Not just any welding helmet.
The lens used for arc welding are numbered.
For eclipse viewing Shade Number 14 is required.
Sold out everywhere long ago.
The Shades can be added, but if stacked total needs to be 15.
My rig uses a Shade Number 11 combined with a Shade Number 5.
I have a shade 10 Pipeliner helmet and shade 5 Oxy/acetylene goggles. Some say add the two shades together and subtract 1. I should be good to go, unless it’s too dark.
I heard that shade 12 is the minimum, 13 better. NASA recommendation:
https://eclipse2017.nasa.gov/safety
I heard that lens shade for welding depends on eye color, with the darker lenses required for blue eyes.
I have brown eyes and use a fairly light lens.