Drywall screws probably aren't a good choice for much more than wood or
their intended use (although they do self-drill thru fiberglas nicely).
The bad feature of most DW screws is that they're brittle, and just snap.

I prefer to use decking screws (for wood projects), which will typically
bend before breaking, but testing a chosen brand? (likely to be imported) is
probably a good idea.

The way the heads are transitioned from the shank isn't very consistent for
either type.. there may be a radius as mentioned, or a combination of a
countersink that blends into a tapered section.

You've neglected to mention what materials are to be fastened, but quality
countersunk-head machine, sheetmetal or wood screws will likely have more
accurate/better matching head geometry for a machine-cut countersunk hole.

If this fastening task is related to an earlier situation of applying a
thin, hard skin over a soft substrate, I'd expect DW screws to be about the
worst choice.

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


"Existential Angst" wrote in message
...
Dayum.... google has not been my friend.... nor Bing....

I found the included angle of bugle head drywall (60-63 deg, fyi), but not
of regular head drywall screws.

The reason I'm looking is to get the right spot drill or c-sink... MSC
carries 82 deg spot drills, as well as a variety of other angles.

Not all FH screws are 82 deg... I was informed that metric FH are in fact
90 deg, some sheetmetal stuff 100 deg, and some aircraft stuff 120 deg.

Which also raises the Q: where did 82 deg come from? 90 deg shore makes
sense to me!!
--
EA

"Wild_Bill" wrote in message
...
Drywall screws probably aren't a good choice for much more than wood or
their intended use (although they do self-drill thru fiberglas nicely).
The bad feature of most DW screws is that they're brittle, and just snap.

And rust like crazy.
The coarse thread has an especially nice "bite", as the root diam to total
diam is much smaller.
Yeah, these things have a good Rockwell, I think. I occasionally use them
(and concrete nails) as scribers.


I prefer to use decking screws (for wood projects), which will typically
bend before breaking, but testing a chosen brand? (likely to be imported)
is probably a good idea.

Decking screws appear to me to be higher quality drywall screws. I have a
bunch of SS DeckFast deck screws: square drive, "auger point" (slit like in
tapping chassis screws), and *two* included angles (one a transition to the
neck) as you mentioned, and raised lines under the head, presumably an
anti-loosening strategy.
Starborn Industries, Avenel, NJ. Not cheap.


The way the heads are transitioned from the shank isn't very consistent
for either type.. there may be a radius as mentioned, or a combination of
a countersink that blends into a tapered section.

You've neglected to mention what materials are to be fastened, but quality
countersunk-head machine, sheetmetal or wood screws will likely have more
accurate/better matching head geometry for a machine-cut countersunk hole.

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.


If this fastening task is related to an earlier situation of applying a
thin, hard skin over a soft substrate, I'd expect DW screws to be about
the worst choice.

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



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


"Existential Angst" wrote in message
...
Dayum.... google has not been my friend.... nor Bing....

I found the included angle of bugle head drywall (60-63 deg, fyi), but
not of regular head drywall screws.

The reason I'm looking is to get the right spot drill or c-sink... MSC
carries 82 deg spot drills, as well as a variety of other angles.

Not all FH screws are 82 deg... I was informed that metric FH are in
fact 90 deg, some sheetmetal stuff 100 deg, and some aircraft stuff 120
deg.

Which also raises the Q: where did 82 deg come from? 90 deg shore
makes sense to me!!
--
EA

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?

"Wild_Bill" wrote in message
...
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).

Good memory!!
Apropos of that excellent discussion, I came up with an elegant solution:
No glue at all!!
I just had delivered 1/32" sheet alum, and 1/2" ply, and I'm just going to
let the alum "float" or slide on the ply substrate, as it will be very well
constrained along all 4 edges, by 3/4 x 1.5 x 1.5 (1/8") channel.

Eventually I WILL use glues of sorts, as I think that altho mechanical
engineering insights in that thread were valid, that I'll still be able to
generate add'l stiffness without the aluminum shearing the top layer of ply
off the wood. It will be an ongoing experiment.

