Micrometer "feel" - Page 6
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  1. #101
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    Let me get a big snowball rolling down hill,... my thoughts and the thoughts of many of the machinists I have worked with over the years are. Ratchets and friction thimbles are for people who do not know how to use a micrometer.


    Standing back ready to duck all the things being thrown in my direction.

  2. #102
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    Very true Gordon, basiclly the orginal poster asking the question just needs to practice using his micrometers like a previous poster noted about the gage block set. Then determine witch method works best his INDIVIDUAL preference.

    It's Friday, the days half over PM'ers

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    Quote Originally Posted by hotbluechips View Post
    one of our employees just bought a mitutoyo quantumike. .00005 resoloution. the whole thimble is a ratchet. No questionn as how to use it. this is a very nice micrometer. and when i set it , everyone who uses it WILL get the same results.
    5-6 years prior to that Quantumike this mic came out from B&S/Tesa. The entire thimble is also the friction device but the big difference is it does not move away from your fingertips as you open it as in every other type of mic I've seen, digital or not. The darker knob on top is for speedier opening and closing being it is a smaller diameter.
    The person with the tiniest hands in the shop will find it comfortable to use and hold in the traditional way a mic is held throughout its entire range of 0-1.2" (at .00005" resolution)
    It might not look it at first blush but it is the most ergonomic mic we've found.


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  5. #104
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    This is insane how passionate people get about the use of a micrometer...

    You guys understand you can BOTH be right, or no?

    The thimbles should be calibrated along with the micrometer's geometric properties. If you are not calibrating your tools, you probably dont have allot of business working to the fourth decimal place.

    A typical calibration house will calibrate the following or atleast emasure it
    -Thimble stiffness and force
    -Zero
    -Deviations form zero in different division schemes
    -Linearity fo the range
    -Flatness of the faces
    -parallels of the faces
    -Check the standards
    -Constantly measure temperature and humidity

    Has anyone ever tried using a micrometer as a go/no go gauge, especially for measuring a cylinder. I find that measuring in the fourth digit on something big and flat is one thing, but cylinders are particularly hard to measure. Also I would think thew ay a person holds the mic might have nearly as much difference as the pressure.

    As said by others the thimble adds consistency weather its right or wrong, if that mic is calibrated to the thimble it should operate consistently and calibrated for that consistency it will be just as good as feel.
    Variables with a micrometer when measuring to 0.0001

    -Temperature
    1. Parts and mikes must be the same temperature
    2. You can't be injecting temperature into that measuring tool, you should nto eb handling it more than 30-40 seconds, or you are probably going to be over heating the instrument.
    3. Temperature fluctuations should be minimized, and measuring on a surface plate and keeping instruments ont hat surface plate can go a long way to keeping temps steady.

    -Force
    1. The thimble gives you the same torque every time, it has been designed to do that, and it should eb calibrated when the micrometer is calibrated.
    2. Feel can work well too, but you need to be experienced and you need to get some quantitative measurements on your feel
    3. (From: Pete M): Thimble stiffness most especially for soft materials can cause a significant force lading to material deformation (Polymers) and at times a micrometer suited for these materials with the addition of a +/- Gage(Indicator) should be used.
    4. (From: Pete M): Thimble force is dependent on the friction of the screw itself, and the thimbles torque generating capacity, an oiled mike with lower friction at the threads will give different results than a non oiled mike.
    -Cleanliness
    1. The mic should be cleaned wit something non abrasive every time it is used
    2. The surface you are measuring must be perfectly clean
    3. beware of raised surfaces, the mic is taking an effective average over a small area.

    -Feel (Not the pressure)
    1. Especially on cylinders, if you are not at a diameter, you are not measuring right, be sure you are at a diameter and not a chord
    2. the mike must be perpendicular to a surface, you might be across a diameter on a cylinder, but the mike can be cocked.

    Can anyone add some more tot his?
    Last edited by vettedude; 07-23-2012 at 12:38 AM.

  6. #105
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    Quote Originally Posted by vettedude View Post
    This is insane how passionate people get about the use of a micrometer...
    Isn't that the truth.

