How might I get this done?

I agree the boring bar / cross slide method would be best for accuracy. Although you can get pretty accurate with a trepan tool; the thing is you have to get it on the first shot, so you need check the set on a piece or pieces of scrap till you have it spot on, then do the bore. I have used it on up to .250" mild steel 3-4" diameter holes without too many issues, I think .500 thick is doable. A couple of pointers if you go this route:
It is best too have a backer or spoil board under the work so the tool doesn't break through too fast and snag, a piece of steel or aluminum would be best but wood or MDF might work in a pinch.
Also on the same note, a medium feed is best, that is enough to get a continuous chip(s) and once going avoid stopping, just keep the same even pressure till your through. Stops and starts are what cause snags as will too heavy a feed. Too little feed may cause rubbing and dull the tool or worse, work-harden the material (depending on what you're cutting).
Keep lube or coolant applied as you go, an oiler with dark cutting oil or a spray bottle with soluble oil, may help to have a second set of hands doing that part.
I used a belt drive 15" Delta drill press slowest speed was 470rpm so it can be done but slower would be better.
One more thing. be sure to tighten the chuck in all three holes and go around twice, it does make a difference. The most common foul up is the tool staging and spinning in the chuck, once that happens the shaft will be chewed up and will likely slip again....
 
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I think you are in for a tough time- you'll have to take many light cuts and your patience will be sorely tested. You'll have to be very careful not to overshoot the size. Good luck
Mark
 
Soft jaws in a 4 jaw chuck, you may have to mill the jaws to hold this particular part but one may do such work with a chuck smaller then the part.

It is time consuming so charge accordingly.

It may also be well out of balance so choose an appropriate speed.

4jaw1.jpg
 
Soft jaws in a 4 jaw chuck, you may have to...
The part is too big to swing in my lathe, thus the dilemma....
I'm working to find a way to hold the part on the cross slide, or attached to my milling attachment..
 
Following up on this post, as I did get the part made.
In the spirit of using what I have to do what I need done... I mounted the milling attachment to the lathe, and clamped a piece of square tubing in it. Then clamped the plate to be bored onto the sq tube. (tube had a 'window' cut in it to clear the cutter.) I made a simple block to hold a boring bar in the 4-jaw chuck. Yes it was well beyond the limits of the setup, but when feeding slowly by hand it made a perfect looking bore. I was quite happy with the result. (sorry for the crappy phone pic)

setupb.jpg
 
Another "well done". Your solution has inspired a new line of "how to do" ideas here. Thanks
Ray
 
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