Peter,
Thanks for the great tip, re securing Jacob's chucks. I agree completely that
using a vertical mill is by far the best solution. I've got a mill, but
unfortunately it's a small one designed for machining small pieces. I've never
seen a circle cutter like you describe, but it's obviously a great tool. I did
invest years ago aith a very heavy duty fly cutter that has a .70" shaft. It's
relatively stable, all things considered, but I've never used it on anything
heavier than .125" aluminum sheet. Good clamping is essential. By changing
belts, I can get my drill press down to 300rpm, but I agree that even that is
too fast. Also, lots of cutting fluid is mandatory, the kind designed
specifically for aluminum.
73,
Jim W8ZR
>
> 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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