I know Rag quilts would be great with flannels and fleece. Would denim be a good candidate? Does just regular quilting cottons fray enough afterwards or should those not be used? I'm thinking of buying the rag die for my Accuquilt Studio and would like to know what fabrics I should avoid using.

I like the denims ones I made, I don't really like the regular cotton ones I made. It didn't fray enough for me.

That's what I was thinking too...

Does the denim fray well ?

I made one from homespun cottons and really liked the way it turned out (pics below). It frayed very well.

I used levis and they frayed well, so I would think new denim would also fray.
The first rag quilts were all made with homespun because it frays really well, it is much different than regular quilting cotton.

Denim will fray well old washed 100 times,new denim yardage it all will look the same when clipped. I have made many and used both in the same quilt and they look good.

denims and cottons all fray good, some tighter weaves you may want to clip alittle more and thin cottons i use multiple layers of to give more body to the frayed area. sometimes people will use a layer of flannel inside to add to the fraying edge.

It really is just a matter of personal preference.

I made several & used denim with flannel & homespun. They all frayed well.