Packing a SP-20 question

Hello! I have been wondering about proper packing on my SP-20. I have a Galley Bed Plate with 040 cylinder undercut. I have Vandercook Tympan, .003 packing sheets and a Mylar sheet.

Everything I can find as to how much packing you need does not mention if the thickness of the bed plate is involved or not.

If I use one piece of Tympan, the mylar and 5 packing sheets. Its not enough to make an impression in 80lb lettra.

Im worried that if I add any more thickness to the packing I may be counterproductive. and of course I do not have a micrometer (Yet)!

Any advice would be great.


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The Arm
9 years ago

Your bed plate and your cylinder packing are doing two very different things. There is only one optimal printing plane and on a Vandercook that is at the height of your bed bearers. The bed plate is part of the system to get your printing surface UP to type high. You cylinder packing is used to get your sheet DOWN to meet the printing surface.

Kyle mentions that he discovered that his bed plate was not a true .050. That is important information which can only be gained by having a good caliper or micrometer in the studio. I have similarly noticed that some tympan I have ordered lately which was presented as .006 was actually less than this, so you may need to be ready to do some measuring.

A good place to begin to make sure all your packing plus the thickness of the sheet you are printing on adds up to .002 more than the cylinder undercut indicated on the nearside edge of your cylinder. You may opt to add a little more from there depending on the properties of your paper and how you like your impression.


Eric Holub
9 years ago

One of the basic and often overlooked tools is the straight-edge.
Place it across the bed bearers or across the cylinder bearers, and you can get a general idea of what’s high or low, adding a little more precision with the use of feeler gauges (which can be improvised from stock of known thickness, or just going for rough approximation).
That is, with straight-edge across bed bearers, if you can slide stock between form and straightedge, form is low. A high form will lift straight-edge above bearers.
(Always bear in mind that the bed bearers define where type-height is supposed to be, and is the level to which the rollers are set.)
Same idea for the cylinder. Packed to Vandercook specs for a kiss impression, packing-plus-stock would be just slightly over bearer, like a sheet of bond paper; in heavy impression work it will be more. With compressible Lettra you have to consider its thickness after impression as the line.

As for the packing instructions from FAG, Heidelberg gave similar diagnostic methods using slur in their cylinder press manuals.

9 years ago

I have just a general note about cylinder packing vs. makeready of the printing form. I found this note in an assembling manual for a FAG proof press from the 1950ies. The manual is in French and German – so I am trying to translate it as accurate as possible.
They say something like „If a photo plate is to low and you have to add some cylinder packing to compensate, your cylinder is running faster than the printing form*, so your halftone dots will be speared towards the end of the pressbed (First row of images).“
*The reason why the cylinder is running faster is because by overpacking the cylinder gets a bigger diameter which results in a longer circumference. That means that the surface of the cylinder needs to move faster to make the same distance than it normally should.
Further they are saying „If the photo plate is too high and the packing is to weak the halftone dots might get smeared towards the begin of the pressbed (Second row of images). If the photo plate and the packing is adjusted perfectly, the halftone dots should be sharp and not smeared in any direction. (Third row of images) To get good printing results the cylinder packing and the makeready of the print form should be perfectly adjusted.“

I know that this is not giving you any more information about how thick the cylinder packing on your Vandercook press needs to be – but just as a general note on how you might be able to analyze wrong packing vs form-makeready with your print results.
Best wishes.

kyle van horn
9 years ago

Sorry – I just re-read your first paragraph. If your packing sheets are .003, then you’ve way under your necessary packing – down somewhere around .023 without the sheet of Crane, and .031 with it.

Vandercook tympan should be .005, your packing is .003, and your mylar is probably the same. Add whatever you like to get up around .043. Good luck!

kyle van horn
9 years ago

We have 2 SP20s at Baltimore Print Studios, and the .040 undercut was the standard for most Vandercooks. The undercut measurement should be counted independent of your bedplate height.

How thick are your packing sheets? Are they the same as your tympan? If so, in your setup you’re looking at 1 typman sheet (.005), 5 packing sheets (combined to .025) and a mylar draw sheet (.003), to a total of .033″. 80# Text-weight Lettra is pretty thin stuff, and (I just measured) seems to be a lean .008″ thick, bringing you to .041 or so”

Depending on what kind of impression you want, and what you’re printing from, adding one more sheet of tympan might push you too far over. You can buy some thinner tympan from NA Graphics, or just use a second sheet of mylar. If you don’t feel like playing by the rules as much, you can use any thin commercial paper stock that comes in the thickness you want. This will wear out faster and will need to be replaced much more frequently than your tympan

If you’re printing from Polymer plates, you can hit it a little harder and get a deeper impression. If you’re printing from wood or metal type, you’ll want to err more on the side of a kiss impression for longer life of your type.

But – if those measurements above seem right, then all the math lines up nicely to your results of not getting any impression. Try adding one more – one slightly over-packed impression won’t hurt anything.

Additionally – and you should check this for yourself – we found when Paul visited our shop that our 18gage bed plates were notably under the necessary .050″ bedplate thickness. We found we’d been overpacking our cylinder to compensate for a low bed. We added a sheet of tympan UNDER our bed plate and this fixed both problems.

The take away lesson is: Buy a cheap digital micrometer – it’ll solve so many problems.

Ray Nichols
9 years ago

Sorry. In that second paragraph above, if when you are set up like I mentioned and no ink is transferred to your paper then you do need to add the plate back on top of the bed of the press and give it another try.

Ray Nichols
9 years ago

Depends on the press. We have a Vandercook SP15 which DOES NOT require a 0.050 plate. The cylinder is undercut to .040. We also have a Vandercook Universal III with the cylinder undercut to 0.040 which DOES require a 0.050 plate.

If when printing, your paper you are printing onto PLUS the packing (tympan, packing sheets and mylar) totals something a little more than 0.043 (fairly normal for KISS printing) AND the 0.050 plate IS NOT on the press, then you need the plate to be on the press.

The point to the 0.050 plate is to be able to remove the plate and print (proof) from a galley or composing stick. Then if you want to print without the galley or composing stick you need to put the plate in with your type or base sitting directly on the plate.

If your type is set up in a galley or composing, you must take the plate out or you will seriously crush your type.

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