alternative retaining rings?

[Erich Hoeber]

Another vote here for the hot glue gun. Quick, cheap, strong and easily reversible.

[Bob Salomon]

Have you actually tried to find a machine shop in the US in past five years? I think Azo grade 3 is easier to find....

Yes. Try Keeble & Shuchat in Palo Alto. They can do it.

[Don Hutton]

My point was Bob, in case you missed it, they are not exactly around every corner like they used to be. Palo Alto is a long way from here.... As an aside, I thought your advice was to "try a machine shop" anyway - not a photographic retailer....

[tim atherton]

hopefully bob is throwing in the air fare? :-)

[Paul Metcalf]

If you have any woodworking skills and tools (table saw, drill press, forstner bits) you can make something like in the photos (see link). Use a 1/2-inch thick piece of wood cut square bigger than the diameter of the lens. Secure in a drill press and drill all the way through a hole that's a smidge bigger than the barrel, then bore a boss using the forstner bit that's a bit bigger than the shoulder of the barrel at the base (where it would normally screw into a retaining ring) and about 1/4-inch into the wood. (An alternative to using a drill press is to bore the boss first, then drill the through-hole using the center punch from the forstner boring bit as a guide. The goal is to have the hole and the boss concentric). Using a lensboard with a hole that's just big enough for the threads to go through, slide this square piece down the barrel and secure with screws into the lensboard. If needed, you can use some felt in the boss-area to apply pressure to secure movement of the lens. I finish my in glossy black paint and use brass screws, looks pretty nifty with brass lenses (especially polished lenses).
http://www.pixagogo.com/4997144154

[Jon Wilson]

At hardware type stores, you can purchase plastic straps which will tighten by threading the strap through a self tightening hole and pulling the end of the strap(tightens tight like a hose clamp), i.e., picture cheap plastic restraint straps which law enforecment use at times in lieu of handcuffs. If someone knows what these plastic binding straps are called, let me me know.

I have used these type of plastic retention straps with old brass lens as a "retaining flange."

[Jon Wilson]

I found a bag of these "plastic straps" and they are called Cable Ties.

[Colin Myers]

As most metal lensboards/lenspanels, tend to be around a sixteenth of an inch in thickness and we may be looking at a fairly large diameter thread on the the old brass lens. I do not think that trying to thread the board itself is a very good idea, as you you may well end up with less than one full thread on the board.
Colin Myers