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sbmathias
12-12-2011, 05:39 PM
Many posts over the years about adapting or building a circular LED light for use on Bridgeport-type mills. I saw this in a recent catalog
http://www.sciplus.com/search.cfm?utm_source=internal&utm_medium=search&utm_content=cf&utm_campaign=celsearchtest&formfield1234567891=0&formfield1234567892=6&formfield1234567894=&term=93413&btnHand.x=0&btnHand.y=0
and wondered if anyone had purchased this for that purpose. Seems like it would work fine if the center could be bored out to fit around the spindle. Looking at the photo, it appears as though there may be a printed circuit board inside that wouldn't withstand the bore, though.

As a related aside, can anyone explain to me why all of the LED projects that members here have done all include substantial heat sinks? Seems to me that if that much heat has to be dissipated, the LEDs would overall be very inefficient. This is contrary to all efficiency claims we all see regularly about LEDs.

Toolguy
12-12-2011, 05:45 PM
Woodcraft Supply has them made for drill presses. They will fit around a Bridgeport spindle.

sbmathias
12-12-2011, 05:57 PM
That looks pretty nice. Is even AC instead of having to keep going through batteries. Thanks!

mygrizzly1022
12-12-2011, 06:22 PM
HI
I used one on my bench top import mill and I found to be in adequate light. I would have to almost always supplement it with another source of light. It was just not bright enough for my 65 year old eyes. I am sure a guy could combine the array from a couple of them to boost the output but it was more time and effort than I was willing to commit at the time.
Your comment about the heat sink suggest that those fellows dug a little deeper into LEDí and their power requirements and light output and built a satisfactory solution that is not as simple or cheap as the model suggested, or the one I used
I modified a suitable halogen desk lamp with some rare earth magnets that allow the flexibility to place the light where it is needed most. This was for me at least a more satisfactory solution.

The one from Wood craft supply I am not familiar with,

Regards... Bert

darryl
12-12-2011, 09:19 PM
Leds are basically point-source emitters. The power used which is not converted to light is lost as heat, and this heat is generated in this small area. As a consequence, there's quite a temperature rise there. This heat has to be drawn out somehow or it will keep getting hotter in that spot.

Most leds are rated for about 50 milliamps maximum, and recommended to be run at about 20 ma. The package is usually able to dissipate the heat because the power level is so low.

Enter the high brightness leds, using more current and/or voltage. The package is no longer able to dissipate the heat quickly enough to keep the led from cooking- thus the need for a heatsink.

I don't know what the actual efficiency of a modern led would be, but even if it was 75% efficient (which they aren't), that means that 25% of the power used would be dissipating as heat. It's most likely that more than 50% of the power will be lost as heat. That's still a pretty efficient way to produce light, by comparison, but still a lot of heat to get rid of considering the small size of the spot producing the light.

Arcane
12-12-2011, 10:26 PM
http://bbs.homeshopmachinist.net/showthread.php?p=704980&highlight=mill+light#post704980