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  • wringing gage blocks?

    Hey guys,

    I have been reading about gage blocks. My understanding is that they are a standard reference for the shop that you can use to check the accuracy of your measuring tools and they can be used in your set-ups.

    I have come across the term "wring" with regard to these blocks. Can somebody tell me what this means and how it is used?

    Thanks,

    Tim

  • #2
    Think of twisting a dish rag to "wring" out the water
    You do that by placing the "Jo" blocks together at 90 degrees to each other, and twist the blocks while exerting a light pressure.

    The blocks are so perfectly made, that all the air is squeezed out and molecular attraction causes them to stick to each other ( like glue !)
    having the air removed is important to maintain "stack up accuracy"

    These blocks were invented by Mr Johanson and were promoted by Henry Ford.
    thats why the term "Jo" blocks occurs with old shop guys.

    Rich
    Green Bay, WI

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    • #3
      Make sure that they are clean and dust free prior to wringing!

      To add to Rich's post with a little "visual"...

      http://www.starrett-webber.com/GB46.html
      Last edited by Glenn Wegman; 08-21-2009, 09:11 PM.

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      • #4
        First quarter machine shop student get the gage block lessons and unless you work in an inspection lab you will never touch them. You will be busy shoveling piles of chips into a dumpster.

        If you have a home shop you best put them inside so they dont rust, you will never use them.

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        • #5
          I have to disagree with you there- I calibrated all my mikes against a relatively cheap set bought at a flea market, all of the mikes were off, some as much as .005 from what they should have been. I discovered issues with my dial calipers too.

          Certainly a 1st class set is probably overkill, but a 30 pc set of middling to low price will help a lot.

          Greg

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          • #6
            That is really neat! I had no idea... just a reminder of how far I have to go before I can legitimately call myself a machinist

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            • #7
              As a machinist in a job shop I never had the need to use them. There was a set at most the shops I worked at but I only once used them and didn't really need to.

              About 1995 I had the opportunity to buy a deluxe set from the International factory here and the last calibration guaranteed them to one millionth of an inch. Well, I wiped them off and lubed them and put them on a shelf and have opened the box a few times to see if they are still ok and not rusty. I did use them twice to check a measuring tool.

              Oh, and yes, you can "wring" several of them together and lift them by the top block and they will stick together. It's just FM.

              I seem to have a few shelf queens in my collection of tools.
              It's only ink and paper

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              • #8
                I have a very small set of gage blocks. They are Starrett, nine pieces from 0.1000" to 2.000". They get occasional use.

                When checking a micrometer to a gage block, particularly one from a cheap set purchased at a flea market, and seeing a difference, how do you know that the micrometer is off and not the gage block? Or, for that matter, that both are not off. About all you can really say is that the two are not in agreement.
                Jim H.

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                • #9
                  No question that in the case of a used out of calibration or cheap set the cert shouldn't be assumed to be correct- but even so, unless they're really a mess the blocks should be good to a tenth or so, plenty for calibrating mikes to a thousanth.

                  No way that approach is good enough for serious metrology, but its a big help for a HSM when stuff made to the same dimension using one measuring tool won't match up with other stuff made to the same dimension as measured by another.

                  I've found it quite interesting to see measurements taken by different mikes converge after calibration, and it does help establish confidence in the feel of dial calipers- its so easy to "press" them to make that OD measurement be what you think it should be and end up out.

                  Greg

                  Comment


                  • #10
                    Slip into a set of "Jo blocks"

                    I don't use mine all that often - but they DO get used and they can be mighty handy - if REALLY required.

                    Here is a pic of three of my "Jo blocks" (I am 72) "wrung" together to both set/check a micrometer and a digital inside caliper.





                    The caliper is accurate to 0.01mm (~0.0004") and I like to make use of that accuracy. If I set the micrometer and the caliper to the "Jo" blocks I can be sure of their accuracy when set. The micrometer and the calipers effectively become comparators rather than individual measuring instruments. I get a much better assurance of accuracy that way than I would if I use the "end of range" guages that came with the micrometer and then used the micrometer to set the caliper.

                    Most times for work that does not require accuracy better than 0.02mm (0.0008"), I leave the slip guages in their box as the usual settings and checks for micrometers are quite accurate enough.

