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  • #16
    Nothing MIDGET about this ego.

    GOD has spoken.
    "four to tow, two to go"

    Comment


    • #17
      I am a fairly new member to this forum, but I am a long standing member of several other bulletin boards in various fields of interest, and all I can say, is that the overall attitude of the folks on this board is typically kind and courteous. I have personally found it to be a "breath of fresh air" so to speak, in the numerous online communities I frequent.

      I have never much understood the point behind "flaming" and the like. I understand that it can be frustrating for folks with more knowledge, and higher skill level than others to answer the same questions over and over, when in most cases the information sought is readily available for one to research and understand on their own. However, in the short time I have been here, I have seen other new members post similar questions to ones I have had, and too which I found my answers and to which those answers turned out to be fairly simple. I have not yet seen one complaint from the long standing members, that we young folks sometimes do not take the initiative to research our own questions before seeking answers from people who quite possibly have just answered it the week before.

      My point being this, if you already think you have all of the answers and knowledge, if you are not here to share said knowledge in a courteous fashion, then what are you doing here friend? I read through your 8 posts last night when you first replied to this thread, most were bullying, demeaning, and condescending. I personally don't think there is room for that attitude in this particular online community.

      As for Rick, I think you do an excellent job in your articles. I read them with great interest, and glean what I can. It is nice to see someone reviewing products and trying to take a scientific approach, and give unbiased information. The beauty of having a brain, is that I can research what is said, and try to form my own conclusions from a more complete picture.

      Later,
      Jason

      Comment


      • #18
        tdmidget,

        If you had researched all of this as carefully as you claim, you would know that the digital interface of the Mitutoyo instrument is different from the chinese versions and as a result, it is NOT compatible with the Shumatech DRO. As for the DRO usage, Rick's other papers indicate that that is something he was doing. Furthermore, people use the Shumatech DRO because it can be made cheaply compared to a commercial DRO. A lot of forum members here make instruments and other things that as a well funded pro, you might have the luxury of just buying.

        Finally, you still don't get the temperature compensation argument. I don't think Rick or anybody else would honestly believe that the cooled part in the caliper is a "true" error. The ratio of the size of the cooled part vs. the size of the part with the cooled caliper does however show that the caliper isn't compensated. Once again, if you had read up on this, you would know that the Shumatech system takes readings off of the caliper electronically using an interface which was probably used for factory testing. As a result of getting the raw data, users of the device are not protected from misinterpreting the precision and accuracy of the results by the caliper's display and instead, signal processing must be done on the shumatech control board. This processing is designed by the users of the system since the shumatech is an open project.

        I am sure that you are very good at what you do in your own right but I must say that you are behaving like a private trying to do a general's job here on this thread. Your attitude in this thread will earn you stars alright but they will be circling your head ala bugs bunny rather than gracing your collar ala Eisenhower.

        I bid you good day.

        --Cameron

        Comment


        • #19
          Notice I made NO reference to a Shumatech DRO. I pointed out that the Mitutoyo Quillmate is a simple and accurate adaptation of a caliper to this application.
          My old man always said "Never argue with someone you have to educate first" Guess he was right.
          And again THERE IS NO SUCH THING AS A TEMPERATURE COMPENSATED CALIPER. I see none of you have been able to find one.
          Last edited by tdmidget; 06-02-2007, 10:03 PM.

          Comment


          • #20
            Metrology is a very demanding science. There are certain procedures and methods that must be followed. I am not a metrologist, but I do have some idea of what is required to calibrate and evaluate precision measuring instruments as well as some of the appropriate terminology.

            tdmidget's statements are correct. Normal measuring instruments are not temperature compensated, but rely on the instrument and part to be at equal temperatures. Precision measuring is done in carefully temperature and humidity controlled rooms, and the part is usually allowed to equilibrate for 24 hours prior to measurement. The parts and instruments are usually handled at the minimum, and held with chamois or other means to prevent the heat of the technician's hands from affecting the measurement.

            Precision measurements are usually taken by differential measurement, comparing the part to a stack of Jo blocks of known accuracy with an accurate DTI.

            To evaluate an instrument such as the HF caliper, a measuring system of at least ten times the accuracy of the caliper must be used, and the calibration carried out under lab conditions. Some idea of the function of the caliper can be made by comparing it to itself, or a known accurate standard, but an accurate assessment of it cannot be made.

