Light Shades

[f350ca]

Need lights out in the shop addition, (especially with the days getting so short). its not going to be heated so thought I'd just use 4 - 100watt light bulbs instead of florescent, tubes.
To direct the light down I need some reflective shades, couldn't find anything reasonably priced so we'll make our own. Bought 4 - 8 quart stainless steel bowls roughly 14 or 15 inches in dia for all of $6.95 each. The idea is to put a hole though the bottom for an electric box strain reliever, that will clamp to the wire above the socket, this way I can move the reflector up and down to get the best reflective pattern.
Any suggestions as to how to find the exact centre of the flat bottom? Need to get pretty close or the shade will hang crooked.
The center finder on my Starret combination square might work, but the slopped side isn't going to be easy to work off.

[TomG]

Throw them in the lathe and drill a pilot hole. I assume you'll be using a hole saw?

Tom

[f350ca]

Have Greenly punches, think thats what their called, 3/8 hole for the pilot bolt and they shear the hole.
The bowls are too big for my chuck I think, that would be too easy

[TomG]

Just back the outside jaws out until they grab the inside of the bowl. You don't need to use the precision part, it's just sheet metal. If you can't grip it tight enough to drill, at least you'll be able to mark the center.

Tom

[DaveH]

Greg,
One way (cheap,cheerful and ruff); if the flat bottom is (say) 6" in diameter I just draw a 6" dia circle with a pair of compass on plain paper cut it out and place it on the flat bottom aligning it up the best I can, then centre punch the centre.
A bit rough and ready

DaveH

[awemawson]

Get two very powerful rare earth magnets of the type with a counter sunk hole in them (cheap as chips on ebay) Stick them together either side of the bowl with a nut & bolt in the outer one for suspension. Adjust until it hangs as you want, then draw round them. Simples !!!

[EdK]

(11-13-2013, 04:09 AM)DaveH Wrote: Greg,
One way (cheap,cheerful and ruff); if the flat bottom is (say) 6" in diameter I just draw a 6" dia circle with a pair of compass on plain paper cut it out and place it on the flat bottom aligning it up the best I can, then centre punch the centre.
A bit rough and ready

DaveH

Dave,

That technique works well for stuff that doesn't need to be accurate to the .001 inches. I use a version of that quite often. I draw it up in CAD and print it 1:1 making sure to include center marks on circles. That makes it easy to use a center punch to mark the hole locations.

Ed

[f350ca]

Great ideas,
Tom I think the sides are to rounded to register on the jaws but still have to see if the chuck will open enough to grab the rim.
The paper circle may work but I like Awemawson's idea with the magnets, it gets the end result even if the bowl isn't spun evenly, who's to say centre is the balance point.

[awemawson]

You could of course just mount a pointed bar vertical in the bench vice, and balance the bowl on it itteratively moving it to get it right .

Andrew

[f350ca]

I over estimated my bowl size, they're only 13 1/2 so they fir in the 3 jaw.



Once the pilot hole was drilled I punched the hole for the strain reliever.



The 100 watt bulb isn't as bright as I thought it would be, will see when we get them all hocked up.



Worked out to about $12 each with the bowl, socket and strain reliever.