|
Larry G -- You could check the Criterion website; I think that a half-inch straight shank is available to fit their small boring head. But it's for a onesy-twosey operation, you'll end up with some high price holes after paying for the boring head. For a through-hole, maybe you should consider making an old-fashioned boring bar . . . it can be as simple as a half-inch rod with a 1/4 inch hole drilled through near one end to take a toolbit. You'd almost certainly want to drill and tap the boring bar axially for a set screw to hold the cutter bit in place. Make a toolbit from 1/4-inch diameter high-speed round stock (the shank of a dull or broken twist drill will work), maybe 5/8 inch long, and grind the end to look like a left-hand lathe tool. Maybe even grind a bit of a flat for the set screw to bear against. Insert the bit into the boring bar, orient the bit correctly so that the sharpened end sticks out of the boring bar by 1/8 inch, and lock it in place with the set screw. Now chuck the boring bar into the drill press, set the press for a real slow speed, and go to town. You'll need to change to a slightly longer bit and repeat the boring to get up to the 1 1/2 inch diameter you want, but I'm not sure that a 1/2 inch drill press would have the moxie to make the cut in one pass even if you had a boring bar that would otherwise let you open up the hole in a single pass. If you need a blind hole, you can do pretty much the same thing but angle the toolbit hole in the boring bar about 45 degrees so that the cutting edge can be set all the way out to the end of the bar. A spade drill might also be worth considering, but as with the boring head, a purchased spade drill will probably set you wallet back a fair chunk. A quick glance at the MSC catalog indicates that you might be able to buy a single 1 1/2 inch spade drill insert for $40 to $50, NOT including the holder. Finally, there are "annular cutters" that would almost certainly work well (Rota-Broach and Jancy Engineering's Slugger are two tradenames), but these guys are expensive too. Of course, if you're working on a cost-plus contract . . . John
| 
