Cutting Tool Engineering
October 2011 / Volume 63 / Issue 10

Don't forget to file

By Tom Lipton

Many metalworking professionals overlook filing as an important skill and pick up a grinder instead. And if you’re out of practice, filing is not something that’s easy to pick up on the fly. Bad filing can be seen from halfway across the shop.

Indeed, superb hand filing is a skill that is learned over a long period of time. One of its major advantages over power methods is extreme control. When you cannot afford to make a mistake removing material in a delicate area, use a file. A file is directly connected to the best computer—your brain. With a power tool, by the time the order to stop makes it to central command, it’s often too late.

Ch04.Fig054.Lipton.File rack.tif
All images courtesy of T. Lipton

Treat files professionally by putting handles on them and hanging them in a rack.

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Keep the file in flat contact through the arc when filing a radius.

When I took metal shop in high school, one of the skills we had to learn was proper filing. The teacher was quite thrifty and would only replace a file if it made a better cake-frosting knife. Whenever a new file was put out in the general population, it was treated like the prom queen. And just like the prom queen, everybody wanted the file but only one guy got it. My trick: if I got the new one, I returned it to one of the extreme ends of the file rack. That way I could swoop in the next day and just grab the end file while everyone else was fingering the others to find the new one.

Our first project was to file and sand a hunk of cold-rolled steel into a perfectly square cube of specific dimensions. If you ever need to think of a devilish little project to keep an apprentice out of your hair for a month or so, this is the ticket. It sounds simple, but to get the sides to size and square is not trivial.

Follow these guidelines for filing:

Grind at least one safe edge on your primary files. This reduces the chances of gouges and keeps you from scratching when filing up to a shoulder on nice machined parts. Also, round the files’ noses, particularly files used in a lathe. There is no reason to have the nose square and sharp unless you scrape paint with it.

A handle on a file significantly improves tool leverage, and you should never use files without handles in a lathe or other power machinery. Besides enhancing safety and efficiency, having handles lets you hang frequently used files in a professional-looking rack and keep them at your fingertips. I use bright blue handles so I can spot mine anywhere in the shop.

If you go in the field with a small tool kit, take at least one file. Make it a versatile, half-round one with a bastard or smooth cut. Half rounds can access acute angle corners and dress a radius.

Get rid of dull files. Impress apprentices by generously giving them your dull castoffs, but resist the temptation to laugh until they have at least walked off with that misty look in their eyes.

Grind an edge on a file for knocking berries loose after welding. The finish from knocking berries off with a file looks more professional than chasing around the entire weldment with a grinder.

When filing a radius, follow the radius through the arc with the file kept in flat contact through the arc to keep it true. The lines from filing follow the radius around the corner. The file needs to be kept flat against the work so the corner is not rolled off to the sides. CTE

TomLipton.tif About the Author: Tom Lipton is a career metalworker who has worked at various job shops that produce parts for the consumer product development, laboratory equipment, medical services and custom machinery design industries. He has received six U.S. patents and lives in Alamo, Calif. Lipton’s column is adapted from information in his book “Metalworking Sink or Swim: Tips and Tricks for Machinists, Welders, and Fabricators,” published by Industrial Press Inc., New York. The publisher can be reached by calling (888) 528-7852 or visiting www.industrialpress.com. By indicating the code CTE-2011 when ordering, CTE readers will receive a 20 percent discount off the book’s list price of $44.95.
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