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What Size Welder Do I Need for 1/8 Inch Steel?

For solid-wire MIG on steel, Miller’s rule is 1 amp for each .001 in, and the published example is 1/8 in at .125 in and 125 A (Miller parameters). All four listed wire sizes include 125 A, and the farm chart’s 1/8 in cells are stick 80–130 A, flux-cored 140–155 A, and TIG 95–130 A (Miller parameters, Welding on the Farm). A published example range that contains 125 A is the Handler 140 at 25–140 A (Handler 140 spec sheet).

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140 amp MIG welder

Published figures

FigureValueSource
Solid-wire MIG, 1/8 in steel.125 in → 125 A (1 amp per .001 in)Miller parameters
.023 in wire at 125 A (MIG wire speed chart)30–130 A window; 3.5 in/amp → 437.5 ipmMiller parameters
.030 in wire at 125 A40–145 A window; 2 in/amp → 250 ipmMiller parameters
.035 in wire at 125 A50–180 A window; 1.6 in/amp → 200 ipmMiller parameters
.045 in wire at 125 A75–250 A window; 1 in/amp → 125 ipmMiller parameters
Stick E6013, 1/8 in80–130 AWelding on the Farm
Flux-cored, 1/8 in140–155 AWelding on the Farm
TIG, 1/8 in95–130 AWelding on the Farm
Handler 140 welding range25–140 A; rated 90 A at 20% duty cycleHandler 140 spec sheet
Millermatic 211, 120 V range30–130 A (240 V range is 30–230 A)Millermatic 211 spec sheet

How to size it

  1. Start from the example that is already worked. Miller states that each .001 in of steel thickness with solid wire takes 1 amp, and that .125 in (1/8 in) is 125 A (Miller parameters). Dividing .125 by .001 lands on the same 125.
  2. Pick a wire whose published window contains 125 A. That is all four listed diameters: .023 in (30–130 A), .030 in (40–145 A), .035 in (50–180 A), and .045 in (75–250 A). The .023 in window tops out at 130 A, so 125 A is near the top of that one (Miller parameters).
  3. Read wire speed from the same example rather than a new formula. At 125 A, Miller lists 437.5 ipm (.023 in, 3.5 in per amp), 250 ipm (.030 in, 2 in per amp), 200 ipm (.035 in, 1.6 in per amp), and 125 ipm (.045 in, 1 in per amp) (Miller parameters). The MIG wire speed chart is the longer wire-speed page.
  4. If the joint is not solid-wire MIG, use the farm chart’s 1/8 in column: stick E6013 80–130 A, flux-cored 140–155 A, TIG 95–130 A (Welding on the Farm).
  5. Treat duty cycle as minutes out of a 10-minute period (Welding on the Farm). The Handler 140’s published duty line is 90 A at 20% (Handler 140 spec sheet). Twenty percent of 10 minutes is 2 minutes of welding, and 10 minus 2 is 8 minutes of cooling, at that 90 A rating. The sheet does not publish a duty cycle at 125 A. Check a machine plate on the duty cycle calculator.

The Handler 140 figures are the published spec sheet, not a shop test. Its range includes 125 A, and a Millermatic 211’s 120 V range of 30–130 A also includes 125 A, while the 240 V range is published at 30–230 A (Handler 140 spec sheet, Millermatic 211 spec sheet).

dual voltage MIG welder 120V 240V

Frequently asked questions

Is 125 amps the MIG figure for 1/8 inch steel?

Yes. Miller’s solid-wire rule is 1 amp per .001 in, and the published example is 1/8 in at .125 in and 125 A (Miller parameters).

Which wire sizes include 125 amps?

.023 in is listed at 30–130 A, .030 in at 40–145 A, .035 in at 50–180 A, and .045 in at 75–250 A, so 125 A sits in all four windows. At that same 125 A example the wire speeds are 437.5, 250, 200, and 125 ipm (Miller parameters).

What do stick, flux-cored, and TIG list for 1/8 inch?

The farm chart’s 1/8 in mild-steel cells are stick E6013 at 80–130 A, flux-cored at 140–155 A, and TIG at 95–130 A (Welding on the Farm).

Does a published 140 amp range include 125 amps?

The Handler 140 spec sheet lists a welding range of 25–140 A, which includes 125 A. Its duty-cycle line is 90 A at 20%, which is 2 minutes of a 10-minute cycle, not a duty rating at 125 A (Handler 140 spec sheet, Welding on the Farm).

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