That time a customer's engineer showed me my speeds and feeds were all wrong

I was running a 3/8 endmill in 6061 aluminum on a Haas VF-2, chip thinning was making me crazy. This older engineer from the customer side walks over and says "you're running that too slow, bump the rpm to 12,000 and double your feed." I thought he was nuts, but I tried it on the next part. Cut time dropped from 4 minutes down to 1 minute 45 seconds per part and the surface finish was way better. Has anyone else had an engineer or old timer teach them something that completely changed how they run a particular material?

3 comments

3 Comments

black.joel27d agoMost Upvoted

Whoa, slow down there. I gotta say, your mileage might vary on those exact numbers. In my experience, that 12,000 rpm on a VF-2 can be pushing it on a 3/8 endmill in aluminum depending on the machine's condition and the holder type. I've seen guys try that and get chatter if the spindle isn't perfectly happy up that high. Not saying the engineer was wrong for your setup, just that chip thinning math can be real sensitive to tool stickout and what kind of holder you're running.

terry_lewis2121d ago

Wait, is this really that big of a deal though? I mean, yeah @black.joel, I get that you had some trouble, but it sounds like that was a specific machine problem more than anything else. Every VF-2 is a little different, and if yours couldn't handle 12k with a 3/8 endmill, that's not the engineer's fault, that's just a tired spindle or a bad holder. I've pushed way harder on aluminum on way older machines and it was fine as long as the setup was clean. People get all worked up about chip thinning math but half the time they just need to check their tool stickout and make sure the drawbar is tight. Feels like you guys are making a mountain out of a molehill here.

west.anna27d ago

See that's the thing, I've actually had the exact opposite experience and it cost me a lot of scrap before I figured it out. I ran a job on a VF-2 with a 3/8 endmill in 6061, tried bumping the rpm up to match that chip thinning formula, and the whole part started chattering so bad it left a wavy surface. The spindle on that machine just wasn't happy past 8,000 rpm with any real stickout, and I ended up having to drop back down to a more conservative speed and feed to get consistent results. The engineer's advice might work great on a newer machine with a perfect toolholder, but on an older or even a well used VF-2, you're asking for trouble if you don't check the machine's actual capability first.