Oh for the good old days when we would drill a series if 1/4" holes around
a circle, knock the center out with a hammer and use a half round file to
clean it up.
I still use that technique to make square holes for a blower inlet.
73,
Gerald K5GW
In a message dated 9/13/2013 6:24:59 A.M. Pacific Daylight Time,
conrad@g0ruz.com writes:
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
__________________________________________________
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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> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
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