You are likely to find variability in the composition of the doors
within the same store, not only between stores. It's all going to depend
on who manufactured them, with what, and for what price point.

My solid core door benchtop consists of really really thin birch veneer
over a core of fine particles. It almost looks like MDF but it's not MDF
as it is not as dense or as heavy as "real" MDF. For a door though, it's
pretty heavy. I routed a recess into the door/top for my router plate
and when routing this stuff you get nice crisp clean edges in it.
They've stayed that way because the router plate seldom leaves its
recess. But when you make through holes, whether for the router or for
bench dogs, the stuff crumbles. I wound up making and applying 3/4
edging to the router cutouts, and applied a thin layer of wood filler
into the recess where the router plate sits just to keep this stuff from
chipping, etc. (The door overhangs the end of the workbench and the
router mounts in the overhang - thus I have a workbench and router table
in one.) The dog holes were a disaster. After a handful of uses the
holes became misshapen and the area around them "mushroomed." The
solution for me was to inlay a 3/4 inch thick strip of hardwood with
suitably sized dog holes in it. I also glued a 1/4 thick strip directly
below (on the underside of the top) to prevent the same from happening
on the bottom. Keep a 3x5 block of pig iron or steel at hand as an
"anvil" because if you do any serious pounding on the door's surface it
will quickly go to hell on you.

I got the door because a neighbor was giving them away in a remodeling
job. It is heavy and flat, and all things considered it has stayed that
way over nearly 10 years in an unheated garage, so I am not dissatisfied
with it. The bench does NOT move no matter what I do to/with/on it. But
if I had to spend my own money on materials I'd go with a couple of
layers of 3/4 plywood and maybe a sacrificial hardboard surface and take
the trouble to get it flat as I do not have access to sufficient
quantity of good hardwood (or money) for a solid wood top.

J.


James Williams wrote:
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I want to use a 30"x80" Solid Core Door Slab for a benchtop for a new
workbench I'm building and have a couple of questions someone might be able
to answer.


I have found at both Lowes & HD, 30"x 80" birch skinned solid core doors, is
there any diff in the two stores doors? Does anyone know what is under the
skins? (mdf, ply, pine, ecte) this is important because I will be drilling
holes for bench dogs and of course need to mount the door to frame via
screws.

Thanks for the help!

JW