TIL why some operators keep burning up their spindle motors on older Fadals

I noticed this guy at the shop next door kept killing spindles on his '94 Fadal 4020, swapping motors every 6 months like it was normal. When I asked about his chip load he just shrugged, turns out he was running full depth of cut with a 1/2 inch endmill at 10,000 rpm in 6061 aluminum without adjusting feed rate. Has anyone else seen older machines get blamed when it's really just pushing the tool too hard?

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oliver_morgan2mo ago

Oh man that's exactly the kind of thing that drives me nuts. I had a guy working for me once who kept complaining our old Haas mini mill couldn't handle roughing passes in stainless steel. Found out later he was taking a full 1 inch depth of cut with a 3/8 endmill at like 6000 rpm and wondering why the spindle started making weird noises after a week. These older machines get a bad reputation but honestly they're built like tanks, just can't fix operator error with a new motor. The problem is people think modern toolpaths can just brute force anything without respecting the machine's torque curve or chip thinning. I swear half the "spindle failures" I've seen in the last few years come down to someone running a tool like they're trying to mill with a cheese grater.

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joseph_torres2mo ago

Right? Two years ago I had a guy try taking a .050" radial engagement in 4140 with a 1/2" rougher at 10k rpm. Screaming like a banshee. Said it must be the machine losing power. I showed him the calculator and he still didn't get it.

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