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Re: [Amps] Workshop Danger

To: amps@contesting.com
Subject: Re: [Amps] Workshop Danger
From: Conrad Farlow <conrad@g0ruz.com>
Reply-to: conrad@g0ruz.com
Date: Fri, 13 Sep 2013 13:12:25 +0000
List-post: <amps@contesting.com">mailto:amps@contesting.com>
For tube sized holes the Q max metal punches have always worked very well for me even on 2mm aluminium. I think that biggest one I have is 75mm. I've gone solid state now so it's less of a problem. I have collected the full set over the years and they are still going strong.

I a hole is bigger than 75mm I usually get someone with appropriate tools to do it for me these days.

__________________________________________________

73

Conrad G0RUZ IO93FR


North Wakefield Radio Club

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On 13/09/2013 12:55, peter chadwick wrote:
Jim,

I have got from somewhere a 'circle cutter'. The difficulty with the plain fly 
cutter is that it is inherently unbalanced and so has a tendency to dig into 
the work and 'pick it up'. My circle cutter is effectively two fly cutters on 
opposite sides of the central shaft: as they can be moved individually, they 
need very careful setting up. Better to use than a drill press is a vertical 
milling machine, because

a)you can get a much finer feed to avoid digging in and

b)you are less likely to have the drill chuck decide to part company with the 
arbor or even the arbor itself get wrenched out and Morse taper damaged if it 
does dig in.


If you have a variable speed drive, that helps a lot too.

Another difficulty you can get is the drill chuck coming off the arbor. With a 
Jacobs chuck, a good way to avoid that is  (using a lathe) drill through the 
base of the chuck in the centre. Tap the hole 6-32. Then drill a corresponding 
hole in the arbor and tap the arbor 4-40. A 4-40 screw and washer attaching the 
chuck to the arbor and they won't come apart, but if you want them to, removing 
the 4-40 screw enables you to use a 6-32 screw to jack them apart. The arbors 
for my mill also have a drawscrew hole tapped 10mm, so a long bolt stops the 
Morse taper arbor shifting.


A kit of suitable clamping dogs and spacers is a good investment: even then, 
I've things move and as a result, break a half inch diameter end mill!

But yes, fly cutters can be dangerous. So can all workshop machines - other 
really nasty ones include a revolving wire brush (it can spit wire bristles at 
you) and a grindstone, especially if some fatherless wotsit has ground 
aluminium on it clogging the pores!


Of course, there's always the nearest smaller size hole saw and a half round 
file....


73

Peter G3RZP
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