Well, I ended up biting the bullet and milling it in my drill press. This will be the one and only time that I abuse my drill press in this manner. I have an XY table for the press and I took very small cuts of about .002 each pass across the compound with a lot of cutting oil. It took quite awhile doing it this way since I took such a small cut each pass and only had a 1/2" end mill to do the work. Actually, it turned out very nice. I indicating everything in to ".000". It didn't sound like a lot of undue strain on the machine, but like I said I won't be doing it again.
Fitter Bill.........that's a really great offer and I truly appreciate it. If I would have seen your post before I did the job, I think I would have taken you up on it.
Dranreb................I thought about trying to mount it up in a chuck, but was a little apprehensive about securing it properly and locating it the necessary position to make such a cut. I guess it could have been done if I would have put a little more effort in it.
On a related note, mostly for any future members with "new to them" lathes, who also want to mount a QCTP on their Atlas 10", what I would say is DON'T MILL YOUR COMPOUND DOWN so you can swing your QCTP properly. I say this because of the thickness of the casting. Although I DIDN'T break through, my measurements afterwards of how much casting thickness is left after doing the milling is very minimal. Yes, there is still casting on the sides of the compound that has the original structural integrity. We'll have to see how long it holds up and whether the compound ends up breaking or not from repeated stress of machining. I machined the radius down to slightly below the level of the flat on the compound, but only by a few thousandths.
If I were going to do it again, I would have just followed my original instinct and made up a "riser" to raise the bottom of the QCTP up above the radius of the compound. Bill C. had the same idea. Theoretically, it would only have to be a couple thousandths thicker than the difference in height between the flat of the compound slot area to the radius of the compound casting, which is about .125 in. I think that would have been the better way to do it. A functional riser made to fit the shape of the flat surface could easily be fabricated and would not rotate when spinning the QCTP. I guess my hindsight is 20/20. If the compound ever does break and I have to get another, I will definitely be making a riser about 5/32" thick to stick under the tool post. Just my two cents.
I will say one thing positive, though. Taking the compound off allowed me to clean up all the gunk underneath it and repair the gib adjusting screws that were frozen in the lock nuts.
Thanks for everyone's advice. Moving on to mounting an old (30+ years), adjustable, swinging-arm type lamp that I acquired from Champion Spark Plug that they were throwing away because it was arcing in the bulb socket area and only turning on intermittently. I replaced the lamp holder for a few dollars. Other than the bad lamp holder, the light looks like brand new. Made in USA, too. I've been storing it for the past 11 or 12 years or so in anticipation of getting a lathe someday and putting it to use. I REALLY want to place the mount for the lamp on the back of the carriage somewhere, but I don't see an adequate place to do so. The casting is not flat and has compound sloping angles to it. I prefer the light to travel with the carriage, so the illumination stays with the cutting area of the workpiece. I might post up a pic in a new thread and ask for some member's advice on how to mount it. If anyone has mounted a light like this on their carriage, please give me your insights. Space is really limited on the back of the carriage with the gib screws and such and, like I said, the top of the casting isn't anywhere near flat. The mount has a "ball" on it, so I am stuck using it.
