Official Luthiers Forum!

I'm making a wood body block plane from a kit. The instructions say to finish
with Tung Oil. They don't mention the sole of the plane. I'm wondering if it's
a good idea to use Tung oil on the sole, or any finish there at all. I'm thinking of using
Tru Oil since I already have that for the rest of the body.
TIA,

Leave it without finish. Anything you put on will rub off and probably mark the surface you are planing. The best finish is a very sharp scraper to get the sole flat.

It depends a bit on what wood is on the plane sole. Traditionally, better-quality wood-bodied planes had lignum vitae or other hard/waxy woods on the sole to make them somewhat 'self-lubricating'.
I'd follow Sebastian's advice and leave it unfinished or use a penetrating-type oil like tung oil or so-called 'Danish' oil. Tru-Oil is actually more like a varnish, so I would not use that as it will certainly wear off quite quickly and cause problems.

Cheers
John

Todd, what's "PU"?

Polyurethane glue- it sticks to oily woods quite well.

Thanks for the update on "PU", polyurethane glue.
Now, what's an example of "PU"? Like, Elmers, etc.?
TIA,

Elmer's Ultimate High Performance Glue
Lepage Ultra PL Premium
Gorilla Glue (Polyurethane- not Gorilla 'Wood Glue' which is a standard PVA glue)

PU glues tend to be clear amber, honey-consistency liquids that require water to cure. Excess glue squeeze-out usually foams. Not gap-filling.

Correction- The Lepage Premium PU is colorless.