It might, if I could find one that didn't have such a tall head...I have
at the most .053" before the screw head touches the board. The screw
also can't protrude through the heat-sink out the back. That's why I
need a 5/16ths long screw.
Steve
-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Monday, September 23, 2013 11:12 AM
To: TechNet E-Mail Forum; Steve Gregory
Subject: RE: [TN] Does anybody know where I can get a 5/16" long 4-40
wafer head machine screw?
Would a nylon screw work? Even if it touches the board it won't short
out anything.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Monday, September 23, 2013 11:22 AM
To: [log in to unmask]
Subject: Re: [TN] Does anybody know where I can get a 5/16" long 4-40
wafer head machine screw?
Hi Ed,
Yeah, I know that it may come down to something like that....CRAP!!
Here's what I'm dealing with. This board we're building has these high
power NPN transistors that get screwed down to a heatsink and then the
board mounts to stand-offs on the heat-sink:
http://stevezeva.homestead.com/Screwhead.jpg
You can see the offending part in the photo. The photo is my first
proposal to our customer with a button head cap screw, I wanted to put
some .050" thick washers on the stand-offs to raise the board a little
bit. But NOOO, the board has a 15-pin D-Sub connector that
straddle-mounts to the end of the board and then goes through a chassis
opening that doesn't allow for any slop at all...not even .050"!!!
What happened is that the part used to be a On Semiconductor TO-218 with
a metal tab (PN# TIP35CG) , but they did a PCN last year
http://www.onsemi.com/pub/docs/pcn/FPCN16827.pdf that changed it to a
TO-274....
So here I are....
Steve
-----Original Message-----
From: Ed Popielarski [mailto:[log in to unmask]]
Sent: Monday, September 23, 2013 10:01 AM
To: TechNet E-Mail Forum; Steve Gregory
Subject: RE: [TN] Does anybody know where I can get a 5/16" long 4-40
wafer head machine screw?
Steve,
You could probably modify these
http://www.mcmaster.com/#90910a714/=omte40 by making a block with 4-40
D&T holes on a matrix (20X20?) and fly cut it in one pass. With 2 blocks
and an electric screw gun you could probably do a few hundred per hour.
If you need "lots", I know a guy with a CNC screw machine that could
make custom screws reasonably.
Ed Popielarski
Engineering Manager
970 NE 21st Ct.
Oak Harbor, Wa. 98277
Ph: 360-675-1322
Fx: 206-624-0965
Cl: 949-581-6601
https://maps.google.com/maps/myplaces?hl=en&ll=48.315753,-122.643578&spn
=0.011188,0.033023&ctz=420&t=m&z=16&iwloc=A
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Monday, September 23, 2013 8:45 AM
To: [log in to unmask]
Subject: Re: [TN] Does anybody know where I can get a 5/16" long 4-40
wafer head machine screw?
Hi Richard!
Thanks! But do you have a link to the vendor where that has the ones
that have a head height of only .030" ? All the ones I'm finding have a
head height of at .059" which is too tall...
Steve
-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Monday, September 23, 2013 9:34 AM
To: TechNet E-Mail Forum; Steve Gregory
Subject: RE: [TN] Does anybody know where I can get a 5/16" long 4-40
wafer head machine screw?
You can use a 5/16" 4-40 cap head screw. Same length but the head is
only .030" thick. I have attached a picture. It won't show up on the
posting, Steve, but you should get it directly.
dean
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Monday, September 23, 2013 10:19 AM
To: [log in to unmask]
Subject: [TN] Does anybody know where I can get a 5/16" long 4-40 wafer
head machine screw?
Morning all,
Looking to find a 5/16" long 4-40 thread wafer head machine screw. It's
to fasten down a TO-247 Power Transistor...don't have any clearance for
the screw head. That's why I'm looking for a thin head. I only have
about .053" clearance for the head of the screw.
Any help would be appreciated...
Steve
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