Holding On – Tooling for Handscrews

Years ago, before CNC lathes existed, machinists made parts “by hand.” By that I mean they pushed levers and turned cranks to operate the machine. In today’s high-tech world, some might find this hard to believe, but it’s true. I know because I was one of those crank-turners and lever-pushers.

My machining career began on a Hardinge Brothers DSM, Five-Nine, Super-Precision, second-operation lathe (a lofty name for a machine, to be sure). We simply called it a handscrew, and I was a handscrew operator.

This odd title generated some interesting questions from my in-laws, but I learned many valuable lessons during my tenure as a handscrew operator. Chief among them was that good tools and the proper toolholding are at least as important as a good machine.

Tooling for a handscrew consisted of hand-sharpened tools, adjustable holders and bushings. There was no cutter compensation on a handscrew, and offsetting tools required a well-placed tap with a brass hammer. Obviously, things have changed since those long-ago days. But handscrews are still around—and so is a lot of the same tooling I used.

Take bushings, for instance. When I was a handscrew operator, I used bushings to hold drills, reamers, chamfer tools—you name it. Back then, I was unaware that bushings, in many cases, are not the best way to hold drills and other center-cutting tools.

But tooling selection is limited for a handscrew, and sometimes I just had to make do with what I had. And, to be fair, bushings have their virtues. They’re cheap and in a pinch are easy to make, which probably accounts for their popularity.

Read the rest: http://www.ctemag.com/dynamic.articles.php?id=256

Leave a Reply

Your email address will not be published. Required fields are marked *