March 2007 Edition

FROM THE SHOP FLOOR

Dave Sterling, Application Engineer Ansco Machine Co.

Sometimes the Best Just Isn’t Good Enough

Unique problems take innovative solutions. Waiting until someone else solves the challenge could mean a long, long wait.

It happens all the time: a tough machining application occurs. You scour through catalogs and pick the brain of every tool salesman you can find. Nobody makes the tool you need. With a little bit of ingenuity, close may be good enough.

We run many large diameter rings on our CNC VTLs, and many of them have deep face grooves. There were two ways of handling them. The first was to take an old self-gripping holder and slowly plunge away at the groove. This produced a huge mess of stringy chips and unpredictable finishes and sizes.

The second was doing a series of plunging and turning passes with a 35° diamond tool. The depth of cut had to be small to avoid insert breakage, and the groove had to be of a sufficient width for the proper plunge angle. This way produced manageable chips, but took forever to complete the grooves.

If the perfect tool for the job doesn’t exist, make it

We posed this question to Mike Houston, an outside salesman for Cunningham Supply, Akron. He had a wild idea. He suggested adapting a Sandvik Bear-Paw grooving system for face grooving. He said the diameters were large enough that with slight modification to the holder, we could get the clearance we needed for a face-grooving application.

It Won’t Work If You Don’t Use It

We were skeptical; the holder and inserts sat in a drawer for a few months. Then came a ring, which was too narrow for the 35° diamond tool, and too intricate for the self-grip holder.

We pulled out the Bear-Paw and called Mike. With a little finesse – read: grinding – we cleared the back of the holder, and tried it out. The Bear-Paw is 0.5" wide with a scooping chip-breaker on the front. It also has large 0.03° radiuses on the corners for strength. It is built to remove metal in a hurry. We started the first plunge, running at 350 spfm and 0.015" per revolution. The machine hummed, and then the chips started to fly! The Bear-Paw performed wonderfully, producing a manageable chip at a high metal-removal rate.

On another machine, we were starting to turn a part that required an 82° chamfer on center in a half-inch bore. The part also required about 0.2" of flat at a specific diameter for finish boring. We could have used a tiny boring bar and contoured it out, but every second was critical.

Not Close Enough for Government Work

No one made a tool at the right diameter without a special grinding operation. That’s when I called my friends at K-Tool in New Oxford, PA. They offered a tool close to what I wanted, and I know they make custom tools.

They made a tool that was the right diameter and angle, and it cut well in the lathe application, but there was a slight problem. Coolant from the lathe’s nozzles only flowed through one of the flutes effectively. It was apparent from a color difference in the chips that some came from the cooled insert and others from a dry cut. Then my brother Jeff, the lathe foreman in the shop, had a bright idea. He decided to make the tools “coolant-thru.” Using a Bridgeport, we drilled a 0.250" hole down the middle of the tool until the point broke through into the cutter flute. With new cooling, the tools cut perfectly.

These are examples of tools that don’t always have to function as originally intended. They may have more uses than is first apparent. Sometimes a little creativity creates a lot of improvement. Sure, tool companies have a staff of engineers that solve problems, but none of them work at your shop. Sometimes a shop has to take the initiative.

Dave is responsible for programming, tool selection and fixture design for 20 CNC machines. He’s been working in a machine shop since age 12, starting by drilling holes on a turret lathe and making simple parts on a Bridgeport.

What do you think?
Will the information in this article increase efficiency or save time, money, or effort? Let us know by e-mail from our website at www.ModernApplicationsNews.com or e-mail the editor at pnofel@nelsonpub.com.