Re: NYC gondola brake details


Dennis Storzek
 

On Fri, Dec 18, 2020 at 02:06 PM, David Soderblom wrote:
How do you cut the piano wire without ruining perfectly good pliers. And do you angle the end to make a “bit” out of it?

I'm sorry, I missed the second part of your question. No, no angle. D bits (also known as single lip cutters) work by the straight edge formed by grinding half the diameter away scraping a tiny chip from the work piece. Of course, urethane resin is rather soft so it doesn't take much scraping to drill a hole. Here is a youtube video that demonstrates making a larger version:
Grinding a D bit
Ignore the multiple diameters, we just need the first step, and it doesn't need to be very long, just back it off repeatedly to clear the chips. These bits don't self center, which is why I use steel piano wire; it's stiff enough to be guided by the hole drilled through the bolster with a twist drill. Once going from crossbearer to crossbearer it can be guided with a pair of tweezers around the spinning bit, or use Schuyler's angle block method. Behind the grind on the tip there is nothing to catch, it's just a smooth wire.

Dennis Storzek

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