Re: [ATM] Figuring help for Lutfu

[Mike Lockwood <melockwo@uiuc.edu>]

Hi,

Jerry wrote:
> Now would be a good time for some others to offer Lutfu some guidance on
> figuring his mirror.
> He has a little bit of a turned down edge.
> I usually don't offer much help on TDE because it is not so simple for me. I
> don't have a simple stroke that does it. I find it depends on just about
> everything. The pitch make up and hardness, lap thickness, the channeling
> depth and width, facet size, micro-facet, no micro-facet, quality of the
> press, weight of the top disk and pressure applied, slurry concentration and
> quantity, temperature of the workplace, duration of work sessions, and of
> course the phase of the moon.

If the pitch is not too soft, I usually recommend some tool-on-top 
work with strokes somewhat longer and W slightly wider than normal, 
say 1/2D rather than the normal 1/3D.

If pressure is kept in the center of the tool, the lap will not tip 
over the edge, and the TOT will wear away the outer zones more 
quickly.  This is the safest way to remove it.

A more advanced technique (also assuming the pitch is not too soft) is 
to start with the disks centered, TOT.  Apply accented pressure with, 
say, the left hand.  Make the left half of a ~1/3D W-stroke, so that 
the lap overhangs more to the left with each stroke.  Reduce pressure 
applied by the left hand to none as the overhang increases to ~1/6D. 
With proper conditions and practice, this efficiently removes a TDE. 
Texereau illustrates a stroke very similar to this to help remove high 
outer zones, I believe.  In the process, the TDE usually is reduced.

If the pitch is soft, work someplace colder.

	Mike Lockwood


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