Loose pinion key on 10x15 C&P old style

The pinion gib key which holds the pinion gear in place on the crank shaft has recently become loose. I’ve tried tapping it back into place, with reluctantly increasing force, but it doesn’t stay. Any ideas why the key would no longer hold after all these years? And more pragmatically, suggestions of what to do? I read an account at http://artletterpress.wordpress.com/2010/03/ in which the writer filed down both the key and the keyway. ?? Thanks for any advice.
Littoral Press

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Some times a shim is needed under the key. Brass, copper or aluminum litho plate works well because it can be cut to size easily with tin snips. It should be the size of the bottom surface of the key and lay under the key in the shaft keyway. Experiment to find a shim that will have the key tight in the gear and the key tab about .25” away from the gear surface.
Hope this helps.
Keep us informed.
James McGraw

the key and or crank shaft can wear after time. you probably have an equal amount of wear or stretch in the pinion. best bet is to just order a new one. measure it. it can be ordered from “Mc Master-Carr.
order the one that matches yours, and, order the one the next size longer. the longer one maybe needed to fit tightly. you may have to then cut off the smaller end of the taper to fit lengthwise.
you have them term for this part correct and can be searched on their web site directly. actually (gib head key)

Your own link is spot on but possibly with small variations,
I.E. as Gib Keys & Woodruff Keys, 1/4 moon style, are designed to be Sacrificial, >to protect the expensive harder shafts and pinions< although replacements are easy to source, here in U.K. hand making/modifying proves to be a more successful option.?
Although the main wear/slack is in the key proper, invariably some is in the slot(s) in the shaft & the pinion, virtually always in an irregular/tapered fashion on the side wall(s) of the slots.!!!
When we make our own, from mild steel plate, virtually *Verbatim* as the link above (your own) we factor in allowances for irregularities, for the worn slots in the shaft and the pinion, constructing the key with the smallest/progressive taper along the length of the key, incorporate the head of the gib (for later extraction if needed) with a return on the head of just less than 90 Degrees, they invariably get damaged with a negative rake making it hard to remove???
We usually construct the key with the Head at least 1/2” high and have the option of utilising a standard Quoin with packing as an extractor. Been done many times. Slide hammer, or wedges, work only, if the head of the Gib is WITHOUT negative wear,!!!
With fine tuning on the fitting of the Key i.e. finest taper/rake possible still tapped in, but with modern liquid locking substance to semi permanently secure.!!

Normally small tube with blue liquid compound, *THREAD LOCK* or U.S.A. equivalent, as used in Cars/Autos, shake proof, rattle proof, etc but will release, or extract, when needed.

For literally ┬úpennies or $cents we acquire, say, a piece of mild steel plate the thickness of the original key-way, 6” x 6” as many experiments as required, to perfect the end result. with just an ordinary, bench vice, hack saw and file(s) as the link above.

Off the shelf is probably fine, but can only be modified downwards, unless you go oversize, by implication D.I.Y from scratch. Good luck

Thanks all for excellent suggestions. For now I have shimmed the key with a 24pt brass thin space, which is just the right width for the keyway. I’ll see if that keeps the pinion key securely in place while printing tomorrow or Thursday.
Littoral Press

You can buy these tapered keys fro McMaster Car