Bookbinding Tools II: Twin-screw presses, part two, how, when, and why?

This is going to be a bit technical-ish even for me. If you skip this one and go on your merry way, I won’t hold it against you. Sometimes I write/draw these things just to get them out of my head.

How modern and classical presses differ & why (maybe)

Jost Amman's woodcut of the bookbinders at work. The book clamped in a finishing press is highlighted and the rest greyed out.

I have indicated a couple of times that there’s an operational difference between the more modern (and by modern here, I mean 18th century) style of book presses and vises and the ones we see in the artwork of the 16th century workspace.

The difference is whether the force applied is pulled, or if it’s pushed.

Every book press is made up of a couple of pieces of heavy timber that are pressing a workpiece between them. As previously mentioned, these differ little between those used by woodworkers and those used by bookbinders, but we’re talking about books right now.

In the classical style of press seen in Jost Amman’s illustrations, and going all the way back to Roman times, a pair of screws are embedded in one timber. That timber (or sometimes a bench top) becomes the fixed face of the press. The active face sits loose on the threaded screws, pushed into the workpiece by a nut that’s threaded onto the screw.

The active chop is being pushed into the workpiece and hangs loose if the nut is loosened.

Book press #1: A Classical 16th century "Jost Amman Style" book press: a fixed chop, a free chop, and a threaded nut pushing the free chop, compressing the work piece against the fixed face.

In the more modern style, a threaded rod of wood or metal is held captured in one face of the press, usually by a key that rides in a groove that was cut into the unthreaded portion of the screw nearest the handle. The screw turns freely in the hole but cannot fall out because of the key while the opposite face of the press moves to and fro on the threads.

The active face (or ‘chop’) of the press is pulled into the workpiece or pushed away depending on which way you turn your screw. Releasing pressure is a one-turn operation.

Book press #2: A "Neo-classical" 18th century style book press: The fixed chop is held captive by a garter or key locked into a groove near the handle of the screw, which pushes/pulls the threaded active chop, to apply or relieve pressur to the work piece.

Put another way, here’s my 16th century-style press, which you’ve seen before.

The big book press from earlier, this time holding an actual book pressed between boards.

And here’s my most recent modern-style press.

20181104_032306

Can we pinpoint when the shift happened between the loose face hanging on the threads, shoved into service by tightening the nuts and the variety where you can just turn the handle and Bob’s your uncle?

That depends on how accurate our old friends Moxon and Félebien were with their drawings.

In Moxon/Félebien, (above), I believe you can see the transition happening. In both images, the nuts are gone, so the active face must be threaded, but there’s no fixed face. The size of the handle on each screw seems to be what pushes the loose face against the threaded one, replacing the nut.

So it was a gradual process of evolution over decades (if not centuries) rather than a single, brilliant, aha! moment we all love to imagine.

Why the change?

I can only guess, but the loose chop hanging on the nuts are much easier to build and more tolerant of what machinists call ‘slop’. As long as your nut and your screw align, the holes in the active face just have to be smaller than the nuts and it will work.

The more modern presses are so very much more finicky about their tolerances. If you follow me on Instagram or the Facebook page, you’ll have watched me struggle with the most recent presss. That one was made in the more modern vein. Everything has to line up perfectly square and because the threads are cut into the active face of the press, the holes must align and be drilled with a high degree of precision.

It might’ve been automation and the incipient industrial revolution that drove the change. Or the changes might’ve been as simple as improved drills bits; I certainly see a correlation between the advent of better twist drills replacing the more common “shell” style and the more persnickety presses replacing the more loosey-goosey variety.

20181104_031543

Does any of this matter?

Probably not, but I would feel remiss if I didn’t mention it. As usual, I will use the tool at hand unless something about the period tool (or press) changes the outcome.

~ Scott


Postscript: Thank you for tolerating the technical failings of the illustrations in this piece. My wife is the engineer in the family; I majored in graphic design and should not be allowed anywhere near a proper CAD program. Hopefully they got the point across.

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