I wasn't familiar with Silk Floss Tree, so I looked it up. It has palmate leaves. Your tree has pinnate leaves so SFT is not your tree. Try Aralia spinosa.

Zanthoxylum ?

Yes, definitely not Chorisia or Aralia.

It looks like it is going to bloom soon, it will make identification easier.

It is not Aralia spinosa which has tripinnately compound leaves and the thorns look different as well.

http://forestry.sfasu.edu/faculty/stovall/dendrology/index.php/fact-sheets-sp-916/photographs/55-aralia-spinosa-devils-walkingstick

Flower cluster visible in second photo

Carol, I'm sure you're correct. I have no personal exoerience of any of these trees. I was dubious about Aralia since most of the images I found were tripinnate. But I also found pictures and statements saying they could be bipinnate. So I risked a suggestion. I'll be interested to see it in flower.

Flora, I just don't see Aralia spinosa as a street tree or tree for a small property . Where I've seen it it suckers like mad. I once grew one but it didn't remain as one and had to be removed. And it's a bit treacherous working around it.

Here's a blog with a follow up posting from someone else that once grew it.

http://usinggeorgianativeplants.blogspot.com/2014/07/giant-flower-at-last.html

Zanthoxylum info :

http://www.foragingtexas.com/2008/08/prickly-ashtoothache-tree.html

Do you know what, Carol? I think there are pix on the web labelled Aralia which are actually Zanthoxylum. Perhaps the fact they are both sometimes referred to as Prickly Ash in common parlance has muddied the waters.

Maybe it's different in some parts of the US but otherwise in general the Aralia tree encountered in gardens is A. elata and not A. spinosa. Not that the tree being asked about here looks very much like either of those - it is instead almost certainly the toothache tree.

http://www.bing.com/images/search?q=Zanthoxylum+Clava-Herculis&FORM=IRIBIP