            The HF spec sheet does not say anything different than the specs I previously quoted for Starrett calipers. HF is possibly a bit more optimistic about the accuracy of their calipers, but dial and digital calipers are at best capable of +- 0.001"/6" of travel. As travel increases, so does the error. The HF sheet states this in a somewhat different manner, but it is still the same number.

            Repeatability is 0.0005", which means that the caliper will read the same, possibly incorrect, dimension of a given part within 0.0005" each time.

            The different dimensions achieved at different temperatures are not errors, but are actual dimensional changes. This displays the reason materials and instruments must be at equilibrium when measurements are taken.

            The end use of the slider whether as a caliper or on a DRO has no bearing on the accuracy of the instrument. It is what it is, and that will not change.

            Rick's write up can be used to understand the operation of the sliders, and when used with his other information on Shumatech applications, is of use to those interested in pursuing that application.
            Jim H.

            Comment


            • #21
              Aside from JC's, response, I'm not really sure what any of you are arguing about. Rick's jitter article was good (although a bit long-winded), but with this new article he seems to be trying to convince himself that the Harbor Freight calipers are more accurate than the manufacturer's +/- 0.001" accuracy spec. Even the highest quality Mitutoyo and Starrett calipers are only accurate to within a thou, and they're built with much better quality components (with stainless-steel beams and carbon-fiber pcb overlays).

              But none of this has much to do with the Shumatech DRO. It just reads pulse counts over a serial interface and displays them. Natively it reads the Sylvac protocol, but many of the Shumatech owners (including myself) use glass scales with the QCC (quadrature) converter, if they need more accuracy than the Chinese scales provide.

              As several people here and on the Shumatech group have pointed out, you can't expect a whole lot of accuracy out of $19 caliper, and although the Sylvac protocol samples and interpolates 20480 steps per inch, the physical caliper itself is far from capable of that accuracy due to the way the Chinese manufacture the zig-zag PCB board mounted to the beam, or the comb sensor points in the reader head, let alone the straightness/flatness of the beam and the repeatability of the mechanical pinion (which is especially subject to wear).

              In any event, there's really not a lot of point in building a Shumatech DRO anymore. When Scott built the Shumatech in 2003, there wasn't such a thing as a budget DRO, and with Scott's design, many of us were able to build a complete DRO system for hundreds less than the cheapest Mitutoyo or Accurite system.

              Fast-forward 4 years, and it will cost you around $350 to build the head unit (including the case, overlays, power supply, internal cables,...), plus scales, connectors, cabling, and a PIC programmer, ... and you're pushing $500. For about the same price, you can buy a Birmingham/Uniq glass scale system with far greater accuracy:

              http://cgi.ebay.com/ws/eBayISAPI.dll...m=120126863867

              Personally, I've switched to Jenix DRO systems on my mill and lathe. I got tired of dealing with the QCC's, the 3-digit display, ...
              I think Chris Melbourne, one of the charter members of the Shumatech group, summed it up perfectly here:

              From: "cba_melbourne"
              To: [email protected]
              Subject: [ShumaTech] Re: Jitter
              Date: Wed, 30 May 2007 03:31:00 -0000

              Brian, I personally feel that, if one wants or needs a DRO without jitter and reliably more accurate than 1/20mm = 0.05mm = 0.002", then it has to be a glass scale. In the long run you save both money and time, probably lots and lots of time. I recommend NOT to go the chinese scale route if one needs better than 0.05mm accuracy.
              ...

              At the time, Scott Shumate designed a wonderfully great DRO for chinese scales, for the first time affordable to te average home/hobby machinist. At the time, there were no "cheap" chinese glass scales, nor cheap chinese DRO display units availabe. Times have changed since.

              If me personally was to start all over today, I would now go for glass scales. Today I would be hard pressed to decide for a diy DRO-350 or one of the chinese/Korean DRO display units available cheap and ready to use from eBay. But since I already have built two DRO-350, any idea to improve on it are highly welcome to me.
              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

              Comment


              • #22
                The only reason I brought up the DRO application is because the DRO application reads raw counts out of the caliper and thus it would be easy to be deluded into believing more accuracy than is possible as information not available on the caliper itself that is available on the DRO system.

