SP-20 roller height problem

I’m having trouble with inconsistent roller height on my SP-20. I’ve set them to type high using my gauge. When I move the cylinder a few more inches down the bed, the rollers are now above height and no longer contact the gauge. When I roll it back towards the dead bar, the return to type high. Do I need my carriage bearings adjusted? What’s causing this and how can I fix it? I’m mid-job, of course…

4 thoughts on “SP-20 roller height problem

  1. Paul Moxon, Moderator - March 16, 2013

    You’re in excellent hands with Perry. Meanwhile, you can read Gerald Lange’s article on carriage bearing adjustment: https://vandercookpress.info/vanderblog/literature/articles/lange-adj/

  2. Jonathan Selikoff - March 16, 2013

    Thanks for responding, Kyle. I posted some additional info over on Briar Press. The sum of it is the rollers are lifting just after the carriage rolls off the spring rack at the head of the bed. So, the rollers are about 5.5″ over the bed when they suddenly lift. I also noticed different carriage bearers engaging or disengaging from the rails at this point. Not sure which are supposed to be engaged when, so it’s hard to know for sure whether that’s correct or not.

    There is no movement in the carriage; I checked that. I haven’t held it down as it moves over the type, though. That’s something to try. I’ve also cleaned all the rails, gear teeth, racks, etc. to ensure that wasn’t part of the issue.

    I’m pretty sure the form rollers are square, but again, something I’ll check in the studio today. I really don’t think it’s the rollers or cores themselves. The rollers were re-covered last year as well.

    Lastly, no bed plate. And I’m checking for type high just in front of the dead bar (where my plate is) as well as further down the bed. Unfortunately the lift happens mid-plate…

    I’ve got Perry Tymeson (someone Paul recommended) coming out next week to look at it.

    I managed to move the job over to my Windmill. Thank goodness for having multiple presses!

  3. kyle van horn - March 15, 2013

    ALSO! Check that the threads on the roller bearing-blocks aren’t caught on the leading edge of the metal tabs they are supposed to rest on – they can be easily mis-aligned when cleaning, and once they’re caught wrong in the press, they can shift all over with the torque of the press and cause a variety of problems. Even having one of the four screws caught may wreak havoc.

  4. kyle van horn - March 15, 2013

    Oof, that’s a tricky one.

    Is there any rocking fore and aft on the carriage (like a teeter-totter front to back)? It acts like you’ve got bearings that are mis-aligned, and it’s reacting to which direction it’s being turned. You could perhaps prove this by holding the front side of the carriage down as you roll forward, the rollers *should* keep contact with your type. Logic should dictate that it would be more likely to keep roller contact on the downward push and lift on the return, but that’s my best guess.

    Other things to look at: Are your form roller bearings square to your cores? You can tell by lifting them in place and spinning them freely by hand – if they’re square, the bearings should be rock steady as the rollers spin. If they wobble back and forth, then you have bent cores (or screws, or bearings) and you’ll get stripes of ink as the rollers traverse the bed. Also (and less likely) you have a bed plate on this press. Be sure it hasn’t slipped or shifted. Be sure also that you’re not checking type-high at the front edge of the press – that section of the press bed is WAY below type-high.

    Good luck!

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