Diecutting for beginners?

What you need is a die, cutting rule mounted in a wood base. This gets locked up in the chase like any other form. Then you need to get a brass plate to put just under you tympan. This protects you platen from getting destroyed by the die.

Where would I get a die made or can I make that myself? And what about the cutting rule?

skip the typan, that will not give you a clean cut.

the cutting die just kisses a thin sheet of metal taped securely to platen. tape on the gauge pins as well.

be sure to take off your rollers first.

you can use .937 or .918 die height, depending on the height of your platen and the thickness of the cutting metal. you will put thin sheets of paper under the metal until the die will cut a thin sheet of paper cleanly and evenly.

most towns have plenty of die makers.

The reason you can’t find any resources to die cut on a 12 by 18 OS C&P?

Back in the day, die cutting was done on a flatbed or cylinder press. The C&P 12by18 OS was not designed for die cutting. It was designed for printing legible type.

BUT! if you insist on wrecking a perfectly good letter press… don’t worry, I do this on a 12x18 double flywheel Kluge every day, die cutting boxes. I’ll walk you through it.

You see those bolts that support your tympan? Back them WAY the hell off at least two full turns evenly, and secure a .035 to .040” stainless steel plate to the tympan.

Place four .918” cut rules in a rectangle shape, more than 12 picas (2”) away from the outer limits, left, right, top and bottom of a chase, and mount the chase in the press.

Secure your lay pins well away from the image area, and hand feed a sheet of stock through with impression on, turning the fly wheel by hand. No Cut? good, we’re halfway there - and you haven’t destroyed the press! Yet.

Turn by one/sixth turn, the lower, and then the upper typman screws outward, increasing the impression evenly, until you get an impression, and repeat. I think you’re with me now.

You will get to a point where one corner of the stock is cut. Stop turning that corner bolt, and increase pressure on the other bolts. As you increase pressure on the other bolts, be advised the pressure on the first corner will increase, and needs to be backed off by one-half of a sixth turn. You are getting closer to even impression.

You will know that all four corners are of exactly the same pressure, when the stock is cut with a distinct SNAP! sound.

When you get to this point, make several impressions, and note that each successive impression is weaker than the first. This is your antique press adjusting to several thousand pounds of pressure PSI, as it was designed for only a few hundred pounds PSI. Adjust the tympan screws outward to match by very small increments -1/12 turn or less.

Congratulations! You have just shortened the life of your antique C&P Old style 12 by 18 press by at least a century!

Platens have long been used for die-cutting as well as cylinder presses. The Universal platen invented by Rev. Galley was offered in both printing and cutting-and-creasing models, well before 1900. And its descendent, the Thompson is still being made for the same purpose.
But I agree that die-cutting on a C&P isn’t good for the press and should be limited to fairly light work. There is a huge difference between putting in a few perfs and slits, and cutting a CD jacket (an increasingly common intent). Such things ought to be farmed out to the experienced.