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I always wanted to learn how to true a machine. I never did. I got some scrapers...

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  • I always wanted to learn how to true a machine. I never did. I got some scrapers...

    Yeah, I finally bought some scrapers. I am afraid to jack some tool up beyond repair, Haha. I dont even know where to start. I have my metal block. Oh Man!! Dont ask and I wont tell you about my fuk up. JR

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  • #2
    Oh? The grind that came with these tools is spot on. I think they are brand new bits. Un ground. JR

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    • #3
      If you lived in Florida, I'd sell you a Bridgeport cheap to work on.

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      • #4
        Personally I find the Andersons hard to use, heavy and rigid....person preference is a bit of flex.....but you've got them so charge ahead. The start should a piece of cast iron, durabar not window weights so its stable and without chill spots. Other materials can be scraped, but its more towards the misery end of the spectrum. Get some good cast iron. Using blue and a surface plate, get it flat. Bonus points for picking a length/size of bar, milling it down, so it can be a dovetail (or some other) reference flat you can then use for scraping other things.

        imo you really want to learn how it all comes together on piece of stock, not a casting. When you get to doing a machine, being able to scrape flat is assumed. Whats needed then is the ability to scrape a whole bunch of flat surfaces in the right relationship to one another (parallel, square, angled etc), then get a perfect fit with its mate...all of which are a new set of challenges. But first step is learning to scrape flat, keep the scraper flat, etc
        Last edited by Mcgyver; 04-02-2022, 05:47 AM.
        in Toronto Ontario - where are you?

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        • #5
          Originally posted by JRouche View Post
          Yeah, I finally bought some scrapers. I am afraid to jack some tool up beyond repair, Haha. I dont even know where to start. I have my metal block. Oh Man!! Dont ask and I wont tell you about my fuk up. JR

          Click image for larger version

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Size:	3.61 MB
ID:	1994841

          Click image for larger version

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Views:	460
Size:	3.07 MB
ID:	1994842


          as mac said, those tools are unground, you cant use them like that, so there's nothing to mess up. You'll need to grind a radius, somewhere in the 60-100 mm range with ~94deg angle. You can use both faces that way. and you need to be able to trim your beard in the reflection. I've just been into scrapping on & off for a year or two. I've struggled with poorly sharpened tools too long, hence the lap in the other thread you posted on.
          "it is no measure of mental health to be well adjusted to a profoundly sick society." -- krishnamurti
          "look deep into nature, and then you will understand everything better." -- albert einstien
          "any intelligent fool can make things bigger and more complex...It takes a touch of genius - and a lot of courage to move in the opposite direction."

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          • #6
            Originally posted by Mcgyver View Post

            imo you really want to learn how it all comes together on piece of stock, not a casting. When you get to doing a machine, being able to scrape flat is assumed. Whats needed then is the ability to scrape a whole bunch of flat surfaces in the right relationship to one another (parallel, square, angled etc), then get a perfect fit with its mate...all of which are a new set of challenges. But first step is learning to scrape flat, keep the scraper flat, etc
            i've been learning how to scrap on & off for ~2 years now & I still haven't touched a casting. I've built a few things to practice on & way less nervous about messing something up. I am going to have to address my lathe soon though, trying to tool up & skill up for that.
            "it is no measure of mental health to be well adjusted to a profoundly sick society." -- krishnamurti
            "look deep into nature, and then you will understand everything better." -- albert einstien
            "any intelligent fool can make things bigger and more complex...It takes a touch of genius - and a lot of courage to move in the opposite direction."

            Comment


            • #7
              Originally posted by RB211 View Post
              If you lived in Florida, I'd sell you a Bridgeport cheap to work on.
              Yeah, I know there is a joke in there some where. Swamp land and the need for me to purchase some? lol JR

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              • #8
                [QUOTE=Mcgyver;n1994849] Bonus points for picking a length/size of bar, milling it down, so it can be a dovetail (or some other) reference flat you can then use for scraping other things./QUOTE]

                And there you go, shattering my dreams of even attempting this new thing. Throw the angles in there, thank you very much

                JR

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                • #9
                  Originally posted by mtraven View Post

