The second failure in making a 24 inch pitch lap

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Chanlunlun
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註冊時間: 週四 09 10月, 2003 21:06

The second failure in making a 24 inch pitch lap

文章 Chanlunlun » 週四 04 3月, 2004 00:11

Dear ATMs,

It is just another failure.

Today we carried out the second pouring of the 24 inch full size lap, just to discover that it was not working. This time we carefully monitor the thickness of all pitch squares and they were blocked onto the glass tool carefully. Everything went right until the final stage – hot pressing the mirror onto the lap to make a perfect fit of theirs curves, but it just did not work.

It was not until hot press stage did we realize that the area of the 24 inch lap was just too big, so big that it was not possible to heat up all the pitch squares to required temperature all at same time. It means that it is not possible, even if it is, not practical at least at the moment, to make a full size lap for polishing of the 24 inch mirror.

So we are forced to take another rememdy – to make a sub-diameter lap ( 17 inch or so ) for polishing. We don』t like a sub-diameter lap not without a reason – in doing so the polishing efficiency will be lower. However in order to spent tens of working hours in making a full size lap – and hope is being vanishingly small – we prefer to spent the same labor on polishing the mirror.

So we are now being left with no option but to work with a sub-diameter lap.

Best regards

Chan Yuk Lun
3-3-2004
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full_size.jpg
The 24 inch full size lap. Although it looks good it does not obey hot pressing. Or put it in this way – in order to press fit the curve it may take tens of hours. We better spent the same labor by polishing with a sub-diameter lap.
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豆豸苗
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文章 豆豸苗 » 週四 04 3月, 2004 00:36

How about making smaller pitch squares instead? :? :? :?
I just guess smaller square would be heated up faster and so, may be easier for the hot press. :roll:

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Wah!
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文章 Wah! » 週四 04 3月, 2004 01:18

可否試試加d細坑在每一個方格上?應該有助吻合.
另外可以試試,油熱瀝青熔液上d未吻合地方.
希望有效吧!

Chanlunlun
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文章: 3828
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週四 04 3月, 2004 11:25

豆豸苗 寫:How about making smaller pitch squares instead? :? :? :?
I just guess smaller square would be heated up faster and so, may be easier for the hot press. :roll:
Dear Miss BeanKitty,

Thanks for your suggestion.

Nevertheless we really don't want to spent any extra effort to make a full size lap. Even if some strategy works it does not worth to spent extra effort on it for it is more economic to better spent such energy on the polishing of trhe mirror itself.

It is time for us to switch to another route.

Anyway thanks for your concern.

Best regards

Chan Yuk Lun
4-3-2004

Chanlunlun
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文章: 3828
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週四 04 3月, 2004 11:33

Wah! 寫:可否試試加d細坑在每一個方格上?應該有助吻合.
另外可以試試,油熱瀝青熔液上d未吻合地方.
希望有效吧!
Dear Mr. Wah!,

Your advice is a good one but be reminded that we need to spent many hours on the 24" lap before it starts to work.

The sitauation now clearly indicates the fact that the 24 inch full size lap does not deserve any extra effort. Accidentally We have a 14 inch tool on hand ( which was used for grinding of the 14" f/5 mirror ) and so we can make a sub-diameter lap within half an hour, instead spending tens of extra hours ( may be even more ) on the poor 24 inch lap.

Mirror making, especially for giant mirror, sometimes callls for crise managemnet. we are now facing with crise. We have to make correct decision.

Best regards

Chan Yuk Lun
4-3-2004

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