What is the cylinder undercut on my press?
Answered by Fritz Klinke
Owner of NA Graphics on LetPress

This is the amount of cylinder face that is lower than the cylinder bearers on the cylinder casting. Although .040" was standard, certain presses had other undercuts going up to .105", and many of these were special application presses, and other weird, unpredictable reasons.

Check what is stamped in the groove of the cylinder where the gripper bar ends on the operator side. Most likely it will read 040K, and that is the amount of packing plus top sheet in thousandths of an inch needed to have the cylinder at .918" above the bed. Adjust plus or minus for the sheet being printed and degree of impression wanted, but to be significantly over .918" changes the diameter of the cylinder and that may cause register problems.

 

 
What is the reason or purpose of a short print stroke? I have a Universal I, according to the manual, the cylinder will travel the whole length of the bed, or if I swing in the hinged blocks at the end of the bed and change the cylinder trip cam (it has two positions) it will print in a short printing stroke.
Answered by Paul Moxon

This is a useful feature with a simple answer: it's a time saving device. Why walk the carriage all the way to the end of the press for a short form at the head of the bed. The grippers release the paper and the cylinder switches to trip mode sooner resulting in a shorter travel back to the feed board. This is an optional feature of the Universal I, but comes standard on the slightly earlier and less common 15-21. A different type of mechanism is found on presses in the 219 family.