Okay, a little slow on completing this project. It got interrupted by surgery to fuse C3 and C4 discs in my neck. Other than that, there's really not much of an excuse.
I finally finished the project, which was to make a set of coasters to match a set of hot plates made a year or so ago. After reviewing all the helpful information, I came to the conclusion I may well have been over-thinking the project. Here's a pictorial of how I approached it.
1. I had a piece of scrap 1/4" aluminum that I turned down to an 1/8" smaller diameter than the coasters. It had a hole milled in the center that was too big, so I plugged it by pressing a piece of scrap brass into it and turning it to the proper inside diameter (3/4"):
2. I clamped this to a piece of scrap plywood and used it as a template to cut out the gasket material. Some of the gasket material was cork; other was automotive. Generally, I was experimenting on which I liked better and which will hold up better under use:
3. I made a punch from a piece of 3/4" aluminum tubing by turning a sharp taper to the INSIDE resulting in the outside edge being clean. This piece fit very snugly into the brass hole on my template:
4. Without moving the template off of the gasket/cork from step 2, I positioned the punch in the template and gave it a sharp whack with a hammer. The result was a set of perfectly shaped holes and very clean punch-out's that I have saved for some future who-knows-what project. I was anticipating I'd need to periodically sharpen the punch, but it held up for the entire project - twelve pieces in all.
5. I positioned the shaped gasket/cork onto the back of the aluminum coasters I had previously made (not covered in this thread). Sandwiching the coaster and gasket together, I clamped them firmly and glued them on with black RTV.
6. The result was a set of coasters that very nicely match my wife's hot plates. (I was looking pretty good when she saw them!) Here are top and bottom views of both - one of the coasters has a cork back; the other has an automotive gasket material back:
P.S.: I made stands for both the hot plates and the coasters. Didn't think to take a picture of the stands by themselves, but you get the idea. That's the reason for the holes.
Thanks to all for the typically sage advice from our seasoned veterans on this project. It actually was less complicated than I imagined it was going to be.
Regards,
Terry