Stainless Steel Slide Plate

[jreit]

Does anyone know why a stainless steel/aluminum/metal plate is used in conjunction with a PTFE surface for slide bearings? Why isn't PTFE used on both sides?
Thank you in advance.

 

[JStephen]

Perhaps the overhanging plate needs to be unyielding (and un-wearing), or else you get a "lip" around the edge of it.
Or it could be that there's no advantage to using PTFE on both surfaces from a friction standpoint, and perhaps a disadvantage cost-wise.

 

[dhengr]

Jreit:
There are all kinds of newer lower friction sliding surface/bearing materials, some well proven, some not so much, yet. Generally the best sliding surface, used to be a woven fiberglass matt material (for strength) which was then impregnated (or filled) with PTFE to form a thin, flat sheet. Most of my long term designs then involved a chrome plated steel bearing surface or plate as the mating surface. Fiberglide was one of the brand names that I used, and I think it is still around. Google it. There are also some plastic type materials which make good low friction, wear blocks, which just get replaced periodically as they wear, depending upon your exact design details. I think you will find that, within reason, on rougher mating surfaces, they claim some of the PTFE is actually transferred from the bearing material, and impregnated into the rough steel surface until it is filled and smooth. Then, another issue with sliding surfaces is that you do not want the surface of the PTFE material sitting open and exposed to picking up dust, grit, grime, etc., which can get impregnated into its surface and cause scratching of the polished metal surface. Thus, the chromed/stl. pl. was usually larger than the PTFE surface, and on top, facing down, to keep the PTFE surface covered and protected. Alternatively, we would put some sort of a protective skirt around the whole slide bearing system. Stainless steel can probably be polished enough to make it work for this system. I’m not so sure about aluminum, since it is slightly porous however you finish it. Maybe anodizing would work, but I’ll bet that’s too weak for the loads involved. Check the literature of some of the companies which make these bearing materials.