This isn’t another one of how my luck usually goes posts.
This is an actual post about scraping.
Scraping you say?
Scraping WHAT, paint? Gaskets?
Nope. Scraping Cast Iron.
Yep, pretty much what I said the first time I had ever heard of it too.
If you have ever owned a precision machine like a metal lathe or a milling machine, the odds are that at some point during the final assemble and test fitting of parts, one or more of the parts that slide along another one were scraped to insure maximum flatness and contact between the two parts.
There is a very quick way to tell if a cast iron machine piece has been scraped to fit better.
You will see a pattern like this on the fitted parts.
There is an art to this process and in the past it was all done by hand in a back breaking and extremely tedious manner using a special hand tool which was obviously called a scraping tool. These weren’t just any kind of scraping tool, they had hardened tips. With the advent of exotic metals, long handles had Tunsten Carbide scraping wafers clamped in the ends and the intervals between having to sharpen the edge got much longer and you could replace the scraping bit. These things ain’t cheap. The one pictured here is $85. Just the replacement bit is $50.
I looked into getting one of them until I saw that.
Eventually, electric powered scrapers were invented which cut the amount of time and effort down to a small fraction of what it used to take to finish scrape pieces. IF, you can get it into where you need it.
One good look at the size of the piece being worked on in that picture ought to give you a clue.
There are literally HUNDREDS of Youtube videos on this process but relatively few classes one could take and this is Old School shit that still has a very real need in the world to this day. It’s a pretty involved process from start to finish which I am not going to go into in detail
but you need Dykem bluing stain, a true flat surface to put the bluing on like a Surface plate and then you rub the piece on the flat side across the surface plate with the dye on it to find high spots that need to be scraped down. You can also put the dye on one piece and then slide the matching piece across it to find the high spots. You do this, scrape the little high spots and then repeat until your tongue is hanging out.
Now you are probably asking yourself what in the hell any of this has to do with me, right?
The Battle of The Mini Lathe continues.
I bought another Tail Stock for my Mini Lathe last year and recently went to do something and discovered that the center line height on the Tail Stock is way too high compared to the spindle.
If it was too low I could just shim it.
Too high is a whole nuther kettle of fish.
I did finally get a surface plate a month ago so that is another weapon in my arsenal but this particular problem involves one piece that a surface plate is useless for, The prism on the ways of the bed that the tail stock slides on.
That bumpy thing on the left..
So I bought some GIANT Sharpies to use instead of Dykem bluing ink and found that the base of the new tail stock is riding way up high on that prism.
Scraping the high spots inside the “V” on the base would allow it to fit lower and thus reduce the center line height.
Unfortunately, this is a relatively small part, about the size of a pack of cigarettes and I don’t have a hand scraping tool.
I ain’t paying $85 to $175 for one either. Even if I did, it would be way too big for this job.
So I made one.
I ordered a little thin strip of Tungsten Carbide off the internet a while back, $12 for a 1/16th by 1/2 inch by 6 inch strip.
I made a holder, broke off an end of the Tungsten, clamped it in the tool and then ground it down on a Diamond encrusted wheel mounted to my old belt driven bench grinder.
Then I dug in my crap, found an old wooden file handle and stuck that on there. Then I tested the scraper on a POS Chineseium Cast Iron Anvil I bought a long time ago that is a beauty of a paper weight because it ain’t no kind of real anvil.
I’m gonna put that in the Win Column.
So now, you can see the strips of blue in the Vee of the bottom plate for the tail stock.
Before I started messing with it, the blueing was right at the very top edge of both sides of that V which was causing it to ride way too high on the prism.
I need to do some scraping with the tool on the blue parts, clean it, reblue the prism on the mini lathe and slide the bottom plate along it again. I want that blue strip to look more like the other side, mostly blue from one end to the other.
That was a whole bunch of post just to get to this point but it was also a whole bunch of work making that little scraper.
Even that is a drop in the ocean compared to how much scraping is going to get done on that damn mini lathe. The cross slide and compound both need to be gone over and scraped after I get done with this tail stock.