But, as it is, the ply itself is stiff enough, just more would be better.



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).

You have a scary memory!! LOL
Indeed, and I found that the coarse drywall screw was actually pretty well
suited for this, esp. with being so hard -- but indeed a bit brittle..
I found some other type screws as well, but I'll have to dig those up --
sumpn with "mixed pitch threads", or sumpn.


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.

Yes, those SS deck screws I have seem very high quality, and "built to
drill".

The FH screw Q was not for sheetmetal, tho, but for that apparatus in a
doorway, with sufficient alum "meat" to c-sink.
I myself would not even contemplate c-sinking sheetmetal -- there's nuthin
to c-sink!!

Same problem exists for FH machine screws in material that's too thin, eg,
1/4-20 FH in 1/8 alum. You wind up enlarging the hole itself.

I solved my problem with the MSC 82 deg spot drill for any #10 FH screw, and
drywall screws, altho not 82 deg, nevertheless "fit". I most likely won't
stick with drywall screws, I'll do sumpn with deck screws, or trad'l
sheetmetal screws, or sleuth down some type of custom/specialty screw, of
which there are an absolutely dizzying array.

--
EA




--
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?

On 2011-09-03, Wild_Bill wrote:

[ ... ]

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.

Another tool which is nice for thin metals is the tool made for
aircraft sheet metal use. The Microstop countersink cage, such as this
one on eBay:

Auction # 280731984065

It chucks in a drill press or a hand drill. It uses special
piloted countersinks which screw into the spindle. It will push down
with the cage until the preset depth is reached (adjustable in 0.001"
steps), at which point the ball bearing will stop the advance with the
cage in contact with the workpiece. IIRC, it has a certain amount of
spring travel before it hits the stop, but I may be mis-remembering that
part.

It would be nice if the eBay auction came with some sample
countersink bits, but this one does not have them.

O.K. This one has two cages, and four bits of different sizes:

Auction # 190569970965

Some bits, such as this one, are drilled for a pilot but you
put your choice of size pilot in and secure it by a setscrew in the body
of the countersink.

Auction # 230633535081

The search term to see several styles and groupings is:

Microstop countersink

Good luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Sat, 3 Sep 2011 18:09:36 -0400, "Existential Angst"
wrote:

The FH screw Q was not for sheetmetal, tho, but for that apparatus in a
doorway, with sufficient alum "meat" to c-sink.
I myself would not even contemplate c-sinking sheetmetal -- there's nuthin
to c-sink!!

If you make up a solid punch..with the shape of the countersink turned
on the end of it..and press it over the hole..then hit it with a hammer
a good lick...it forms a nice countersink depression that your screw
fits right into.

Ive made up a number of these for people who were doing doors and so
forth when I ran an alarm company.

Gunner

--
"The danger to America is not Barack Obama but a citizenry
capable of entrusting a man like him with the Presidency.
It will be far easier to limit and undo the follies of an
Obama presidency than to restore the necessary common sense
and good judgment to a depraved electorate willing to have
such a man for their? president.. Blaming the prince of the
fools should not blind anyone to the vast confederacy of
fools that made him their prince".

On Sat, 3 Sep 2011 18:09:36 -0400, "Existential Angst"
wrote:

"Wild_Bill" wrote in message
...
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).

Good memory!!
Apropos of that excellent discussion, I came up with an elegant solution:
No glue at all!!
I just had delivered 1/32" sheet alum, and 1/2" ply, and I'm just going to
let the alum "float" or slide on the ply substrate, as it will be very well
constrained along all 4 edges, by 3/4 x 1.5 x 1.5 (1/8") channel.

Eventually I WILL use glues of sorts, as I think that altho mechanical
engineering insights in that thread were valid, that I'll still be able to
generate add'l stiffness without the aluminum shearing the top layer of ply
off the wood. It will be an ongoing experiment.

But, as it is, the ply itself is stiff enough, just more would be better.

Industrial type contact cement would be an easy way to bond the
alumininum to the plywood and might work for you.



