[Amps] Workshop Danger

[Jim Garland]

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