Cutting Tool Engineering
July 2012 / Volume 64 / Issue 7

Deciphering the donut deflector

By Tom Lipton

A few years ago, I was at one of our customer’s facilities—a big government research lab—installing equipment we had supplied. I noticed when we entered that off to one side was a small machine and mechanical workshop to support the activities in the equipment bay where we were working. At one point, we stopped to take a break and talk with the technician we were working with.

Now, if you haven’t figured it out yet, I’m a huge “gearhead” through and through. I love looking at machinery and, if there is an opportunity for getting a shop tour, I always ask. So I asked our escort if he would give us a quick tour of the shop. He readily agreed.

It was a nice little shop. We were not allowed to carry a camera, so I don’t have any pictures to share.

The shop was well-equipped to help the engineers and scientists working in the bay do pretty much whatever they needed to do. For example, the shop had a little sheet-metal brake and a Rotex punch for making brackets and guards.

About half way through the tour, we got to the manual lathe. It was nothing special, just a good, plain, American-made engine lathe—except for one major difference.

Just to set the stage a little: This is a government laboratory where they routinely handle and work with nuclear materials. You’re almost afraid to ask questions because you may be prying into the forbidden world of national security and black ops. The fact that we had an escort assigned to us while we worked in a mundane, unclassified area gives you some idea.

On the rear of the headstock of the lathe was some kind of special stainless fitting. I have seen many lathes and the purpose of this peculiar fitting was definitely not obvious. It was a very serious piece of hardware, more like what you would see in a vacuum chamber. It was completely out of place on this nondescript lathe.

Immediately, my mind was trying to decipher the secret of this fitting and why it would be on a simple, manual lathe. The fitting consisted of a thick stainless flange attached directly to the machine. To this was welded a 90° tube, which terminated in a fancy, high-vacuum Conflat flange. The whole thing was electropolished to gleaming perfection.

Some of the uses I came up with involved extracting chips and fumes from noxious radioactive materials or perhaps some kind of innovative, vacuum-holding setup. In this lab, the possible uses were mind-boggling. It could be almost anything. Finally, I asked our escort if he knew the function of this beautiful piece of gleaming stainless steel. He said, “It’s a donut deflector.”

Now, I was really curious. What the heck was a donut? Some code name for a super-secret part that dwells inside the core of a nuclear weapon? An experimental magnetic component for a phased fusion reactor? What the heck was a donut and why did it need to be deflected?

I didn’t want to probe or put our escort in the position of being downrange of a firing squad for betraying any classified information by answering my barrage of questions, but I needed to know what a donut was and how the deflector worked.

He laughed and said, “Well, the donuts don’t really get deflected. You see, Billy Bob brings a dozen of the best glazed donuts you ever tasted every Wednesday. He always puts them on the desk here.” He pointed to a spot on the desk directly in line with the lathe spindle.

“One time, some moron was running the lathe and blew a bunch of chips down the spindle bore and they shot out and got all over a steaming, fresh batch of donuts and wrecked the whole batch,” he continued, while a tear formed in the corner of his eye. “We built this deflector to keep any chips from landing on the desk and the donuts.”

All I could manage was a weak, “Oh.” You know that sound an air mattress makes when you pull the plug and roll it up—“pfffhhh?” That’s how I felt.

We then left the shop and finished our work. All I could think about was the thousand bucks of man-hours for the sake of a dozen donuts. CTE

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 By indicating the code CTE-2012 when ordering, CTE readers will receive a 20 percent discount off the book’s list price of $44.95.
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