Filing Tips

Some Scrapers Too

Boy, there’s a zinger of a title. Probably lost a few of readers with that one. I have some information to offer, but honestly, my own expertise is limited to my needs. I recall visiting with a machinist many years ago who proudly showed me a gorgeous angle finder he made during his training. You would have thought it had been machined to get such results, but he said it was a file exercise he made during his training. Before they let him loose on a Bridgeport, it was all hacksaws and files. That was the moment when I began thinking about the power of tools that take little bites. If you stop at the right moment, you can tune the results to the thousandths of an inch (I think Konrad Sauer knows this).

Much of what I have to offer is about how you might adjust your technique, but I will start with some crude definitions. I use mill files, which have a single row of cutters at a slight angle to the length of the file. Other files have a double cut, which is better for removing material faster, but leaves a rougher surface. On double cut files, the teeth criss cross each other.

Bastard Cut Mill File

The different types of files can be confusing. There are rough, coarse, bastard, smooth and dead or super smooth. I want a file that will remove material relatively quickly but more importantly (because I’m sharpening, not shaping soft steel) leave a smooth surface. For most of my filing, I use a bastard or smooth file, which are easily purchased at any hardward store. If you take one thing from reading this, please let it be that files only cut in one direction and should not be in contact both directions. All it does is dull the file and freak me out. Here is a short video of me lightly filing a scraper. Notice the “draw filing” technique where the file is pulled towards me at a skew.

I always follow the file with diamond hones when sharpening scrapers, so I’m not concerned about getting the finest file result. However, if you are one of the army of people I’ve met who say “I can never get a scraper to work" then get yourself a bastard cut or smooth mill file and draw it down the edge, as I show in the video above, and get to scraping. The filing action will turn a small burr on both edges and be ready to cut. Yes, the burr will be more ragged than a stoned edge, but it will cut. It will also be weaker and dull more quickly, but you can try your hand at flattening the burr by running the oiled burnisher along the face of the scraper, careful to keep full contact with the face and not round the edge, then run down the edge with the burnisher and tip very slightly off 90 degrees and voila! Burr. This one will be less ragged and stronger.

On a mill file, the rows of cutting edges are at an angle, this skew does what a skew always does, it lowers the cutting angle, curls the shavings to the side and reduces the pressure needed to make the cut, all while leaving a better surface. I think the action of a snow plow offers a good comparison. Skewing the file itself can also pay dividends by increasing the effect. I also like to pull the file rather than push it, I feel better control.

A Sweet Shaving

In the image below, you can see the different angles that you can pull a file and get good cutting action. The blue line indicates the angle of the cutting edge on the bottom of the file when it is in a position to cut. The red lines on the two files on the right show when the cutters won’t cut because the angle of the edge in relation to the file actually makes it go past where it can cut. To be honest, I never noticed this until recently because I am left handed and am most comfortable using the file with the handle on the left side when pulling, which can cut even when perpendicular to the scraper.

Lastly, I’ll just say, working on a sharp portion of the file is essential. The only reason a sharp file doesn’t cut you, is that your flesh won’t fit between the cutters. When rested lightly on the edge of a scraper, a sharp file should “grab” and take very little pressure to cut. After multiple burnishings, the surface might be very compressed and hardened, like crust on bread. The first few passes with the file might skate on the surface and have trouble cutting. A little extra pressure can help here, just lighten up once you break through to the softer steel.

I’ll leave it there, I hope you’ll get yourself a fresh file, put it to work, and then store it in a very safe place. I don’t know about you, but I needed that

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