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The 20 " grind has begun


JRM

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You can use the fixed post machine to parabolise however the turntable will need to be running very slowly, push the tool  over the   mirror as described in my last post by hand, you can of cause use a arm as Nigel suggested.

The back and fourth motion of the tool  should dominate .

Don't forget to press the tool to get good contact prior to figuring, then work the mirror for 20mins then test it.

Don't press to hard when figuring  you could end up with a rough surface.

The tool  should feel like its  heavily lubricated when figuring, when the tool is in good contact with the mirror and the water and polishing powder mix is correct.

:)

 

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  • 1 year later...

Hi Everyone,

  Yes I am still above ground lol, hard to believe its been almost two years since last I pushed glass, where does the time go.

Health wise I am in much better shape now and ready to start again. I made a 13" pitch lap this weekend with gugolz 55 pitch

and done a couple trips around the barrel so to speak ( hour and a half worth) with room temps around 67-68 degrees just to get

a feel for the softer pitch, all seems fine to me, so the project is soon to be back on.

We leave for vacation in sunny Florida Thursday  and come back on the 12th, so it begins again after we return.

Here is a short video of me figuring with the 13" lap

1 mirror figuring.mp4

Rick M

 

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Hi Rick,

Good to see that you have resumed work on the mirror. Looking at your video I see that you are using a 13 inch lap, if you are parabolising the mirror I would recommend something around 10 inch in diameter. A 13 inch lap will be slow at adding correction. I usually use a 50 % (or even smaller) diameter lap for figuring which seems to work well. Also a 'w' stroke like the one you are using tends to be slower at adding correction than a stroke across the mirror with a slight offset so that the centre of the lap is not passing through the centre of the mirror. Good luck, will be watching your progress with interest.

John

 

 

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Thanks all,

I believe you are right John,the W stroke in the video was just a test so to speak and the time spent was to see how 

I myself would be able to handle the whole pushing and lifting of the glass to the test stand, all seems good.

but where I have a softer pitch,I will try it with the 13 first and go from there.

Rick M

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  • 4 weeks later...

Still going...

    Hi All,

Vacation is over, so I did a few trips with the 13" lap, then made a 10" star  lap and have been using that for a couple hours, the curve is generating nicely, I have already

made it farther then before so things are going nicely (knock on wood)

In the last few hours of figuring I have learned the 10" lap does gives you a lot more control with the figure, the 13" lap i have set aside to use for smoothing if needed but

the 10" star lap is leaving a much smoother surface then I had thought it would.

I am keeping my work room at 68-69 degree F which helps in itself.

the gugolz 55 pitch is working better then the 64 did also so softer pitch has been a help.

will keep you updated

 

Rick M

 

 

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  • 4 weeks later...

Hi All,

 Still pushing away with the 10" slightly scalloped lap, I lost the center high and have been working it down but man it takes more work

then I would have though, I have increased my session time as the 15 minute sets were to short, been doing 45 minutes on average to

correct the center with some CoC and mostly slightly off center strokes out past the edge by just a tad.

I end every session with a full W stroke two trips around just to try to keep things smooth and zone free, other then that all is good.

Rick M

Oh, still trying to find a program for creating and printing a 20" couder mask, any ideas would be great?

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