What is this old timey circular cutting tool?

[jim gossage]

After my father in law died I inherited some heavy duty cutting tools, about 15 or so of various size from <1" to over 2". He used these when he worked at Northrup sometime between 1950 and 1980. I can't quite figure out what they are. My first thought was a hole saw for metal or wood. They don't seem sharp enough for wood. I tried one on a 1/8" thick piece of mild steel and it seemed to be working at first (slow speed + cutting oil), but then just got too hot and stopped cutting 1/16" in. Anyone in the woodworking collective have any ideas?

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[Ken Fitzgerald]

Here's a possibility. https://www.aerotools.com/shop/ati/71714-at413-27.html It's still for sale.

[Doug Garson]

Sure looks like a hole saw, odd that the center pilot isn't a drill bit, just a round bar? Is it just dull?

[Adam Herman]

AT is aircraft tool, an old manufacture. for cutting steel or aluminum depending on grind. also known as an annular cutter. run slow with a lot of down pressure in a mag drill or milling machine or gear drive drill press.

[Rich Engelhardt]

https://www.aerotools.com/shop/ati/71714-at413-27.html

Here you go.

[jim gossage]

Thanks guys. Looks like they are precision hole saws for thin metal. What I don't understand is why the cutter wall is so thick, almost 1/8". I would think that would just mean the need for more pressure and more heat when cutting?

[Bill Dufour]

anular cutter. The teeth are either carbide tipped or very dull. Hard to tell with the lighting in the photo. I do not see any set which wood cutting will need.
Bill D

[Alex Zeller]

A tip for anyone using a hole saw is to drill the pilot hole first and then use a steel rod when drilling by hand. The drill bit flutes can catch on the edge of the hole allowing the hole saw to drift. Looking at that picture I would say it's a hole saw specifically for non ferrous sheet metals like aluminum and copper. Using it on steel will dull the teeth. The shallow depth of the gullet would make them useless for much more than something thin.

[jim gossage]

Interestingly, according to their catalog they are "For cutting thin skins and corrugations in aluminum, steel, and other nonferrous material. The hole saw can be resharpened many times and isdesigned for use in a portable power unit or in standard machine tools." Made from "high-speed tool steel."