The man is Harry Memelink. I've used his tools for many years. They are excellent - I believe the best hollowing tool there is, but Rolly Munro's newest design is very nearly as good. The problem with Harry, in my opinion, is that he is a great designer and not so good as a businessman. Too bad, but that's the way it seems to be, as you are finding out.
I used to use Harry's Exocet for rough hollowing and Rolly's for finishing, but I now use Rolly's tool for both.
The broken piece (a retainer?) I may be able to help you with. I have a small supply of Exocet parts. Email me (I'm in the Resource Directory) and describe the part.
As for using the tool, the main thing to remember is that it must be right on center, as is the case with any guarded ring tool. Slightly above center and the guard keeps you out of the cut. Slightly below center and the body of the cutter keeps you out of the cut. I suggest you use it on pieces of scrap wood mounted faceplate style until you get the hang of it, then try hollowing in where it is out of sight. Remember that this type of tool is very efficient, and the cutter/guard gap need not be too wide. Keep it small and you'll find the tool easy to control and a joy to use. Unlike ring tools, guarded ring tools are used with the cutter held level horizontally.
The cutters come in two styles - round and elliptical. I much prefer the round style, as it does not try to take too much of a bite as does the elliptical cutter at times. This is due to the geometry. If you look at the cutter and determine how much cutting edge is actually contacting the wood when taking a 1/8" cut, you'll see why this is.
If you can find a supplier, the cost of a cutter (last I knew) was about $60. The same price for a guard. Cutter and guard must match in style. I helped a friend buy a set from Harry a couple years ago, and it took six months to get it all. Very frustrating, with a number of communications between Harry & my friend & I.
The tools show up on EBay occasionally, and others can be found on web sites about turning. Often, they come up for sale because the user did not understand how to use them correctly.
If you are unable to get a part for your tool, I'd recommend Rolly's new design. It's simpler, stronger and much easier to obtain, despite their popularity at Albuquerque, which basically sold out the entire stock for a while.
Either of these tools can be mounted on the end of a good boring bar, where they will hollow a large form in record time. I'm a partner in a company that can help with that, too.
