Miller big 40

[jengelking]

I m looking at a old miller big 40 does anybody know the amprage on the machine the guy says its a 300 amp machine but I thought it was a 400 amp please somebody let me know

[sourdough]

You would think 40 would indicate 400 amps but it doesnt. They are not 400 amp machines. I couldn't tell you the exact amperage, but I have had this conversation many times. I couldn't even tell you what the 40 signifies, to be truthful.

[jengelking]

Ok thanks

[leightrepairs]

Here is a generic manual for a big 40. http://www.millerwelds.com/om/o450n_mil.pdf

[aevald]

Hello jengelking, It is a 400 amp machine, it is 300 amps at 100% duty cycle. Best regards, Allan