# Making lens gaskets



## tvodrd (Mar 28, 2004)

This post (and the contact one) are really additions to the CR2II how-to.

I use a silicone rubber gasket instead of an O-ring to seal the front of my lights. A 1/16 section O-ring requires about .050" axially, vs about .010" for the compressed gasket. I make them from McMaster cat# 86915k12 .020" thick transparent silicone rubber sheet. A 12" x 12" is about $14. The CR2II "how to" has a drawing for the gasket. It's no doubt possible to cut one with an Exacto/scissors, but making a punch aint all that hard. To make the punch you need to start with a face groove with the same ID and OD as the gasket. To cut the face groove, first I make a cutter. Start with a piece of steel (alloy doesn't really matter) larger than your gasket OD and turn one end so it will fit your tailstock chuck. Turn it around and turn about .1" to the gasket OD and bore about .1" to the desired gasket ID. You now have a .1" long piece of tubing sticking out of the part. With a bench grinder or mototool, grind it into a single tooth cutter. The sketch below is crude but I think gives you the idea. I used a piece of 5/8" steel tubing I had laying around as my tailstock chuck will hold it.






Now that you have the face groove cutter, chuck it in the tailstock. Turn and face a piece of _aluminum_ (T6, I hope /ubbthreads/images/graemlins/grin.gif ) to slightly larger in diameter (.05-.10") than the gasket. Slow the lathe down cause you cutter isn't HSS (High Speed Steel) and cut the face groove .02-.03" deep. Use 
cutting fluid! Now drill a relief hole .05-.10" smaller in diameter than the desired gasket ID. Put on your magnifying safety glasses, cause this is the hard part. Using a 60-90deg included cutter (V-tool for external threading will work fine) "sharpen" the inside and outside cutting edges. 
The sketch below shows what it should look like.





Place the silicone sheet (remove the protective backings) on some polyethylene sheet. Using a drill press or mill quill or arbor press or vise, or even hammer, punch your gaskets!

The high tech guys would make the cutter out of A2 and heat treat it. 

Larry


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## Chief_Wiggum (Mar 28, 2004)

Very nice, Larry. I've been having trouble making concentric circles with two punches. Now I know how you do it (and I'm even more dangerous because of it /ubbthreads/images/graemlins/grin.gif )


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## tvodrd (Mar 28, 2004)

/ubbthreads/images/graemlins/grin.gif Mike,

If you need some of those dimensions, be happy to save you some work.

Larry


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## cy (Mar 28, 2004)

Larry, Thanks, that is slick. I alway wondered how you did that. It seems tool making is a major part of the learning proccess.

off topic: how do you setup to turn a fraen down for firefly and/or CR2? 

Thanks,
CY


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## SKYWLKR (Mar 29, 2004)

Why not just turn a solid bar (or even tube is it's the right size :it could be steel or Al or what ever) down to size, bore it a bit.

then bevel it on both sides (or bevel it after the recess is cut) and the cut the recess with a fine tiped tool or grind a cutter from HSS, that would give the grove needed.

seems like a special cutter is an unnessisary step and you could end up with a much more durable tool.


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## tvodrd (Mar 29, 2004)

Cy, I'll get to turning optics. It's another case of making a small tool to take some of the "sport" outta it /ubbthreads/images/graemlins/grin.gif

SKYWLKR, that's a .030" wide groove. All I have is a couple bench grinders- no tool and cutter grinder or surface grinder. I have ground tools for face grooves. Locating the groove in the workpiece usually requires some real creativity or making a trial cut, measuring, refacing the part and adjusting. Using an improvised cutter like above in the tailstock puts the right ID and OD for the gasket without having to get "creative."

Larry


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## cy (Mar 29, 2004)

Thanks Larry, looking forward to your tutorial on turning optics. /ubbthreads/images/graemlins/grin.gif


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