Big holes are painful!
Some thoughts in my own (personal) order of preference:
- The lathe does them best for me, but that's not an option here because the part is too big.
- If you had CNC, you can interpolate the hole. This is where a small endmill cuts out a circular slug (or you can convert the whole hole to chips). The manual alternative is to put the workpiece on a rotary table and let the smaller endmill make a bigger hole.
- Next up are those pesky Blacksmith drills, which I agree, we prefer to call Silver and Deming. These work really well for me, but I have a big mill. Still, even my crappy import drill press does ok with them, so maybe it's alright. I just have a cheap import set, but I do find touching them up in my Drill Doctor helps a lot.
Past this point, we're into shear desperation. None of these is fun, but they all will work reasonably well given patience:
- I have a trepanning cutter. It cost something like $30 from one of the big houses. It works pretty well. Surprisingly well. But I've only ever used it on sheet metal. I shiver a bit at the idea of 1/2" steel plate.
- Hole saws. Once again, this has all been done on sheet metal in my shop, so I can't say how well it works.
- For larger holes, my plasma cutter works pretty nice, but it's likely a bit much for only a 1" hole.
If 'twere me, I'd invest in the Silver and Deming set. You'll use them more than you'd think.
But what about the boring head? Man, that is a real slow job on a mill. Of course an automatic head is really pretty nice, but they're so expensive I've been afraid to even try the Wohlhaupter I got a deal on. Crank through whatever depth of cut you can get, haul it out of the hole, loosen gib screws, change diameter with the dial, tighten gib screws, go through another cutting cycle. Man, life is short at 0.020 or 0.040 or whatever. BTW, it is really painful if you have the cheap import boring bars as well. At least get one good boring bar to fit your boring head!
I believe in boring heads strictly to make a finish pass to clean up and accurize these days, though I have made bigger holes with one at times.
Cheers,
BW