Micrometer barrel adjustment
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    Question Micrometer barrel adjustment

    A new boy here, so first let me briefly introduce myself...

    I'm a retired electronics engineer, who occasionally dabbles in machining as an adjunct to my hobby electronic projects (e.g. CNC drilling/routing then bending sheet metal for electronics enclosures, chassis etc). Thus I occasionally have need to measure sheet thicknesses, and so on.

    So I recently bought a cheap micrometer screw gauge from China. It seems reasonably well made, but arrived with the zero setting a little way off. Easily corrected by rotating the sleeve using the supplied spanner. But I am burdened with being a bit of a perfectionist (though I can settle for a compromise when the cost of perfectionism is too high! )

    The remaining problem that I don't know how to adjust is illustrated in a few of the attached photos of my micrometer. (Excuse the orange cast at the top of most photos –zero_1476deves.jpg1mm_mark_1477devs.jpgratchet_off_1480devs.jpgthimble_end_1498deves.jpgsplit_taper-_nut_removed_1500deves.jpg I took these outside the house for better lighting, but our bright orange wall reflected onto the table I was working on!) Here's a list of the photos and what each is trying to show...

    Zero_1476devEs
    - This shows my 'problem': when the micrometer is closed and the scale shows zero, the spindle-end of the thimble is not aligned with the 0mm line on the sleeve, by quite some distance!

    1mm_mark_1477devS
    - To show how much it's off, I've (roughly) aligned the thimble end with the 1mm sleeve mark, and the thimble scale then shows it is about 0.25mm out of alignment.

    In case it gives some clues to how this misalignment might be corrected, I've then photographed the micrometer in three successive stages of disassembly (I took four disassembly photos, but since I'm only allowed to attach five photos total, I had to omit one ):
    Ratchet_off_1480devS
    Thimble_end_1498devEs
    Split_taper,_nut_removed_1500devEs
    - That's about as far as I can dismantle it without, perhaps, needing special tools.

    So, am I being too much of a perfectionist in expecting the barrel end to better align with the sleeve marks? If not, how might I correct this misalignment? All positive suggestions will be much appreciated! If you need other photos, just yell!

    Daniel

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    One option. The sleeve is a friction fit on the micrometer body so it can be rotated slightly. Knowing this you might be able to wangle it back and forth a bit while exerting pressure to slightly withdraw it. If you can move it back out you can get the line closer to the end of the thimble, It will of course leave a corresponding gap towards that left end, but that's a trade off you'll have to assess and choose.

    With micrometers I own, the thimble is mated to the screw on a taper. This would ordinarily prevent any easy adjustment to re position those two components so the thimble and sleeve line up to your satisfaction, but you might investigate to see if yours is different. I see that you haven't separated screw from thimble so I can't tell if there might be more to know.

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    A few points.

    1) Bad idea to be a "perfectionist" and buy the cheapest possible Chinese mics. Just sayin'

    2) As TGTool said, these look to have the thimble attached to the spindle by a tapered socket, held by a screw through the ratchet end. To the extent that rotating the barrel (usual fine adjustment) isn't enough to line things up - you can remove and thimble, rotate it to a better setting, re-attach, and then do a fine adjustment by rotating the sleeve with fixed markings.

    Assuming there's a taper mate -- if they don't separate by hand, it's possible to drill a spindle hole-sized hole through a block of softwood - insert spindle with the barrel end down - and every so lightly try a brass pin punch through the end of the spindle to drive it out. A little heat on the outside (small heat gun) can help expand the female taper in the barrel.

    3) Before doing any adjustments, be sure the faces are clean of all oil and debris. Final step is often to get a piece of 25% or so cotton rag paper (nothing smooth faced - as are most copier and printer papers today), lightly clamp it between the faces, and slowly draw it across the faces.

    4) If the micrometers (just one or a set??) have a sort of squishy feel as they close to zero (or around a mic standard), the faces are likely not quite parallel or the threads a bit loose. I'd at least consider a better 1" mic if that's the case. Yours look to be roughly copied from one of the Mitutoyo designs, which itself was roughly copied by Vis and other Polish mic brands decades ago. Just from appearances, the Mitutoyos would have been entry level A- quality, the Polish ones maybe a "B", and yours hoping to graduate to something better?

