Got a tech type topic and I'll post here cuz there are so many tech type things in this thread (the most recent being Jim's thaw-out posts), but it just seems too bad there isn't a separate thread on tech stuff (non tree related) because the various topics would be easier to find later.
Awhile back, Kyle posted some stuff (probably earlier somewhere in
this thread ) which included a vid link called 'rebuilding older machines by hand scraping'
https://www.youtube.com/watch?v=REeGn4hN1Bg&feature=youtu.be The concept piqued my interest cuz it struck me as something I know absolutely nothing about. Well, the only thing I know about machines (the milling type and other kinds which are used to build things and other machines most of us use every day) is that modern life couldnt exist without these machines. So about 2 months went by before I finally watched the vid, and afterwards I was more in the dark than before
so I PM'd Kyle some questions and he very kindly answered all the questions and more. He has a knack for explaining things imo.
So on the chance that others might find the Qs and As interesting or informative:
Q: Hey how you doing?
Random note here- you posted a vid awhile back about scraping machines to get them flat and square again. I finally watched it tonite. Waaaa, I don't get it!
Ok, thru wear, a machine's flat surface could become unflat. So you want to make it straight again. Well my 2 main questions are: How the f can you expect to get metal perfectly square by hand-scraping high spots, that would seem to create the furthest thing from uniform, straight, and square?? And, how the heck can hand-power cut down high spots in hard metal? I must be missing something huge here
Thanks much if you care to answer here. You have offered many good technical answers on stuff at The House, maybe you can edify me on this topic too.
Btw, I PM'd you just cuz I didn't want to bore the masses by posting these questions.
A: I'm doing well, thank you
and I agree this would bore the shit out of most people lol. The way it works is you aren't going for surface finish, you are shaving off the high spots to make it a flat surface. They use a razor sharp carbide edge, and plane off the cast iron (or whatever it's made of). When you are sanding wood, you stop, run your hand over it to feel for roughness, then sand that spot. It's basically the same process. They use blue dye to mark the surface, then use what's called a surface plate (very very flat surface) to rub against it. The spots where the dye is rubbed off are high, so they scrape them down. This is repeated over and over again, till they reach a predetermined spots per square inch. They do the marking process with the dye and surface plate, and then count how many high spots there are. When using even a surface grinder, there are waves made from the wear and warpage of the machine, so that will be transferred to the surface. By hand scraping, they don't have that, because the only tool is the scraper.
For some reason it won't let me post a picture, but if you google hand scraped machine ways you will see the surface looks almost mottled, like there are little divots all over. That's because there are lol. But these are beneath the surface, and by scraping till the required spots per inch are met, the higher surface is perfectly flat. These divots are actually beneficial in most surfaces, especially machine ways and mating surfaces. If they were completely smooth, the oil wouldn't have anywhere to hide, and the surfaces actually stick together. This is actually how gage blocks work, they lap the surfaces so smooth that when you stack them they stick together like they were magnetized. Gaskets also need some surface irregularities, so they grip. Otherwise they have a tendency to be pushed out. Pipe flanges actually have deep grooves machined in a circular pattern so the gasket is locked in place. The surfaces are perfectly flat, but the grooves bite the gasket. In machine ways, after they are done scraping it smooth, they often do a process called flaking, which adds random cuts all over the surface so it holds more oil.
If this stuff interests you, you might want to check out a book series by David Gingery called build your own metal working shop from scrap. He actually traces the history of the industrial revolution and makes an aluminum foundry, then builds a lathe, then a scraper, mill, drill press, brake, and then accessories for everything. While it's way easier and better to just buy machine tools, how he goes about solving problems while building stuff is the true lesson. These same problems were encountered during the invention of these tools, and it's really a chicken or egg story. He doesn't have anything machined by someone else, so he uses hand scraping to machine all of his castings. He does use some bolts, plate, and threaded rod, but he literally makes everything else himself lol.