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  • Black Granite Surface PLates

    MSC has a sale on the import black granite surface plates with free shipping on orders over $25.
    I always wanted a knock-a-round plate for stuff like inking and rubbing parts and when I need to tape a piece of sandpaper down and work a part flat etc. I won't use my good Starrett plate for anything like this.
    These are graded just like any other plate, tool room grade etc. But........ are they really as graded??

    JL..................

  • #2
    I have found them to be perfectly good in general. You can get a bad one of anything made, if unlucky.
    Kansas City area

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    • #3
      Your sandpaper backing paper isn't perfectly flat, it will also ripple and create rounded edges around the part. An import surface plate will be more than enough

      (woodcraft also sells them)

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      • #4
        For layout and holding a piece of emery they will be more than good enough. What is "inking". Are you meaning bluing as in scraping? That is something you should reserve for your best plate, its the most demanding of accuracy of any work you're likely to do.
        in Toronto Ontario - where are you?

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        • #5
          Originally posted by Mcgyver View Post
          For layout and holding a piece of emery they will be more than good enough. What is "inking". Are you meaning bluing as in scraping? That is something you should reserve for your best plate, its the most demanding of accuracy of any work you're likely to do.
          If you're doing demanding work then I'd agree. But if working something to a "flat enough" grade there's nothing wrong with a lower grade of plate. It all just depends on what sort of final product we require.
          Chilliwack BC, Canada

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          • #6
            I have two "chinese tombstones".

            They blue up fine against each other, but were bought years apart, from different sources. Barring an outlandish coincidence, they are both flat enough for any normal scraping reference use, and have proved to be so. As mentioned, you can get a bad one of anything, but in general they seem to be fine.
            1601

            Keep eye on ball.
            Hashim Khan

            Comment


            • #7
              Originally posted by BCRider View Post
              If you're doing demanding work then I'd agree. But if working something to a "flat enough" grade there's nothing wrong with a lower grade of plate. It all just depends on what sort of final product we require.
              I think that's kind of what I said....or at least meant. Remember, Joe says he has a good plate so its not a question of whether a crap plate is good enough. If you are reserving one for the most demanding work, that's obviously the one to use for blueing (if that is what inking means) where you need the most accuracy. What are any of us up to that would need more accuracy than that? Unlike milling or grinding, with scraping you can't just move the tolerance around ie 'people who say good ' nuff' lol....you are somewhat constrained by whats a normal thickness of blue and the small DOC.


              I have two "chinese tombstones". They blue up fine against each other
              how did you do you that? I think it would be a challenge to assess how thick the blue is, and hence how well they matched. Unlike a scraped part, it s difficult to get a read of granite and also know there was no rocking. Plus you need do to in different directions.

              I can tell you scraping to a crap plate can be very frustrating. Take a largish piece of cast iron, say 8x8 or 10 x 10 and scrap it flat. Notice as you're trying to move from zones to points you get different readings every time as you spot. Arg. BTDT, waste of time.

              In any event, the point is not whether a crap plate good enough or not, you go with what you've got. its that if you have choice as the OP declared, having more than one plate, its a no brainer that you use the higher grade banded one (assuming its in good shape, not worn out) that should be the one to use for scraping. It may all be academic as we still don't what inking is. Perhaps Joe is tattooing up the plates
              Last edited by Mcgyver; 12-07-2016, 08:52 AM.
              in Toronto Ontario - where are you?

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              • #8
                One thing about a black granite versus pink. They clean up easier. In my experience it is very hard to get all the blueing out. Besides I think that Starrett uses pink as if it is something special. Remember granite and glass were initially war time substitutes as cast iron surface plates could not be produced fast enough. Lapping is a lot faster than scrapping. In a home shop most times a shop grade plate is fine. Inspection would be nice. Lab rated is overkill
                Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.

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                • #9
                  Originally posted by Mcgyver View Post
                  ...


                  how did you do you that? I think it would be a challenge to assess how thick the blue is, and hence how well they matched. Unlike a scraped part, it s difficult to get a read of granite and also know there was no rocking. Plus you need do to in different directions.

                  ...
                  How do you spread blue on the plate normally to scrape to an iron piece?

                  Right... that's how I did it for the assessment. IIRC, I did check it with an iron piece (short straightedge) to verify that the blue was normal. Both are black granite so the blue is harder to see. Normally one can judge pretty well from the sheen the blue gives the otherwise slightly dull surface, but that is not a "measurement".

                  Yes, checked in two directions, and took care to keep from allowing tilt.

                  Is it a perfect check? No. I have thought of rigging up a Repeat-O-Meter with a scraped block, a smaller scraped block, and an indicator, to verify if there are any humps or valleys on the two, but have not bothered as of yet. I would probably want an indicator significantly more sensitive than the ones I have.

                  But what is scraped to one also checks as flat by the other, so with that as a secondary check, I declared them to be both as flat as they needed to be.
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    Originally posted by Mcgyver View Post
                    I think that's kind of what I said....or at least meant. .....
                    Ah... fair enough. I'd taken it to be that you intended that ANY scraping jobs should use the Starret.

