VFD

1WildRT said

Exactly... Older machines don't spin fast enough for carbide insert tooling... Might consider a motor pulley change, you lose torque but gain SFM & as long as you don't take huge cuts it works pretty well... My small lathe can still take .120 cuts without showing any sign of being overloaded..

The big lathe will take .400 without much trouble... I rarely take more than .125 in a single pass...

Click to expand...

How fast is "fast enough"? We got a Clausing lathe at work built in 1975 and it's a tank, weighs 2500 lbs and has a 10hp (I think) motor with a hydraulically-controlled variable speed (basically like a CVT) along with 3-speed gearbox in the head. I think it maxes out around 3600 RPM but I've never run it anywhere near that fast, generally 200-1000 RPM for turning most parts which are generally 1-2" diameter and most of the tools we have are the replaceable-carbide-insert type. I've gotten pretty good at using it but I'm not a machinist, basically taught myself using YouTube videos and a couple books.

When researching this lathe it seems most people who have had the hydraulic variable-speed system fail just locked out that part and added a VFD to control the motor. Replacement parts for the drive system are long gone and it's kind of a PITA to work on.