                    Most times for bores etc. I use these and a micrometer as I can "hold" an accuracy of 0.01mm (~0.0004") with care although most work is pretty easy at 0.02mm (0.0008"):


                    Otherwise I use machinists rulers and digital calipers. I do give my carpenters 1 metre (black and white - for optimum contrast in a dark shop or job) a good work out too as they are very accurate and as they have "inch" on one side and mm on the other they have a built-in metric/inch conversion scale!!

                    Its just a matter of using the tools for the level of accuracy that the job warrants.

                    My advice is to get a good set of slip guages as they are not expensive and are quit useful - and at times essential. They are available at Little Machine Shop and CDCO Tools (both in th USA) which are very good traders in all respects.

                    Comment


                    • #11
                      Somewhat OT reply

                      I remember that as an undergraduate Physics I set up a demonstration where I passed light between a pair of "Jo" blocks that were shimmed apart a fraction of the wave length of light (probably green) and it was polarized. I don't remember all of the details but it did work. There was some fringing since the light source was a mix of wavelengths but it did work. This was a few decades before lasers (generating a single wavelength) were discovered

                      Vernon
                      Last edited by TxBaylea; 08-21-2009, 11:06 PM.

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                      • #12
                        I have two sets of Starrett/Webber grade 2 gage blocks and I send one set to Webber every year for certification. After finding the best set, I keep that set certified yearly and use the second set for sine plates, sine bars, and the compound magnetic sine chuck on the surface grinder. I use them weekly as I have a Sunnen horizontal honing machine and a universal ID OD cylindrical grinder and I set bore gages using them and also verify micrometers regularly before any finish work. I wouldn't be without them! I guess it depends on what type and tolerance work you do.

                        Glenn

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                        • #13
                          Originally posted by TxBaylea
                          I remember that as an undergraduate I set up a demonstration where I passed light between a pair of "Jo" blocks that were shimmed apart a fraction of the wave length of light (probably green). I don't remember all of the details but it did work. There was some fringing but it did work.

                          Vernon
                          Ok.. so... whats fringing?

                          Thanks guys, I really appreciate your responses. I just bought a digital mic and was checking it for accuracy when I realized that I could not be sure that my standard was accurate. Hence the search for gage blocks.

                          Tim

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                          • #14
                            I have a good set bought at an auction that I use all the time, but they also have the base, scribers, "in between" type of set-up, the good webber set with all the trimmings. Mostly I use them in setting gauges like indicals, or doing comparative measurements with an indicator or height gauge.

                            As for the wringing, keep them clean as noted, but I also like to use a very small piece of chamois to do a quick clean of dust and dirt before wringing. If you don't want to do this, use a piece of paper on a surface plate (keep all of this clean) to clean the mating surfaces then give a quick/light blow on them to get a very thin film of moisture for wringing. I have known some machinists to do a quick wipe by their nose (not in their nose) to get a very thin film of very light oil on them (not gooped on).

                            I use them frequently in setting sine bars for inspection or for very close angle milling, setting tapers on a lathe with a sine bar, and grinding angles on a surface grinder with a sine plate or sine vise. If a "production" type of mill/grind job, I do make my own "master gauge block", comparative to a set of actual blocks (grind a piece of un heat treated A2).

                            Depends upon what you want to do and how deep you want to get in it.

                            I calibrate mics on gauge pins though for the most part, bought a few of the real high quality type a few years back for when I need to calibrate for turning work. I still use gauge blocks for when milling parts calibration. Had this beat in my head in my apprenticeship to do this for whatever it may be worth, just secondary.
                            Last edited by spope14; 08-21-2009, 11:43 PM.
                            CCBW, MAH

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                            • #15
                              Originally posted by tmc_31
                              Ok.. so... whats fringing?
                              Tim
                              When you have two VERY flat plates (at least one transparent), in close contact, and illuminate them with one wavelength of light:
                              If they are PERFECTLY aligned (flat to one another), the reflected light will be uniform. If you move them apart, the light will dim, and then become bright.
                              If there is a very slight tilt, light and dark bands will be seen (fringes). The distance between the band is ONE wavelength of the illuminating light. A very small number. For example, a red Helium Neon laser has a wavelength of 6328 Angstroms, or about 25 millionths. It is common in the Telescope/Laser business to align and machine stuff to BETTER than 25 millionths over several inches. Mirrors are an example. I've had mirrors machined, in Aluminum, to 8 millionths over a 14" diameter.

                              Dave J.

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