SP-20 No Impression

I’m working on the rebuild of my (previously) dismantled SP-20 and I’m finally ready to test the impression. After calculating the correct amount of packing for a .019″ sheet (.024) on a cylinder with an undercut of 040 I proceeded to attempt a blind proof. There was nothing, not even when I added another .006 packing. Upon closer inspection, the cylinder bearers are not in contact with the bed bearers by about 3pts or .0417″. When I put the press into trip, that distance increases further. So far, I can’t seem too close the gap by adjusting the carriage bearings that ride the under rails or any of the bearings for that matter. I’m not as familiar with the SP series, but I would imagine that the cylinder bearers are supposed to touch the bed bearers. Of note, the trip plungers are working and retract when switched to print mode, so I don’t think that’s the issue. Thoughts on what would lift the cylinder  out of contact with the bed bearers?

 

10 thoughts on “SP-20 No Impression

  1. Paul Moxon, Moderator - September 4, 2022

    I was chatting with Dave Seat, who said he adjusts the top bearings first with a .003″ gap and then bottom bearings at .015″, nearly the opposite of what I do. We agreed that it might not make a difference whether the gap is greater on the top or bottom but that the elliptic of the bearings should initially be parallel to the bed and outward. And that the side plate are kept parallel to the bed.

  2. Jess Snow - September 4, 2022

    Thank you Dan and Paul for patiently working through this with me. I realized that I had the trip bearings incorrectly in place as Paul stated after much communication. What really helped was when
    I was directed to look at the drawings on page vi of Paul’s book which showed the correct orientation. The trip bearings were lifting the cylinder too high. I’ve since rotated the bearings and am getting an even impression!

    However, I have some adjusting to do since the press now is very difficulty to roll down the bed and there’s a bit of a squeal in the area around the the trip plungers that occurs in both trip and print. But it’s worse in print. It might be that .003 is too tight an adjustment? I’ve read through many times the adjustment section and will keep working at it.

    Couple thoughts, I feel like the paper I’m using to do the adjustment might be compressing and that’s causing me to get a too tight adjustment? I’ve also noticed that as I tighten the nuts, the bearings also tighten against the rails. Is there a best practice in which nut you tighten first and how tight?

  3. Paul Moxon, Moderator - August 30, 2022

    Jess and I have been discussing her press restoration since the beginning of her adventure. Originally, the eccentrics on the SP20 were parallel to the bed, with the apogee (or long node) for each bearing facing outward. See the attached image. In my experience, adjusting the bottom impression bearings is easier than the top trip bearings.

  4. The Arm NYC - August 30, 2022

    Here are the pictures that show the eccentric positions on an SP-20 at Cooper. I am not sure how close these would be to the ideal positions on your press as they are adjusted to compensate for wear and subtle differences in the machining. Is there anything else I could document for you that might be helpful?

    DGM

  5. Jess Snow - August 24, 2022

    I got a chance to take a look at my friend’s SP-20 a couple days ago (when I updated her electrical) and familiarize myself with it. So, I’m going to go back to trying to adjust the eccentrics again soon. I think what was concerning was just how high the cylinder is from the bed bearers. I was thinking that maybe it was beyond what the eccentrics could adjust for. But I’ll tackle it again. Dan, I would still appreciate any pictures of your SP-20 eccentric positions. Thank you!
    Jess

  6. The Arm NYC - August 23, 2022

    You should definitely have bearer-on-bearer contact on print. Is the issue eccentrics settings? I am unfortunately not back in the company of an SP-20 until Monday of next week at Cooper Union, but we can compare photos then.

    DGM

  7. Eric Holub - August 22, 2022

    My SP-20 was .918″, and I’ve only seen one .968″ out of a dozen in the SP series.
    Setting the impression bearings that hold the cylinder down on impression and the bearings that hold the carriage up in trip is a very tricky business, and mis-adjustment increases wear. But I haven’t made this adjustment in over a decade, so I can’t give the best method. I will say that when both sets of bearings are set correctly, the form rollers will be at the same level on both trip and print.
    A pox on all disassemblers.

  8. Jess Snow - August 19, 2022

    It is interesting though that the distance the cylinder is away from the form is pretty darn close to the 050. I should check with Fritz to confirm specs on my SN.

  9. Jess Snow - August 19, 2022

    Hi Dan! My press is not stamped galley height. And when I put a piece of type next to the bed rails they are the same height. But even if it were galley height, aren’t the bed rails and cylinder guide plates supposed to touch when in print? Mine don’t touch. It’s as if it’s stuck in trip. Although when i put it in trip the cylinder raises even higher.

  10. The Arm NYC - August 19, 2022

    Most SP-20 Vandercooks are .968 bed. Did you check your bed? It is usually stamped near the bed pin on the operator’s side.

    DGM

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