Making a large-ish hole in aluminum plate

On a large-ish lathe with a 4 jaw chuck plus a boring bar you could make the offset hole with ease
 
Not adding anything other than a picture. I'd use a boring head like the one pictured below. Start with the spindle on center of the hole and drill the largest hole possible with a hole saw or drill bit. Then change to the boring head with a boring bar mounted. There's a micrometer dial on the side which adjusts the bottom of the head relative to the base. Pretty much the same principle as moving the cross-slide on the carriage of a lathe. The micrometer screw on my 2" heads is the change in radius (some are diameter). Adjust the head so the bar just scrapes and make a scratch pass. Return the quill to full up (or table down), shut off the spindle and adjust the micrometer screw for a deeper pass until you're to size.

The photo below is of a Harbor Freight 2" head and 1/2" shank boring bars. Mine were from Enco years ago, can't speak to the quality (or lack thereof) of the HF product.

Bruce



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Thanks, everyone. The next time I have to do something like this, I'll be armed with a lot more ideas.
 
All of the above plus this. I've been studying different setups for boreing steam engine cylinders. You can put an adjustable boring bar (one with a bit that sticks out the side and is locked in place with a setscrew) in a 3 jaw chuck and then stand the plate on it's side with a starter hole, center and fasten to the slide. Cheap and very simple. This is shown in some setups for boring castings with only a small lathe.
 
You could chuck it up in a four jaw on the lathe and use a drill and a boring bar as well.
 
BGHansen said:
The photo below is of a Harbor Freight 2" head and 1/2" shank boring bars. Mine were from Enco years ago, can't speak to the quality (or lack thereof) of the HF product.
Click to expand...

The HF and most of the really cheap import boring bar sets that come in those 9 piece sets have a serious design flaw in them. They work just fine in a lathe where you can adjust the center height of the tool but don't work well in a boring head because the cutting edge of the carbide is not on the centerline of the tool. TOT has a great shot of this in his video at a little after the 10 minute mark:


I fought trying to get a good cut with some of these forever. Could never figure out why they would work great on the lathe but would suck on the mill until I saw Tony's video and it was one of those "son of a ....." moments.
 
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spike7638 said:
I made this:
View attachment 308234
out of some scrap dock a day or two ago (that explains the two extra holes -- one near the bottom, one at the edge of the main hole). The large hole is 1.125 (+/- .05 !), and I made it by chucking up a cheap hole-saw into a chuck in the milling machine and gradually working my way through the 1/4" aluminum plate. It was blind luck that I had a hole-saw of the size I needed, and after I sharpened up the teeth a bit, it all went OK. But before I found that hole-saw, I was saying to myself, "How the heck am I gonna cut this hole? I don't have any 1 1/8 drills..."

In wood, I'd probably use a trammel cutter, which tends to cut a rough hole, and then smoothed things up a bit with rasps/sandpaper/whatever. If the lathes at the shop had 4-jaw chucks, I could have squared off the piece (the bottom inch isn't needed, but it didn't need to be cut off either) and cut the hole on a lathe. But supposing that the thing above -- rectangular, with the hole off-center --- really was what I needed, is there something like a trammel-cutter (but perhaps a little more sophisticated and less subject to vibration, etc.) that I could have used in the milling machine?
Click to expand...
Boring in the mill!! The best way to do it is to center the starting hole. You can drill it until it is big enough to start boring and keep on boring. When you get close to a finished size start checking for a fit.
 
MrWhoopee said:
Ooh, ooh, I almost forgot!

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Those are great for general drilling also. I am still on the same on that has drilled well over 100 holes in truck frames. I think one thing going for them, is the cutting surface changes as you progress through the hole, so they do not get as hot as a conventional drill. Also work great in sheet metal. Just wish I could find one that would make the 2" holes in thin metal, needed for gauges.

Recommend to every one, if you have not tried one, give them a chance before blowing them off as a gimmick.
 
Superburban said:
Those are great for general drilling also. I am still on the same on that has drilled well over 100 holes in truck frames. I think one thing going for them, is the cutting surface changes as you progress through the hole, so they do not get as hot as a conventional drill. Also work great in sheet metal. Just wish I could find one that would make the 2" holes in thin metal, needed for gauges.

Recommend to every one, if you have not tried one, give them a chance before blowing them off as a gimmick.
Click to expand...

Yes! They cut so smoothly and are self piloting.

You can get a 52mm (2.047)

Amazon.com: Chiloskit 4-52mm HSS Large Unibit Step Drill Bit for Metal Hole Cuter Wood Drill Bit Set : Industrial & Scientific

Buy Chiloskit 4-52mm HSS Large Unibit Step Drill Bit for Metal Hole Cuter Wood Drill Bit Set: Step Drill Bits - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
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