Try these guys -- their brochure says they offer both abrasive water-jet and plasma cutting in the size range you need, for nickel alloys and stainless steel. They apparently have a San Francisco office.
I am making a decorative "ceiling flange", to bridge the gap, between a new stainless steel fireplace flue and the edge of the hole in the wooden ceiling through which this flue passes.
Here is a before picture.
Please note, that this is the old flue. It has terra cotta inside of galvanized steel.
The new flue will be a galvanized steel flue, inside a 14 ga stainless steel sleeve around which this ceiling flange will be installed. The new flue will have a smaller diameter than the old one, so the gap in the photo will be wider.
I knew someone was going to mention that. I know I could get this in 14 ga or
10 ga and be done with it. However, 1/2" will look a great deal better. A thin one will just look wimpy, and a thicker one will look just right. It's all about aesthetics, not just function. I will post a picture when it's done.
I know the plate will weigh about 25 lbs, so it will be hollowed out from the back, to reduce the weight to about 10 lbs, which will help a great deal during installation.
So why don't I have the whole thing fabricated out of thinner stainless steel sheet? Cost. The fabrication of such a plate, i.e. a 14 ga sheet welded onto
14 ga ring and cleaned up, and then drilled with a 6 hole bolt circle will cost about 5 times as much as a machined 1/2" stainless steel washer.
I have quotes for that already. I am now just trying to get the raw material as cheaply as possible. I already have the machinist lined up who will face both sides of the plate, which will most likely be warped from the heat of plasma cutting, trim the OD and ID to spec and hollow out the back and drill and countersink the holes for the screws.
It will, of course, have your signature inlaid gold ring and rivets...?
Even if you forego the ring, I don't see how you could possibly resist a nice triangular arrangement of gold rivets. Probably need, what, about 1" thick rod to keep them in scale?
Seriously, it might make sense to just forget machining the back and save the bucks, other than drilling the mounting holes -- the difference in weight isn't going to make all that much difference, given you will need to fasten it to the framing in any case. And if you get it water-jet cut, there won't be any distortion. I'm not sure what is cheaper with that size stock, plasma or water-jet, but not machining it might make up the difference in any case. Might not distort even with a plasma cutter -- you see that fancy scroll-work CNC cut stuff all the time, and it doesn't warp, although of course it's much thinner than 1/2 inch stock. . Regards,