metric 123 blocks??

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metric 123 blocks??

This topic has 17 replies, 12 voices, and was last updated 3 December 2015 at 14:50 by Vic.

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2 December 2015 at 11:17 #214876
Michael Cox 1
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@michaelcox1
I have just finished making an extended micrometer, see:

http://mikesworkshop.weebly.com/extended-micrometer.html

This is based on a design by mklotz.

It is fine "as is" for relative measurements but in order to make absolute measurement I need some standard precision blocks that are 25, 50 and 75 mm long to provide calibration standards.

I have some imperial 123 blocks that are certified to 0.0005" but what I really require is the metric equivalent of a 123 block i.e a 25 x 50 x 75 mm block. This would make a good calibration standard for the micrometer.

Do precision 25 x 50 x 75 mm block exist? If they do who supplies them?

Any ideas?

Mike
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2 December 2015 at 11:17 #31105
Michael Cox 1
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@michaelcox1
2 December 2015 at 11:23 #214877
John Stevenson 1
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@johnstevenson1
Mike,

You would be better off with slip gauges.
2 December 2015 at 12:31 #214884
Robbo
Participant
@robbo
How about Stevensons 10-20-40 or 20 -40-80 mm blocks from ArcEuroTrade? Not what you asked for I know,but needs must sometimes
2 December 2015 at 12:46 #214885
Martin Connelly
Participant
@martinconnelly55370
I bought some individual Mitutoyo gauge blocks in May.

611675-131 50mm £33.67 +vat

611635-131 25mm £25.12 +vat

Just letting you know the cost if you go this route.

Martin
2 December 2015 at 12:54 #214888
pgk pgk
Participant
@pgkpgk17461
A bit of 'googling' found this (scroll down for the metric ones) **LINK**

And on aliexpress **LINK**

pgk
2 December 2015 at 14:50 #214899
steve de24
Participant
@stevede2433577
Would the outer diameter of ball bearing races serve your purpose? Anyone know what typical tolerances they are ground to? Steve
2 December 2015 at 15:52 #214903
Chris Evans 6
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@chrisevans6
I would just use the Imperial ones you have and a calculator. Job done for no cost.
2 December 2015 at 16:32 #214905
Neil Wyatt
Moderator
@neilwyatt
Hi Mike:

Google 'micrometer standards' and you will find sources of the little bars with plastic insulating handles that are used to, well, set micrometers. Cheaper than gauge blocks.

Neil
2 December 2015 at 16:55 #214906
steve de24
Participant
@stevede2433577
I think Chris has made the most sensible suggestion. Just use 1", 2" & 3" instead of 25, 50 & 75 mm and calibrate the micrometer at the 0.4mm, 0.8 and 1.2mm points on the micrometer scale instead of calibrating using the 0.0 point.
2 December 2015 at 17:19 #214908
Tony Pratt 1
Participant
@tonypratt1
I would go with slip gauges every time.

Tony
2 December 2015 at 18:59 #214919
Vic
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@vic
Looking at that tool I wouldn't bother, I'd just use a digital caliper or buy a large Mic.
2 December 2015 at 19:55 #214930
Michael Cox 1
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@michaelcox1
Vic, would you care to elaborate why you think the tool is so bad.

Mike
2 December 2015 at 21:21 #214934
KWIL
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@kwil
The extending bar is probably too flexible for "precise" measurement? Micrometer frames are usually very stiff.
2 December 2015 at 21:57 #214939
John Haine
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@johnhaine32865
Since 1959 the inch has been defined as exactly 2.54 cm so your imperial 123 blocks if made to standard since that date should have precise metric equivalents. Even if before the difference will be so small that you wouldn't be able to measure it.
3 December 2015 at 14:24 #214988
Michael Cox 1
Participant
@michaelcox1
Thanks for all the responses. They have provided some interesting things to follow up on.

Mike
3 December 2015 at 14:49 #214991
Vic
Participant
@vic
Posted by Michael Cox 1 on 02/12/2015 19:55:38:

Vic, would you care to elaborate why you think the tool is so bad.

Mike

Too many ways for errors to creep in. I can't help thinking if it was such a good idea it would have been done 60 years ago. I've also seen lots of cheap second hand Mics available over the years.
3 December 2015 at 14:50 #214992
Vic
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@vic
Posted by KWIL on 02/12/2015 21:21:58:

The extending bar is probably too flexible for "precise" measurement? Micrometer frames are usually very stiff.

Exactly.
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