"BottleBob" wrote in message
...
On Sunday, April 21, 2013 12:38:01 PM UTC-7, Existential Angst wrote:
Awl --
I've taken to form tapping aluminum (cnc rigid tapping mode), and have
noticed a wide variety of geometries in these taps.
The name-brand form taps I have (Nachi, Emuge) almost look like cut or
hand
taps, as they have between 2 and 5 sharp-edged flutes.
I have others which have no flutes whatsoever (they look almost like a
screw!), and others with a slight recess instead of a true groove,, and
one
that looks almost oval.
Any insights into the preferred style of form tap? Does this style vary
with context, metal, etc.??
Suggestions on best bang fer the form tap buck?
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EA
EA:
You're asking this in rec.crafts.guns.politics?? Silly Wabbit, you might
have better luck in Practical Machinist. g
Why, I'm trying to save RCM!!
And which simultaneously demonstrates that know-it-all assholes like
Kidding/PlimpBoi don't know jack**** about anything, and have essentially
zero to contribute that isn't Limbaugh-type rabid vituperative (and
incorrect) opinion.
Form taps really don't have FLUTES per se, but most have LOBES. The
vertical grooves on the taps (if it has them - not all do), is to
primarily get lubrication to the working area of the tap,
Lobes, ok..... but goddamm, those lobes are perty sharp!
Which I think then helps the deformation process. In a sense, perhaps they
ARE cutting, but not by way of actually removing the material, but *parting*
it -- ie, the deformation process.
and secondarily to relieve pressure in blind hole tapping.
This is inneresting.
What I think these lobes do in INCREASE the literal pressure of the tap lobe
into the alum (like a nail has higher pressure affecting wood, visavis the
head of the hammer itself, ie, a literal application of F/A), but in a
smaller *total area* at a time, which ultimately reduces the total *torque*
being applied to the tool/material at any given instant.
Which leads me to believe that these lobe-less taps are really amping up the
req'd torque/ horsepower, cruising for breakage. On top of reducing
lubrication, and poss. actually trying to compress coolant in a blind hole.
--
EA
The following is an old article from Cutting Tool Engineering magazine,
but it still contains good basic info.
http://www.ctemag.com/dynamic.articles.php?id=197
--
BottleBob
http://home.earthlink.net/~bottlbob