From: "Tom Stokes" 
To: ,
        "Amateur Telescope Makers" 
Reply-To: "Tom Stokes" 


What strikes me about your tools is that they seem to have an excessive
height.  This could be causing a very lopsided pressure distribution on the
face of the tool and preventing a smooth operation.

Tom Stokes
http://home.pacbell.net/tstokes features my mirror grinding machine.


----- Original Message -----
From: "John Murray" 
To: "'Mirror Matic'" ;
"Amateur Telescope
Makers" 
Sent: Tuesday, March 18, 2003 2:15 AM Subject: [M-O-M] Still refusing to
spin properly............


> G'day Everyone,
> Well, after a week of experimenting with different turntable and
> ecentric speeds(30 - 70rpm T/T, 4 - 20rpm Ecc). 3 different tools (2 x
> 5, 1 x 6.4"), (different sizes and construction) flipping the blank to
> give a flat surface to start with, casting against the original curved
> surface etc etc etc. The bloody tools still refuse to spin properly. I
> believe that the tool on the outside edge is travelling around 1/2 speed
> relative to the blank instead of virtually no relative speed difference
> on the outside where the edge of the tool and blank meet. Am I clear
> there?
> The toggle has been constructed with 3 pieces of oil impregnated
> high density vinyl. An inner one, an outer one and a bush which
> seperates the other 2 pieces. I've lubed this with water, oil and
> finally graphite powder. There appears to be no slop in the toggle and
> it rotates with no binding or friction that I can detect. I have tried
> sweeping the tool across the blank to no avail, also, stationary overarm
> with around 1/2" of wag again to no avail. The annoying thing is that
> the first spiral cast tool I made spun beautifully. It just fell apart!
> The latest tool (5") with 1/8" gaps seperating the 1" tiles
> (laid horizontal) started the blank going very, very slightly convex
> with the edge of the tool around 1/8" (no more) overhang from the edge
> of the blank? That surprised me. Sweeping had no effect on the tools
> rotation.
> I'm considering adding a drive to the overarm to drive the tool.
> Any thoughts or suggestions? Using the newest feature in the link in my
> signature will show some of the tools that have been used, not all
> though.
>
>
> Cheers
>
> John Murray
> Whyalla
> South Australia
> Our ATM page is at
> http://astronomy.sa86net.com
>
>
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--- BBBS/NT v4.00 MP