I have a couple of questions regarding roller adjustment on my SP-15. Recently when checking the roller height, I discovered that the ink stripe on the gauge was about twice as thick in the middle of both rollers than on the ends, leading me to think that the rollers are for some reason slightly sagging or bowing towards the middle (although this is not apparent when looking at them straight on). Secondly, when testing the roller height at different points along the bed, the height increases the further the carriage is rolled down the length of the bed. I’ve checked with a level in both directions and the readings say the press is not out of balance. These rollers came with the press so I’m not certain of their age, but they have no visible defects that I can see. I brought one along to a class I took with Paul several months back and he (and his durometer) were of the opinion that the roller was in very good condition. Any advice about how to correct either of these issues would be much appreciated. Thanks!
–Sylvia
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Eric,
Thanks for clarifying which type of calipers, I will probably order them. Meanwhile, I did a somewhat unscientific measurement with a tape measure (type used for sewing) and found that repeated measurements of middle and ends of rollers all showed that the front roller is equal circumference at all points, and the back roller is equal at end nearest the operator’s side and the middle, but 1/16 inch narrower at the farther end.
I will not have a chance to ink up the press until next week, so will then try the jerk-stripe test as you suggest. But I’m wondering, if swelling and/or wear turn out not to be the problem, is there anything else I should look for as a cause of the middle sagging?
Thanks,
Sylvia
Another simple test is the jerk-stripe: with press inked up and running, lift the rollers out of contact and stop motor. Then drop rollers for a few seconds and lift again. Advance the carriage and look at the contact stripe left on the ink drum. Ideally, it should be an even stripe, but it will show if roller ends are shrunken or swollen. Roller ends can go either way, and I could show you examples of either condition in working rollers in my shop.
The kind of caliper I suggested earlier is not the micrometer caliper you might find at the hardware store, but the kind like earwig pincers, whaich are just called external calipers (there is an internal caliper as well). They can be used to FEEL the differences in diameter, can also be used to measure diameters by comparing the gap to a ruler.
Alex & Gerald,
Thanks for your comments. Thus far, I have printed only small images on the press, and yes I do notice that the impression is lighter on the outside areas than in the middle, but in most cases I’ve been able to compensate with makeready techniques and still get a satisfactory result. I take the roller reading at whatever point on the bed the plate is positioned.
Gerald, it is good to know that it is typical for the readings to be different at various points along the bed. I imagine if and when I ever want to print something larger, it will be more challenging to get a good overall impression.
My local hardware store had only a couple of calipers available and neither looked precise enough. I may decide to order calipers online and if so I will report back as to if the rollers really have swelled in the center (though as you said Gerald, it is usually the ends that typically swell).
Sylvia
Sylvia
Usually it is just the opposite, the rollers tend to swell on the ends and the register of the middle of the roller/s would be much less.
In regard to the second issue, where to take the reading, or that the reading differs along the bed…. Well, the correct place to take the reading is where it is more convenient to you. Doesn’t matter to the press, you could take the reading at the front, middle, and back and they will all be different. Best to think of it as a personal reference and go on from there. Basically, get intimate with your press. It’s been down a long road, a bit tired and all, and sometimes cranky. Have to rely on familiarity sometimes more than mathematics.
Gerald
have you checked the impression from side to side, and end to end? If it changes the same way then that will eliminate the rollers as the problem. It sounds like your rollers are belled – the center slightly swollen – which explains why the ends of the roller print lighter. If your impression is even then it’s your rollers for sure. But the second problem seems like a separate issue. If the impression lightens as you advance the cylinder, then you know those two problems are related and aren’t due to the rollers. If your impression is even as you advance the cylinder then the problem is only with the rollers.
good luck,
alex
Eric,
So far I’ve tried a level, straightedge, lowering and looking under the rollers for differences, but can find no unevenness as yet. Testing with calipers is a good idea; I’ll see what the hardware store has to offer. Thanks.
Rollers may be a different diameter at the ends due to swelling or shrinkage. I would take a straightedge to the roller, or set it on a flat surface and look underneath for daylight, or ink it and roll it on a sheet of paper, all as ways to test for low areas. Or check the diameter at different points using machinist calipers. For concentricity I would block up the roller bearings until the roller wsa just touching a flat surface, then turn it and look and feel for varying contact.
Hi Paul,
Yes, the further the carriage is rolled down the bed, the strike on the gauge gets narrower and then about 3/4 of the way down the bed disappears altogether as the rollers by then are too high to contact the gauge.
I will try the 1/2 turn and recheck as you suggest, but I have been encountering this problem for some time now during the printing of several different projects, and multiple readings have been consistent.
No, it is not a galley bed press.
Re: shims under cylinder gear rack–I live in a somewhat remote Vandercookless area, so if you could take a photo on Saturday as you mention that would be a big help. Thank you!
When you say that the height increases the further the carriage is rolled down the length of the bed, do you mean that the strike on the setting gauge is narrower? Here are three thoughts:
1) Flat spots may have developed on the rollers from the oscillating roller having rested against them when the press was not in use. Raise the roller lift arm and rotate the cores half a turn by hand and take another reading.
2) Is this a galley bed press? If so there many be something under the bed plate or it may be springy or bent.
3) It’s possible that the shims under the cylinder gear rack at the feed board end were removed. Compare with another SP15 in your area. I will see an SP15 on Saturday and take a photo if necessary.