Joe

No worries.  Your estimate is very good.  Up to about 120 amps (normal for 1/8 inch E7018) You can run your buzz box pretty much continuously.

If you really think about it, it's hard to run anything close to 100% dudy cycle with SMAW anyhow. With changing electrodes and chippin slag and all that.

Joe, dont even worry about that "duty cycle"! Do your best, if you're a hobby welder it wont effect you. Any time you're welding, and all of a sudden your weld is getting real wierd, that's when to stop. You're not going to hurt the machine by doing this. Have fun, and learn a bunch!!

You would be surprised how seldom you will actually weld for 20% of the time.  Just replacing electrodes takes something off.  And then there will be a clamp in the way, something that needs a clamp, have to reposition yourself, etc.  If you stop to look at what you just did (practicing) you will never get to 20% and as you said lower settings generally increase duty cycle, so does starting with a cold machine for the first cycle or two.  Have fun.
Bill

Actual duty cycle = ((rated amperage/actual amperage) squared) times rated duty cycle

Example: 200 amp machine rated at 20% duty cycle. You will be welding with 150 amps, what is the duty cycle at 150 amps?

actual duty cycle = (200 amps/150 amps) squared times 20% = (1.333 times 1.333) times 20% = 1.778 times 20% = about 35% duty cycle

You can weld for three and a half minutes at 150 amps out of every 10 minute cycle without overheating the transformer and destroying the machine.

Happy New Year!

Best regards - Al

Also, just to add to the above, almost all machines have a thermal cut-out that will operate to stop your welding if you exceed the duty cycle for any length of time, and after the transfomer cools, can be re-set (or will re-set automatically). See your manual on this, and weld with no fear!