Offen imperial bore mic gauge.

[Graeme SeedParticipant @graemeseed34272]

Hi All, here’s an Offen, UK made, extremely well made bore gauge. Complete set, including a pin to engage/disengage the friction thimble. Measuring between 0.485/0.965, 0.080 between changes of anvils. There is a line above the datum zero which corresponds to 9/10ths, as a vernier would do. Photos show different settings but I can’t see the correlation between datum and vernier to read 1/10th. Each thou is divided for 2/10ths. I can see 1/2 a small division but that’s a guess, where is a true reading? Thanks, Graeme.

 

[JasonBModerator @jasonb]

There was a thread a few months ago about reading the different types of 1/10th scales.

[Graeme SeedParticipant @graemeseed34272]

Hi Jason, I can’t believe in search, anything about Offer bore gauge, your assistance please.

what’s confusing is that anything on the datum line added to 10ths above the line always equals 9. The photos show this.

[Graeme SeedParticipant @graemeseed34272]

Hi Jason, I can’t find anything in search, anything about Offen bore gauge, your assistance please.

what’s confusing is that anything on the datum line added to 10ths above the line always equals 9. The photos show this.

[JasonB]

On JasonB Said:

There was a thread a few months ago about reading the different types of 1/10th scales.

On Graeme Seed Said:

Hi Jason, I can’t find anything in search, anything about Offen bore gauge, your assistance please.

what’s confusing is that anything on the datum line added to 10ths above the line always equals 9. The photos show this.

I think this was the thread on tenths, but Graeme was party to it

Somethings missing or is it in plain sight?

There was a previous one about Offen, but again Graeme will be aware of it.

Offen screw type telescopic gauge.

Bill

[Graeme SeedParticipant @graemeseed34272]

Thanks for finding the threads Bill. Yes, I started these threads, one about the shardlow mic but the Offen one didn’t continue to tenths. Michael G sent the copywrite docs, but these don’t explain tenths either.  One of my photos with datum at 5 is slightly out of parallax. Strangely, having both cataracts done, I can see that the tool must be rotated to see the exact position of the top line even though they’re only 3/16″ apart. The upper line is there for some reason and on datum zero, it reads 9. Maybe the tool only reads to 2 tenths, but why the line? Going to 9 strongly suggests a vernier scale but there’s no scale at the line!! Move the thimble anywhere and nothing correlates to a vernier number. I’m mystified but enjoying trying to fathom this out. Graeme.

[Nigel Graham 2Participant @nigelgraham2]

My thought is a vernier effect but to “half-tenths”, i.e. 0.0005″, only.

You could experiment if you have another bore-measuring instrument by comparing results of measuring various accurately-made items like bearings.

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