    For as much as most people use larger mics, the Chinese ones might do for larger stuff, IF one has proper standards to adjust them. But the perfectionist in you might appreciate having a quality mic for the 95% or so of measurements you'll make 0-1"?

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    The zero line up is of such little importance. I like to set my true at one of the standards like .250 - .500 or 12 mm.
    on job checking might be the near Jo- Block.
    Some years ago three apprentices bought a three micrometer set that would stay locked..so after checking a part ypu had to go back and check the micrometer.

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    Quote Originally Posted by PeteM View Post
    Bad idea to be a "perfectionist" and buy the cheapest possible Chinese mics.
    It's hard to add to that

    I am though curious as to how much "cheap" is.

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    AUD31.30 including 'free' postage and Australian GST of 10%.

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    Default Thanks for the suggestions

    Thanks for all your replies – much appreciated. And sorry for this delayed reply – I was expecting e-mails to tell me when someone replied to my post, as happens on many other forum pages. Clearly the default here is for that feature to be 'off' (I've now found where to select that option, and turned it on).

    PeteM's first point is well taken. :-) I guess my approach is, being a cash-poor pensioner, to buy cheap stuff and then 'fix' it (when required and possible) to make it work like a 'good' one!

    A few good approaches have been suggested here, and at some future time (maybe when I've completed some higher priority hobby projects) I might 'have a go' to see if I can improve the alignment.

    Thanks again for all the good suggestions.

    Daniel

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    Quote Originally Posted by DanielF View Post
    Thanks for all your replies – much appreciated. And sorry for this delayed reply – I was expecting e-mails to tell me when someone replied to my post, as happens on many other forum pages. Clearly the default here is for that feature to be 'off' (I've now found where to select that option, and turned it on).

    PeteM's first point is well taken. :-) I guess my approach is, being a cash-poor pensioner, to buy cheap stuff and then 'fix' it (when required and possible) to make it work like a 'good' one!

    A few good approaches have been suggested here, and at some future time (maybe when I've completed some higher priority hobby projects) I might 'have a go' to see if I can improve the alignment.

    Thanks again for all the good suggestions.

    Daniel
    The point made by michiganbuck in post#4 is relevant. Even when getting it "spot on" at zero it is also crucial to see if it is off at other dimensions and if so by how much.

    Getting back to "cheap". There's inexpensive, cheap and dirt cheap. Just my opinion but "dirt cheap" are a waste of money.

    I know from experience, and naively surprised first time I saw it, but even a reputable brand name doesn't mean part or all of it wasn't made somewhere else. First time I saw another brand name on measuring equipment was at the VIS factory in Poland 25 years ago.

    I know a measuring tool company in China and not only is what they make cheaper than for example Mitutoyo but just as good and sometimes better. Sometimes they sell with their own name on the tool but often (depending on quantity) a specific brand name.

    The safest way to buy "inexpensive" yet good is from a reputable dealer.

    As per DIN863 (the standard most micrometers are made to) the max inaccuracy allowed for a 0 - 25mm micrometer is 0.004mm. That's for one with a 0.01mm display. Micrometers with 0.001mm displays are usually more accurate and of course cost more.

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    Quote Originally Posted by DanielF View Post
    AUD31.30 including 'free' postage and Australian GST of 10%.
    Mitutoyo 103-137 is about 60 AUD+GST if you are bit lucky with campaigns (or dare to order from china!)
    OK, almost double price but so is quality. Your mic looks like cheapo quality even for chinese no-name.

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    Matti,

    Thanks for your research! Via eBay: from India, AUD55+GST, and from China AUD73+GST. But I don't trust either of those countries to supply genuine products rather than counterfeits! In Australia, AUD98 including GST and postage, so a good deal more than my Shenhai micrometer!

    I'm no connoisseur of micrometers (couldn't you guess!), but mine looks quite well made to me, apart from the need to re-set the zero, and the lines/thimble misalignment (which is only a minor issue).

    Daniel

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    Gordon,

    Thanks for your comments, and I appreciate your sharing your experience.

    I read michiganbuck's post#4, but didn't understand any of it except the first two sentences. And since I don't agree with his statement: "The zero line up is of such little importance", I moved on. If your zero is out, all measurements will be out!

