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Ratchet or friction micrometer ?

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  • Ratchet or friction micrometer ?

    I have a ratchet Mitutoyo, vernier scales, works great. Click,click,click, lock it and read it. My darn eyesight just sucks now days trying to discriminate the lines. Been thinking of buying a LCD display Mitutoyo. Or should I say my wife will be giving this to me for our 31th anniversary. My boy will have some use for my old one.
    Never have used a friction mic. Does the thimble just stop turning when the target is reached?
    Would this just be a personal preference between the two?
    I would imagine they are the same accuracy one way or the other depending on the user.
    What's the difference?
    Thanks
    Ted

  • #2
    Can we vote for neither? The ones I've used did not agree with what I was feeling.
    Gene

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    • #3
      As you probably already know, with the ratchet type you hold the frame of the micrometer with your little finger wrapped around it so the thumb and first finger can reach out to the ratchet knob. The friction type is a bit more forgiving as the entire barrel of the friction micrometer is available, and yes, the barrel just floats (keeps spinning) when you bottom out at just the right pressure.

      When I was a wee nipper I was taught to close the mic at what I thought would be a perfect zero reading but without looking at it as I closed it. By doing this I would not be able to know when I had zeroed out and unintentionally allow my eyes to subconsciously influence my "feel". I would do this over and over until I could nail the zero every time to the tenth (not easy). Then I'd repeat this at different thicknesses and then over telescope gages. Once you develop a "feel" to a high pitch of accuracy you no longer need to use either the ratchet or friction barrel stops. If I have an important dimension to nail today (within a half thou) I pre-test the accuracy of the mic I am using with a jo-block or standard first and test my feel to it before I begin to take measurements.

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      • #4
        I prefer the ratchet type because you don't have to use it if you don't want as it is out of the way and the thimble is solid. The friction thimble type you don't have much choice because the whole thimble moves. I have a bunch of Mitutoyo digital mics and they are great. I bought a new Starrett digital and it was so bad I sent it back. The Starrett was only available with the friction thimble which had a terrible feel and the digital display was very slow responding.
        Mark Hockett

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        • #5
          I don't believe in "Zen and the Art of the Micrometer"

          To me, it either works, (ie., works consistently) or doesn't work.

          To wit; position micrometer, advance the barrel to close to but not touching the diameter of the workpiece, then in a consistent and smooth motion contact the workpiece while letting the ratchet or friction thimble do its work.

          If you're getting inconsistent results, it's either the mic is position incorrectly along the diameter or skewed, or there's a small piece of contaminent in the way, but it shouldn't be an issue of "the feel" or "the magic touch is lacking".

          Anyways, to the original question, I have both and like them both. I don't think you'll go wrong with whatever you choose.
          Gary


          Appearance is Everything...

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          • #6
            For home shop use you probably don't need either. As long as you develop a consistent "feel" you should be able to repeat to a couple tenths.

            The main use of ratchet/friction devices is in industry where multiple users are expected to get the same measurement. One may have a light touch and the other may think it's a c-clamp. So, one of the two torque/pressure limiting devices is needed to cut down on user to user variation.

            Research a couple decades back said that using a ratchet could lead to a sort of impact wrench effect -- it got a tiny bit tighter the more it turned. So, a company should have a standard practice along the lines of three clicks and you're done. Friction types are just a bit more forgiving.

            What most folks want is both a speeder at the end -- to get the micrometer quickly to adjustment -- and a comfortable means of controlling pressure when it's needed. It's a bummer to have either a ratchet of friction thimble start spinning as you speed a mic to size.

            The old Millers Falls mics had a good approach to this, with a speeder on the end and a ratchet built right into the end of the thimble. Brown & Sharpe had their convertible friction/fixed thimble. Mitutoyo made a number of well designed mics (speeder plus friction thimble) and even Scherr-Tumico made one. Lufkin had a model with the friction thimble well placed. One of my favorites is the Etalon MicroRapid; sadly only sold in metric models now.

            Bottom line is to try a bunch of quality mics and find one you like. FWIW, I've set my hands on a couple hundred mics and would have to say that while the Starrett models have maybe a bit better than average accuracy (certainly not the best), their ergonomics are just average IMO.

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            • #7
              Paaper or plastic. Peanut butter or chocolate. After one there's too many choices.

              I've used all three (plain thimble is one of the choices) but I prefer my own sense of touch un-influenced by looking at the thimble as DATo illustrates. Soon as you look at the thimble you start "wishing on" or "wishing off" whatever shouldn't be there.

