rasumfrasum
Cobalt are good
The secret is to drill at a low speed, a drop of oil helps

After years of struggling like your DH I bought a bench drill
Not expensive -- made in China -- heaven to use

A different world to hand electric/drills

cog

Cobalt and a suitable lubricant are fine.
Any lubricant is better than nothing, but one labeled for taping is better.

If you ony have a few holes use high speed steel and throw the bit away when you are done (or save it for drywall/plaster/abrasive use).

I just drilled over a dozen 1 inch holes in 3/8 steel plate
using a bi-metal hole saw and plenty of cutting oil.
I used a drill press at 240 RPM. Slower would have been better.
I got the bit at Lowes for about $10.
One Inch Bi-Metal Hole Saw at Lowes.

I got these bits at Harbor Freight.
They work well too if you step up the hole sizes and use plenty of oil.
I stepped 1/4 to 1/2 to 7/8 with plenty of cutting oil.

Pooh Bear

Thanks all for the suggestions. DH did get a drill press to use and will try drilling the holes at a slower rpm and with more oil. We're making "rejas", iron gates for the doors and grills for the windows, on our spanish colonial style adobe house here in the andes mountains of Peru and DH has tons of holes to drill. Something like 300 just for our house and that many more for our guest house. Some friends are coming to visit from the U.S. in a few weeks so we're going to have them bring a drill sharpener with them as well as some good carbide bits which we can't find here.

Rasumfrasum

This table may be of some help
Sorry it's in metric

25mm is about the same as one inch

Your DH will already know to alter the belts for setting the drill speed

Thank you, cogla, that table is very helpful.