LED light - problem with heatsink - The Planted Tank Forum
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post #1 of 14 (permalink) Old 02-20-2011, 06:27 PM Thread Starter
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LED light - problem with heatsink

I am building a new LED light with Cree bars from http://www.easy2led.com and my intention was to drill holes in the heatsink and attach the bars with screws.

Well, half of the screws snapped when driving them into the heatsink! I used those screws: http://www.smallparts.com/plated-ste...head_style=Pan

OK, I admit that I'll have to drill new holes, but what are the recomendations for the hole diameter and screw type?
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post #2 of 14 (permalink) Old 02-20-2011, 06:43 PM
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You could try using a self-tapping sheet metal screw with a 1/4", or 3/8" hex drive on it to get enough torque to go into the heatsink, leaving no need to drill a pilot hole first.

"an ounce of prevention is better than a pound of cure"
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post #3 of 14 (permalink) Old 02-20-2011, 09:00 PM
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Self-tapping screws is a good idea, since the first part of those is a drill, which drills the right diameter for the screw to cut its own threads, but not be over torqued doing it. http://www.smallparts.com/stainless-...qid=1298239165 I would use a smaller diameter drill to drill starting holes even with these.
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post #4 of 14 (permalink) Old 02-20-2011, 09:09 PM
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^^Agreed!
If you do happen to over torque the screw so it spins freely, just grab another, it should bite into the aluminum easily enough the second tyme.

"an ounce of prevention is better than a pound of cure"
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post #5 of 14 (permalink) Old 02-20-2011, 09:16 PM
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Self-tapping screws don't often drill through the thick plate of many heatsinks very well.


If you do try self-tapping screws, get some that are about 1/4" or 3/8" longer than your baseplate... and even then, just buy a few to try them out.

Make sure that you use a plastic washer underneath the head of the self-tapper, they are often a bit bigger than other screws. You wouldn't want it contacting a solder pad or you'll ground out on the heatsink.
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post #6 of 14 (permalink) Old 02-20-2011, 09:17 PM
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And +100 to Hoppy, if you pre-drill the holes using something just shy of the screw thread thickness, you might be alright.
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post #7 of 14 (permalink) Old 02-21-2011, 06:14 PM Thread Starter
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Quote:
Originally Posted by redfishsc View Post
Self-tapping screws don't often drill through the thick plate of many heatsinks very well.
True, indeed. My heatsink is almost 1/4" thick.
I have drilled holes 1/64" smaller than the screw and the screws snapped!
I will try this weekend with new screws and a bigger drill.
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post #8 of 14 (permalink) Old 02-21-2011, 09:08 PM
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When I tried attaching LEDs with screws I just tapped the holes to #4-40, using a combination drill-tap designed for that purpose, or, a tap drill plus a second operation tapping the holes. I found I could use a cordless drill/driver to do the drilling and the tapping if I was careful - no drills or taps broken.

Hoppy
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post #9 of 14 (permalink) Old 02-21-2011, 09:50 PM
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I'm much too lazy (and busy) to drill/tap lol. Thermal tape or thermal epoxy is almost always what I use
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post #10 of 14 (permalink) Old 02-21-2011, 10:54 PM
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Quote:
Originally Posted by redfishsc View Post
I'm much too lazy (and busy) to drill/tap lol. Thermal tape or thermal epoxy is almost always what I use
I removed all of the screws and used thermal adhesive instead, when I found it too hard to avoid shorting out the LEDs. I haven't looked back

Hoppy
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post #11 of 14 (permalink) Old 02-22-2011, 03:04 PM
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Quote:
Originally Posted by hoppy View Post
i removed all of the screws and used thermal adhesive instead, when i found it too hard to avoid shorting out the leds. I haven't looked back:d
+1.
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post #12 of 14 (permalink) Old 02-22-2011, 05:07 PM Thread Starter
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Quote:
Originally Posted by Hoppy View Post
I removed all of the screws and used thermal adhesive instead, when I found it too hard to avoid shorting out the LEDs. I haven't looked back
Well, those strips are designed to be screwed or glued. I decided to screw them in order to easily upgrade in the future.

Those drill-taps are like this?


Never saw them before
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post #13 of 14 (permalink) Old 02-22-2011, 07:11 PM
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Quote:
Originally Posted by MosMike View Post
Well, those strips are designed to be screwed or glued. I decided to screw them in order to easily upgrade in the future.

Those drill-taps are like this?


Never saw them before
Yes, that is what I used. My local Ace Hardware had them the first time I needed one, but I lost that one, and the store no longer had them when I needed one again. It worked extremely well for me, using a cordless drill/driver, at very slow speed.

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post #14 of 14 (permalink) Old 02-22-2011, 08:02 PM
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Your gonna need a proper drill and tap if you wanna get it looking nice. You need to use some kind of lubricant to tap it properly and clean out all the debris and de-burr it before you put in your screws. Otherwise your gonna need to glue them.

Took me hours to finish mines but I'm happy the way they turned out

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