              That and heat from your hands, a sunny day with light streaming through the clerestory windows, the blast from the space heaters, coolant chill, heat build-up from machining. Sometimes taking a reliable reading in an open shop is like working a shift in a coal mine in a white shirt - not even the best of intensions results in complete success.
              Last edited by Forrest Addy; 08-07-2011, 05:45 PM.

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              • #8
                Originally posted by DATo
                When I was a wee nipper I was taught to close the mic at what I thought would be a perfect zero reading but without looking at it as I closed it. By doing this I would not be able to know when I had zeroed out and unintentionally allow my eyes to subconsciously influence my "feel". I would do this over and over until I could nail the zero every time to the tenth (not easy). Then I'd repeat this at different thicknesses and then over telescope gages. Once you develop a "feel" to a high pitch of accuracy you no longer need to use either the ratchet or friction barrel stops. If I have an important dimension to nail today (within a half thou) I pre-test the accuracy of the mic I am using with a jo-block or standard first and test my feel to it before I begin to take measurements.
                I count about 10 yes's.
                Gene

                Comment


                • #9
                  So, with the ratchet types you have a choice of the ratchet handle on the end, or old school by feel on the main thimble ?
                  Do the friction mics only have one thimble?
                  Sorry for the stupid questions.
                  Never had an opportunity to use a friction mic before.

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                  • #10
                    I've got mics with friction thimbles (Tesa) but that's just the outer sleeve and you can still hold the upper end for feel. So, like the ratchet you can use either way.
                    .
                    "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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                    • #11
                      I too have both friction & ratchet thimble mics, but rely on feel as this is the way I was taught.

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                      • #12
                        Can I vote for both...in one?

                        The newest version of the MItutoyo Absolute IP65-rated digital electronic, (which also happens to have the most exquisite manual feel) has a beautiful execution of a ratchet thimble within the friction thimble. It's model number 293-344 for the switchable 0-25mm/0-1" model, and it is easily the nicest micrometer I've ever handled.

                        It's classified by Mitutoyo to be "ratchet thimble", but does not have the traditional ratcheted "speeder" at the end of the thimble. The ratchet "lumps" are built into the friction thimble, and it's just impossible to describe in words how nice it is. The mechanical thimble still has the inch scale with Vernier for "tenths', but the huge LCD readout is so nice and easy to read that you may never look at the analog scale.

                        Mind you I own a lot of Starrett and Mitutoyo, and Starrett's HQ is just 40 minutes from my door by backroads. I have the slick little Mituoyo 101-117, Starrett No.734 and No.230RL in 0-1" mics, and the Mitutoyo 293-340 1-2" that has the ratchet stop (speeder) thimble, but now lust for the 293-344 I'd used at my employer's shop. I referred a friend to this particular one, and he got it for $129.95 from General Tool & Supply of Attleboro MA.

                        Here's a link to the PDF describing them. I'd need to sell off one of my other perfectly serviceable micrometers to make room, but I just might do it. It's that good.

                        http://www.mitutoyo.com/pdf/ABS1813-293.pdf
                        Last edited by PixMan; 08-07-2011, 07:27 PM.

                        Comment


                        • #13
                          One other thing to mention, though I know I am preaching to the choir where experienced machinists are concerned, is to close the mic from time to time fairly snugly but not tight over some clean paper and pull the paper out from between the anvil and piston of the mic. Almost always you will see some dirt there on the paper and that dirt has thickness. So clean the mic before you use it to determine an important dimension.

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                          • #14
                            Originally posted by DATo
                            One other thing to mention, though I know I am preaching to the choir where experienced machinists are concerned, is to close the mic from time to time fairly snugly but not tight over some clean paper and pull the paper out from between the anvil and piston of the mic. Almost always you will see some dirt there on the paper and that dirt has thickness. So clean the mic before you use it to determine an important dimension.
                            Number one.
                            Gene

                            Comment


                            • #15
                              I've got both friction and ratchet...and like a lot of others, I never use the friction or ratchet feature.

                              Of the two though, I tend to prefer the ratchet type. It still has some sense of "feel" about it. I find the friction thimble has no "feel" to it at all.

                              Whatever you have, take Forrest's advice and practice. Ball bearing races and ball bearings are good to practice on because they're accurately to size and easy to get. Just don't look at the thimble while you measure something that you know the correct size of.
                              ----------
                              Try to make a living, not a killing. -- Utah Phillips
                              Don't believe everything you know. -- Bumper sticker
                              Everybody is ignorant, only on different subjects. -- Will Rogers
                              There are lots of people who mistake their imagination for their memory. - Josh Billings
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