[swarfmaker]

It is mounted on a ceramic tile cutter, and is used to cut round holes in the tiles for pipes etc.
I have used it in bathroom and kitchen renovations. In the photos the actual cutter is the wrong way around. It also has a carbide tip and should be facing the same way as the centre drill.

 

[swarfmaker]

like this

 

[Tinkerguy]

Joe, That there is a circle cutting attachment for making round holes for ceramic flooring tile. It's an accessory for a tile cutting tool that has two round beams that guide the tile scoring wheel and breaker arm. The saddle of your part clamps onto these 2 round beams. The crank rotates a short arm fitted with a carbide bit which you can position over the tile and you can adjust the rotating arm to set the radius of the hole you wish to core out. The curved handle raises the cutting arm and the spring in the barrel applies pressure as you rotate the crank. You either have this tile cutter or this orphaned circle cutter got separated from it.
Ed - Model maker and recently retired shop teacher.

 

[DaninVan]

Ronald wins at 1:04AM !

 

[firesurfer]

So close! I found this item at Walmart. 42.95 Grizzly G8206 3-In-1 16" Pro Tile Cutter

 

[ruterionas]

maybe stirring?