New Chatter-Eliminating End Mill Survives Cutting Copper-Beryllium Mold Material for 100 Hours
 

Sometimes it's the unexpected things in life that pay off - like getting a free end mill to try, and then finding out that it can be pushed to extreme limits with minor wear.

 

Lance Rushton and Jerry Lockhart are partners in a small company that does plastic injection and die-cast molds, forging dies, metal forming, and coining. They specialize in prototype dies made from tough mold steels, beryllium, and titanium. Their background and experience includes working for Black Diamond Sports Equipment that makes mountain climbing gear, ski gear, and other outdoor products. At Diamond both of them learned how to do coining, stamping and metal forming. After their supervisor quit, each partner had their turn at running the shop in a 'baptism of fire.' "It turned out


Lance Rushton and Jerry Lockhart of L and R Design (Salt Lake City, UT) discovered how a free cutter would open the door for faster and more precise mold making.
to be the best thing for us, because we got to work on things we never would have before," says Rushton. "It made us what we are today. It gave us the confidence and the skill to be in the trenches and under the pressure that this industry provides. I mean, the world ends if your tooling isn't done on time," he adds.

 

"I was at a point in my career at Black Diamond where I couldn't go any higher in the company. I was making good money, had a great job, and loved it. But, I really didn't have any place to go. I decided the next step for me (I was 29 at the time) was to start my own business. So I bought a little CNC knee-mill, and put it in my garage while I still had my job at Black Diamond. I did a lot of untended side work on it," remarks Rushton.

     

After Rushton left, Lockhart was made supervisor at Black Diamond. He too realized that going on his own was his best career track for the long run. So he joined Rushton last year. "The rest of the story is just a bunch of hard work," says Lockhart.

 

One thing both partners learned about was how insert and solid-carbide cutters react in tough mold materials. Rushton remarks, "We've tried insert cutters. But since we run untended while doing roughing cuts, if you're not right there if a cutter fails, it often destroys itself and the mold. With a destroyed cutter, you have to wait to get a new one, because you're programmed for it, and they're usually special order. For what we do, we found the insert-style cutter just doesn't work for us, especially since we do so much untended machining. If you ruin a cutter, you've ruined your work, and it's hard on the machine when you destroy a cutter. It literally welds the cutter to your work. So, you can imagine how you feel when you've got an $80,000 machine that you're paying $1,500.00 a month lease payment on, which is now welding instead of machining. It brings tears to your eyes, it really does! Not only that, but you've got a piece of material in there that costs $600 or $700 that might have $8,000 worth of work done to it, and you've just welded your cutter to it. We went to solid carbide cutters for this reason."
 


This 1/8" diameter WhisperKut end mill was used to cut tough beryllium-copper mold material with an easy life of 100 hours. The mold is beneath the cutter. The part is behind it. The part is a component for a snap-together plastic flooring.

"Several months ago our representative from T & L Tooling (Salt Lake City, UT) stopped by. We buy Dura-Mill (Malta, NY) roughers and finishing end mills from the company. Whenever they have a new product they let us try it. They gave us a solid-carbide Dura-Mill WhisperKut coated 1/2"-diameter end mill. Pretty much the same grade of tooling that we buy, or at least we thought. I was cutting on a mold one day and we ran out of 1/2" roughers. So, we have this sample tool that we've gotten free, and I loaded it in the spindle. T & L told us it could go diameter deep, and we said 'it's not a rougher.' It doesn't have serrated edges, but it has this really unusual flute style. We tried it diameter deep, because that's how we run a rougher. I think 'O.K., I'll just leave the same feeds and speeds.' T & L said it would rough, the literature they gave us says

it will rough, even though it looks like a finishing tool. I put it in the spindle, pushed the Go button, and I was terrified. I thought this cutter would shatter. But the spindle load meter showed that it took less load then our other 1/2" dia. cutters, and it threw this beautiful chip. It made almost no sound. So it's great, but it's also brand new. Maybe in half an hour it's going to wear out. This WhisperKut end mill ran on that job probably eight hours. It ran flawlessly roughing the whole thing. I was pretty impressed and I told Dura-Mill I was impressed. This is a good tool, I like this thing," says Rushton.