    - Leigh

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    Quote Originally Posted by vettedude View Post
    . . .
    -Force
    1. The thimble gives you the same torque every time, it has been designed to do that, and it should eb calibrated when the micrometer is calibrated. . . . Can anyone add some more tot his?
    FWIW, a slight amendment to an otherwise excellent list. Few ordinary mics provide a means of changing the the torque/force/feel. Rather, most ratchet and friction type spindles operate with a fixed and reasonably firm torque. As long as it (the torque, and hopefully the pressure) stays the same from measure to measure, it should conform to its calibration.

    In those cases where torque (or even better pressure on the anvils) must be controlled, usually to a lower level, a special micrometer must be used. There are, for example, mics with a graduated spring loaded anvil (usually with a non-rotating spindle) for softer and low pressure items. Mics with a +/- indicator at the anvil end may also have a means of altering spindle pressure.

    One of the slight problems with both ratchets and friction thimbles is that oiling the spindle or tightening the adjustment nut will change the force.

  8. #107
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    Quote Originally Posted by PeteM View Post
    In those cases where torque (or even better pressure on the anvils) must be controlled, usually to a lower level, a special micrometer must be used. There are, for example, mics with a graduated spring loaded anvil (usually with a non-rotating spindle) for softer and low pressure items. Mics with a +/- indicator at the anvil end may also have a means of altering spindle pressure.
    Correct, I should have included this, when measuring polymers especially, the materials are much softer, due to the significantly low modulus.

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    Quote Originally Posted by Gordon B. Clarke View Post
    I don't get that. If the ratchet/friction thimble is used to calibrate and measure how can it be even a "slight" problem?

    Gordon
    I will try to explain,

    -The friction thimble delivers torque, and not force
    -Torque is not constantly delivered as force within a screw, and is very dependent on screw friction.
    -There is a calibration of this torquing mechanism that should keep the equipment properly working for a while, however if lubricant is added, the above will come into effect.
    -For a metal part this is not an issue, and the part can be inspected with a stiff or loose thimble making no discernible difference of the micrometer due to high part stiffness.
    -For a polymer or soft part (thin metallic ring is an example), the friction thimble has the ability to deliver force such that the part will deform

    So for certain cases developing a feel for torque could be an advantage.
    The goal of tightening the mike is only to get the mike perpendicular and parallel wit surfaces you are measuring, not to deform the part. If you were to develop a feel you could probably determine by that feel if you were deforming the material or actually "feeling" for parallel and perpendicular. Also, I disagree with what was said earlier about not ringing the mike, the mike surfaces might need some amount of ringing to remove trapped gas.

    Also on very clean metal surfaces there should be an amount of friction that you can hear with the mike, in the form of squelching. I would need to do some research to know if the screeching is at a point of adequate pressure, or over pressure. These ratchets are on the mikes for good reason, to eliminate error, not to dumb the tool down. you can calibrate the tools to read correctly based on a given pressure, its harder to calibrate for different people on the same mike.

    Does that help?

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    Quote Originally Posted by Gordon B. Clarke View Post
    I don't get that. If the ratchet/friction thimble is used to calibrate and measure how can it be even a "slight" problem?

    Gordon
    Simple, the mic is calibrated. The user is told to come back in 6mos, a year, etc. Meantime the mic gets a bit gummed up, so they clean it, oil it, maybe fiddle with the spindle adjustment nut. The mic is still within its calibration period, the geometry may not have changed (though the spindle may be a tiny bit loose), but the pressure on the anvils will be different. As vettedude notes, it especially makes a difference with soft materials.

    It's the same principle by which torque on a bolt can yield significantly different clamping forces depending upon lubrication, the class of fit, etc.

    An observant user will check their own mics, but lots of folks in industry don't bother.

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    I just noticed that using the ratchet on my starrett depth mic will lift the base off the part. It must be dirty or need lube, I guess.

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    Quote Originally Posted by lowCountryCamo View Post
    I just noticed that using the ratchet on my starrett depth mic will lift the base off the part. It must be dirty or need lube, I guess.
    Insufficient downward pressure on the mic base. You need to push down quite hard because there's significant upward pressure.

    - Leigh

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  14. #112
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    That is a sure sign that you should use a lighter feel on the thimble and forego using the ratchet stop.

    Lord Byron

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    The ISO9001 inspector is usually referred as an "annoying idiot" but when loads of parts are coming back from customer, workshops usually develop something which finally resembles ISO9001. Maybe its cheaper to use ISO9001 from the start ? How high one values his stubborness ? According to my observations, it is usually valued highly

    I have observed that when everything is done right, usually no "highly valued long experience" is needed. Mic's ratchet replaces the need for 80 year old col. Sanders or Pai Mai in the corner who does measurements "by the feel" and is always right even when dimensions are wrong.

