Somethings missing or is it in plain sight?

[Graeme SeedParticipant @graemeseed34272]

Hi All, I have got a 0-1 outside mic, with, tenths, but only 5 on its scale!. It measures to 1/2 thou only with its scales. Where’s the other 5 tenths? Surely not guesswork.  Many mics have 10 graduations, but not this one.     Graeme.

[JasonBModerator @jasonb]

 It measures to 1/2 thou only with its scales

Not sure how to interpret that, could be taken two ways.

1

That is unusual as most mics read to 1 whole thou on the main scale so that is why they need 10 divisions to read 1/10ths

But if yours is reading to 0.0005 on the main scale then having the vernier divide that by 5 would give 1/10th per division

2

If there are 5 divisions I can’t see how one division would give you readings only to half a thou.

I would think that each division is more likely to be 0.0002″ as 1 divided by 5 is 0.2

 

A picture would help

 

[Graeme SeedParticipant @graemeseed34272]

thanks for reply Jason, here are some photos, hope they are in correct order. You need to start from the bottom. Wrong order. 1 = 0, 2 = 0.5, 3 = reads 5, 4 = 0.7, 5= nothing lines up, something is missing.   

[Graeme SeedParticipant @graemeseed34272]

the mic is a Shardlow 0VX6, very nice. 1952 ish?

[Graeme SeedParticipant @graemeseed34272]

there are 5 vernier divisions, each one is 1/10th, move it 5 divisions and you have 1/2 thou, where’s the other  1/2 thou measured? I haven’t got 10 divisions! Graeme.

[Howard LewisParticipant @howardlewis46836]

Are you sure that the graduations on the Thimble don’t constitute a vernier scale?

In which case, you would read off against where the lines on Barrel and Thimble align, just like any other vernier, rather thasn directly. Thimble numbreading 0.001 +, with one of Barrel graduations aligning perfectly with one on the Thimble (Say 3) in which case 0.001 + 0.0003 = 0.0013)

Should be obvious, as with both Zeroes aligned the intermediate graduations will not align precisely (Possibly 5th  graduation on the Vernier scale will align with a 4th or 6th on the barrel, but with the others very slightly out of line.

Howard

[Martin Johnson 1Participant @martinjohnson1]

Once you get to 0.0005, the next thou division up wll start to align, so you then take the next thou upand knock off n tenths.  Hence you are not five lines short of a micrometer.

Martin

[BazyleParticipant @bazyle]

Move it to a .0005 position by eye on the course division on the thimble and confirm you are reading that correctly. Then move it on a tiny bit to .0006 and see whether something aligns with the “1” again.
My M&W has 9+0 vernier marks but I can’t really see if they are any different spacing from yours.

[Graeme SeedParticipant @graemeseed34272]

thanks Howard. i can assure you it’s a vernier scale. Nothing can align again until the vernier reaches it top zero, go past 5 and theres nothing to align to.

[Graeme SeedParticipant @graemeseed34272]

Sorry Martin, but you are miles off.

[Graeme SeedParticipant @graemeseed34272]

Afraid not Bazyle. Your M& W has 10 numbers, so every 10th comes into an alignment, not so with mine, go past 5 and there’s nothing to align.

[MacolmParticipant @macolm]

Perhaps the barrel should be fitted further to the right, and currently covers some more markings?

[GordonHParticipant @gordonh]

Graham,

Please could you show a picture or two showing the barrel and vernier for readings greater than say, 0.215 so my thoughts can be confirmed or disproved?

Go past 5 on the vernier and your measurement is greater than X+ 0.0005. The next alignment will be with 24 on the thimble and 1 on the vernier. That’s 1/10 of a thou greater than the 5/10 thou you have just past, so X + 6/10 thou and so on.

Gordon

[peak4Participant @peak4]

Just been out to the workshop, briefly as it’s freezing out there, so not tried to set up for photographs.

I have several Shardlow tenths mics, but my only one with 5 vernier divisions is an internal one; the rest all have 10.

All those with 0-10 on the vernier have that scale going further around the barrel as one would expect.