    But I see his point about [also] checking at 12mm, but really that depends on what range you are most frequently measuring. In my case, mostly thin sheet materials (e.g. 1.6mm aluminium for my recent CNC hobby project).

    I take your point about 'dirt cheap' being a waste of money, but as I said to Matti, I think mine is quite well made. I checked it against a >60-year-old Keilpart 15mm micro, and it appears to make comparable measurements (hard to be sure without a precision reference block to measure). And it sure is much easier to use and read than that rusty Keilpart and the other >60-year-old rusty 12mm micro I own (so rusty I can't decipher its name; possibly 'ARA' or ABA')!

    Daniel

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    Daniel, on many micrometers, the zero adjustment is done by moving the piece that Starrett calls the "sleeve".

    This is the graduated piece that doesn't revolve.

    starrett.jpgstarrett1.jpg

    The sleeve is held in place by friction, and the usual adjustment means is via a hooked wrench into the small hole that can be found on the rear of the sleeve(the side that you don't usually look at.

    starrett2.jpg

    Most of the time, you would simply be adjusting the sleeve rotationally, in order to line up the horizontal "zero" line on the thimble with the horizontal "Reading Line" on the Sleeve.

    But you can also slide the sleeve further toward or away from the frame.

    If your micrometer has this type of adjustable sleeve then you should be able to move the sleeve further away from the frame, so that the edge of the Thimble bisects the vertical Zero line on the Reading Line.

    You will probably have to use the wrench to rotate the sleeve, and while rotating it, apply a sideways force to get it to move away from the frame. Then once it is where you want it from "side-to-side, rotate it again to get it back in place with the Horizontal Zero line on the Thimble aligned with the Reading Line when the mic is closed.

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    awander,

    Yes, TGTool (post #2) suggested this method, and it's the one I'll probably try first, being easier to do than the other suggestions. But thanks for your elaboration of the method. And yes, my micro does have this rotating sleeve, and came with the required spanner, which I've already used to correct the zero reading.

    Daniel

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    Quote Originally Posted by DanielF View Post
    I read michiganbuck's post#4, but didn't understand any of it except the first two sentences. And since I don't agree with his statement: "The zero line up is of such little importance", I moved on. If your zero is out, all measurements will be out!
    Thanks for the giggle. Buck is about the most experienced grinder hand posting here, so you might consider that he knows what he is talking about.

    If your mikes have error in the screw (everything has error) then if you set it at zero, the error at 1" will be twice as large as if you set it at .500.

    Think about that for a second ...

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    Quote Originally Posted by EmanuelGoldstein View Post
    If your mikes have error in the screw (everything has error) then if you set it at zero, the error at 1" will be twice as large as if you set it at .500.
    In your example "variation" is better than "error".

    Semantics maybe but everything doesn't have "an error". Everything is either within tolerance (spec) or it isn't. Outside tolerance (spec) is an error.

    With measuring equipment I like to see a reference to a standard so I have an idea as to what to expect.

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    Emanuel,

    Agreed (subject to Gordon's clarification), but since most of my measurements are closer to zero than 13mm, I prefer to minimise my error at the zero end.

    Daniel

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    Rather than a micrometer maybe what you should be using is something like this for sheet metal. Measure in either 0.01mm or 0.001mm depending on how much you're willing to spend or the indicator dial you might already have.

    thickness.jpg

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    Gordon,

    Very interesting! I've not seen anything like that before. But now I've looked, I could buy one for under AUD30, with aluminium-alloy body.

    Or a plastic one like this
    digital_thickness_gauge.jpg
    for under AUD10 landed.

    But I think I have enough measuring instruments for now, so will resist adding another!

    Daniel

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    Quote Originally Posted by DanielF View Post
    Gordon,

    Very interesting! I've not seen anything like that before. But now I've looked, I could buy one for under AUD30, with aluminium-alloy body.

    Or a plastic one like this
    digital_thickness_gauge.jpg
    for under AUD10 landed.

    But I think I have enough measuring instruments for now, so will resist adding another!

    Daniel
    Daniel,

    Who can ever have enough instruments?

    Gordon

    P.S. Go for what you need - not for cheap

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