I need to use 1/4-20 FH cap screws, but the head on these is really large,
and a pain to c-sink.
It seems that a head size of about a #10 or #12 FH screw would do me just
Also, smaller heads allow you to c-sink thinner material for such a screw.
Is there such a thing as a 1/4-20 thread, with a smallish flat head (allen)?
I know I've seen these, just can't remember where, or if they were custom
Name of this item, if any? Sources?
Any reason you couldn't go smaller and use more of them? I've seen
and used socket heads with the one size smaller head, but they came
with the equipment, not something I got off the shelf at a hardware
store. I look on the use of specialty stuff like that as a failure in
design. Leads to the "missing tooth", where somebody drops the screw,
can't find it and can't replace it off the shelf, so the hole remains
empty. If you do it, provide some blind tapped holes for spares.
Self-clinching studs might be a possibility. Several kinds are
illustrated at and
[*] Picture is from article an article with other relevant links:
Although self-clinching studs are specialty items, they aren't
subject to the particular problem you mention because they are
fastened in place (interference fit).
There are "undercut flat head" screws for use in thin material. The
head diameter is normal, but the cone of the head is truncated where
it joins the screw's body. But I've never seen them with hex sockets.
You are aware that hex socket flat heads are larger in diameter than
standard machine screws?
If a head size of #10 or #12 will do you, why do you want to use
The larger diameter body of the 1/4 - 20 will not give more strength
if the head is going to rip out.
Now if you are fastening high strength materials, look at 1/4-28
Consider going with a smaller thread or rater than FH socket head cap
screw go with 100 deg flat head machine screw.
Socket head (allen), 82 deg., head diameter .531, head length .161
Flat head machine screw, 82 deg., head diameter .477, head length .153
Flat head machine screw (phillips or slot), 100 deg., head diameter .
470, head length .110
For thinner material it is possible to go with flat head machine screw
undercut head. The head length is reduced to 70% of the normal screws
(above). Down side, you need to make sure mating part countersink is
to the proper depth and diameter.
"Low head" --Mcmaster-Carr has them
If you search using the astm spec you will most likely find other suppliers
who stock them.
Here is an example having 1/4in long threads :
Alloy Steel Low Head Socket Cap Screw 1/4"-20 Thread, 1/4" Length
In stock at $5.52 per Pack
This product is sold in Packs of 10
Inch Thread Size
Minimum Tensile Strength
American Society for Testing and Materials (ASTM)
Also--if you want to eliminate counter bore / sinking altogether then you
might consider using "button head" instead--the head on which is domed and
so they won't easily snag clothing etc.
part number 91253A533 if the link won't take you there.
Sheeit Charlie, the head on that screw is bigger than what I've got!!
.531 vs. 500!!
I would like the head diameter to be .375.
Regarding the other suggestion to just use a smaller screw, I think 1/4-20
is the minimum I can use, as there is a torque situation, which I can't
address by using more.
Regarding the other comment on a smaller head pulling out, I don't think
that would be an issue -- the torque situation is not THAT bad!!.
I spose I could always turn down these heads, from the bottom of the head on
out, at 82 deg... if I can grab enough of the thread in a collet. Iow, I'd
be making a bit of a shoulder FH screw.....
It would also be nice to get these in SS, and I certainly won't relish
turning those down, but I may not have a choice.
Well, you certainly can't tell from the link/page that these are
reduced-head flat heads.... or that they are flat head *at all* -- typical
HF. Also, I'd be buying a lot of other crap in this kit just to get one
sized screw -- IFF that size is even in the kit.... hmmm, it seems there
are 10 of the size I need.... hmmm, 10 out of 383.... :) :(
And what, HF don't give prices anymore?? Not even in the shopping cart....
You know, I joined that Inside track club thing, it took HF over a year to
sign me up.... what a waste, afaict, but then I haven't really explored it.
Any real benefits?
I seem to recall some security torx-type screws with reduced flat heads....
MH should have sumpn sumpn on this, but I don't know if the 24th ed would
have a complete list, as some of these heads seem sort of recent/modern.
I have an idea I'll wind up turning these things down, much as I would like
Altho, if I got set up to do 1,000 at a time, or sent out 10,000, it might
not be that bad.... a cheap source certainly would be better, tho.
Mebbe for 10,000, I could order a run from a screw house.
'Course, you know what will happen, right?
I'll order their minimum run, proly 10,000, and after I use 10 of'em, the
design will change.... goodgawd....
This kit is something like $10, has what you want, and will serve for many
other future projects. If the time you'll spend hunting for the same thing
in a perfect retail quantity is not worth $10, then I'm sorry for
May I also suggest you look in the furniture fixit hardware bits at Home
Depot, where they sell similar thin flathead screws.