Planning to build a wardrobe out of OSB plates, however, I fear clothes might get stuck on the material and tear up. What's a simple and cost-effective way to get this smooth? Coating or sanding maybe? Does anyone have some experience with this and can offer some advice?
Straightforward enough job. We stabilize wood like that all the time.
I'd start by painting the piece with a thin coat of either Amercote or West System Epoxy, just to freeze the splinters so they won't keep redeveloping as you prep. Then a very thorough sanding with a jitterbug sander until there are no high spots whatsoever. Then one more shot with the West System, then a sand-down just to knock the high spots off, if any. Then prep & paint.
How much money did you say you'd be saving by using OSB instead of finish plywood?
OSB comes in various grades. Often the two sides are different grades.
7/16 and 1/2 inch are used as sheathing. The inside face isn't as solid as the outside face, but doesn't have inked stuff all over it.
5/8 and 3/4 are often used for subfloors and subroof. They are sanded flat on the top face, and are tight on the bottom face. They make an acceptable living space floor with an optional coat of stain and a coat of varnish.
Given how much time even making a wooden crate takes, I wouldn't use OSB for furniture, but instead would either do it right, and make it out of baltic birch. Catch it on sale.
OR I would make it from dimension lumber throughout. 2x2 framing, 1x4 or 1x6 sides. Dimension lumber will look nicer, is easier to sand. If you go with a wood stain, read up on staining softwoods first. There are tricks to getting it even.