Re: [Harp-L] Re:Was American Chestnut combs, now stainless steel(Vern Smith, Dave Payne)



A few years ago I led a group who cooperated in making over a hundred SS Hohner 270 chromatic combs. We encountered and solved some technical challenges. Now there are over a hundred happy harpers tootling away on their SS 270s. The CNC machine had trouble tapping the 1-72 screw holes and we eventually did it by drilling out to #2 and tapping by hand. It turned out to be more trouble and cost than we had anticipated but most participants in the project seem happy with the result.

You could not make a chromatic comb with a laser because the laser can't penetrate to a controlled depth. I would be interested in knowing how accurately the laser could control the edges of the chambers. Did the laser cut the front, back and sides?

There are good reasons for making and using a stainless steel comb. One is just the challenge of overcoming the engineering problems. Others include heft, long life, imperviousness to moisture & corrosion, precise & stable dimensions, strong steel screw threads and good looks. However, it won't sound perceptibly different from the same set of reedplates on a comb of any other type of metal, plastic, or wood.

I have a still-open, long-standing $1000 wager that no one can hear differences in sound arising from differences in comb material in otherwise identical harmonicas under controlled conditions. Wanna bet? ;o)

Vern

----- Original Message ----- From: "Seth Galitzer" <sethgali@xxxxxxxxx>
To: "geoff atkins" <geoffatkins@xxxxxxxxxxxxxx>
Cc: <harp-l@xxxxxxxxxx>
Sent: Thursday, June 11, 2009 6:51 AM
Subject: Re: [Harp-L] Re:Was American Chestnut combs, now stainless steel(Vern Smith, Dave Payne)



Sounds like this is going to be one mother of a heavy harp. It'd be
interesting to see how it sounds compared to other metal combs (eg
aluminum or brass). Also sounds like fun!


Seth

geoff atkins wrote:
(Reply to Recommendations and caveats for drilling procedures in Stainless)

Thanks Vern and Dave!

The "drilling expert" that was lined-up backed out, so I'm on my own.
In tests he tells me he has drilled 60 holes in 316 from the same cobalt
drill bit, with sharpness left for more.
My drill press is in good order, it's German, not Taiwanese. (I also have a
German metal-working lathe and gas and arc welding gear in my "little shop
of horrors").


I'm getting some cobalt drills (-with spares!) tomorrow, as I've found that
titanium-coated drills over here are often of suspect quality. In some cases
HSS has lasted longer.
I received a tip about the actual drilling: use motorcyle chain lubricant,
which has a high specific heat, and drill in 2 sec bursts onto lightly
centre-punched holes. Low revs is a must, as you said , Dave.
Also I've been told to set the bit in the chuck so that it projects only
half an inch or so. The steel is 304 grade, which is softer than the 316.


I'll make a jig, as the combs are dimensioned to fit Hohner reedplates, in
which the end holes are cunningly offset. My S/S blanks have all the sharp
corners removed, so every reed plate will need working upon also.
I'm going to give Vern's Idea a try, the tapping of the finer holes is a
worthwhile benefit, thank you for the excellent suggestion. I've already got
the tap and die kit from past tasks, and will probably use a 2mm OD metric
thread.
I have several 3-stage sets of taps.


Initially the intention is to put stock covers on. I've quite a lot of
spares, as the Hohner importer to South Africa doesn't bring-in reed plates,
so a complete harp has to be bought every time a reed breaks.


Special covers are the next task, to achieve full-length coverage. Instead
of stamping 24 pieces, they will be laser cut out of 0.5mm plate. Somehow
tin snips don't feel right... :)
The pressing will need a male and female die pair and I have a couple of 20
ton hydraulic jacks begging to be used. But that's for later.


Best Regards Geoff Atkins

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The beatings will continue until morale has improved.
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