    Its not terribly expensive to have couple of high quality digital mics, gauge blocks and gauge block holders in workshop. Instead of expensive calibration, comparative method could be used. And I dont "believe" in any of my measuring equipment, I better check it once or twice - mics with gauge blocks, tool height setters with gauge blocks (w. holder) and gauge blocks by comparing different lengths by wringing. Takes about 10 minutes in month.

    This metrology opens a big can of worms, especially if it additionaly involves environment measuring, electronics measurements etc etc but becuase something is annoyning does not make it avoidable or what ? Like cooling tank cleaning, it has do be done.

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  17. #114
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    Gordon, If I read your question correctly, the smaller black thimble is neither a ratchet or a slip friction device. It is fixed to the anvil and so can be used for more or less pressure on the part. Being a smaller diameter it seems to help prevent excess torque and pressure on the part to be measured.

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    Quote Originally Posted by Gordon B. Clarke View Post
    Huh? Either I wrote it wrong or you did misunderstand. These new type of digital micrometers have most of the thimble as the ratchet. The small "bit" on the back isn't intended for "feeling" measurement pressure but for rotating faster than if the large diameter part of the thimble is used.
    Huh? Sorry I didn't realize it wasn't supposed to be used for both 'feel' measuring and faster rotation (even though it does so quite nicely, thanks)

    Quote Originally Posted by Gordon B. Clarke View Post
    Back in the "good old days" when a micrometer ratchet was at the rear end of the thimble I often used the palm of my hand to turn the thimble quickly.
    Small world. Back in the day I did that too. Imagine that? With that smaller knob you can actually spin the movement quite handily. A Quik Mic it ain't but it's still allows for fast movement to get near size.

    Quote Originally Posted by Gordon B. Clarke View Post
    I've got the feeling you haven't tried using one of the new digital micrometers.
    Gordon
    Actually, I have but certainly not every type that has hit the scene. If you get the feeling I haven't used the micrometer pictured you would be sorely mistaken.

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    Quote Originally Posted by Gordon B. Clarke View Post
    It isn't intended to be used for both. Just for faster rotation. That you choose to use it for something it wasn't intended to be used for is of course up to you
    Gordon
    Not to belabor the point... Aw heck, it needs belaboring!
    How and where did you come up with this absolute statement?
    The speeder knob is the only decent way you can add more pressure if desired.
    Just stand corrected and know that most humans are wrong once in a while

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    Quote Originally Posted by Gordon B. Clarke View Post
    When one stops and thinks about how many instructions and warnings there are on just about everything sold nowadays it's strange that no manufacturer of hand held measuring equipment has ever written how they recommend how it be held and used. They've probably read too many threads like this

    Gordon
    Starrett and B&S both wrote small handbooks that discussed the reading and use of micrometers at length. Most quality makers include some sort of instructions on use and reading (for example, Mitutoyo). Still, using a mic properly is considered pretty basic. Most hammers won't come with more than rudimentary instructions on their use.

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    Do large 8"-32"new inside mic's have a ratchet i havent looked guess i should outa curiosity but the one i use on occation does not so i must know how to "feel" weither i am in the right spot then check with a OD mic "with no ratchet" just to double/triple check the size. where i work they will most likly not buy a new one unless the old one gets damaged hmm thers a thought .......oh prolly not

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    Quote Originally Posted by Dirtywiskers View Post
    Do large 8"-32"new inside mic's have a ratchet . . .

    None that I've seen. Inside mics are generally used inside bores and swung a bit to find the maximum diameter. A ratchet would interfere with that. So, here's a case that depends on feel.

    There are specialized ID gages that apply a constant tension, often with a dial to indicate the max reading.

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    Quote Originally Posted by xdmp22 View Post
    Best thing you can do is buy a "standard" aka guage block...if your mic is 1"-2" get a 1" or 1.5" the guage block will be accurate to .00005 or better....if the mic doesn't measure what the block is...then your mic is off or your feel is off......

    Use the block to check your mic...(which you should do anyway from time to time) get your "feel" from keeping it at the size of the block....
    Also, especially if I'm using someone elses instrument, the first thing I do is acquaint myself with it's zero and try to replicate the same pressure when measuring.


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