bodega

Let's talk about screws for a second....
« on: October 25, 2009, 10:38:43 PM »
Hi all,

I've been thinking for a while about how I've been mounting pcbs inside my enclosures, and it's not been pretty. I started to wonder if anyone makes screws with a perfectly flat, thin and wide head - perhaps a half-mm thick.

I've been googling it, and I can see these are the usual suspects:



It seems strange that there's not some kind of screw where at that line they've drawn, there's just a kind of flat disc. Hopefully that makes sense.

If I could get one of these mythical screws, then that would be on one side of the bottom of the enclosure, and on the other side would be a spacer, the pcb, and a keps nut. No more worrying about the head of a hex nut scratching the piece of gear below.

Are these actually available anywhere? If so, enlighten me!

If not, anybody want to go into the screw (I know, I know...) business?

thanks!
Matthew


shabtek

Re: Let's talk about screws for a second....
« Reply #1 on: October 25, 2009, 10:48:26 PM »
flat head. is flush with bottom when countersunk properly

filister is a flat disk but not flush.

what about some kind of die mechanism to make a little dimple instead of countersinking: like you sometimes see for a toroid mounting bolt?

mcmastercarr.com  has lots of info on fasteners.



"really fine players do not use stomp boxes or master volume, they match the amp to the room and turn it up to 11.  Stevie Ray, BB King, Albert King, Duane Allman, Dicky Betts, Louis Armstrong"
   -CJ

bodega

Re: Let's talk about screws for a second....
« Reply #2 on: October 25, 2009, 10:55:57 PM »
I'm specifically thinking of how we would typically use it: in an AWG 18 or 19 enclosure. A flathead wouldn't work so well in that application.

A Fillister would be better, or at least it looks like a step in the right direction. But still not a "flat-washer-head" screw, like would be ideal.

That McMasterCarr.com is pretty impressive! They've got this, which looks close, although the "height" is still a bit thick, as you'd expect of a thumb screw:


Dan Kennedy

Re: Let's talk about screws for a second....
« Reply #3 on: October 25, 2009, 11:20:28 PM »
You want to look at aircraft screws. Specifically designed for thin sheet metal.

100 degree countersunk, you have to buy a corresponding countersink tool, but
they will sit flush with  .031 material, roughly .5mm


burdij

Re: Let's talk about screws for a second....
« Reply #4 on: October 25, 2009, 11:35:25 PM »
Try "cheese head" in McMaster. Metric sizes only, though.

jsteiger

Re: Let's talk about screws for a second....
« Reply #5 on: October 25, 2009, 11:35:50 PM »
Try searching for a 100 degree undercut flat head screw. This screw is not shown in your drawing of screw head types.
Visit the CAPI store at http://www.capi-gear.com

CAPI is not affiliated with, endorsed by, or sponsored by API.

Re: Let's talk about screws for a second....
« Reply #6 on: October 25, 2009, 11:46:05 PM »
Gus once mentioned rivnuts... basically a small rivet with a threaded hollow center. works like a rivet and when in place works like a threaded hole in the  metal. then you mount the pcb and screw it down. You may still have to countersink to get a decent flush mount, but when you're done, on top you're working with screwdrivers and not nutdrivers. 

12volts

Re: Let's talk about screws for a second....
« Reply #7 on: October 26, 2009, 04:40:13 AM »
You need to look at Captive Fasteners or PEM fasteners. Those are the industry standard.

http://www.captive-fastener.com/catalog.html
http://www.pemnet.com/fastening_products/pem-self-clinching-fastener.htm

You will be astounded at what is available.


owel

Re: Let's talk about screws for a second....
« Reply #8 on: October 26, 2009, 09:34:57 AM »
Try an adhesive-backed PCB mount. (top plastic part looks like the locking mechanism PC/mobo makers use).
Just peel the sticker sheet and stick to your bottom panel.
No drilling needed on the case.

Also, +1 on the undercut screw. You'd have to countersink your holes though.

bodega

Re: Let's talk about screws for a second....
« Reply #9 on: October 26, 2009, 09:40:07 AM »
Try an adhesive-backed PCB mount. (top plastic part looks like the locking mechanism PC/mobo makers use).
Just peel the sticker sheet and stick to your bottom panel.
No drilling needed on the case.

Do you mean something like this?

http://www.mouser.com/catalog/specsheets/EPD-200446.pdf



bodega

Re: Let's talk about screws for a second....
« Reply #11 on: October 26, 2009, 09:49:46 AM »
Nice.  8)

kato

Re: Let's talk about screws for a second....
« Reply #12 on: November 15, 2009, 06:24:17 PM »
If you're searching at mcmaster carr, you might want to search on "cinch stud."

Speedskater

Re: Let's talk about screws for a second....
« Reply #13 on: November 16, 2009, 11:00:44 AM »
Someone in one of the forums recently posted this link.  They have lot's of small sizes and will ship small quantities.   

http://www.jrhobbyhardware.com/shop/
Kevin

3nity

Re: Let's talk about screws for a second....
« Reply #14 on: November 16, 2009, 11:09:53 AM »
what i've done its buy 1/4 threaded  spacers...
then i glued them to the bottom with epoxy....
They stay in place and you can screw the pcb in and out any time you want..
Thanks..
Life is a path, death the destination.


 

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