According to pogo :
Go back to McMaster-Carr and get a box of the same size, but
black finished Allen head capscrews, which will be much harder. (And
probably a box of 100 will cost less than four or five from Home Depot.
:-)
Good idea. But to make sure I am not getting the same kind of metal, what
could I look or ask for ?
Well ... assuming that your screw was a 1" long one, and looking
in the MSC catalog for the 8-32 size which you say you are using (and I
would suggest 10-32 anyway for that), the prices for a box of 100 range
from $5.64 for the "import" (which is still pretty good from MSC) up to
$16.87 for the ones made by "Unbrako" (which are really tough steel).
I see that they have the same screws in 25 screw packages ("Made
in USA", but with no brand) for only $4.13
The 10-32 screws in the same length range from $7.15 (for the
import screws) to $17.17 for the Unbrako. (And with a similar 50-screw
pack of unbranded "Made in USA" screws at $10.57.)
Any of these would be much better than the ones which you picked
up from the local Home Depot. *Some* local hardware stores will stock
good screws, but it is hard to predict which will and which won't. I
would not trust anything from Home Depot if you need strength.
I don't have anything resembling a recent McMaster Carr catalog,
so I can't get the prices for you from there.
Anyway -- the description in the MSC catalog is "Alloy Allen
head cap screws".
What is the screw thread? It looks something like 10-32.
8-32. That is based strictly on the tap I used. I don't have a screw thread
gauge ( what do you call it ? ) right now, so I just place the screw against
the tap until I get one that lines up with the threads perfectly, then I
make a test run on something and see how the screw works. I do have a
plastic "catch-all" gauge from Home Depot and the screw fits in the #8 hole.
There are thread pitch gauges (many folding blades with a
sawtooth edge to match the thread pitch for checking), and there are
plates into which the screws can be fitted for checking the size and
pitch. The latter is sold under the name "Screw Checkr" (or perhaps
"Screw Checker"), and I got mine from MSC -- they show up frequently in
their sales flyers once you get on their mailing list. I have and use
both.
What drill did you use to make the hole? IIRC, the tap drill
for a 10-32 is a #21 "wire size" drill. No fractional size is close
enough to do the job right.
The only markings I can see on the drill bit are
25
ST
HS
one under another just like I typed it above.
O.K. It is a #25, and the "HS" means "high speed steel". The
"ST" might be a maker's mark.
Anyway, looking up the recommended tap drill for an 8-32, the
size should be a #29. (Except that for some reason, the table in
Machinery's Handbook gives the same size for 8-32 and for 8-36, but
another table gives differing sizes, both of which are close to the #29
drill bit.
And the table does say that I correctly remembered a #21 for
tapping a 10-32 thread. (Note that the larger the number, the smaller
the drill bit in the wire (number) sizes.
So -- you used too large a drill bit for drilling the hole for
tapping. You now have little choice other than going up to the next
screw size (10-32). And you'll need a set of Allen wrenches (also
called "hex keys" for driving the screws which I suggested.
Normally, I don't bother with the handbook, because the HUOT
drill indexes in which my drill bits are stored have the sizes for
common threads on the hinged metal base which holds the first row of
drill bits.
(You *did* use a tap to make the threads in the
hole, did you not? You don't want to use any kind of self-tapping screw
for this kind of thing, you really want to have a proper tap to cut the
threads without the screw being involved.
Yep - I used a tap. I'm new but now that new! Pretty close, though!
I think it is the size of the hole and also that the end of the screw is
tapered too
much (before I even use i) for the depth of the hole that has the threads I
cut in it.
It has a tapered point? That almost sounds like a supposed
"self-tapping" screw, which is designed for use in mild sheet metal, not
in tapped holes.
It is more a matter of *where* you get it. The ones which I
described above should do quite well -- either from your McMaster Carr,
or from MSC. I prefer MSC, simply because it is not like pulling teeth
to get a catalog from them, and the catalog has pages of choices of
screws. The black oxide finished ones tend to be rather painfully hard.
I'll give a thorough look over the next couple of days and
post back here to see if I am on the right track.
Try the MSC catalog on their web site. You have above the
description to look for, and their URL is (IIRC)
http://www.mscdirect.com/
The following URL shows a photo with inset of the bushing and screw for
reference:
http://www.waycoolgear.com/ebay/wheel.jpg
But no photo of either the hole or the stripped thread, both of
which would have been more useful in diagnosing the problem
I just posted a new photo in this thread, although I'm not sure how much it
will help.
I *had* some perfect ones and accidentally deleted them from the
camera. It took me forever to get just the one I posted today so I went with
it.
I apologize if I've gotten too basic in what I sad, but your
wording of your question, and what you did not say suggested that you
needed this level of detail.
You got it all perfect as far as I am concerned! Thanks!
Glad to help.
I have a cheapo tap from Sears, and a few from a friend of
mine that used to do this stuff in his younger days.
The ones from your friend may be better quality taps --
depending. I would not expect a good one from Sears, either.
Thanks again for all of the help! Hope what I have written here helps you to
help me !
I think so. What I have not found is your newly-posted photo
(though the URL might be in some other branch of this thread). I could
not find it by working uphill from the previous URL, as indexing of the
directories is turned off.
Good Luck,
DoN.
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