What is Metal Scraping?

what is scraping scraping is a way of using a hand tool or a handheld power tool to remove really small amounts of metal with each stroke or scrape to make something really flat now if you're like me I thought milling machines made things really flat well it ends up they don't there's a whole bunch of things tool pressure machine deflection material deflection and that's just not what milling machines do wait at a really really flat level and then I found out about surface grinders and I thought well that's what surface grinders do surface grinders go back and forth and make things incredibly flat well they do but they don't there's some drawbacks to grinders it's a complicated machine that the machine itself can have tram air or wear in it especially as that table moves left to right you're also holding the workpiece down when you hold it down like you guys saw in the video we did on making a surface grinding this parallel you either have a vise or you have a magnetic Chuck and that is inducing stress and that may twist the part so that's the beauty of scraping you can do it in a natural state so card here to a half an hour video on the Richard King scraping class that we did that walks through a whole bunch of stuff but this video is not teaching you how to scrape it's just what is scraping the beauty of scraping is we use a master and by master it's something like this surface plate I have a problem with my surface plate I don't know if it's calibrated or good we need to check on that click subscribe because we've got some videos coming on how you can check your surface plate and maybe see just how good it is or if you need to get it lapped in the beauty of a surface plate is their granite they're relatively stable compared to metal and you can get them incredibly flat and then once we've got that flat the way we scrape is we take an object and we put bluing compound down on the surface plate and then we simply rub our part and what's going to happen is the blue shows you where it's touching and the low spots aren't touching now that's actually an incredibly small it's a peak in a valley so you're thinking John you just told me this was incredibly flat well it's flat across the mean height of the distance one of the other problems with using a surface grinder yes you get a beautiful finish and it's relatively flat over the whole thing but just like these two gauge blocks when they're perfectly flat they'll actually do what's called ringing they'll stick together that's pretty cool right well that's not good for two surfaces like a dove tail or a Gib in a machine that are supposed to contact each other so what you do is scraping is you scrape for what's called points per inch so let's say this is one inch by one inch what you want is approximately 20 points per inch that's showing nine now these points should be bigger such that you've got about forty to fifty percent of the area covered by highs how do you get those points again it's a simple hand-tool the handful takes a really long time the by XPower scrapers make quick work of it and that's the beauty of this you make a pass you blew it up you see where your high spots are you either dive bomb or hit those individual high spots as you start to get the part flattened out once you get it flattened out you keep scraping till you get the right amount of points per square inch again why is scraping great you can't always put a whole part of a machine onto a surface grinder even if surface grinding were the right technique why they could be hot it can be huge you may not be able to afford or get to a surface grinder that big with a simple hand tool like this or the powered version you can scrape any machine you have to take you out there's also something called flaky I used to think flaking was scraping flaking is something you do after scraping to create deeper pockets for oil to to not only sit in but to create a little channel for it to slowly work its way through basically keeping the oil there flaking might be a thousand to 2,000 s deep this scrape marks believe it or not are only two to five ten thousandths of an inch deep don't believe me let's take a look this is a ten thousandth of an inch indicator that's really sensitive to prove that I have a piece of shim stock that's one point five thousandths thick that's about one-third the thickness of a piece of printer paper I'm going to go ahead and preload this indicator I'm going to take this piece of shim stock and just gently slide it in here and it's going to bounce around a little because I'm moving it wobbling it but you can see just how sensitive this needle is you can also see what hopefully a blue spot that means that's a high spot so let's go over that blue spot we've got our indicator on zero now watch this is amazing I'm going to move off the blue spot look half a thousand maybe five six cents that is awesome that is crazy to me so let's prove just how flat this parallel is we can't just run this indicator across it because you're going to bounce through the peaks and valleys let's lift it up and let's use a gauge block and that will show the median Heights because that's what I care about so we'll go over here to the side preloader to zero come off come back on we're at zero move to the middle let's come onto the block I'm getting about a tenth and a half there amazing and let's go to the end just a hair over 110-thousand of an inch that is crazy across 24 inches we're getting reading 110 to two ten thousandth of an inch of deviation in both flatness and parallelism so why should you care about scraping well first of all it's just awesome it's like the science and the core behind how we got so good at building machine because so many things are scraped tormach machines have scraped away so much more to this that's so cool are you ever going to use scraping I found this stare at level in a tool box that I bought at an auction and I took it down there and sure enough it was not perfectly flat and by the way take a look at this this was the surface ground parallel that I blued up now the fact that surface grinding makes it so fide it's actually tricky to blew it because of the stiction so may not be a perfect reading but it also just goes to show you surface grinders as they travel may not be as perfect as scraping crazy so I scraped in my little starett level super-fun project this is easy to do with a hand scraper if you want to learn more there's a link in the video description to the DVD that Richard King puts out that's the class that I just took and again link in the video description to a 30-minute video down at Keith's record shop on scraping such a cool thing more to come click Subscribe if you enjoy otherwise take care folks see you soon [Music]

Channel: NYC CNC

Views: 119,017

Rating: 4.9214048 out of 5

Keywords: hand scraping, scraping, richard king, biax, parallel, keith rucker, flat, metrology, how to, machine shop, nyc cnc, DIY, machining, cast iron, tormach, surface plate

Id: 7QOCE1-fB6Y

Length: 6min 49sec (409 seconds)

Published: Sat Jan 28 2017