Strongest non-metallic screws?

There aren't too many non-metallic options for 4-40 socket cap screws, assuming you mean socket head cap screws. Ceramic might be an option, but finding a 4-40 socket head cap screw in ceramic will be difficult. I have seen ceramic 4-40 hex head screws.

There are many more material options in larger sizes, but 4-40 severely limits your options. Some other non-metallic materials available for larger screw sizes are Teflon, PVC, and fiberglass (I think its actually polyurethane with glass fibers). You might be able to find some of these materials in 4-40.

Is there any chance you could use a high quality stainless steel that is non-magnetic? Alternatively, could brass or aluminum be used? I realize these don't meet your requirement of being non-metallic, but I'm trying to offer some possibilities without knowing the details of your application.

Silly me I thought you guys were in NM

If it's got to be plastic rather than just non-magnetic metallic

then your best bet is soem sort of glass filled plastic

look on "page 43"

been a while since I've done any work in minature plastic but nylon or delrin would be good choices but there are more exotic plastics as well. Whether you can get screws in them off the shelf?

you can PayPal my consulting fee..............

cheers Bob

Since you are in a laser and electronics group I'll ask the question, are you sure non-metalltic is enough of a specification? Or do you need some specific dielectric properties? As to strength, since you provide no load info you'll have to assess that yourself at this point.

-- Ed Ruf Lifetime AMA# 344007 ( snipped-for-privacy@EdwardG.Ruf.com)

I'm not sure how readily-available it would be as a pre-made screw, but Garolite is good stuff. It's easy to get the material.

I have a project now where I'm using Garolite G-9 and threading it with

8 mm fine threads and it is as strong as brass (which is what it replaced). It is dielectric, non-magnetic, and easy to machine.

Don Kansas City

Also McMaster-Carr carries ceramic machine screws and nuts, tensile strength of 4400 psi. As well as polycarbonate, nylon and PTFE.

Also found PEEK

Drake Plastics makes screws from Torlon and PEEK

There may be alternatives to using non-metallic (plastic or ceramic) screws. You haven't said why you need a nonmetal, so that makes it difficult to suggest solutions.

If you need a nonmetal to electrically isolate a piece, you can use a metal bolt and nut if you put a plastic washer under the nut, and a plastic sleeve to isolate the bolt from its hole.

Olin Perry Norton