Old timer at my first shop gave me bad advice about speeds and feeds

When I started running CNC mills back in 2017, this guy named Jerry who had been there since the 80s told me to always run my end mills at 50% of the suggested RPM. He said it kept the tool from burning up and made the cuts smoother. I followed his advice for almost a year until I wrecked a $300 part on a medical job because the tool chattered so bad. Turns out he was running machines from a different era with HSS tooling, and I was using carbide inserts. After a service tech showed me the proper speeds, my scrap rate dropped from like 15% down to under 2% in three months. Has anybody else gotten handed down advice that was totally wrong for modern machines?

2 comments

2 Comments

ivan_harris17h agoTop Commenter

Huh, so Jerry was basically running everything like it was 1985 with a belt drive spindle, right? Did he also tell you to use coolant like a garden hose and never touch the rapid override? I'm curious if there were other gems from that era that had you chasing your tail before you figured out modern tooling.

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miles_robinson2014h ago

Ngl that sounds exactly like my first shop where the old timer swore by carbide scrapers over modern inserts.