flatheads

In our terminology, that's a flathead. Holes are countersunk, using a cutting tool called a countersink.

Google arrested me for interrogation, but I escaped. Never saw the picture.

ng been in that industry you might not know the correct term in "countersun k". That means the head is flay on top and though it could have any type of mating method broached or cut into it, there is a taper at the bottom of t he head, which accomplishes what you apparently want.

I like the flat heads with an Allen wrench drive. I get the feeling that they are harder to over torque. (The Allen wrench flexes instead, but it's nothing I've tested.)

George H.

, they are simply too hard to use.

hole in the board is not that critical, however then you make tightening t orque critical as over tightening will break the board. So the workers or r obotics must have clutches on their tools. And of course you should be usin g machine screws, not be cutting the thread during assemble, they need to a lready be cut.

ing though. You just need accurate positioning of the standoffs or whatever you are using. Another thing is that for machine screws the workers or rob ots should put it to the hole and turn backwards until it drops, though goi ng a full turn would work 99.9 % of the time without having to sense that. But dealing with that is the job of the process engineer. They do get it do ne one way or the other. Actually it is surprising how much assembly is sti ll done by hand, but there is a reason for that.

We want a screw that hangs on the electric driver tip. That would be a hex, torx, or a square drive. And we don't want loose lockwashers, which means captive washers or none. We don't want production fiddling with loose fasteners and screwdrivers, and we don't want loose parts falling into the box.

Allen drive screws are nice.

aving been in that industry you might not know the correct term in "counter sunk". That means the head is flay on top and though it could have any type of mating method broached or cut into it, there is a taper at the bottom o f the head, which accomplishes what you apparently want.

pg

Yeah we have students put thing together and figure a Allen wrench is easier to find than a torx. (Doing our bit to de-escalate the screw/ drive/ security arms race.)

Hey I googled conical washers... but found you want to call them counter sunk wahsers. Someone should make a brass one. (Just another option.)

George H.

You should never get anywhere near that torque.

There's less metal in the neck of the screw with Allen drive compared with Phillips, so I'd expect an Allen flathead to be really easy to shear off.

Cheers

Phil Hobbs

There is more than one type of countersunk screw, but I don't know of any other type of flat head screw. If the bottom of the head has any other shape it has a different name like, pan head, cheese head or flat fillister. There are more shapes for screw heads than there are names and many names overlap.

Well for 4-40 screw one I have the drive is 1/16" inch Allen. here,

George H.

Oh, flathead _screws_ -- I thought you meant one of these:

You could also use shoulder screws into unplated holes, but then you'd have to figure out how close to the holes you could get with copper so's you'd have continuity to the spacers. It'd be less forgiving of mismatch, but still about as "precision" as you could hope for with screws.

For real precision, get spacers with shoulders, and fit them into unplated holes on the boards. Prolly have to get custom spacers, or do some hard looking to find what you need.

Right. I'm thinking that we wouldn't have a cold-flow problem. I've only had FR4 cold-flow troubles at higher temperatures.

Does your thing seem to work OK?

John - numerous times I've used 1/2 inch standoffs as you mention, but with swageable types (Keystone). These are mounted on 3/16 holes and soldered with other components in pot/wave times. Probably soldering would have to be a secondary operation now. They served as a ground connection in one application but four signals as you suggest should cause no trouble. The standoffs are nickel plated brass.

Hul

John Lark> We want to mount a small PC board maybe half an inch above a bigger

Really? Fastenal still carries 770 different types of slotted, flathead screws. Fastenal is an industrial hardware and tool supplier. They have two stores within 15 miles of here.

Yep, works fine. Stays tight.