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

["geoff atkins" <geoffatkins@xxxxxxxxxxxxxx>]

(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