Best way to bore a 3" hole in 1/2" Al Plate

"jroncallo roncallo @snet.net>" through a 1/2" 6061 AL plate. I have a lathe with a 3 jaw chuck or

Hole saw then bar? Trepan with hole cutter?

You can rough cut the holes with the milling machine and an endmill, then finish with a boring head or boring bar. HTH

"jroncallo roncallo @snet.net>" through a 1/2" 6061 AL plate. I have a lathe with a 3 jaw chuck or

======== Invest in a hole saw and arbor. Starrett and Morse are two good brand names. Trick is to drill a small (1/2 inch) hole to the inside of the track of the saw so that the metal swarf has somewhere to go. Saws will cut slightly oversize holes.

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?PARTPG=INSRAR2&PMAKA=990-0572&PMPXNO=3008691you will also need a mandral/arbor to drive the saw than likley your local mill supply has these in stock.

FWIW -- I have found off-brand/cheap holesaws/kits to be very expensive when the cost of ruined material and your time is figured in.

Unka' George [George McDuffee] ============ Merchants have no country. The mere spot they stand on does not constitute so strong an attachment as that from which they draw their gains.

Thomas Jefferson (1743-1826), U.S. president. Letter, 17 March 1814.

How about a Holex?

A bit pricy perhaps.

-Brian

Take a piece of round stock that will fit your boring head, cut a slot in middle of one end wide enough to put a piece of HSS parting tool in by silver soldering. Grind relief, orient it properly in boring head and go to it.

I should make one of those for myself. It took way too long to make a 2" hole is steel today starting with a 1/2" hole.

Wes

Rough out the holes with a plasma cutter, then locate your plate on the mill using MDF as a sacrificial backing, then bore the holes which should go quickly with nearly all of the waste removed. If you don't have a plasma cutter, chain drill around the inside using a 1/2" 135° screw length drill bit, using your DRO to quickly locate each hole center which you'd of course precalculate using Excel or similar spreadsheet. If you chain drill correctly the holes will just connect.

The hole saw idea is also a good one - remember, 800 sfm is the correct cutting speed for aluminum and absolutely use cutting fluid. I just use kerosene, works great, but guys on this NG have been touting cleaning fluid containing d-limonene, a citrus extract. Kerosene works great if you have it.

Grant

hole saw

"jroncallo roncallo @snet.net>" through a 1/2" 6061 AL plate. I have a lathe with a 3 jaw chuck or

Thanks for the replies. It apears that quick and cheap seems to be the hole saw approach. I never used a hole saw on AL and I kind of thought it would just clog. But I only have 4 of them to make so I'll just bite the bullet and cut away. I like the idea of the 1/2" hole just inside the track.

Thanks John Roncallo

With a CNC mill, you just orbit the cutter to cut out a blank, then make a finish pass to get a clean hole.

If you have a large boring head, you can put a trepanning tool in the outermost hole and carve out a narrow trough just smaller than the desired diameter. Then, once you have your hole roughed out, you can use a regular boring tool to finsh the hole to the final diameter.

A trepanning tool can just be a chunk of drill rod or similar stuff that you grind to a narrow blade. Sort of like a lathe cutoff tool but set up so you can mount it in boring head and it won't drag on the sides of the groove as you cut it. It will need to have over 1/2" of length ground to fit in the 3" diameter groove. Wear ear protection, these things squeal like crazy, but can do the hole in a couple minutes.

You could also try a hole saw, maybe you could find one in 2.75" diameter.

Jon

Get a 2-½ or 2-¾" hole saw--use plenty water base coolant-cut slow--finish on mill.