I don't recall the details about the earlier discussion wrt
metal-over-substrate, but it wasn't about wood-epoxy filler products, not
that I recall.

A while ago you were asking about adding a skin over foam or MDF or maybe
some other substrate(s).

Then there was an even earlier topic of screws with deep/aggressive threads,
such as those used for plastics.. but you were contemplating using them in
metal (mounting a device to metal door frames, IIRC).

I assume that you're aware that countersinking thin materials/sheetmetal can
be a little troublesome since common cutting tools will tend to lift the
material, making consistent countersink dimensions problematic.

Using a multi-flute countersink cutter which doesn't have any, or little
cutting edge relief angle (like dressing a drill points' relief angles for
drilling brass) so the cutting forces are more like that of a reamer -
scraping away the metal.. should eliminate lifting of the thin materials.

Sheetmetal screw threads are very reliable in wood, although depending upon
which particular wood and the screw size (diameter), predrilling may be a
good idea.
Driving sheetmetal screws into dry hardwoods will likely cause a lot of
pressure, and possibly splitting when not predrilled (definite maybe).

Predrilling doesn't necessarily mean a HSS twist drill, when doing
carpentry-type stuff.. a nail with the head removed, mounted in a drill (or
flutedYankee drill) will generally suffice.

The cutting points of decking screws (at a more premium price, but probably
a better quality fastener) can eliminate the need for drilling in most S-P-F
woods, but maybe not in dry hardwoods YMMV.

--
WB
..........


"Existential Angst" wrote in message
...

Attaching metal apparatus to wood.
From a c-sink pov, I should proly go to sheetmetal, but from a
drilling/grabbing pov, I really like coarse drywall screws, whose threads
are deeper, sharper.



Oh, the wood filler/epoxy thread.... Why are drywall screws bad for that,
besides rusting like crazy?
What is a good choice?