Been thinking that expanding foam insulation in a spray can might work to make reel seat arbors or even foam cores for grips. If it will work this could make a few cores at a time. Anybody got an idea what the density of these products is? I have looked at several different brands but none indicate a density on the can.

You'll be disappointed. All the one-part foam in a can products are fairly soft. Not at all like the premium two-part expanding urethane products.

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I agree with Tom, having tried that route in the past. Inconsistent density, large holes in foam, etc.

I've thought about the spray-can product myself. I've seen the cheap stuff at various places but the product I had in mind used to be called (maybe still is) FIRE-STOP. It's designed for sealing riser conduits against fire from travaling upward in high-rise buildings. It wasn't cheap as I remember either. It did however set quite hard & very solid!

Raymond Adams
Eventually, all things merge, and a river runs through it..

I've tried the Home Depot brand and it gets a big thumbs down