Confused! Blocking Alloy and Leap Pads

[eyedoc04]

For some reason, this really seems to confuse me. Do they do the same job? Are they interchangable?

Thanks for any help!

[John R]

Leap pads for glazing, blocking alloy for working uncuts.....

[eyedoc04]

By glazing do you mean edge polishing?

Thanks.

[rsandr]

By glazing do you mean edge polishing?

Thanks.

Glazing=lens edging.

[eyedoc04]

Thanks for your help!

[rsandr]

Thanks for your help!

No problem.

Alloy is used for sticking a button (to clamp it in the generator etc) to a lens blank before surfacing it to make an uncut.

It is a shame somebody doesn't come up with a tape to replace alloy blocking.

[LENNY]

Velcro!?

[Jacqui]

Actually, we used to use alloy blocking for edging. Could still use it, but leap pads and plastic blocks are just as good and cheaper.

[rsandr]

Velcro!?

I imagine the use of Velcro would generate static.

So no use to anyone with a Vista generator.

[loncoa]

Alloy can also be used as the block, meaning it is molded onto the back of a raw lens in a mold which makes holes for the generator and fining/polishing machines to grab onto. Then you don't need the little metal blocks to attach to the lens. This saves you from having to buy or to pick out blocks(there are different blocks for different base curves). I've also used a system which had a type of wax rather than alloy. Alloy while useful, has things like lead, indium, cadmium and mercury in it which I'm sure you know are harmful to handle and breathe in the extreme. Most people who perform these duties wear rubber gloves and dust masks but I'm not too sure how safe that even is.

[rsandr]

Alloy can also be used as the block, meaning it is molded onto the back of a raw lens in a mold which makes holes for the generator and fining/polishing machines to grab onto. Then you don't need the little metal blocks to attach to the lens.

Is there not a lot of alloy worn away by the cyl machine pins?

[loncoa]

Very little, and each block of this type is only used once and is then reclaimed and recast.

[RGC_man]

Whatever happened to suction pads?

[Dave Nelson]

or pine pitch.

[Jacqui]

This is the way we blocked lenses for surfacing when I first started, back in the Jurrasic Age.

Dave: We used pitch to block lenses for surfacing the plus side of glass lenses, slabs, seg reductions, etc. Did all the work on a sphere polisher by hand.