Friction Fingers

Hi All!

My SP-15 has the round bases on which friction fingers mount, but no friction fingers, friction finger stiffeners, or screws that hold these things to the brackets.

Consequently, I don’t actually know what these fingers are for. do they help keep the tail end of the paper from hitting the form?

Should I acquire some?

Thanks,

Greg

Friction Fingers

9 thoughts on “Friction Fingers

  • November 2, 2012 at 10:18 pm
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    In addition to friction fingers, on the late model Vandercooks, you would also want star wheels to aid in holding the paper. These are in addition to holding the sheet to the cylinder as it makes its travel with your hand. If you let the sheet flap in the breeze even the friction fingers and star wheels aren’t going to serve as a solution. If you have an auto with tower and tapes you are home free.

  • November 2, 2012 at 8:42 pm
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    I’ll do some research on this question this weekend. Two grippers pose a real problem because there just isn’t enough surface area under the head of the gripper to have much holding capacity. Grippers also gum up and don’t seat all the way in the down position, so that lessens their gripping potential. On my SP-15, I currently have a problem gripper and I manually push it down to seat on the gripper bar for each impression–and I’ve been too lazy to take it apart and clean it. If I had to make my living, or even do much work with this press, getting it to work properly would be a priority. Given careful attention to placing a sheet accurately to the cylinder sheet guides and the feed table side guide, I’d place a bet that register problems are arising from the sheet slipping or pulling loose in the grippers.

  • November 2, 2012 at 4:48 pm
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    Fritz, I have suspected that our grippers may not be holding the paper tight enough, especially with thicker stiffer sheets. Is there a test to diagnose this, other than just yanking on the paper, which might not be a reliable test? Both our SP-15s have the minimal gripper bar, ie, two grippers and two guides.

  • November 2, 2012 at 1:16 pm
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    The cylinder assembly prints for both the SP-15 and -20 show the friction fingers set snug to the cylinder surface. There are no notes on the prints as to how tight these should be set, but if not snug to the cylinder, there is very little room above the type or plate for these to drag without hitting the face of the printing surface.

    We make the friction fingers for the SP-15 out of spring steel because the originally specified phenolic board ones are not possible, and I have tried with several sources. They need to be kept clean so no dirt or residual ink picked up from previously printed sheets transfer to the paper. Where tail slap occurs and the trailing edge of the paper is marked with ink, with or without friction fingers, a piece of 5 pica wide furniture turned on edge and locked in the form at the closest point to the last image element to print can help eliminate the slur on the ends of a sheet.

    Problems with register may relate to several items but often over looked are the grippers. A sheet of paper has to be firmly held by all of the grippers in contact with the sheet, and with use and abuse, grippers, gripper springs, and the surface of the gripper bar may factor in. The gripper bar has to be clean, the gripper heads true and flat to the surface of the gripper bar, and the springs not broken or binding up so they don’t function properly. Often Vandercook would put a diamond shaped pattern into the surface of the gripper bar to help hold a sheet of paper in place or mechanically roughen the underside of the gripper head for increased grip. On the Universal I made for Champ Decal, heavier duty springs and roughened gripper heads were specified because the slick decal paper had a tendency to slip in the grippers. I worked with Champ Decal with this press and they often had to do multi-color runs in tight register for the model railroad decals they manufactured. I have the original Vandercook file on this particular press where these solutions were worked out. Until Rich Meyers died several years ago, and he was the original owner of this press, this Universal I had printed tens of thousands of decal sheets. It also had an ink monitor that was perhaps the only one still in use.

  • November 2, 2012 at 9:38 am
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    Woops, sorry about the huge photo. Here is a better-sized one.

  • November 2, 2012 at 9:34 am
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    I recently replaced these on an SP-15 that I work with. Fritz did not seem to have the resin fingers, and the part number I asked for came as metal fingers.

    I removed the cross-rod and disassembled and cleaned everything. The attached photo shows the parts I had to work with (top to bottom): the collar with detent, the fingers from Fritz, support springs (for the old resin fingers?), broken ends of the resin fingers, curved washer, lockwasher, and screw. Off to the side are the dog-end setscrews which run in a groove in the cross-rod to prevent rotation.

    On reassembly I found that the ends of the metal fingers were too low: they did not contact the impression cylinder, and were low enough to foul type and furniture. I took them off again and gently straightened the last bit of the curve that matches the collar. This raised the fingers enough that they now contact the cylinder and clear the type.

    They weren’t quite the correct part but sometimes I have to make do. I have not had a chance to try out the press since installing them, though. I think the main concern with the metal fingers over the resin ones is that the metal ones might be more likely to mark the paper.

  • November 2, 2012 at 8:42 am
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    There is a cross-rod in front of the cylinder, behind the rear form roller. The fingers are attached to collars on that rod. The collars have pins that fit into dimples on the cross rod for lateral position.
    Placement of the fingers is important on any Vandercook. On models with metal spring fingers, they will abrade the grippers or damage the sheet guides if placed in line with them. The fiber fingers on an SP-15 can also be damaged themselves if not positioned in their intended places as indicated by the dimples.

  • November 2, 2012 at 7:30 am
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    I’m interested in learning more about these friction fingers, especially if they help registration. There is a recent post on LETPRESS that is exactly what I was about to post about myself, namely, registration issues with our SP-15. Where do these fingers go on an SP-15? I’d like to see if we have them, and if not, if we can get them.

  • October 28, 2012 at 9:37 pm
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    Yes, fingers prevents the end of the paper from hitting and can also keep the sheet in register. The fingers are made of phenolic, laminated layers of paper and synthetic resin. NA Graphics should have them in stock.

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