Appropriate Screw for 2mm hole in ABS

Any reasons why not to use 2mm screws? I would use 2x4 (mm).

designing:

A 2mm machine screw is slightly smaller in diameter than 2mm, so it would certainly be an easy fit. The board might not be all that secure, though.

Are you suggesting a 2mm sheet metal screw, or some other self-tapping screw whose nominal diameter is the hole size, not the OD of the screw threads? If so, what?

ave

an M2 screw will fit through a 2mm hole ;)a M2.5 should be a perfect fit, size wise but the thread is a big fine for plastic.

any who, first hit "bopla screw" on google is:

-Lasse

Just a note: I sent an email to Rose+Bopla, not really expecting a reply. I just got a call from Candice at their US office, who was very helpful and is going to make sure that someone even _more_ helpful calls on Tuesday! After I figured out it wasn't a sales call (who responds to emails with a _human voice?!?_ I was delighted.

Wow. I was already happy because they're nice enclosures -- this is even better.

es have

Yes, 2mm normal body diameter, self-tapping, with the threads slightly bigger.

Tell them to include the screws, so they won't screw their future customers.

Well ... that diameter is pretty close to the tap drill size for a 3-48 screw. So -- you could tap it to that size -- or get one of the self-tapping screws (sort of like dull-pointed wood screws with less taper) for use in plastics.

Or -- you could heat and push in a knurled metal nut for a smaller screw -- say an 0-80, because the OD of the thread for anything larger will be too large to work with the existing holes.

Not sure how well a thread-forming tap would work in the plastic involved, otherwise I would advise those to form standard threads.

Good Luck, DoN.

Done very often with plastic cases. Should not be a problem holding PCB.

Threaded fasteners are all designed to provide specified fastening for a mated thread count of 3 threads. Granted, many application where a bolt gets turned down a blind hole results in many more then 3 threads of captivation, the design spec gives us all we need with only 3.

So, IF the bosses are already threaded, your screw only needs to be your PCB thickness plus say 4 or 5 thread pitches more.

If they are not threaded, you use the same formula for whatever size screw (#4 or #6) you decide to thread the hole with and use. If you intend to use a washer for the screw to bear against instead of your PCB, you would also add that thickness. For metal cases, one usually leaves one of the PCB mount holes as a grounding point. For metal some use thread locking compounds. For plastic, you shouldn't need it as you will not be meeting any vibe specs anyway. :-) also with plastic, you could opt to press (or melt) in PEM nuts instead of threading holes in plastic.

After all that the screws are usually already made so you have to choose one from the lengths available that most closely matches your final requisite length sum.

"Flexural Modulus".

Absolutely perfect choice. A variant of sheet metal and wood screw thread topology.

Very informational link/page, thanks.

Yes -- but it depends on the plastic involved. Yes, the cases are likely to be made of a plastic which will gracefully accept thread-forming taps (and should be so made) -- but *some* plastics don't like the stresses involved, don't flow well enough, or (perhaps) are sensitive to lubricants (e.g. Plexiglass/Acrylic will develop cracks radiating from any point which combines stress and oils.)

Enjoy, DoN.

Tim:-

This is a ME question. Suggest that you refer to data from companies that make screws designed specifically for threading into plastic, don't guess on this one. Here is a starting point:

You should be able to request the ABS resin spec sheet from the manufacturer, otherwise use a generic ABS resin spec eg. maybe

Best regards,

-sp (currently in Jena, former East Germany)

designing:

Yup. I was hoping that either s.e.d would have someone who's done this before (apparently not!) or that r.c.m would have some semi-ME types with concrete suggestions.

So far I've gotten two leads to Accument, if the case manufacturer doesn't get back to me then I'll probably see if Accument will sell me a couple of hundred screws, or point me to a catalog distributor.

I'm really hoping that the case manufacturer (who designed the bosses, after all) has a recommended screw, but they're all off for the long weekend.

es have

I already posted the link to boplas site with the recommended screw for different boss sizes:

-Lasse

designing:

I've been following this (I'm curious about the proper fastener, as well). The Bopla link above is helpful but the numbers cross right back to itself.

The 2.5 mm size makes sense but trying to find the right piece at, way McMaster-Carr is proving to be a challenge.

designing:

This

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Try Ababa.

designing:

It's their German site, and in-house numbers which don't seem to be available at Digi-Key. So it's not necessarily help for ordering the parts from an establishment that's going to want to deal in small quantities, in the US, unless Rose + Bopla does themselves. It's certainly not a help in getting an independent source.

But who knows -- I have a promise that a human being from Rose + Bopla will be contacting me Tuesday; we'll see.

osses have

ok I thought with a part number you would be able to get it from where you got the boxes

any who, something like this:

-Lasse