plastic 'lenses' - what material?

Acrylic is fine for this, its reasonably scratch and oil resistant compared to Polycarbonate although nowhere near as impact resistant. Acrylic is cheap and readily available so easy to renew as required. The (hypothetically) best stuff to use would be a transparent Nylon

6/12 but finding lens or sheet in this stuff is pretty much impossible.

Peter

Makrolon

Peter

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Make it roll on what ?

-- Regards,

John Stevenson Nottingham, England.

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Makrolon (Polycarbonate) has saved me from the peaceful intent of many greenies armed with iron staves but it has the scratch resistance of Plasticine.

Even if you need only magnifying glasses look at

. Not quite the DIY solution but the hardened coating does work in oily workshops.

OK, I'll try the acrylic as it's what's to hand. Next thing is to see what sort of a mess I can make of it with a Rotabroach cutter if I've got one with the right ID

Thanks Tim

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You'll get a nice collection of cracks at the cutting surface. At least when oil is getting there.

Nick

Scribe your shape and use a piercing saw with a narrow slot table.

I suggested Makrolon over ordinary acrylic as it has very high impact resistance. We use it a lot for our control panel covers on the mobile chargers for the railways, and it is pretty good at scratch resistance as well, having a slightly 'hardened' face.

We don't use anything thin enough for your goggles though, ours is 6mm thick.

Peter

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Not goggles, Peter. It's for the speed dial and dial clock/micrometer bed stop on my lathe.

Thanks Tim

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Peter, the problem with Polycarbonate is although it is tough enough to resist hammer blows it has a relatively 'soft' surface that can often be scratched just by wiping with a tissue. We used to coat PC products with a polysiloxane coating which improves this dramatically to the point where you can rub it with wire wool and still not scratch it, but often the coating costs more than the part. It is also has a very poor resistance to many common household chemicals and oils which can quickly discolour it and cause stress cracking and crazing.

Whist Acrylic will shatter under the same abuse that PC will take it does have a 'harder' surface and is not quite so bothered by chemicals. Bath and sink tap handles are made from Acrylic for example, as are those clear salt & pepper mills that you can buy.

One thing to watch out for on Acrylic is to avoid using Superglue/Cyanoacrylate adhesive near it, as the fumes outgassed from this will cause it to fog and turn opaque.

Peter

Well, there's a novel thought - using hand tools!

I don't actually have a piercing saw or a narrow slot table, though if the Rotabroach approach doesn't work I'll dig out my grandfather's fretsaw & a sheet of ply and give that a whirl.

Cheers Tim

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Tim

Hi, thirty five years ago when I was an apprentice during our time in the "instrument shop", they used to get us making "gauge glasses" by mounting some thin acrylic sheet between two plywood pads (one on faceplate, smaller one on rotating centre in tailstock) and in effect tre-panning to the required diameter. Worked well in those days although we used to put felt between ply and acrylic as any movement would score the sheet. Light cuts worked well in those days. Of course I don't know if your glasses are circular or not but just an idea.

regards

Keith

But that is polycarbonate, which others are advising against.