[Harp-L] Replacing slide bumpers/jeweling a slide
Fri Sep 16 16:24:51 EDT 2016
>>> On Sep 16, 2016, at 1:00 PM, robert mcgraw <harpbob at xxxxx <mailto:harpbob at xxxxx>> wrote:
>>> What does "jeweling the slide" mean exactly?
>> Chromatics have a multi part mouthpiece system. The mouthpiece is usually cast, sometimes machined. But the other 3 parts are ‘punched’
So, assuming an over the comb gasket, a u-channel, and a slide, these are punched from one side. This leaves the other side with a bit of sharpness.
This is all, of course, dependent on the fit of the male and female dies and how many punch sequences have been done on that one set of dies.
So..if you take a slide and run it between your fingers you may notice some sharpness to one side of the slide. What you want to do is
(in machinists parlance) ‘break’ those sharp edges. Most people use fine sandpaper, fine emory, an emory board, a file, or some other unnecessarily
abrasive tool. You don’t want to do that. The plating is there for a reason. You don’t want to dull it.
The best thing to do is scrape the edges of the SHARP side of the slide. You will be scraping the edges of ALL the openings in the slide. And you
scrape ALL those edges. There are 4 edges to each hole.
A straight tuned slide has more holes in it and this means there is less metal to metal surface area and this ‘should’ lessen friction. BUT beings that
there ARE more holes, there are also more edges TO the holes and sharp edges can give you enough friction to counteract the lesser amount of metal
A cross tuned slide has less holes, and while there is more metal to metal contact, there are also less edges to the lesser number of holes. So, in theory
a cross tuned slide should have less drag.
I scrape the edges of the holes with a pointed exacto blade which I hold at a 45 degree angle to the slide holes and from one corner to the other I scrape
lightly. Each hole, each side. THEN I finish off by rubbing that surface with a metal polish. Nothing too abrasive. This is fussy work and takes some time,
but I have always said “If you don’t do your own work on your chromo, it could cost you a small fortune to PLAY chromo”.
smo-joe the 4M company (Mars machining metallurgy & manufacturing, p.o. box 777 Mars, Pa.)
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