Threading aluminum square tube to attach star LEDs - The Planted Tank Forum
 
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post #1 of 9 (permalink) Old 07-01-2013, 04:03 PM Thread Starter
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Question Threading aluminum square tube to attach star LEDs

Hi All,

I am weighing out ways to attach star LEDs to the square tube. I am using it as a heat sink. The tube wall is 1/20" thick. I want to attach the LEDs with computer case screws (M3). I will be using insulated washers & thermal paste.
I am a complete noob with threads and taps.
1. Do I really need to tap the aluminum? Can I use a smaller size drill bit (i would guess 2.5mm) and use M3 screws without threading?
2. If I have to tap, what size tap should I get? I looked up the tap size sheets and it was too confusing to find a product online. (lazy me)

Of course I don't want to drill through both tube walls and use 1.5" inch nut-bolts.

The main reason I am thinking of screwing LEDs to the tube is so that I can easily remove the LEDs when I want to.

Thanks for your help!

-Ashish
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post #2 of 9 (permalink) Old 07-01-2013, 07:12 PM
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You can get self tapping screws that are about the same size as computer screws. That way you won't have to tap a bunch of tiny holes.


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post #3 of 9 (permalink) Old 07-01-2013, 07:13 PM
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1/20" is fairly thin. This has advantages and disadvantages. The advantage is that it'll be less "effort" to work it (less material to drill/tap through). The disadvantage is, it's SO thin it'll be easy to distort and get a really poor thermal transfer beneath the LED.

Do you have a drill press? Have you done much metal work in the past?

As far as the drill and tap size, I'd assume it's coarse thread, i.e. M3 x .5mm. The nice thing about metric is, you don't need a drill size chart, you just subtract the pitch from the diameter and that's your drill size: 3 - .5 = 2.5, so you need a 2.5mm drill for the M3x.5 tap.

Are you totally in love with that screw? There are self tapping screws available in similar sizes which would eliminate the need for the tap. Can you use those screws without a tap? Probably, in soft aluminum, but SHOULD you? As mentioned above, material this thin is easy to mangle.
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post #4 of 9 (permalink) Old 07-01-2013, 08:05 PM Thread Starter
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Thanks a lot!
I don't have a drill press, just a power hand drill. I have no metal work experience. Just some wood work. I have done tapping on wood and 1 cm plastic.
I am not in love with the screw just something i am familiar with that I thought I could use.

Bending..... that would suck! May be I will end up sticking the LEDs then!
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post #5 of 9 (permalink) Old 07-01-2013, 08:19 PM
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I strongly favor thermal epoxy for HPLEDs mounted to star mcpcbs. Cheap, quick, easy. If you blow one and need to add another in it's place, you can just glue it right next to the old one. Or pop the old one off with a pry bar and a careful hammer blow.
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post #6 of 9 (permalink) Old 07-01-2013, 09:30 PM Thread Starter
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Quote:
Originally Posted by All your base View Post
I strongly favor thermal epoxy for HPLEDs mounted to star mcpcbs. Cheap, quick, easy. If you blow one and need to add another in it's place, you can just glue it right next to the old one. Or pop the old one off with a pry bar and a careful hammer blow.
Thanks a lot.... Looks like thats the route I will go....
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post #7 of 9 (permalink) Old 07-01-2013, 10:41 PM
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Can you get rid of the star all togrther? Mount the LED bead itself to the bar with theral epoxy only.
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post #8 of 9 (permalink) Old 07-01-2013, 11:09 PM Thread Starter
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Originally Posted by stevenfryman View Post
Can you get rid of the star all togrther? Mount the LED bead itself to the bar with theral epoxy only.
I dont think I understand what you mean by mounting the LED bead on the bar. How to connect the wires? As far as I know, the common 3W LEDs available out there have connectors on their backs. In order to solder them, you have to use reflow soldering. Sort of hard to do reliably at home....
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post #9 of 9 (permalink) Old 07-06-2013, 02:02 AM
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Do not afraid unknown, your design will work
this is my LED light:
http://i1278.photobucket.com/albums/...psf6450845.jpg
LEDs are attached to 5mm sick aluminum bar.
It is very easy to replace any LED, change a color or put it in another place. I've found it is very flexible.
In a fact, in a first design it was a lot of red, then to add white LEDs was a peace of cake.
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