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Making a CI surface plate

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  • #46
    Originally posted by nc5a View Post


    Jerry's comment has a bit ring to it. Who knows, this could be the start of the Mcphearson Gauge.
    That could get confusing --- names already been claimed for a specific type of suspension/shock absorber ...

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    • #47
      I might be missing something too.

      Does the bar need to be flat along the whole length because you are checking for the accuracy of the sharpening? Or is it primarily used just at the ends to set the height of the wheels from the blade? Because if it's the first then you want something stiff and flat along the entire length. If the second then you only really need it to be exact for some test pads at each end. These two options will certainly set a lot of your parameters.

      And I agree with the others that if you really and truly do need to chase down the trueness and flatness of the bar to within .001 then you need to start with something a lot bulkier. If the critical dimension was the 4 inches where it has to be straight and parallel to .001 or less that's one thing. But if it's the 3/4" dimension that is the important one then I strongly suspect that just how it is handled will cause it to flex out of true by that much. Especially if the weight of the mower will be resting on it while the reel height is being checked. Even doubling might not be good enough in that case. Even cast iron is still effectively a big spring after all.

      I'm like many of the others here that I don't know exactly how you want to use the plate. But even with a tolerance of + .001" surface grinding would be easily good enough. Heck, other than the surface finish even milling it on a bigger milling machine with reasonable condition bed ways would give you that sort of accuracy across that length.

      If you can live with something bulkier then you might consider a thick wall rectangular tube that has mounting pads added and trued up and then with the mounting pads as the clamping reference the reference surface is milled with light cuts and perhaps surface or blanchard ground to give a nice working surface. Something like 4x2x 1/4 tubing should be stiff enough to hold to the stated accuracy.

      I also wonder if for setting the HOC that it's more important to be matched heights at the ends to .001'ish and that the actual height would be a little more open like .005'ish.
      Chilliwack BC, Canada

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      • #48
        Originally posted by nc5a View Post
        Who knows, this could be the start of the Mcphearson Gauge.
        if he makes a ton of money from it, he'll be doing the Mcphearson strut
        Last edited by Mcgyver; 01-10-2022, 09:25 AM.
        in Toronto Ontario - where are you?

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        • #49
          Originally posted by Mcgyver View Post

          if he makes a ton of money from it, he'll be doing the the Mcphearson strut
          Alright --- go to your room and sit in the corner for 1/2 hour... and don't come back out till you know you can behave yourself lol

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          • #50
            Originally posted by rmcphearson View Post
            Yes, if I can have them made of granite that will work. I don’t know where to go for that and I suspect CI will be adequate and cost less. My customers want their gauges to measure to an accuracy of 001”. So my plate that they are using to calibrate their gauges needs to be of similar accuracy. The prototype was milled, there was a .003” bow in the middle. That was not acceptable. Y’all have me wondering if 3/4 is not thick enough.

            Thanks for the suggestions. Even if I farm this out to a grinding shop, I need and want to learn to scrape to make more prototypes and maybe even sell some prototypes. I’m ordering the scraping tools and supplies now.

            I’ll post a video of the tool soon.
            I haven't seen this mentioned elsewhere in this thread.

            As a rule of thumb, calibration standards are usually specified at an accuracy several times greater than the characteristic being measured, factors between 4x and 10x are common. If you need to calibrate a tool to 0.001" accuracy, your standard, following this rule of thumb, needs to be between 0.00025 and 0.0001".



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            • #51
              Originally posted by rmcphearson View Post
              https://youtu.be/0PqFFPVxjXI
              This shows just two of many brands of gauges. There is a market for a tool to calibrate them accurately.

              I’d like to discuss home shop machinist stuff relating to my plate…

              Thank you to those of you helping.
              Roland, after reading your first post again and watching your videos I understand your project a little better. So you want to make a special plate to calibrate and set the depth of cut gauges. In such case I would agree that .001" flatness is required. For that you would need a plate with substantial rigidity, 3/4" thick material is out of the question. The suggestions in my previous posts are still applicable.

              What I don't understand is why do you need a special plate. What's wrong with a standard 18 x 24" granite plate? It is more than accurate enough for your needs and it does not cost that much. It does not have a counterbore, but do you really need one? Just put 2 gage blocks on a surface plate and set you DOC gauge on top of them and zero the indicator. Of course, that would mean the death of your project...

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              • #52
                Originally posted by genea View Post

                I haven't seen this mentioned elsewhere in this thread.