                As far as actually trying to take measurements with the instrument, I think that tdmidget and JCHannum are right about procedures and temperatures. Just because Rick proved that the caliper isn't temperature compensated, which lots of others knew, it doesn't invalidate the method he used to prove it. I don't think anyone seriously believes that the contraction of the part being measured when cooled is actually an error in the instument.

                I don't have a dog in this fight and will likely never own a shumatech DRO. I mainly argued this trying to put it in perspective of what I think Rick was thinking and why he did what he did since I have read some of his other articles.

                It takes a lot more guts to publish an article like Rick's than it does to rip it to shreds via ad hominem attacks. If tdmidget had been a touch more polite in his critique, I probably wouldn't have bothered on this thread at all. From personal experience however, I hate to see somebody who obviously put in honest work on something get flamed rather than constructively criticized.

                As I've said before on this thread, it's not education that makes you right, it's being right that makes you right. While Rick's paper may not be the pinnacle of metrology practice or the last word on HF caliper accuracy, he asked a few questions and tried to answer them which is more than many have done. I salute him for this.

                I'm done on this thread as there really wasn't much substance here to begin with and my motivation was mainly defending someone from critique that seemed mean and out of context. I may test an HF caliper against my gage blocks one of these days however.

                --Cameron

                Comment


                • #23
                  Let's get back to the basic requirement - use of available "DRO" sources.

                  Well the air seems to have cleared and the dust settled - which is more than can be said for the discussion topic.

                  Up-front I will say that I have a brand new "still in the boxes" set of "real" DRO's that I was going to fit on my mill - lathe - perhaps later.

                  My requirement is for a cheap but functional reliable "DRO" for use in my shop in its normal everyday environment. "Super-dooper" machining is not generally required. But if needed I'll either buy the required machine or "farm it out" - if I can't do it "in house".

                  My first, and to this stage only (thanks to Rick's excellent on-going work) consideration was to use sets of digital calipers (other than the jaws and depth guage).

                  Given the considered advice to date from ckelloug, Rick and others in a similar vein that still remains a viable option for me.

                  And I wanted to know the "ins" and "outs" of using it.

                  My concern is that I cannot be sure that just turning the hand-wheels and "counting off" will do the job. I could set up a "measuring rod" pre-set and use a DTI to ensure the machine travel was what was required. But it is a bit of a PITA and using the beam, reader, "re-set" and "zeroing" facilities included therein I could get a reasonably good "DRO".

                  If it is consistently accurate to say +/- 0.001" over say 12.000" (+/- 0.02mm over 300mm here) that will do me very well indeed. At such low cost I can more than afford to "waste" them and keep "spares" if needs be.

                  Its a risk I take as they are not warranted to be "suds-resistant" either - OK?

                  Now I already do have a 300mm digital height guage and a set of Class 2 ("Chinese" slip guages) as well.

                  So far as I can tell, and as good as I need, all of these items have digital display's or "Read-outs". And despite the purists definition/s or opinions otherwise - they DRO's and that is what I want and need and that is what I've got.

                  Thanks mightily to Rick and ckelloug as I now know "where I'm at" and can now proceed with confidence in my equipment and their advice.

                  The acrimony on this site was not a total loss at all as if it had not been so spiteful and so personal and vindictive so early in the piece ckelloug would not have intervened and participated at the very professional (in every)way and level that he has - thank you.

                  And Rick, I hope that there has been some gold assayed from the dross and to continue the analogy, there have been some remarkable diamonds (rough and smooth) that are priceless members of this forum who put their heads up and tool a chance at having it shot off. Please do continue and get advice and re-do etc. as you have done as it has been top-rate so far as I am concerned.

                  I've re-read what I've said in regard to some or Rick's previous posts and I regret some of the things I said - and I apologise unreservedly - notwithstanding that I meant well at the time - and still do.

                  Now let's move on positively and keep focused on the issues - and no more "playing the man instead of the ball" stuff.

                  Thank you.

                  Comment


                  • #24
                    Originally posted by tdmidget
                    And again THERE IS NO SUCH THING AS A TEMPERATURE COMPENSATED CALIPER. I see none of you have been able to find one.
                    BOLLOCKS

                    That's been there years.


                    .
                    .

