You need a large mechanical shear or you get warpage. For that, you need a machine shop.

Just use the magnetic paint over a piece of masonite.

hollysprings, i read that the magnetic paint doesn't work that well. do you have a good brand you can recommend? otherwise, thanks for the tips on the warpage. i will try to find a machine shop to cut the metal for me. thanks!

Most small machine shops will do it for a song. Also have them price the sheet metal for you as they may charge less than an MSC or Grainger would.

I bought a piece of steel sheet metal in the plumbing section of Home Depot for $10 and easily cut it with a good pair of tin snips. Glued it on a piece of quarter-inch thick luan, painted it with chalkboard paint, stuck a homemade frame around it and made myself a magnetic chalkboard for the inside of the pantry door.

I would say the easiest part of the entire project was the cutting. You should probably wear gloves because the edge gets sharp, but I didn't and managed to emerge unscathed.

"small machine shops"

Look for a sheet metal fabricator.

You can cut with minimal deformation using aircraft snips instead of tin snips.

They also have a lot more leverage than tin snips.

The right and left aircraft snips will only deform the piece you are removing.

I'm not really sure what the difference is, but that may have been what I used. It was sort of a giant scissors. We had them in the house so they can't be anything too fancy though.

"It was sort of a giant scissors."

Those sound like tin snips.

Aviation snips (AKA aircraft snips) use a linkage to get more cutting force and when used correctly the wast piece is what bends for the left and right handed cutter (green and red handles).

The straight cutter yellow handles) will require some bending of both pieces for clearance unless you use blind straight cutters that remove a strip of metal about 1/8 inch wide (they use three blades with only the middle one moving).

Here is a link that might be useful: Pics of aircraft/aviation snips

wi-sailorgirl, that is great news! what gauge sheet metal did you buy at Homedepot?

brickeeye, thanks for the advice! i will look for the aircraft snips. hoping they sell at homedepot..

holly-kay thanks for the tip about the metal shop. i was thinking it would be more costly to go this route, but seems not..

i will try the home depot route first. just because it is right around the corner from me.. if it doesn't turn out,
i guess my fallback will be to look for the metal shops.
will post back results! thank you everyone!

HD has Weiss brand aircraft snips.

Make sure you have heavy enough leather gloves.

The edges of freshly cut sheet metal are razor sharp and the oil on steel makes for slow healing from the bottom up of must cuts.

Bone deep cuts occur with relative ease.

I don't honestly know what gauge it was, but it's not too thick (hence why I mounted it on the luan). Just make sure you go to the plumbing department for it. I think it was a 24"x30" sheet. Its real purpose if for behind sinks or where you are soddering pipe close to a wall to prevent starting a fire.

Another option is just to have it cut to your exact size by the place that supplies the metal. Lots of places supply metal cut to your specs, either for no additional charge or for a nominal charge.

thanks angie! i will call around if my home depot efforts fail.

wi-sailorgirl, thanks again for the advice. i am off to HD now!

brickeeye, sounds scary. i will pick up a pair of thick gloves too. thanks for the warning!

Grinder works, too, with no distortion; possibly some bluing at the edges. Lots of sparks, tho'.
Casey

what's the thickness of the sheet you are planning to use? I will recommend snips if the sheet is thinner. Here is a video about various snips, might be helpful. https://www.youtube.com/watch?v=qAOQfUaRZyw&app=desktop

I got this link few days back when I was asking my friend to assist me with some work. I work for a sheet metal fabrication company (www.bayviewmetals.com) and there we mostly use machines to do the most of the cutting and because of that I was losing the skills and knowledge. This video really helped me a lot. Do check it.

''You can cut with minimal deformation using aircraft snips instead of tin snips."

Good to know! Problem for ME is that i think I have also used such tools to cut heavy steel and they still did not bend the waste pieces back and away from the cutting line.

I have cut corrugated steel barn siding with a variety of implements, including (but not necessarily limited too): snips, reciprocating saw and circular saw. Snips were useless after about four inches of cut, I reeeeally should have used ears plugs when using the reciprocating saw and it was difficult to control, but the circular saw did not do too badly as long as you stayed well clear of the flying steel chips. :o/

BUT, that is a lot heavier than what you are likely to use for your chalkboard. I digressed, but you should be good with a light-gauge steel and good aviation snips.