Form tap geometry

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?
Reply to
Existential Angst
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I prefer Balix as it's what I've used the most frequently. I've had very good success with them. I have no comment on tap geometry. All I have ever been interested in is the end result and how long the tap will last:
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Your balax taps seem to have 1 groove. My nachi 1/4-20 has two; emuge 1/4-20 has 4, the 5/16, 3/8 has 5.
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Sheeit, I paid list for those muthafuckas..... ahma haveta to talk to haas about that.... LOL
My no-name 5/16 stuff has no groove at all, looks perfectly round, like a screw.
Don't know what it all means. One implication might be this:
With at least one groove, the tap can release air/coolant from a blind hole. One of my worries with the no-groove imports is that they might could trap/compress coolant in a blind hole, and, well, coolant is incompressible.... Don't know if that's a valid concern, but the thought did occur.
Reply to
Existential Angst
Since I'm still 'sperimenting w/ the gr510, which has all kinds of load indicators'n'shit, I'll tap with the emuge and the imports, see if I there is a detectable load difference, as well any diffs in the fit/appearance of the tapped hole itself.
Reply to
Existential Angst
EA:
You're asking this in rec.crafts.guns.politics?? Silly Wabbit, you might have better luck in Practical Machinist.
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, and secondarily to relieve pressure in blind hole tapping.
The following is an old article from Cutting Tool Engineering magazine, but it still contains good basic info.
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Reply to
BottleBob
BottleBob fired this volley in news:f410705d-7bec- snipped-for-privacy@googlegroups.com:
What he said.
If it actually has sharpened flutes, it's a cutting tap, not a thread- forming tap.
LLoyd
Reply to
Lloyd E. Sponenburgh
Why, I'm trying to save RCM!!
And which simultaneously demonstrates that know-it-all assholes like Kidding/PlimpBoi don't know jackshit about anything, and have essentially zero to contribute that isn't Limbaugh-type rabid vituperative (and incorrect) opinion.
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.
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.
Reply to
Existential Angst
Double check and see if its perfectly round or not. A lot of form taps have a slight "dip" in one side which is where air is released. Some have a single groove along the side of a round tap. Same reason. Blind holes dont release coolant when you stick a plug in them.
Gunner
Reply to
Gunner Asch
The 5/16 imiports I have are perfectly round!! It probably is risky using these in a thru hole, never mind a blind hole. Plug indeed. I wanted to compare these to the emuge's, but breaking taps even in scrap gives me the willies.... lol
Reply to
Existential Angst
Years ago when I first started using form taps I had some that appeared to be perfectly round, however they were tri-lobed. Measuring with a micrometer they seemed round, using a vee block and an indicator showed the lobing. Eric
Reply to
etpm
Mine must have some subtle lobing, indeed!! I'll try to discern any, but it's gotta be minimal....
Reply to
Existential Angst
Roll them between your fingers or on a surface plate, I doubt they are "perfectly" round. Too much friction for one thing.
I prefer the ones with at least one groove, on aluminum I go fairly fast and the more pronounced the groove to let trapped air/coolant out, the better.
Remove 333 to reply. Randy
Reply to
Randy333

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