Author: eddiec ★2017
Date: 2017-05-08 09:13
I acquired an instrument where, on one key, about a half inch long, the hinge rod seems to be too large for the tube. I don't know how it got to this state, but judging by the marring on the rod, someone had to work hard to get it out. Its a Patricola from around 1996.
The tube and rod seem reasonably straight; the rod is just too big.
The rod had some high spots from marring, so I turned it some to take those off. It still didn't fit, so I turned it some more and it goes most of the way through now, but it may take a lot more turning to get it all the way. It is down to 1.84 mm.
Most of the rods seem to be about 1.88 mm / 0.074". This seems to be an odd size. I pulled a rod off a Selmer Signet and measured it at 1.92 mm / 0.075" - reasonably close to a #48 drill. This mainly matters if I end up having to fabricate a new rod. (Other measurements for those looking for reference info: the threads seem to be 1.7mm OD, 1.39 mm ID, 0.35mm pitch).
My caliber can't directly measure the key tube's diameter accurately, but I can say that the exit diameter is about 0.05 mm smaller than the entry.. I would think they should be the same. Maybe this is a semi-finished replacement key, or was re-plated, in either case expecting some finishing work.
I could keep turning down the rod, but it may end up with too much play at the post. Or I could drill out the tube with the smallest size bit that has some "bite" to it, or possibly file it with a tiny round file, but I'm not sure that would achieve a good round hole.
Or at last resort, hire someone who knows what they are doing. Somehow, my natural instinct is to avoid taking power tools to keywork.
Any advice? Thanks!
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