                  You can use both faces that way. and you need to be able to trim your beard in the reflection. I've just been into scrapping on & off for a year or two. I've struggled with poorly sharpened tools too long, hence the lap in the other thread you posted on.

                  as mac said, those tools are unground, you cant use them like that, so there's nothing to mess up. You'll need to grind a radius, somewhere in the 60-100 mm range with ~94deg angle.
                  Thank you.. I didnt know the keenness of the tool was that important.
                  \I am used to sharpening tools.
                  Thanks. JR

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                  • #10
                    The sharpness is really important because the DOC is so small. If you're taking off a tenth, your edge has to be much finer than a tenth or it will just bounce along the surface. You kind of get into a zone when doing this, or at least I do, then you notice something wrong, a disturbance in the zen, things aren't that good anymore.....that's the work telling you its time to resharpen. And when you need an edge so fine as to be able to take off a tenth, that happens quite frequently. Probably should make a lap before you get that cast iron lol. 10 micron diamond paste is just the thing
                    Last edited by Mcgyver; 04-02-2022, 08:17 AM.
                    in Toronto Ontario - where are you?

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                    • #11
                      Take one of Richard King's classes. He holds them on the left coast almost yearly.

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                      • #12
                        Learning how to "true" a machine and learning how to scrape are two different things.

                        -D
                        DZER

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                        • #13
                          Originally posted by Doozer View Post
                          Learning how to "true" a machine and learning how to scrape are two different things.

                          -D
                          yeah, but they end up going together.... the goal of scraping is to have the machine trued-up as far as the geometric relation of the axes.

                          Those appear to have HSS blades, although the scrapers will accept carbide, and carbide can be brazed to the HSS blades. Hss is "ok", I have some, but it dulls faster.

                          You want a radius in the wide direction, as noted, and the edges should be about 5 degrees negative rake in the thin direction. It's convenient to grind two edges, so you can flip the tool over for a fresh edge before re-sharpening.

                          "Scraping" is really just the process, the goal is correct alignment (or "truing") of the scraped parts. In the process, you look for details, the pattern of spots you see when bluing from a known flat surface, and also the character of the spots. That tells you what you need to do to improve the scraped surface.

                          The "alignment" part is looking at the entire surface, and what it's relation is to other surfaces. That can tell you where you need to scrape more to bring down the high end of an undesired angle, etc.

                          So it's a combination of paying attention to overall characteristics, and the details of any given surface.

                          You need to have the detail part "down", so you start by practicing getting a flat surface with a suitable number of contact "points" per square inch (or cm) for the use it will be put to (reference surface; 40 points per square inch, sliding surface; 15-20, non-moving surface; 10-12. Also the percentage of area that is contact point, vs low spots. Then move on to making it both flat AND aligned (parallel, perpendicular, or at a particular angle) to other surfaces.

                          ideally, the surface "comes in" to flat at the same time it is in perfect alignment. So the two considerations are worked on together.

                          Sounds hard, really just takes practice and a certain ability to visualize the relation of parts.
                          Last edited by J Tiers; 04-02-2022, 01:30 PM.
                          CNC machines only go through the motions

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                          • #14
                            If you have the scrapers I'm guessing that you have the surface plate and some flavor of transfer ink/dye already too.

                            I'd think just starting with a block of metal with a milled face would be a good place. Or if you want to work on something you can actually use perhaps buy a cheap angle plate and scrape one face? Then as a next step check the corner for square and scrape the other face so it's both flat and square to the first face?

                            Got any of the cheap Kurt style milling vises? I wouldn't want to do one of those as a first project but scraping the base first so it's flatter than stock would be another good project. Then the bed rails for flat and parallel to the base. And then true up the fixed and sliding blocks for flat and square. In the end you could easily end up with a primo vise you can trust for quality work while learning a lot about scraping and truing.... or become an alcoholic in frustration....
                            Chilliwack BC, Canada

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                            • #15
                              Lots of good advice for the op. Scraping a surface flat to a reference is actually easy. Add more surfaces and the water gets deep, very deep, very fast. Good part is you need more tools, lots more tools. Like a box level, granite square, camel back straight edge, thinner shorter scrapers, squareness checker and maybe a cylinder square. Don’t forget an angle straight edge for dovetails.

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