Re: [ATM] General questions before getting starting on a 6F6.

[Mike Lockwood <melockwo@uiuc.edu>]

Anthony,

Anthony Anconetani wrote:
> Mike, I stumbled onto your website from GotGrit. I really like your 10
> F5.5 design. I hope to build something similar once I have a little more
> experience. Anyway, from the first part of your Mirror Musings page,
> here are some questions:

Thanks.  I was going to sell the 10" F/5.5, but it's so darned 
lightweight and fun to use that I may not.

> You comment that one should read at least two other pieces of
> literature, I've read Berry's book and I'm planning on purchasing
> Texereau's from Willmann Bell. Do these seem like a complete selection?
> I've noticed some things seemed to have changed over the years. For
> example steel hogging tools and tile tools versus glass tools. Is there
> a more recent text that I should consider?

Those are what I started with.  Combined with web resources, you 
should do fine.  Just realize that Berry is not an optical expert, and 
Texereau is now a bit dated in terms of materials.  We generally use 
aluminum oxide instead of emery, and cerium oxide polishes faster than 
rouge.  We also use tile tools for pregenerated blanks, and when glass 
tools are too expensive.

> I'm surprised that one would need to grind the back of a mirror and tool
> to 320. How much extra 80, 120,180, 220 and 320 should I plan on
> ordering for a 6 inch mirror?

Grinding the back flat is most important on larger, thinner mirrors. 
With a 6" blank it's sort of optional, since the mirror cell will be a 
simple 3-point cell, and a rough mirror back will not cause too much 
problem.  It's a nice touch if you have a flat tool.

If you get a grit kit, you should have plenty of extra abrasive to do 
some work on the back, if you decide to.

> I'm planning on doing the initial hogging with some kind of steel item
> (I don't know what yet...) and then switching to a tile tool. Should I
> plan on fine grinding the back of the tile tool? How well does dental
> stone on the back of the tool hold up to direct grinding? Does the tool
> need to go to 320?

Really, I'd recommend two glass disks for this first mirror.  The back 
of a tile tool will not work for grinding against the back of a glass 
disk.  You'd have to make another tile tool.

I guess I need to clarify my article a bit for this case.  (It has 
changed from a figuring page to one with figuring and grinding advice.)

> What are generation marks in a blank?

Marks from using diamond tooling to make the blank concave.  Saves a 
lot of work (and grit) on big mirrors.

> And lastly, I took your advice on United Lens. They we're a really nice
> bunch of folks. I look forward to seeing the blank. And I hope I get a
> chance to send them more business.

UL is great.  If they haven't shipped your order yet, add another 6" 
disk to it for a grinding tool.

	Mike L.

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