                    Mind you if I had a good plate and a cheap import plate I'd likely use the good one for anything involving dye marking and scraping. For that sort of use why work with second best even if the job doesn't need to be THAT close? And with an import to use for sand paper lapping and other such jobs it would keep the abrasives away from the Starret. And that's what having a second plate is all about anyway. Right? So it looks like you were right the first time in a round about way? Circular logic at it's best?
                    Chilliwack BC, Canada

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                    • #11
                      Originally posted by BCRider View Post
                      Ah... fair enough. I'd taken it to be that you intended that ANY scraping jobs should use the Starret.
                      .
                      I did mean that.....what I didn't intend mean was some idea like "the only way is with such and such a plate". You can, and I have, used a crap plate, but it can be bloody frustrating. I agree with you the idea of usings abrasives is best done on the cheapo

                      Mind you if I had a good plate and a cheap import plate I'd likely use the good one for anything involving dye marking and scraping
                      why? I don't think wear is overt using the plate; spotting is almost lubricated by the blue

                      imo its the most demanding of work our shops will see, its the work the good plate should be used for. I might be difficult explain if you haven't done a lot of scraping, but I tried to convey the idea it just doesn't lend itself to low classes work: accuracy from scraping is mix of of the thickness of the blue and DOC and the reference flat.....they all kind of want to be in the range for it to work. It just doesn't lend itself well to say, "well today scraping to 1/2 a thou is good enough". It just doesn't work like that...you could try but you might go mental lol. A reference much flatter than the DOC is what you typical, but one less flat would be very frustrating. This is I grant a unconventional way of looking it, just trying to explain that there is sort of an accuracy sweet spot for scraping....driven by a appropriateness of flat reference, blue depth and DOC. Its also not a hard and fast thing, how good is good and how crap is crap (who believes the offshore certs?)....but all things being equal,....

                      I would say abrasives and laying out are for sure for the cheapo, tenths indicator inspections and bluing for scraping are the for the good one.
                      Last edited by Mcgyver; 12-07-2016, 02:24 PM.
                      in Toronto Ontario - where are you?

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                      • #12
                        [QUOTE=Mcgyver;1084274.....
                        why?

                        imo its the most demanding of work our shops will see, its the work the good plate should be used for. I might be difficult explain if you haven't done a lot of scraping, but I tried to convey the idea it just doesn't lend itself to low classes work: accuracy from scraping is mix of of the thickness of the blue and DOC and the reference flat.....they all kind of want to be in the range for it to work. It just doesn't lend itself well to say, "well today scraping to 1/2 a thou is good enough". It just doesn't work like that...you could try but you might go mental lol. A reference much flatter than the DOC is what you typical, but one less flat would be very frustrating. This is I grant a unconventional way of looking it, just trying to explain the reality and some the they whys as the accuracy sweet spot for scraping

                        .....[/QUOTE]

                        With scraping you don;t necessarily hit a specific tolerance on the low side.

                        It has TWO components of accuracy aside from the plate, as you know (but others may not).

                        1) The number of contact points per unit square (commonly an inch)

                        2) The degree to which you can see different heights of contact points as being different (not a "measurement"). ideally there are sufficient points per inch, and they are all the same height within the ability to distinguish them.

                        They are related. Thicker blue contacts points that are lower as well as higher, and that gives you more or less points with thickness. And, to some extent the thickness affects whether the high spots create "bulls-eyes" that show you that they ARE the highest points.

                        A crap plate is one that is not flat, basically, so it would fail to show you similar markings all over a truly flat surface. Therefore you will assume the need to work over the flat surface, and end up making it un-flat. More likely, you would simply make a surface that is not flat, conforming to one position on the plate. if you mark vs a different area, your marks will change.

                        In the worst case, you end up chasing your tail all over as the marks change depending on just where you put down the part do do the marking.
                        1601

                        Keep eye on ball.
                        Hashim Khan

                        Comment


                        • #13
                          Originally posted by J Tiers View Post
                          How do you spread blue on the plate normally to scrape to an iron piece? .
                          yeah, i figure that out. but very smooth surfaces do not spot well and are harder to read - ie why a ground surface makes a poor reference for bluing. They are also heavy so hard to know if you got any rocking. Without 3 and a lot of care, its doesn't tell you that much. I guess it gives some comfort its not a washboard
                          in Toronto Ontario - where are you?

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                          • #14
                            Originally posted by Mcgyver View Post
                            I would say abrasives and laying out are for sure for the cheapo, tenths indicator inspections and bluing for scraping are the for the good one.
                            I think that's what BCRider was saying.

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                            • #15
                              Originally posted by J Tiers View Post
                              In the worst case, you end up chasing your tail all over as the marks change depending on just where you put down the part do do the marking.
                              No one dies, but that is still a bloody awful case and why you want to use your best plate. actually there is a worse one, your plate is smooth but not flat. say convex. you make a reference from it, replicating the curve and proceed to scrape this error into some big machine rebuild.

                              Blue thickness can be varied somewhat (there is a optimal thickness you end up with for finish work) but DOC is a also both a constraint and there is what I will call (with license to make the point) the sweet spot of accuracy when scraping. Of the three DOC is not easily varied, its a around a tenth on point with a hand scraper. Those unfamiliar (and I know you're not one) might think anyone involved in scraping is a hotie totie HSM elitist or such BS conclusions with all this talk of tenths.....but the reality is that's just what a typical pair of Mark I arms generate. That and the fact that machine tool bearing surfaces do benefit from that level of accuracy.

                              In most things we do its reasonable to say well I only need .002" on this part so I'm just going to make to the .002" I need, even if on the previous job you needed something smaller. You use the machines in a manner that produces the part within tolerance. Scraping isn't like that its not sensible to extend that sort of thinking to it because it just creates frustrations
                              Last edited by Mcgyver; 12-07-2016, 03:54 PM.
                              in Toronto Ontario - where are you?

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