The 0-10 vernier scale equates to 0-9 thou on the thimble, again as one might expect.
That internal Shardlow mic, and a couple of non tenths external mics, have intermediate ½ thou divisions on the thimble;  The 0-5 vernier scale measures 0-4½ on the thimble, so one would need to use a half division for the other part of the scale.

I wonder if your thimble may have been swapped under a previous owner?

In a way, for the internal mic, it makes sense just to have 0-5 as, if being used to measure a bored hole on a lathe, the second half of the vernier from 6-10 wouldn’t easily be visible as the workpiece would obstruct the view.
This is particularly the case, since on the Sharlow 0-10 mic(s), the vernier doesn’t start until +3 thou round the thimble.

Moore & Wright, Etalon, Mitutoyo, Chesterman, and others have their 0-10 vernier divisions starting along the main zero line on the body, whereas on my own Shardlow, Starrett, and Smart & Brown, the 0-10 vernier scale only commences at 3 thou round on the thimble.
On the 0-5 Shardlow vernier, it does commence on the zero as per Graeme’s photos.

Since Sharlow were one of the initial Sheffield makers, I wonder if they followed a US practice initially commencing the 1-10 marking a bit further round the body. Some of their first mics were base on a Slocomb design.

M&W, Shardlow, & Chesterman, were the three initial mic manufacturers in Sheffield, M&W took over Shardlow (Shardlow/GKN) and obviously continued to make mics, whereas Chesterman later specialised in linear devices like vernier callipers & height gauges.

M&W dropped quite a few of the more interesting Shardlow designs after the takeover, such as the direct reading “Speedread” copy of the Slocomb, and the really oddball AngloMetric.

The latter uses a 50tpi thread, so 20 thou per thimble revolution; metric readings are taken using a second curved red line around the body. 14:16ish on the video below; having got a couple, I can see why they didn’t catch on.

Far easier to use are the Mitutoyo counting/direct-reading ones, which are available as all imperial, all metric, or counting metric with imperial vernier, and vice versa.

The Shardlow Speedread direct reading mic has numbers of thou (or mm) in little windows; the  vernier scale around the body is 0-10 but the thimble is not enumerated at all, you just read the tenths off the body vernier.

Personally I do like the ones with the sloping main lines as per the above photos.

See also this catalogue;

https://archive.org/details/shardlow-micrometers-list-sm-6/001%20Shardlow%20Micrometers%20List%20SM-6/page/n1/mode/2up?q=shardlow

Bill

[old martParticipant @oldmart]

If that barrel is original, I recon the mic was designed to measure in 0.0002″ not tenths. I do have mics in tenths and also in microns, but if the mic is adjusted exactly it is easy to just read them as well without bothering with the vernier scale.

I remember posting a question about the Shardlow mic in the lab in the 60’s when I was in electroplating which measured metric and imperial, it got lots of excellent answers, they never caught on, too fiddly to use.

[Graeme SeedParticipant @graemeseed34272]

Hi , he barrel is in its correct position. Photos of others of this ilk verify this. Graeme.

[Graeme SeedParticipant @graemeseed34272]

Hi Gordon, can you clarify to us. I’ve tried your suggestion but doesn’t compute with what I see. For instance lets say you have measured something to 0.345, The mic is now set and cannot rotate further, your suggestion implies moving the spindle more, which would create a G clamp effect? Graeme.

[Graeme SeedParticipant @graemeseed34272]

Hello peak4, thanks for your informative reply and interesting video. I’ve got a notion that I shall take up the commentators offer of a guided tour of the museum metrology dept. I’m only 20 miles from Sheffield.

My mic is a model 1V and has the original thimble and angled lines sloping to the right with numbers below the datum line. There are models with lines sloping to the left with numbers above. This mic  has the zero below to enable room for the vernier engravings to be administered, if the zero was above or in line with the datum line, there would be no room for the engravings to start. This is the reason for your mic starting its vernier travel from 3 thou. The datum line is the set point for zero, vernier scales can start anywhere on the circumference of the barrel as long as the zero aligns with a whole number line on the thimble at zero [ not a half thou etc], yours starts at 3 purely for convenience for vision of the scale. If your vernier has 10 lines etc you can see any amount of 10ths you have reached, not so with the 5 increments that I have. Which model is yours? I can look out for one for my collection. If you have a mic with 5 vernier increments, measure a slip gauge of 0.1003 and read off the result, try a 0.1007 and  you wont see a result [only a guess], but there is a result there somewhere and its staring right at you, but where? Graeme [thanks for spelling my name correctly]

