Methods to shorten optics?

Machinists, I'm looking for advice on how you set up to shorten the front of the NX05 in a lathe. I have a setup to turn down the diameter using delrin holders with the collet chuck and tailstock, but a good way to shorten the front escapes me. Also, what supplies do you use to re-polish to the original glass like surface finish? Thanks!

Dan C

i machined a small delrin piece that has a small nub on the front which fits into the "hole" of hte optic. this only works with the nx05, and a larger nub needs to be made for the 30mm. i haven't found a good way to do it with the freans yet.
chuck the delrin piece into the chuck, then press the optic on. using very fast rpms and face it very lightly. the trick is to not take too much off at a time.

i bought some cheapo polish at an automotive store which works well, though the name escapes me.

Dan,

I don't think there is a single best way to shorten the buggers. It depends on the diameter you have turned them. For the bunch of 7/16" dia ones I just did, i just parted them off with a narrow cut-off tool. When you have just turned the stock flange off, it can get trickier. I once made a fem. conical piece with 2 screws at the edge to hold the optic in. I milled between the screws then loosened the screws and rotated the optic and tightened them against the milled area so I could mill the rest. Brute force (coarse sandpaper or even a strip sander) works- just leaves a little more progressively finer wet sanding before final polish. For final polish, I have been using "Mcguiar's Mirror Glaze #17 clear plastic cleaner" for several years with good sucess. It's a very fine abrasive polish. They have it Ace Hardware.

Larry

I liked Roth's idea, couldn't you take it a step further and make a conical recess in the delrin jig leaving an internal nib that would also "cup" the optic leaving an exposed portion to turn down or part off? In wood turning, guys often make plywood jigs that conform to the bases of unique shapes so they can be faced or hollowed.

TSG /ubbthreads/images/graemlins/grin.gif

well, the piece i built is a little over an inch long, and has a cup on the other side, where the optic is pressed into for machining that annoying little tab off. i also have a nifty little live center specifically designed to hold the optic in place while turning /ubbthreads/images/graemlins/wink.gif

Hey, what if you made the conical recess to "seat" the optic in and then thru-drilled the jig for a steel or aluminum pin that would fit into the base of the optic and put a set screw throught the side of the jig to lock the pin at depth you would then have the pin acting as a nib and the cup to support the cut. I am not the best machinist so I am just throwing out Ideas here. /ubbthreads/images/graemlins/blush.gif

TSG /ubbthreads/images/graemlins/grin.gif

I have it on Very good authority that on the Fraens at least, reducing the diameter by as little as 10% reduces total light output by as much as 30%.

I just got this technically verified information Today, direct from a Fraen Manufacturing representative.

[ QUOTE ]
MR Bulk said:
I have it on Very good authority that on the Fraens at least, reducing the diameter by as little as 10% reduces total light output by as much as 30%.

[/ QUOTE ]

Where does the 30% go?

out the sides i think...

from what i've heard also, while cutting down an nx05 or 30mm doesn't hurt the bea, too much, cutting down the frean is a totally different thing.

Yeah what Roth said. Must remember that initial light emission is 360 degrees. Those angles of dispersion are caught by the sides of the optic or reflector. That is why on average, the longer and deeper a reflector/optic, the more concentrated a spot you get, while a shorter/shallower reflector/optic allows a lot of the light dispersal to simply bounce, undirected, out the front in no particular straightforward direction.

I think that's 180° radiation.
Rob

Well AK-shully, if'n we're bein' that precise, it would be better represented as "half a sphere", or hemispherical, when describing the directional photonic emissive pattern. 360 degrees would be a two-dimensional view of the emitter from above.

And the "180 degree radiation" would be if viewed two-dimensionally from the side.

But if using that characterization then the Lambertian dome is in fact emitting light BELOW the slug's mounting surface plane when raised even slightly on a pedestal, and provides an actual emission pattern GREATER than 180 degrees, and in fact is closer to 190 or even 200 degrees. This has been observed in actual trials, which is why the ideal position of certain reflectors, such as a Mag's, is actually slightly below the shoulder of the Luxeon's black casing.