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  #81  
Old 16-05-2018, 08:06 PM
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Lognic04 (Logan)
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I ran out of 80 grit! the ring is VERY nearly gone - about 1.5mm left. Not sure what the best thing to do here is? Switch to fine grit?
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  #82  
Old 16-05-2018, 10:31 PM
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Originally Posted by Lognic04 View Post
I ran out of 80 grit! the ring is VERY nearly gone - about 1.5mm left. Not sure what the best thing to do here is? Switch to fine grit?
I suggest you take a break and get more 80 grit on Saturday. Progress will be slower with 120.

Rod
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  #83  
Old 17-05-2018, 07:55 AM
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I suggest you take a break and get more 80 grit on Saturday. Progress will be slower with 120.

Rod
Hi Rod, I think that I am so close to it being done that after a few 120 wets it will be spherical - the ring is only about 2mm big now anyway.
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  #84  
Old 17-05-2018, 07:02 PM
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Switched to 120 grit now, and the ring is near gone. Boy, was that an ordeal to clean up all the 80 grit mess!
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  #85  
Old 19-05-2018, 10:28 PM
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Caught up with everyone today at the IMS! While I was there, i got the mirror and tool mated perfectly, and now it just needs a few more wets to finally spherise it and then on to 320 and finer!
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  #86  
Old 20-05-2018, 11:12 AM
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I did a few more 120 grit wets, used an eyepiece as a magnifier and can confirm that there are no 80 pits left! On to 320 grit, as i dont have 240.
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  #87  
Old 20-05-2018, 12:42 PM
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Looking for pits after 120 grit!
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  #88  
Old 20-05-2018, 03:48 PM
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Grr, just finished a wet only to find quite a few bad scratches!!!
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  #89  
Old 20-05-2018, 04:53 PM
Billyboy78 (Bill)
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Make sure you maintain a nicely rounded chamfer around the edge of tool and the mirror. When stopping you move the tool 3/4 of the way off then lift it up, leaving the edge of the tool on the mirror.......SCRATCH.
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  #90  
Old 20-05-2018, 05:30 PM
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Grr, just finished a wet only to find quite a few bad scratches!!!
Hi Logan

Frustrating I know! But at least it's right at the beginning of a finer grade abrasive. A couple of wets at 120 will remove them quickly. You might even be able to grind them out at 320 but I think you'll find it quicker with 120.

Bill is right. Be careful how you lift the mirror off the tool. When you start a wet, gently place the mirror or tool on top and make a few very short strokes with no pressure. This helps reduce the size of any larger bits of grit.

Scratches look ugly but even if you have a few on your mirror at then end they make almost no difference to its performance. I would get rid of these since you are only just out of rough grinding but if I had a couple at the end of fine grinding, I would just leave them.

Rod
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  #91  
Old 20-05-2018, 07:19 PM
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Thanks guys - how should i be taking the mirror off safely?
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  #92  
Old 22-05-2018, 03:41 AM
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Thanks guys - how should i be taking the mirror off safely?
Hi Logan

Just try to limit the pressure downward and lift it rather than drag it off.

Your mirror bevel is quite large and you are using a tile tool so I doubt that's the problem.

Also check the grit at the start of the wet. I usually gently run my fingers over the grit after I have added water to it. if you feel something sharp and even, clean off the grit and try again.

Hope that helps.

Rod
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  #93  
Old 23-05-2018, 07:19 PM
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How do i check how deep a pit is? i have a 0.5mm long fracture or something from 80 grit - i want to know if i should go back to 120 grit.
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  #94  
Old 24-05-2018, 08:34 AM
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How do i check how deep a pit is? i have a 0.5mm long fracture or something from 80 grit - i want to know if i should go back to 120 grit.
Hi Logan

Some people check with a magnifier.

I normally use 240 after 120 but I suspect 320 will just take a bit longer to remove pits etc. I suggest you continue for 30 minutes or so with 320. See if the pit is getting smaller. If it doesn’t reduce noticeably, do a few wets with 120 to get rid of it.

Rod
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  #95  
Old 24-05-2018, 07:45 PM
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I think i might need to go back to 120 - really annoying! but i have only done a few wets since last post.
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  #96  
Old 24-05-2018, 09:40 PM
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Also i think a bit of an issue is i didn't do #240 grit?
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  #97  
Old 25-05-2018, 06:51 AM
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You may have got some contamination from 80 grit. You must ensure that when moving onto a finer grit all traces of the old grit are removed and no containers that were used to house the old grit be simply washed and used for the finer grid. You need new containers. I used different sauce bottle to hold and dispense the wet grit.

Use some plastic drop sheet over the whole surface and under the mirror on the grinding bench. Then when going fine get new drop sheets,

The items that must be reused, such as mirror and tool must be washed thoroughly and again do not use any brush used for coarse scrubbing for the finer powders, get a new brush.

A couple of fine scratches here and there won't hurt too much but too many finer ones and your mirror will suffer in contrast. Of course if your anything like me you'll keep going until that last scratch has gone! Just might take a while. I think 240 grit would have been good to have but of course one uses what one has available and can get by.
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  #98  
Old 25-05-2018, 11:35 AM
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Quote:
Originally Posted by astro744 View Post
You may have got some contamination from 80 grit. You must ensure that when moving onto a finer grit all traces of the old grit are removed and no containers that were used to house the old grit be simply washed and used for the finer grid. You need new containers. I used different sauce bottle to hold and dispense the wet grit.

Use some plastic drop sheet over the whole surface and under the mirror on the grinding bench. Then when going fine get new drop sheets,

The items that must be reused, such as mirror and tool must be washed thoroughly and again do not use any brush used for coarse scrubbing for the finer powders, get a new brush.

A couple of fine scratches here and there won't hurt too much but too many finer ones and your mirror will suffer in contrast. Of course if your anything like me you'll keep going until that last scratch has gone! Just might take a while. I think 240 grit would have been good to have but of course one uses what one has available and can get by.
The scratches are gone now, now its only some pits hanging around from 80 or 120!
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  #99  
Old 04-06-2018, 09:47 PM
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Ok, i'll admit it - ive been a bit lazy lately! Soon, it will be done! NOT giving up no way!!!
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  #100  
Old 17-06-2018, 09:31 PM
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Had a great ASV meeting yesterday! Gout an hour and a half of #320 done. Today, about 40 minutes. Another hour and a half or so is what it needs maybe until 25u. Gotta beat Stefan!
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