Lathe Feeds and Speeds

[ellett88]

Hi,

 

Im just starting out on a cnc lathe and cant figure out my feeds and speeds. I am using SECO book ( they have all their inserts and holders plus formulas for calculating feeds and speeds) but the numbers im getting dont seem right.

 

Does anyone have an easier way to calculate feeds, speeds, cut depths, finising roughing, etc.

 

Thanks

[rdshear]

RPM = Cutting speed (surface feet/min) *12 / PI * diameter being turned.

 

Feed in IPM would be = RPM * Chip load

Feed in IPR would be = Chip load

 

(IPM = Inches per Minute)

(IPR = Inches per Revolution)

 

Insert rated for 800 SF Cutting a 6" diameter with .016 chip load would be:

 

800*12/PI*6 or 509 RPM

509RPM * .016 Chip load = 8.1 IPM

.016 Chip load = .016 IPR

 

Hope this helps

 

Rick

[Columbo™]

try this speed and feed link

[ellett88]

Ok, what does PI mean, and is SF cutting speed?

[rob@fain]

IPM=inches per minute

SFM=surface feet per minute

[Guest]

PI pronounce "pie"

 

Is a constant 3.1415

[ellett88]

ok gotcha! Thanks guys!

 

Now one more question. the feed rates seem too slow for industry, i have now question they're correct in relarionship to the rpm, is they're a way of speeding them up? should i just increase them by 10 20 30 etc percent together?

[calnet42]

More accurately, PI = 3.141592653589..etc...etc

(it is actually has no theoretical end and doesn't repeat)

So, rounded off to .0001 would be 3.1416

Small difference, I know.....

 

P.S. I think the record was 1.24 trillion places , I don't know if there is a new one.

[Gary]

No Ricks 6.00 in example above is pretty real life. You can speed it up 30% and end up changing inserts so much you loose time. Lathe work goes way quicker as far as metal removal then on the mills. You will like it.

Gary

[heavychevy2155]

Those speeds and feeds from the manufacture are just starting points. You will get the "feel" of what the machine can do and what is a happy medium of tool life and speed. Just take it slow and easy, speed will come with time. Most modern lathes move so fast you want have time to react to a missed place decimal point or other programming error.I really enjoy running my Okuma and Howa lathe, it just keeps on making beautiful parts.