Simple Questions...

[Kim Lau]

Is there a certain amount of material to leave on the blade before HT?
Im making my first knife outta 3/32 O1 steel.

 

[L6steel]

Kim, unless you're going to convex grind it, 3/32" is awful thin steel to start with! If you are going to convex grind it, I would heat treat it first. Just drill all the holes and maybe take a file and just start the plunge prior to heat treat.

 

[Stacy E. Apelt - Bladesmith]

3/32(.09375) is thin, but not too thin for a slicer. I agree, don't grind much of an edge prior to HT. A coating with PCB or Turco will keep the fire scale down during HT and make the final sanding much easier.
I occasionally start with .0625 steel

On most blades you want to leave an edge of about .030-.040 and a little extra ( .010-.020) on the sides to allow for the removal of the scale and decarb after HT. On a thin blade like your,sand to 400 grit prior to HT. Clean it up with 220 and then go directly to stones and fine sandpaper after HT.You will only be removing a tiny bit to finish the bevels.
Stacy