[ATM] Updated pictures of 8"f6 mirror............

[Mike Lockwood]

Hi,

John and Bernadine Murray wrote:
> 	Uhmm, I thought I answered this in one of my post but I can't find
> it...... The lap was made from a mould by pitchlaps.com. Over approximately
> 7 hours of polishing I'd say about 50% closed.

Aha.  That's all I was looking for.

Did that Gugolz 64 sit around for a while before you used it?

If they've only closed that far in 7 hours of polishing, then the 
pitch is ACTING a little bit hard, but not super hard.  Let me elaborate.

The thing that controls channel closing is the interaction between the 
pressure applied to the tool/mirror, the amount of polishing compound, 
and the hardness of the pitch.

So, things you might try to make the pitch ACT softer (without really 
softening it):

1.)  Heat the pitch lap and mirror a little bit in warm (not hot) 
water.  I'm talking water that is ~10C warmer than ambient working 
temperature.  Press for ~5 minutes.  Polish for 10 minutes and see if 
the surface form improves.  (This is tricky as it can throw the mirror 
out of thermal equilibrium.)
2.)  Use thinner polising compound.  Too much and you never get real 
contact between the mirror and pitch.
3.)  Apply a bit more downward pressure when polishing.

I'm just trying to get you (and others) to see how these variables 
interact.  Once you understand that, you can successfully work with 
pitch over a wider range of hardnesses.

> I agree with you about standard questions etc. The devil is in the details
> and I sometimes find myself realising I haven't mentioned something AFTER I
> post to the list... Doh!!!

Happens to me just about every day.

	Mike Lockwood