed at all.

Saturday I roped the rocker in place and took it out of its cradle just enough to make sure there was no spare change or other stuff laying against the cradle.

Tapping the cam follower with a heavy mallet using light thoughts. This was not enough pursuation. But it’s not like I can just order another one of these parts. (Though, I do think Dave Churchman has a catalog number)

Sevulan, the cam follower has a taper to it. I though everyone knew that. The stamped end is the small end and it is placed in the raceway first. Carl


I must have missed that day in Letterpress 101, but thanks for that.

It isn’t really noticeable until you get a micrometer out. I would think this could be the cause of that grinding noise, and why the sleeve no longer rotates freely throughout its entire travel. Thanks, i will make sure it is oriented right.

The binding of the rocker has disappeared after taking the rocker off its cradle and cleaning all metal to metal surfaces.

I want to thank everyone for the input. The rest will be straightforward.

Mike Moore