Techniques for Turning Optics?

Once I get my next batch of 30mm optics from Elektro Lumens, I'd like to get them to desired diameter by turning instead of belt sanding, which always seems to result in scratches and a barely circular, rough circumference.

I can only think of two ways to "chuck" the optics:
<ul type="square"> [*]1) chucking the very edge of the optics and using a live tailstock center inserted in the emitter hole at the bottom or
[*]2) boring out a 1.5" rod to a conical depression, filling it with "Blue Tack". and sticking the optics into it, being careful to keep it centered. [/list]
With 1), you can't turn the chucked edge. 2) will probably work if the cuts are kept light enough not force the optics off-center.

Any other ideas?

Otokoyama,

I have been reasonably successful in turning down a few of these. I initially chuck the optic on the reduced shoulder of the backside of lip with the face of the optic pointing out. I then turn down the OD of the very front to the final diameter I am after or as much as possible. This new cut shoulder can then be used for holding the optic with the LED end facing out. I then turn the back side to the final OD I am after and bring the cut as close to the chuck as possible. The optic can be reversed in the chuck once again and turned from the other side. You may end up with a thin fin of plastic that can easily be removed by breaking it off and hand filing or dressing.

Hope that helps.

Another possible helpful tip is using very fine and ultra fine wet/dry paper, wet, on the optic surfaces while spining in the lathe. This works great in preparing the optic for final polish. I use cheap paper napkins and Flitz metal polish to provide a final polish on the optic (still turning in the lathe).

- Don

One of these days I'm gonna have to get a lathe! Anyone know if those small benchtop types are any good for turning optics, flashlight-size diameters, etc?

I've done over a dozen using thin, double-sided or "carpet" tape. Face-off a piece of stock slightly smaller in diameter than you plan to turn the optic, and apply the DS tape. Get a pin that fits the LS cavity and put it in the tailstock chuck to initially center the optic when pressing it against the DS tape. Remove it before turning the optic. Take light .005-.010 cuts. When done, Start with wet 600 grit sandpaper, progressing to 1800, if you can get some, and finish with acrylic polish. Works like a champ!

Larry

I use a method similar to tvord's. Main difference is I use a piece of wood and turn it about 1/8th larger than the piece to be turned and slightly recess the face to the piece's diameter. This aids in centering the piece. Use light cuts to turn down the piece to the diameter desired and make a narrow shoulder on the wood . Use a live center to keep the piece against the DS carpet tape. The shoulder turned on the wood helps to keep from rounding over the edge of the piece when sanding and polishing.

If yu are going to do more than one it is a quick job to face off the wood and turn another recess without removing the wood from the chuck.

Wood turners use DS tape to hold some fairly large pieces(like bowl lids) of wood while turning .

whiskypapa3,

/ubbthreads/images/graemlins/thumbsup.gifNever occurred to me to center it at the headstock end. Only problem for me is my tailstock is #4MT and the seal drag on my live center is too great, plus the point gorks the dome of the internal lens. /ubbthreads/images/graemlins/grin.gif It's possible to build a small, spring-loaded, teflon-lined, ball bearing live center to press the optics against a piece of sandpaper which has been double-sided taped to a "spud" in the headstock. This will really take all the "sport" out of it! (Yes, the front of the optic will have to be repolished- no biggie,) (I haven't finished mine.) (Hope you are lurking, DSpeck /ubbthreads/images/graemlins/grin.gif )

Larry

Thanks! There are more ways to do this than I would have thought. I especially like whiskypapa3's slight recess to help center the piece on the headstock end.

I hadn't considered double-sided tape. I'd rather not have any workpiece bust free and go into orbit through my face, but the optics are fairly light. I'm assuming that this doesn't leave any gunk on the optics.

i've found that when things bust out of the lathe...they usually go downward /ubbthreads/images/graemlins/icon15.gif

i have tried it one way, but ended up breaking 2 optics /ubbthreads/images/graemlins/frown.gif

i have an idea for another way to do it, i think it is very similar to what whiskypapa was talking about.

Point in hole of optics.

I forgot that I ground off the tip of most of my live centers to 1/8th in. It usually goes into a 3/16th or 1/4in hole in the stock so the point really isn't needed. Got tired of scratching the back of my hand on it while changing work pieces.

Rule of things flying off a (wood) lathe;

Small expensive parts will fly under the bench you last swept under five years ago or in my case during the Johnson administration.

Big heavy parts will sail across the shop into the shelves and knock off all the little jars and cans of paint you meant to throw out five years ago (again Johnson.