Sunday, June 22, 2008

Broken Screws

It may be a little hard to see, and I really needed a macro zoom shot to really give fine detail, but what you are looking at is the right side of the Pearl's platen. The clips that hold the tympan paper in place (bales? bails?) have been removed. They are held in place by four round-head screws with apparently are made of brass. The upside of brass is relative resistance to corrosion. The downside is the relative softness of the metal. The screws on the left side were easily removed, but the screws on the right side were damaged. The upper screw had it's head broken off, leaving the shaft protruding about one quarter inch, which was fortunate. A liberal application of Marvel's Mystery Oil, a delicate gripping of the channel locks and it was a done deal. The lower screw was not so easy, though. It was broken off beneath the surface and then some. Standard screw extractors could not reach. What to do?

I really wasn't certain IF these screws were brass, or if they were case hardened. I just took a gamble. As an Optician of three decades, I still carry my old finishing tools - the kind you'll never see at modern Optical dispensaries these days. I took my hand twist drill, popped in an 0.70mm carbide bit and with about ten minutes low pressure twisting, managed a reasonably clean dibbit square in the centre of the broken shaft. I then widened and deepened it with an 0.90mm Carbide. Then I used a fine taper reamer, essentially a needle pointed file that truncates to about 3mm. After about 45 minutes of patient drilling and filing, I managed a hole just smaller than my smallest steel optical flat-head screwdriver. This I gently tapped into place, applied a generous dowsing of Marvel's Mystery, and with a gentle application of torque, the screw freed up and came out easily with no damage to the threads. More than likely I will replace these with stainless steel round-heads.
All for now, stay tuned.

G. Johanson, Settlement Printer
Florida Pioneer Settlement for the Creative Arts
Barberville , Florida.

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