                    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                    Comment


                    • #25
                      Originally posted by John Stevenson
                      BOLLOCKS

                      That's been there years.


                      .
                      Howling,-
                      True British understatement.

                      Rigger

                      Comment


                      • #26
                        Maybe 3rd time is a charm

                        OK guys, I'm ready to climb back on top of that barn with my copper rod during the lightning storm.

                        Version 3 of my article is now ready for peer review. I especially encourage my most pasionate critics to give it a close read and tell me what you think.

                        You can find the article at

                        http://rick.sparber.org/Articles/PAC/PAC3.pdf

                        Thanks in advance to all that take the time to contribute to this review. All of us are smarter than any one of us.

                        Rick Sparber
                        Rick Sparber

                        [email protected]
                        web site: rick.sparber.org

                        Comment


                        • #27
                          Rick did you read Laslo's post and attachment? If so , why beat this dead horse? When even the most ardent early proponents of this make do system now say that you can buy a real one, more accurate, and ultimately cheaper, what's the point? Does everyone here adhere to Wareagle's avatar "Why buy it for $2.00 when you can make it for $20.00"? If this is a hobby, for making model engines aircraft, widgets, whatever, then why waste time making junk when you could buy the item and go to work. As an analogy, if you were stamp collectors, instead if buying, trading, and pasting stamps in an album you would go out, cut a tree, build yourself a tiny papermill and waste the rest of your life before you got to the stamps making an album to put them in.


                          Some men , you just can't reach. What we got here is failure to communicate.

                          Comment


                          • #28
                            Originally posted by rgsparber
                            OK guys, I'm ready to climb back on top of that barn with my copper rod during the lightning storm.

                            Version 3 of my article is now ready for peer review. I especially encourage my most pasionate critics to give it a close read and tell me what you think.

                            You can find the article at

                            http://rick.sparber.org/Articles/PAC/PAC3.pdf

                            Thanks in advance to all that take the time to contribute to this review. All of us are smarter than any one of us.

                            Rick Sparber
                            I think you should discuss the hysteresis inherent in digital calipers and how it's different visually from hysteresis found in analog calipers. This has to do with slop in the mechanism found in both styles of caliper, but compounded by rounding errors unique to digital calipers, and illustrated by interesting errors introduced with the ability to zero a digital caliper even when between or near the edge of a sensor step.

                            Comment


                            • #29
                              Originally posted by dp
                              I think you should discuss the hysteresis inherent in digital calipers and how it's different visually from hysteresis found in analog calipers. This has to do with slop in the mechanism found in both styles of caliper, but compounded by rounding errors unique to digital calipers, and illustrated by interesting errors introduced with the ability to zero a digital caliper even when between or near the edge of a sensor step.
                              DP,

                              I don't recall ever seeing hysteresis in my digital caliper. Can you suggest an experiment that will flush it out?

                              A single "sensor step" on these calipers is about 0.05 thou. that is 10 times smaller than the smallest displayed value.

                              Rick
                              Rick Sparber

                              [email protected]
                              web site: rick.sparber.org

                              Comment


                              • #30
                                Originally posted by tdmidget
                                Rick did you read Laslo's post and attachment? If so , why beat this dead horse? When even the most ardent early proponents of this make do system now say that you can buy a real one, more accurate, and ultimately cheaper, what's the point? Does everyone here adhere to Wareagle's avatar "Why buy it for $2.00 when you can make it for $20.00"? If this is a hobby, for making model engines aircraft, widgets, whatever, then why waste time making junk when you could buy the item and go to work. As an analogy, if you were stamp collectors, instead if buying, trading, and pasting stamps in an album you would go out, cut a tree, build yourself a tiny papermill and waste the rest of your life before you got to the stamps making an album to put them in.


                                Some men , you just can't reach. What we got here is failure to communicate.
                                td,

                                I'm confused by your comment. The article is not about the Shumatech DRO, just the Harbor Freight caliper.

                                I have made a major reversal in my position in this latest version. I do maintain that $17 is still a great buy for the accuracy and repeatability that you get from this caliper.

                                Rick
                                Last edited by rgsparber; 06-05-2007, 07:49 PM.
                                Rick Sparber

                                [email protected]
                                web site: rick.sparber.org

                                Comment

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