I've tried a lot of things. Glides that are nailed to the end of the leg always seem to pull out, and tear the floor up if not caught in time. Soft plastic mushrooms. Felt wears out and also captures grit. Polished steel works, but seems to come only in nail-style glides. And so on.
Gradually a list of requirements formed:
1. Must attach using a screw. No nails!
2. Must have a hard smooth durable surface that will not accumulate or embed grit.
3. It should not wear out in less than ten years.
4. It cannot rust or corrode in indoor service. Outdoor service a plus.
5. It would be nice if they accommodate slightly uneven floors.
6. It would be nice if they weren't too expensive.
I did think of polished thick (stainless) steel washers countersunk to accept a flat head wood screw. These can be found, but they are something like $5 per washer. I could make them, but it would be a lot of washers to make. And I'm not the first to have this problem, so there has to be a commercial product.
Then I thought of engineering plastics, the expensive kinds that don’t so easily mushroom under pressure. Delrin jumped to mind, as it is quite strong and hard, can be press fit (does not creep), and is very slippery. Makes good bearings. This I could also machine, and a lot more easily than with stainless steel.
On a lark, I googled on "delrin chair glide". Bingo - somebody already makes them. So I bought a bunch and installed them on the four dining room chairs several months ago. They worked very well, so I installed them on the six kitchen chairs in May 2014. And replaced two failing nail-style glides just in time to save the floor. (These glides can also be used for tables, but I don’t recall if I installed any glides on the tables.)
The glides I'm using are "Forever Glides" from Max-Tech Products, Inc, Englewood, CO. I got them from Sportys Tool Shop because Sportys had a reasonable price, and had all the styles and colors. Transaction was smooth. Cost less than $1 per chair leg, when bought in a pack of 20.
Each glide consists of four parts: Bottom and top, both of injection-molded delrin, a piece of double-stick foam tape that goes between top and bottom, and a steel sheet-metal screw that attaches the top to the chair leg. The double-stick foam tape looks like the neoprene stuff used to attach trim to automobiles. (It may in fact be EPDM, according to the patents. If EPDM, beware of oil.) These glides are actually rated for outdoor use on patios.
Although not mentioned in the installation instructions, it's useful to make a drill guide out of a small block of aluminum so the drilled holes will be perpendicular to the bottoms of the chair legs and the screws will go in straight.
For those interested in the gritty details, the US patent numbers are 5,680,673; 7,762,506; and patent application 2008/0148522. Also 7,762,506. There are other patents not listed here.
This was first posted as “Chair Glides” on Rec.Crafts.Metalworking, on 26 May 2014, years before I joined Rec.Woodworking. There have been no problems whatsoever with the Forever Glides. They just work.