[Graeme SeedParticipant @graemeseed34272]

Hi old mart, thanks for your reply. I see your reasoning about 2 tenths, but this mic has 1 tenths, move it 5 increments and it shows 1/2 thou. Is not using a vernier scale not guesswork??? You will be close but never as perfect as the inscribed lines etc. Yes, the Anglometric mic is very slow to use, but a wonderful micrometer. Thanks, Graeme.

[Graeme SeedParticipant @graemeseed34272]

Hi All, can one of the forum members do an AI search? I haven’t a clue about these things. The words computer introduction to my workplace in 1990s made me shudder, I was pencil and paper and slide rule, it’s a bit beyond me. This might supply an answer to my original question. Thanks Graeme.

[JasonBModerator @jasonb]

If the divisions were meant to represent 2/10 I would have expected them to be numbered 2, 4, 6, 8, 0 rather than 1,2,3,4,5

I’ll have to play with my 10 division mic to see what line sup if you are a 10th or two undersize. But does seem a bit odd if you are expected to take a reading that is 2 divs under and subtract that from the full thou to get say 0.0008

Maybe that is why it is a rare one, the 5 divs did not catch on?

Any chance of a photo showing the markings along teh body when it is opene dup a bit.

[JasonBModerator @jasonb]

Picture of a 1/2 thou thimble in this thread which would only need 5divs on the venier

https://www.practicalmachinist.com/forum/threads/inch-metric-micrometer.236054/

[Graeme SeedParticipant @graemeseed34272]

Hi Jason, yes, correct 1/2 thou is 5 divisions. I’m measuring in whole thous and little bits and have discovered the secret of the missing 5.

The answer is the positioning of the numbers on the right. They are not attributed to lines but to spaces. The rule of thumb with this type of mic is, left to right for alignment of lines up to 5, then right to left for alignment of centre of a gap to the vernier line, read the 10ths on the left side. Here’s an example of 0.0008. the photo shows over the half of the thou, so you have 0.5 thou+****. Next find the 0.0003 using what I’ve described about. Find any line that in the centre of any gap and read off on the left Add this to your 1/2 thou. Hey Presto.

[Phil PParticipant @philp]

Have you got any slip gauges that you could use to prove your findings ?
I must say I have my doubts about a micrometer designed to guess the gaps between the lines.

Google search “how to read an imperial vernier micrometer with only five divisions”

Reading an imperial vernier micrometer with only five lines (divisions) on the vernier scale allows you to measure to the nearest 0.0002″ (two ten-thousandths of an inch). This is a specialized version of the more common 10-line (0.0001″) vernier.

The Basic Principle
Each line on the vernier scale (0 through 4, or sometimes just 5 ticks) represents two ten-thousandths of an inch (0.0002″).

Step-by-Step Reading Method
Read the Sleeve (Main Scale): Identify the largest number visible (0.1″, 0.2″, etc.). Then, count the small 0.025″ lines past that number.Example: Past .300″ mark, and 2 small lines visible (2 x .025 = .050″). Subtotal: 0.350″
Read the Thimble: Find the line on the rotating thimble that has passed the horizontal datum line on the sleeve. Each line is 0.001″.Example: The 16th line is just past the datum line. Subtotal: 0.016″
Read the Vernier (5 Lines): Look for the one vernier line (0–5) that aligns perfectly with any line on the thimble. Multiply this line number by 0.0002″.Example: The 3rd line aligns. 3 x 0.0002″ = 0.0006″
Add Them Together: Sleeve + Thimble + Vernier = Total Reading.Example: 0.350″ + 0.016″ + 0.0006″ = 0.3666″

Phil P

[MacolmParticipant @macolm]

Seems fair enough. This dates from the days before arithmetic became math, and when a semi-skilled machine operator could confidently do the necessary sums his work entailed on a proper sheet of foolscap.

[Author]

Posts