Re: 1st slide grind


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Posted by Lee Stofer on December 12, 2002 at 08:04:09:

In Reply to: 1st slide grind posted by tubachopper on December 11, 2002 at 19:08:18:

Have you considered taking it to a competent repairman? It is possible to fix this slide and not trash it, but caution is recommended here. The slide in question is nickel plated brass, with a layer of copper in-between, and if you work down to this the results will not be pretty, either in appearance or performance. Also, the slide tubes are not normally fitted very tightly on these horns, so I would suspect that there is an alignment problem. The problem could be caused by 1) an out-of-round tube, where lapping it would only make it leak, 2) bad alignment, which lapping won't help, 3) corrosion on the inner slides, which could be better addressed by a chem-cleaning, 4) a small dent in one or both of the slide tubes, which could be best fixed with expanding dent tools, not lapping, or 5) poor fit, which could best be remedied by a brass repairman with real lapping compounds, from 1,000 to 1,500 grit. In my earlier days, I tried steel wool, etc., but never do that now, as I now know that using sandpaper or steel wool is woefully inaccurate.

Although these instruments tend to be primitive and fragile, they can be made to play well-enough. I know some people are having a field day bashing the St. Pete, but that brand is not the only one with problems. Someone brought me a 56J not too long ago, complaining of the same problem. The #1 job was to measure alignment, which must be within two thousandths of an inch for the slide to have a chance of working well. The outer slide tubes were twenty-two thousandths out-of-parallel. After heating and tweaking the braces, getting the alignment to where it matched the slide itself within 1/2 of a thousandth of an inch, and lapping the slide tubes with ultra-fine lapping compound, the customer has a vented 1st that pulls like a trombone handslide.

Lee Stofer


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