                As a rule of thumb, calibration standards are usually specified at an accuracy several times greater than the characteristic being measured, factors between 4x and 10x are common. If you need to calibrate a tool to 0.001" accuracy, your standard, following this rule of thumb, needs to be between 0.00025 and 0.0001".


                Excellent info. Thank you.
                -Roland
                Golf Course Mechanic

                Bedminster NJ

                Comment


                • #53
                  Originally posted by mikey553 View Post



                  What I don't understand is why do you need a special plate. What's wrong with a standard 18 x 24" granite plate? It is more than accurate enough for your needs and it does not cost that much. It does not have a counterbore, but do you really need one? Just put 2 gage blocks on a surface plate and set you DOC gauge on top of them and zero the indicator.
                  That would calibrate the distance from the indicator tip (crown of the mushroom) of the blade catch to the business surface of the gauge. That’s not how the gauge works. The distance being measured is from the underside of the catch to the business surface of the gauge. You’ll see when I upload the video to my YouTube channel.
                  -Roland
                  Golf Course Mechanic

                  Bedminster NJ

                  Comment


                  • #54
                    Originally posted by A.K. Boomer View Post
                    Wow that's still a chunk of stone... thanks for letting us know, by all the staining it looks like it gets it's fair share of use...

                    It almost looks regulation billiard table size --- you thinking what im thinking? little bit of felt and some rails and you have the worlds most precision pool table....
                    If it was made from black granite there would be no fingerprints or discoloration visible, a black plate always looks pristine

                    I use a black granite plate for small parts at the machine, this does not require a forklift to move.
                    8 X 12 X 3" Starrett


                    Cost less then $300.00

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                    • #55
                      Here are the short videos that explain my plate. Yes, they are awful and yes I misspelled gauge. I don’t want customers to see this. I’m posting them here purely for feedback about manufacturing them.
                      https://youtube.com/shorts/GrujdS1s97g?feature=share
                      https://youtube.com/shorts/nBaMCzqDe98?feature=share
                      https://youtube.com/shorts/eEfpZIHSlRQ?feature=share
                      https://youtube.com/shorts/biBma2_qkCU?feature=share

                      I have ordered two grey iron 24” straightedge rough castings from two vendors here on the west coast. If I can get one of them to widen the molds to 4” for me I think I’ll be in business.
                      -Roland
                      Golf Course Mechanic

                      Bedminster NJ

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                      • #56
                        Roland, I have watched your videos, but failed to understand the purpose of the counterbore. Maybe you are trying to measure the thickness of the remaining lip? But you can use standard gage blocks to set the gage to size. By the way Grizzly sells the 18 x 24 x 3" surface plate for $80.
                        Good luck with your project, but I am done with it.

                        Comment


                        • #57
                          After watching videos I’d think a few gage blocks to calibrate the indicator and checking flatness of the flat iron gage on the edge of a surface plate, one side at a time, would accomplish same thing.

                          Heck, a carpenter square would show if the flat iron was warped. Body heat during use will probably move it further than you are trying to measure.

                          More power to you if you can sell’em though.

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                          • #58
                            Y’all are trying to poke holes in my plate! That’s not nice! But it is necessary. Y’all are correct, there is a multi step alternative. It don’t happen. There’s a lengthy explanation which i will not attempt.

                            This reminds me of the time I was on watch duty on a frigate off the mouth of the Amazon and a passing ship desperate for drinkable water kept ignoring my advice to “cast your buckets down where you are.” They thought I was three sheets to the wind.
                            Last edited by rmcphearson; 01-11-2022, 11:39 AM.
                            -Roland
                            Golf Course Mechanic

                            Bedminster NJ

                            Comment


                            • #59
                              Originally posted by rmcphearson View Post
                              Y’all are trying to poke holes in my plate! That’s not nice! But it is necessary. Y’all are correct, there is a multi step alternative. It don’t happen.

                              This reminds me of the time I was on watch duty on a frigate off the mouth of the Amazon and a passing ship desperate for drinkable water kept ignoring my advice to “cast your buckets down where you are.” They thought I was three sheets to the wind.
                              Because the Amazon river has such a large flow, the salt water is displaced by fresh from the mouth of the Amazon.

                              Comment


                              • #60
                                I gotta tell you, it has been quite a while since I have been on a golf course, but I am going to visit one as soon as I can. I really have to see this layer of grass that is 1/8" or less thick. I want pictures.
                                Paul A.
                                SE Texas

                                And if you look REAL close at an analog signal,
                                You will find that it has discrete steps.

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