# Turning Optics



## tvodrd (Apr 3, 2004)

How to turn optics has been a frequent topic for mods. This is for those with lathes. For the first few I turned (Small 123) I faced a piece of stock and applied thin double-sided tape. I improvised a pin to center the optic against the tape and took light cuts with a carefully sharpened HSS cutter. The next time I needed to turn a few, I made a spring-loaded livecenter with a female conical teflon recess. I faced a piece of stock and glued some thin rubber sheet on it. With the livecenter pressing the optic against the rubber, I was able to take heavier cuts. I gave that one to Roth and made a much better one:





All the parts except for the thrust bearing and washers are avainable from McMaster. BofM:
1) 6061K11 1/4" dia X 6" hardened precision shaft ~$3.15
1) 57155K154 1/4 X 1/2 X3/16 double shielded flanged ball bearing ~$6.20
2) 57155k57 1/4 X 1/2 X 3/16 double shielded ball bearing ~$5.10ea
1pkg of 12) 9712K61 Belleville disc spring washers ~$3.60/pk
1ft) 8546K13 1/2" dia Teflon rod ~$4.25/ft
Unfortunately, McMaster doesn't list 1/4" thrust bearings, so you'll have to find a bearing supply.
1) Torrington NTA-411 thrust bearing ~$2
2) Torrington TRB-411 thrust race (washer) ~$1ea

I used a bench grinder to make a 2" length of the hardened shafting. I drilled a 1/4" hole abt 1/4" deep in a 1/2" long piece of 1/2"dia aluminum and Loctite'd it onto the shaft. Next I counterbored a 7/16" hole abt 1/4" deep into the aluminum end of the assembly. I then turned some teflon to press into the counterbore and pressed it in. Leave some excess sticking out the front! Finally, I cut a 60deg included cone into the teflon with a countersink. Slide on the disc springs, thrust bearing set, the flanged bearing, a ball bearing, a spacer, the other ball bearing, and an O-ring to keep things from sliding off.





Using the live center is easy. Put it into the tail stock and hand tighten it. Overtightening it will bust the ball bearings! Fold a small piece of sandpaper to go between the optic and a spud in the chuck and use the live center to press it against it. You can also use thin rubber sheet or glue the sandpaper to the spud. Put a drop of oil on the thrust bearing and go at it. I found I can take .050 deep cuts in a single pass!

The CR2II optic is a lucky break if you have 5C collet capability. I am able to chuck the face in a 45/64" collet. After turning the OD and step, I back out the livecenter/tailstock and have just enough optic left to allow parting with a 1/16" wide blade. Sure makes the shortening a lot easier!

The livecenter will cost you $25 or so but for me has been a very good investment!

Larry


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## jtice (Apr 3, 2004)

Hey, thanks alot Larry! /ubbthreads/images/graemlins/thumbsup.gif

This has been talked about many times in chat as well, and we never really liked any of our ideas. /ubbthreads/images/graemlins/icon15.gif

Your setup looks great, 
I always wondered how you cranked out all those turned optics. /ubbthreads/images/graemlins/smile.gif


Thanks

-John


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## tvodrd (Apr 3, 2004)

Hi John,

The livecenter does take a lot of the "sport" out of it. It will work fine with the 30mm's, and let me get down to 7/16" for the NLS's. I managed to shove an optic into the collet yesterday when I got a little greedy and cut too far into the flange /ubbthreads/images/graemlins/icon15.gif . A collet stop would have prevented that. McMaster also stocks 2000 grit wet/dry sandpaper, which used wet is a good start on final polish.

Larry


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## XtremePyro (Apr 3, 2004)

I get my 2000 grit wet dry at walmart in the autobody section.
Still gotta love Mcmaster-Carr though.

Tim


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## cy (Apr 4, 2004)

Thanks a HUGE bunch!!!!

Another WOW.... that's how you do that /ubbthreads/images/graemlins/ooo.gif /ubbthreads/images/graemlins/ooo.gif /ubbthreads/images/graemlins/ooo.gif

A 5C collet is getting higher on my wish list. 

Thanks again for sharing /ubbthreads/images/graemlins/thumbsup.gif


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## jtice (Apr 5, 2004)

This brings up something I wanted to ask about before.

I notice that you lathe is very different from most, as it doesnt have a normal chuke.
Is that what you guys are calling a collet?

Seems that you would have to have alot of different size collets to use differnt dia. stock.

I assume collets are better? and hold the stock better?


