Correct lathe speed

Southtowns27

Southtowns27

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Hi guys, this is my first post here. I'm wondering how to pick the correct lathe spindle rpm and feed rates for cutting various materials. I've faked my way through several projects, but just curious if there's a chart out there someplace or a good "rule of thumb".
Kinda OT, but does anyone know how I can determine the build date of my South Bend 9A?
Thanks in advance!
 
Get acquainted with the math process IMO. Using a calculators fine, just know whats what. Then get a cutting speed chart and it's easy enough. What ever number you reach, I would cut in half and work up till it's happy.

If your gonna play with it on a project, practice before your finish cut
 
What I'very used is 4 x cutting speed (inches per minute) /part diameter
 
Nothing wrong with calculators for a start point. But that's all it is. The optimum speed "depends" on a great many variables with the exact machine and its condition being one of the biggest factors.

You can't beat experience when cutting metal. Don't be afraid to try things.

Karl
 
Karl_T said:
Nothing wrong with calculators for a start point. But that's all it is. The optimum speed "depends" on a great many variables with the exact machine and its condition being one of the biggest factors.

You can't beat experience when cutting metal. Don't be afraid to try things.

Karl
Click to expand...
Yep...I don't have a clue what speeds my lathe turns. I just know about where to set it and then let the machine and part tell me if I need to make changes. 90% of the time it's the same speed for 90% of the jobs. Not including drilling a larger hole, threading, or parting in which it is slowed way down.
 
FWIW, I don't pay any attention to feed/speeds. I run my lathe at any speed that looks right and cuts well. Only when using reamers I am careful about going too fast.
 
Oh by all means use a calculator. Just know what your doing. I dont calculate much any more as you get to know kinda were to be. And I like to find that limit. Where any more and something aint happy.
Karl_T said:
Nothing wrong with calculators for a start point. But that's all it is. The optimum speed "depends" on a great many variables with the exact machine and its condition being one of the biggest factors.

You can't beat experience when cutting metal. Don't be afraid to try things.

Karl
Click to expand...
 
Thanks guys, helps a lot!
I did check out one of those speed charts. I didn't realize that carbide is supposed to be run *that* much faster. My tooling is HSS right now, but I think down the road I'd like to pick up some stuff with the replaceable carbide inserts so I don't have to keep grinding tools.
 
I hope it is obvious but because it hasn't been said, I will say it. The cutting speed is related to how fast the surface being cut is moving past the tool - referred to as FPM (feet per minute) or IPS (inches per second) or something like that. In one revolution of the lathe, a piece of 1" round bar travels 3.14" (pi) past the tool. Diameter matters! A 6" round at the same lathe RPM is moving 18.9" of material past the cutter in the same amount of time.

Like others I use "what works" and when I'm hogging out aluminum (which I do a lot of) I use speeds much faster than recommended. The most important implication of your choice is productivity vs. heat. To a lesser degree, speed will affect surface finish as well. With steel you can watch the chip color for a heat guideline.

Turning and facing can generally be done much faster than parting. Parting too fast is the root of most people's trouble with parting.
 
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