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  1. #1
    Nova419's Avatar
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    Default blanks delievered today



    I purchased 3 8" blanks from william bell which arrived today. after grinding for about 5 hours I've all most gotten all of the mold marks and pits out off all 6 sides. Just a few pits left on the top's and I need to grind out about .002-.003 inches too finish off the bottoms. Sagita on the ground surfaces is around .001 +/- .001 inches compared to a reference flat.

    This is my first time grinding and I'm having a lot of issues with the blanks binding after about 2 turns around the barrel. I've been forcing past that point and going 4 or five turns since it seems like most of the work starts happening right when the blanks start sticking on strokes. As soon as the blanks start sticking my sharpie grid disappears (except in the low spots) every few wets they bond together mid-stroke and I have too submerged them and give it a good knock with the side of my hand to get them apart. Is there anything I can do that will let the blanks suck up together but not lock up? I'm worried that the problem will amplify when I switch to finer grits.

    I also ended up making my own sphereometer; i used dental plaster and the lid too a 50 pack CD tray to make the base. Pulled 8mm ball bearings out of a sealed bearing pack then epoxy welded to 1/4 inch bolts for the feet. mounting the dial caliper was easy, just drilled a 3/8 inch hole right through the middle and epoxy welded it in.

    This is turning out to be one hell of a project; it's going to take me a long time to get these mirrors finished. I haven't even put much thought into a base yet lol.

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  3. #2
    plateglass's Avatar
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    Hey nova419 take a look at my diamond trail post you mite gets a few ideas

  4. #3
    Nova419's Avatar
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    Default

    I may try that after I grind out a few mirrors the old fashion way. I need more experience before I try any thing like that.
    Will start working on 120 grit tomorrow; ended up ordering a lot more grit and moved up to 60 grit in order too take out an air bubble i ran into (air bubbles really really suck). after finishing up #80 today my sagita is around .0002- .0001 on all three surfaces (in reference too .0001 surface plate) hopefully things should go faster now; I'm anxious too get down to polishing.

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  6. #4
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    Congrats on the glass!
    Can't wait to see your progress on it
    Name: Gus OTAs: ED 100 PRO refractor, Orion ST80 (not the CF), 8" Dob stuck in Canada Mounts:HEQ5PRO Synscan mount, Manfrotto Tripod CAMS: Guidecam Philips SPC900 webcams (4), Canon unmodded-450D DSLR

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