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## MoonRise (Apr 5, 2004)

A collet holds only one size 'thing' plus/minus a few thou. It self centers the work and has no adjustments. If you only work one size stock, a collet might save set-up time. But if you have multiple stock sizes, you need collets to fit each and every stock size or you need a chuck.

A chuck holds from min capacity to max capacity, for small lathes that's about 3/32 to 4 inches or so. A chuck can be 3 jaw or 4 jaw, and be self-centering or have independent jaws. With a 4 jaw independent chuck, you could grasp non-round stock and turn it or turn offset sections. But you have to spend more time on set-up. /ubbthreads/images/graemlins/smile.gif


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## jtice (Apr 5, 2004)

Mike,

Thanks alot, I thought thats how they worked.

I have a 3" 3 jaw self centering chuck.
I tend to use alot of different size stocks, so I think I will stick with it.


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## Chief_Wiggum (Apr 5, 2004)

Like Mike was saying the collet is for a particular size stock. I happen to know that Larry buys precision ground Al for projects. So for making say, 10, bodies all he has to do is cut the stock to lenght, install the proper collet in the closer and go to town. When one body is done, open the collet, install the next blank, repeat.

Faster than setting up an independant 4 jaw, more accurate and repeatable than the 3 jaw scroll chucks.

If I ever get a larger lathe, a 5C closer and a full set of quality closers will be one of my first purchases.


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## tvodrd (Apr 5, 2004)

The collet set at work goes from 1/32" to 1 1/8" by 1/64" steps. I also have them for common size hex and square stock. (Try indicating a piece of square stock in an independent 4-jaw /ubbthreads/images/graemlins/grin.gif ) yeah there's a lot of them /ubbthreads/images/graemlins/grin.gif . Also have 3-jaw, 4-jaw independent and 6 jaw. The camlock spindle (D4 I think) makes for pretty quick changeover. IMO collets have many advantages. Less distortion of thin wall parts, excellent repeatability, and can be used with an internal depth stop. They also make "emergency" or blank collets in many materials and head diameters which can be bored to the size desired. Ours has a lever closer which makes it possible to remove/replace workpieces without stopping the spindle. Comes in kinda handy when you are running off 10 of something. /ubbthreads/images/graemlins/grin.gif

Larry


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## tvodrd (Apr 5, 2004)

That was fast Mike, (While I was typing.) I might mention they also make square and hex collet blocks. These hold a collet with a threaded lock ring and are great in conjunction with a mill vise for milling hex's, etc. It is also possible to chuck one in a 3-jaw scroll chuck if it is large enough. 

Larry


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## ErickThakrar (Apr 15, 2004)

Not sure if I'm speaking out of line here, being a newbie and all, but there is a type of abrasive that does exceptionally well for creating a highly polished surface. It's called Micro-Mesh and is a cloth-backed cushioned abrasive that can be used wet or dry. Grits start at 1500 (roughly equivalent to 600 grit w&D paper) and goes all the way up to 12000 grit. Yes, 12000 grit. I've used it on any manner of materials. From plastic to steel to ivory. Works really well and lasts much longer than standard papers. You can get an incredible polish on metal or even wood with this stuff. It's probably available online somewhere, but the only place I've found carries it on a regular basis is Rockler's woodworking stores. www.rockler.com has it as well I believe. 
This stuff is originally designed to polish cockpits made from acrylic or polycarbonate and should be nigh perfect for getting a good polish on an optic or reflector. 
Check it out, I doubt you'll be disappointed.


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## tvodrd (Apr 17, 2004)

Erick,

Not out of line at all- that's what this forum is for. And welcome! I am definately going to try some- 2000 grit wet/dry isn't fine enough!

Larry


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## tvodrd (Apr 26, 2004)

Erick,

I received the Micro-Mesh 4000 and 12000 grit today. The stuff is amazing! Thank you for the tip! /ubbthreads/images/graemlins/bowdown.gif

Larry


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## ErickThakrar (Apr 26, 2004)

cool, glad to hear it. You should try out the 6000 and 8000 as well. Excellent to make the intermediate stages between the 4000 and 12000 much, much faster /ubbthreads/images/graemlins/smile.gif I really do love that stuff. Some of the best abrasive I've used.


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## ErickThakrar (Apr 26, 2004)

Oops, forgot to say this. Don't EVER use it with any solvents. water is fine and if you add a little liquid soap to the water it makes it last longer as well. Solvents will cause it to delaminate and that's a bad thing.


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## PEU (Apr 27, 2004)

I found this web page 
$1.75 each or 7 x $10.5

enjoy


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