 

After the mold roughing was done, it did finish passes. After this, Rushton put it back in his toolbox. Later he cut a large engine harmonic balancer for a race car with it. "I thought well this job is perfect for the free cutter. I've already made money with it. So I thought, 'O.K., I'll just put it in the spindle and abuse it until it breaks.' The part took me all day. It was a two-sided part, a lot of roughing. Conservatively I'd say it cut another four to six hours. It was fine when I took it out of the spindle. So I stuck it back in the toolbox. I cut one or two other parts with it after that, short-run jobs. I told Lockhart that this WhisperKut is really a great cutter," says Rushton.

     

Later Lockhart used it to rough for another four hours and it was still fine. "We hadn't paid a dime for it, and it wasn't chipped yet. It was still in pretty good shape. Then I ran it one more time after that. I ran it for another five or six hours. So I'd say that cutter cut conservatively about 22 hours," says Lockhart.

     

"I told T & L that this WhisperKut end mill is awesome. I've made a ton of money with it and it hasn't broken, it was worn, but was still useable. We probably could have still cut a few more things with it," adds Rushton.

     

Rushton then bought a full complement of WhisperKut coated end mills. Using a 1/8" end mill, they tried it out on MoldMax¨ Copper Beryllium with a Rc of 32. This 1/8" dia. tool cut for 100 hours straight without breaking.

     

"When you're building a mold, you don't program super aggressively. You're at home counting on the mold to be cut in the morning without problems when you come back if you're running untended. At the same time, you have to make money. So, you get one shot at it. But you could lose the customer because you're not cutting the material fast enough. Therefore, a balance has to be made. You're not pushing cutters as hard as you can, but you're pushing them as hard as you dare," remarks Rushton.

     

He adds, "I don't know that a different type of solid-carbide cutter would go 20 hours in this type of material, maybe 12. Our depth of cut was relatively low. It ranges from 0.012 to 0.030" at it's deepest points depending on where it was in the 3-D step that this mold has. It's traversing at between 15 and 25" a minute at around a spindle speed of 8,000 rpm, which is 250-260 surface feet and a chip load of 0.002-0.003".

     

"The other advantage of the WhisperKut is not just faster cutting. I was watching the spindle load meter the whole time I was using the cutter and it took less horsepower and was quieter, much less chatter. It tells me I could probably take the roughing passes closer to finish passes, because you're not getting the chatter or tool flex. You can also use it as a finishing tool. We didn't run any finishing passes with it, because we were trying to make money with it by pushing it hard. We still didn't break it. Finish tooling lasts forever if you do good roughing. So the more you can rough, the longer your finishing tool is going to last.'

     

Lockhart said that in mold steel they've used a solid-carbide end mill to do ribbing cuts to form one-inch squares in a mold. He said they never had an 1/8" dia. end mill go longer than 20-25 hours.

     

"It's the craziest looking shape ground on the WhisperKut flutes that I've ever seen," says Rushton. "I was so worried about plunging with it, because it has one flute that goes past center. Now some companies have end mills like this, but the WhisperKut's flute goes drastically past center. It has a drastic geometric deviation from your standard tool. As you hold this end mill in your hand and you're comparing it to standard tooling, you're thinking that this end mill is the funniest looking thing I've seen. But its performance speaks for itself."

     

In an email to Dura-Mill Rushton said, "Your WhisperKut line of end mills is the single most productive metal removal system that I've seen in my 15 years as a tool maker. You and your design and manufacturing staff should take a bow."

     

For more information contact:

      David Walrath

      Dura-Mill, Inc.

      16 Stonebreak Road

      Malta, NY 12020

      800-444-6455

      Fax: 518-899-7869

      www.duramill.com