Heat Sink tap/thread size

wicked1 · 22nd August 2009, 09:23 PM

Is there a standard size to use for threading the holes for mounting mosfets?
Also, where to get the screws/bolts? Everything at the local hardware store was far too long.

jackinnj · 22nd August 2009, 09:28 PM

Mcmaster-Carr has almost everything you'll need in the category of nuts n bolts. Note that the mounting holes for the Fairchild devices are a wee bit smaller than the Vishay parts -- they will only take a 6-32 screw if you drill them out a bit.

wicked1 · 24th August 2009, 01:26 PM

After seeing that website for the first time, all I can say is WOW! That's a lot of fasteners!
I'm building my chassis where I bolt bars and angles to my side heatsinks, and mount the top and bottom, front and back to those. Is there a standard depth to sink the bolts, to ensure a good hold? 1/4" has to be good.. How about 1/8inch? that's 4 threads deep.

Thanks again! (Sorry for the basic questions, but this is my first time building a chassis like this, and each question is potentially saving me some money!)

(Hey, would a physical construction forum be a good idea? For speaker/amp, metal/wood/etc.. construction questions?)

AndrewT · 24th August 2009, 01:40 PM

in steel the thread should engage at least 1.5diameters.
In (softer) aluminium try for at least 3diameters.

If you expect repeated removal and refixing to full torque then you can double these engagement lengths.

jackinnj · 24th August 2009, 02:41 PM

Here's how Krohn-Hite made up their chassis -- you can find the types of materials they used (small aluminum extrusions) on the web -- lots of 6-32 screws -- I point out KH as most of their stuff wasn't made in the gazillions -- HP could have cast aluminum chassis for their spectrum analyzers but it looks like the 1970's and 80's era KH equipment were job-shopped:

wicked1 · 24th August 2009, 02:52 PM

Ive got to say, this is a lot of fun.. It's like building an erector set, and then building something w/ it! Looks like my wood shop better get used to metal filings, because I see a new hobby developing.

Im not totally new to metalwork, but most of what Ive done is just a lot of drilling holes for front panels.
http://www.sdiy.org/wicked1/images/facelift.JPG

22nd August 2009, 09:23 PM	#1
wicked1 diyAudio Member Join Date: Jan 2008	Heat Sink tap/thread size Is there a standard size to use for threading the holes for mounting mosfets? Also, where to get the screws/bolts? Everything at the local hardware store was far too long.

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22nd August 2009, 09:28 PM	#2
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	Mcmaster-Carr has almost everything you'll need in the category of nuts n bolts. Note that the mounting holes for the Fairchild devices are a wee bit smaller than the Vishay parts -- they will only take a 6-32 screw if you drill them out a bit.

24th August 2009, 01:26 PM	#3
wicked1 diyAudio Member Join Date: Jan 2008	After seeing that website for the first time, all I can say is WOW! That's a lot of fasteners! I'm building my chassis where I bolt bars and angles to my side heatsinks, and mount the top and bottom, front and back to those. Is there a standard depth to sink the bolts, to ensure a good hold? 1/4" has to be good.. How about 1/8inch? that's 4 threads deep. Thanks again! (Sorry for the basic questions, but this is my first time building a chassis like this, and each question is potentially saving me some money!) (Hey, would a physical construction forum be a good idea? For speaker/amp, metal/wood/etc.. construction questions?)

24th August 2009, 01:40 PM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	in steel the thread should engage at least 1.5diameters. In (softer) aluminium try for at least 3diameters. If you expect repeated removal and refixing to full torque then you can double these engagement lengths.

24th August 2009, 02:41 PM	#5
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	Here's how Krohn-Hite made up their chassis -- you can find the types of materials they used (small aluminum extrusions) on the web -- lots of 6-32 screws -- I point out KH as most of their stuff wasn't made in the gazillions -- HP could have cast aluminum chassis for their spectrum analyzers but it looks like the 1970's and 80's era KH equipment were job-shopped:

24th August 2009, 02:52 PM	#6
wicked1 diyAudio Member Join Date: Jan 2008	Ive got to say, this is a lot of fun.. It's like building an erector set, and then building something w/ it! Looks like my wood shop better get used to metal filings, because I see a new hobby developing. Im not totally new to metalwork, but most of what Ive done is just a lot of drilling holes for front panels. http://www.sdiy.org/wicked1/images/facelift.JPG