Peter,
Below is a couple of links for carbide, TIN, and cobalt tipped taps. I
would say they ship to the UK with no problems. OSG may have a
distributor there also.
http://www.discount-tools.com/michpictorial.htm
http://www.osgtool.com/catalogtap.asp?TapType=Straight%20Flute
Will
On Sun, 23 Jan 2005 13:52:34 -0500, Will Matney <craxd1@ezwv.com> wrote:
On Sun, 23 Jan 2005 13:02:11 -0500, <G3rzp@aol.com> wrote:
Will said:
"My guess is because 4-40 screws have more holding power than a 4-36
screw
does. This is due to more threads in the thickness of whatever it's
screwed into, either tapped material or a nut. Fine threads are always
used in places where more holding power is needed in a thin section.
Coarse threads are for thicker sections."
This is true up to a point. It's generally reckoned that if you have
three threads engaged, that will give sufficient strength in most
materials. However, softer materials benefit from using a coarse
thread, because although the core and overall diameters are the same,
there's more meat in each thread.
Correct, fine threads are for metallic uses like steel and aluminum
(tapped or with a nut). Deep, coarse threads are used for wood,
fibergalss, and composite materials like the insualtion board in
mention. That is if it is to be tapped and used without a nut. But if a
nut is used, the unified thread system is then used with either coarse
or fine threads. Some of the other threads like Buttrus and Acme are
used for linear motion or in jacks, etc.
All of which is why I tend to use Unified
coarse threads (or even BSW!)in places where I'm using soft materials
like aluminium, teflon, tufnol, polythene and even fibreglass. The last
is very rough on tools, blunting them very rapidly, and carbide tipped
tools are desirable. However, I haven't seen any carbide taps yet!!!
We have carbide taps here and others with a TIN (Titanium Nitride)
coating. Just that carbide and TIN costs more than a HSS one. Carbide
can be bad to break off to so they have to be used with that in mind.
One point worth remembering is that plain carbon steel is harder than
HSS (High Speed Steel) at low temperatures. HSS is used extensively
where speed of metal removal is important, as in industrial machining,
but for a lot of the stuff we do in home brewing, it's not worthwhile -
certainly for taps and dies which are only used in hand tools.
Generally most tool steels in the rough are soft or as annealed. After
they are shaped into a tool they are then hardened before they are
ground. There's two types available here, water and oil hardening. HHS
blanks (like drill rod) though are soft and not worth a quarter if not
hardened. There are pre-hardened HSS blanks for boring bars and for use
in fly cutters though. They are already shaped and made to be ground
away as they are used up.
73
Peter W6/G3RZP (where it's warm and sunny, for you guys in the mid
west and on the east coast!)
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