On Tue, 13 Oct 2009 15:12:37 +0100, "ian field"
wrote:
"Archimedes' Lever" wrote in message
.. .
On Sun, 11 Oct 2009 17:16:24 +0100, "ian field"
wrote:
"Archimedes' Lever" wrote in message
...
On Sat, 10 Oct 2009 10:11:16 -0700, Jim Thompson
wrote:
1/4"-20 tap calls for 0.201" tap drill (13/64")
Into a steel 1/8" panel, tap is hard enough to turn that handles flex
:-(
Is that normal, or do I need to go up one or more drill sizes?
...Jim Thompson
1/4 - 20 through a mere 1/8 hole is too coarse a thread for that little
thickness. Use a #10 or a metric.
Also, tapping a hole has a bit of art to it. If you do not know the
limits of the metals the handles and taps, etc. are made of, you will
not
know the tricks of performing the task, like the one where you only turn
a 1/4 turn or so at a time, and then back off and then go back in, and
you slowly work the tap, not attempt to make the turns all in one fell
swoop, and yes, some sort of lube is needed.
If you insist on the 1/4 - 20, then you can use the edges of the drill
to open up the hole a little bit. Makes the tapped hole a bit looser as
well, however.
Ideally, a panel that thin for a hole and subsequent bolt that size
should get a boss welded onto the back side of the hole so that the
number of threads is increased You should tap the boss first as it will
harden up when welded, and then you chase the tap back down through the
hole again after it has cooled.
1/4 - 20 can hold a pretty big load. Surely you could use a smaller
fastener, like a #10 or such.
Can you get Taptite screws in that size?
That is a brand name, not a screw type. So, it is unfamiliar over
here.
Here, we have PEMs, and KEPs and the like.
A search for "pem" comes up with punched in threaded inserts,
"KEP" produces
no relevant results.
"KEP" Nuts have an attached lock washer... convenient for working in
tight places. I always keep a box of 8-32 and 10-32 kep nuts on-hand.
Searching "taptite USA" finds a number of suppliers, sheet as thin as 1/8"
might be a bit tricky with taptites, normal industry practice would be to
drill the hole small and punch form the hole to the tapping size.
Up one drill size plus cutting oil did the trick. All 24 holes now
tapped ;-)
...Jim Thompson
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