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).

You have a scary memory!! LOL
Indeed, and I found that the coarse drywall screw was actually pretty well
suited for this, esp. with being so hard -- but indeed a bit brittle..
I found some other type screws as well, but I'll have to dig those up --
sumpn with "mixed pitch threads", or sumpn.

My choice in screws for this application would be what I call "cabinet
screws" They have a conventional countersink head, a straight shank,
and fairly deep threads. The screws are meant for use with wood or
particle board and thus have threads deeper than a wood screw, but a
bit less than a true particle board screw. Unlike sheetrock screws
they aren't brittle.

"Jim Levie" wrote in message
...
On Sat, 3 Sep 2011 18:09:36 -0400, "Existential Angst"
wrote:

"Wild_Bill" wrote in message
...
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).

Good memory!!
Apropos of that excellent discussion, I came up with an elegant solution:
No glue at all!!
I just had delivered 1/32" sheet alum, and 1/2" ply, and I'm just going to
let the alum "float" or slide on the ply substrate, as it will be very
well
constrained along all 4 edges, by 3/4 x 1.5 x 1.5 (1/8") channel.

Eventually I WILL use glues of sorts, as I think that altho mechanical
engineering insights in that thread were valid, that I'll still be able to
generate add'l stiffness without the aluminum shearing the top layer of
ply
off the wood. It will be an ongoing experiment.

But, as it is, the ply itself is stiff enough, just more would be better.

Industrial type contact cement would be an easy way to bond the
alumininum to the plywood and might work for you.

Contact cement was mentioned a few times.
I wonder if one type of adhesive will be less prone to shearing off a ply
layer than other types.
I spose if the adhesive itself has some kind of give.....

Also, with contact cement, I"ll get a free buzz.....





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).

You have a scary memory!! LOL
Indeed, and I found that the coarse drywall screw was actually pretty well
suited for this, esp. with being so hard -- but indeed a bit brittle..
I found some other type screws as well, but I'll have to dig those up --
sumpn with "mixed pitch threads", or sumpn.

My choice in screws for this application would be what I call "cabinet
screws" They have a conventional countersink head, a straight shank,
and fairly deep threads. The screws are meant for use with wood or
particle board and thus have threads deeper than a wood screw, but a
bit less than a true particle board screw. Unlike sheetrock screws
they aren't brittle.

Bingo! Dats what I had gotten!! Couldn't remember.
NOW to see if I can find them.....

Indeed, a sturdier screw, not so brittle.

--
EA

On Sun, 4 Sep 2011 14:51:07 -0400, "Existential Angst"
wrote:

"Jim Levie" wrote in message
.. .
On Sat, 3 Sep 2011 18:09:36 -0400, "Existential Angst"

My choice in screws for this application would be what I call "cabinet
screws" They have a conventional countersink head, a straight shank,
and fairly deep threads. The screws are meant for use with wood or
particle board and thus have threads deeper than a wood screw, but a
bit less than a true particle board screw. Unlike sheetrock screws
they aren't brittle.

Bingo! Dats what I had gotten!! Couldn't remember.
NOW to see if I can find them.....

Indeed, a sturdier screw, not so brittle.
McFeely's

"Jim Levie" wrote in message
...
On Sun, 4 Sep 2011 14:51:07 -0400, "Existential Angst"
wrote:

"Jim Levie" wrote in message
. ..
On Sat, 3 Sep 2011 18:09:36 -0400, "Existential Angst"

My choice in screws for this application would be what I call "cabinet
screws" They have a conventional countersink head, a straight shank,
and fairly deep threads. The screws are meant for use with wood or
particle board and thus have threads deeper than a wood screw, but a
bit less than a true particle board screw. Unlike sheetrock screws
they aren't brittle.

Bingo! Dats what I had gotten!! Couldn't remember.
NOW to see if I can find them.....

Indeed, a sturdier screw, not so brittle.
McFeely's

I meant "find them in my house'..... iny idears??

I get the McFeely's catalog, btw -- well done, good company.
--
EA