SP20 chattering

I’ve been having an issue with my Vandercook SP20 making a loud chattering noise when I print. It is from the contact between the rear rubber roller and the oscillating roller causing it to skip when it is cranked. It also appears to be the non operator side of the rubber roller that is having the problem. I can go for days without having any issues, and then it will start happening again. I’ve allready snapped the crescent bit inside the oscillating roller once from this. Lowering the roller adding more ink and oiling all seem to help, (sometimes). Any advice?

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If you replaced the oscillator crescent but didn’t replace the worm gear that drives it, that might be the problem. Chipped points on the worm can give an intermittant failure in lateral motion. It is a good idea to replace both worm and crescent at the same time, maybe even the crescent holder.
I did see this on a Vandercook 219, and the problem increased when less ink was used, because it took more energy to split the ink film, and the oscillating mechanism was stressed by that. Slather on the ink and the chattering stopped. Or add tack reducer or the like.
Of course, lubrication is critical, and you use vaseline on the worm and crescent, and graphite grease on the post of the crescent, but once the points of the worm or crescent are gone, it is time to replace them. Unfortunately, you can’t get a replacement for the throat of the oscillating roller, so regular vaseline lubrication is especially important there.

It sounds like your rear form roller’s gear is not properly engaging with the rack.

When I have seen this happen:
1. rear form roller is adjusted too high
2. starter gear on the rack is bent or missing
3. Nyliners in roller blocks are worn or missing
4. motor driving the drum is set to run the wrong direction
5. oscillating roller crescent overtightened or damaged
6. form is over type-high

Look for these possibilities and hopefully you’ll find your solution. Keep us informed!

Daniel Morris
The Arm Letterpress
Brooklyn, NY

Thanks for the feedback, I will check these things out and hopefully correct the issue. Very much appreciated.

Or you can see if Dave and Beth Seat are going through your area…they are magicians and can fix anything on a Vandercook. Their website is
It looks like they might be heading your way right about now.