Somethings missing or is it in plain sight?

[Graeme Seed]

On Graeme Seed Said:

Sorry Martin, but you are miles off.

Sorry to have wasted your time.

Martin

[Graeme SeedParticipant @graemeseed34272]

It wasn’t created to “guess” anything. It’s right in front of you to see. This mic has 2 vernier scales directly opposite each other. Look at the photos and you will see the progression of the lines from gap to gap and the numbers are there almost in the middle. The numbers refer to the gaps. At the other end the numbers refer to the lines. The End.  Photos to come.

[Graeme SeedParticipant @graemeseed34272]

1.0007 slip gauge, You have 1/2 thou as the barrel is past the 5, your looking for another 0.0002. The 2 line on the sleeve end is opposite the 2 space at the other end, Its in the middle so it 2 tenths or anywhere in that space.

[peak4Participant @peak4]

I’ve been out playing again, having found an external mic with a 0-5 vernier.
It’s a Tesa, rather than a Shardlow, and actually numbered 1-2-3-4-0, but the principle is the same.
For the digits up to full thou, obviously read as normal off the thimble, the tenths digit reads off the body vernier scale as expected.
Firstly the internal Shardlow, but with all that leverage, it’s hard to get fully repeatable results each time.
I set it up with 0.4″ + 0.1007″ slips, giving a total of 0.5007″

Close up

All a bit fiddly, so swapping to an external Tesa shown here with a protection slip

Next we have just a plain protection slip 0.1″ side view close up

0.1003″ side view

Then 0.1005″ from the same perspective, so the half line on the thimble lines up with the zero on the body.

But from the top view of the same 0.1005″ the long line on the thimble ties up with the 5 on the body (Or perhaps confusingly on the Tesa, a zero, but it’s still above the 4) so still showing the same result

Now for 0.1009″ Half line on the thimble lines up with 4 on the vernier, so 0.1005″ + 0.0004″ = 0.1009″

Bill

[peak4Participant @peak4]

Graeme, which side of Sheffield are you by 20 miles?
If it’s the Buxton side, you’re welcome to a brew any time.

The Hawley Collection do a series of occasional free one hour lectures starting 2pm; you’re already seen the link to a previous one in this thread. Lots more on Their Youtube Channel
Next one is not metrology, Heavy Springs Trade, but will provide me with an excuse to pop over on the bus to Kelham Island. It’s a 20 minute walk from Sheffield Interchange.

I really can’t find the advert for it, but tickets are still available
https://www.eventbrite.co.uk/e/the-sheffield-heavy-spring-trade-tickets-1984324823965

Bill

[Graeme SeedParticipant @graemeseed34272]

Hi peak4, great reply thanks. Your internal mic is the same as mine except that you have 1/2 thous on the thimble scale and I don’t. The half line of 2 on thimble coincides with 2 as vernier so 0.0002, exactly as I’m saying, albeit I can see 1/2 thou and a middle  without a line

Now for your 1.0009 — The mic is set at the top zero with thimble line at 5 1/2 reading over 0.0005, correct.  The vernier 4 coincides with the 1/2 HALF on the thimble . It’s exactly what I’m saying, its 1.0009.
The vernier reading which is added to the 0.0005 will always be on centre small line. My mic also has something that yours doesn’t  – my thimble is numbered to 25 [24 then 0] yours only has increments of 5’s, but it does have the halves which mine doesn’t. I hope that our conversation has clarified my initial question to all involved in answering and wish everyone a happy Easter.

Are you the ex telephone engineer? If so, we conversed a while back. I’m in Honley, near Holmfirth.

[peak4Participant @peak4]

Yes I’m ex GPO & BT, now retired to Buxton from Sheffield.
Only worked on Holmfirth occasionally doing a bit of fibre splicing.

The thimble on the Shardlow internal has all the thou markings, whereas the Tesa only increments in 5s
Assorted mics I have seem to vary, sometimes even within the same brand.

Bill

[Julie AnnParticipant @julieann]

Thanks to peak4 for the erudite explanation, complete with quality pictures showing both the reference line and vernier lines in a single picture.

Julie

[Graham MeekParticipant @grahammeek88282]

For my part I think the wrong Thimble has been put on the Micrometer. The one shown by Peak4 on his Internal Micrometer makes more sense and there is no need for guess work.

Regards

Gray,

 

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