taper vs plug taps

I've noticed that most of my taps are more like a plug tap than a taper tap, expecially in small sizes.
So I wonder how many use plug taps instead of taper taps.
Wes
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Plug taps are generally used when tapping by hand. A taper tap has slight advantage in through holes in a production environment, but not much of an advantage on short run or repair work.
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Roger Shoaf
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Want to give that some more thought, Roger?
Plug taps are generally used when power tapping, where starting the thread isn't an issue. There is almost no need nor reason to use a taper tap in a production environment. Fact is, they're pretty much relegated to hand taps.
Through holes are generally tapped with spiral pointed gun taps, and anything less is a stupid idea. You can tap a hole and be back out of it in something like 5 seconds by using that kind of tap.
There's lots more to this issue than how simple it appears, depending on many variables.
Harold
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[snip]

Most of my tapping is performed using a Bridgeport or lathe. (sometimes an electric drill in control panels).
The most crooked hole I have ever made was with a 5/8 NC taper tap by hand. I got it a bit crooked and it kept going and going off axis.
My curiosity was peaked by thinking, all these taps cut one thread per revolution. To some degree, the torque required should be the same unless the depth of cut is a major factor since Bottom > plug > taper.
Elucidation on the subject will be well received.
Wes
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On Feb 15, 10:56 am, snipped-for-privacy@lycos.com wrote:

I won't claim any expertise here, but I think that is a bad assumption.
Each of the taps - unless it is a tap whose taper length exceeds the thickness of the material - will remove one full thread's worth of material with every revolution. The torque necessary to remove that material depends on the amount of material removed, but it also depends on the width of the cut. A bottoming tap without any taper might remove all of the material with one tooth. A taper tap with the taper ground for six threads would cut over at least six teeth, or six times the number of flutes. I'd have to think about that one a bit - I suppose the accuracy of the tap would determine how many teeth actually do any cutting.
I think a long taper tap might be like a taper reamer. You take off very little material with each turn of a taper reamer but, because of the long length of cut, it takes a lot of torque to turn.
John Martin
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wrote:

The problem with bottoming taps is the point load, or load per tooth. It's dead easy to break a tooth in tough materials---whereas with plug or taper taps, the chip load per tooth is much lighter. Load on the shank may or may not be the same. As a result, those of us with experience tend to avoid bottoming taps, but instead use a modified plug tap that has been somewhat shortened, and go in a tapped hole to remove just the small amount needed to establish full depth. The shortened tap usually allows for a couple more turns. Just like a bottoming tap, they don't start well, but are good for cleaning out the tapered portion of an existing tapped hole.
It's usually desirable, if you're trying for a full thread depth, to use taps progressively (when hand tapping), so each tap removes a little more of the material, yielding less for the bottom tap to remove. That lowers the point load.
You likely realize that there are variables, and what works one time may not another. Doesn't hurt to have a background in tapping, so you have experience to call on to address questions that may arise.
Harold
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Harold and Susan Vordos wrote: .......those of us with experience tend to avoid

Thank you! I always did this. Once a coworker asked for some flat-bottom taps. I told him just to grind off the tip of a spiral point tap leaving two or three tapered threads and he looked at me like I was an idiot (in a polite way).
BTW, isn't that point just for holding the tap between centers for grinding?
Randy
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Randy Replogle wrote:

It is. And you can grind it off, because sharpening them isn't worth it in most cases.
Nick
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I can't see any other reason for it to exist, although it is helpful in getting the tap in the hole when production tapping with a tapping head. The blunted end is harder to center visually.
Harold
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On Sat, 17 Feb 2007 19:18:26 GMT, "Harold and Susan Vordos"

That point on the tap is for the foreman's use. He counts the little dents left by that point when you miss the hole when production tapping. That way he can tell if you are paying attention. ERS
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slight
an
solvent.
a
Harold,
Allow me to explain my thinking on this, and perhaps you will still disabuse me of my ignorance, but I will graciously stand corrected if that is the case.
I was thinking that since the load on each cutting tooth on a taper tap would be lower then the tool life would be extended. Consider if you will a circumstance where multiple through holes are to be tapped. For the sake of the example let us assume that the plate to be tapped is about 1 diameter thick.
A tap would have to be cycled into the hole until the first full thread cleared the bottom of the hole. If a taper tap had to make 15 complete revolutions to a plug tap making only 7 complete revolutions then the time difference per hole would be a little over double. If the tap were running at 100 rpm, 14 revolutions would be 14/100 of a minute and 30 revolutions would 30/100 of a minute so the net effect on the cycle time would be 10 seconds, but if by having smaller size chips and longer tool life more cycles could be squeezed out of the tap before it needed to be replaced, then those factors might be greater than the cycle time loss.
Also if the quality of the thread is better by taking a smaller bite per revolution, then that may be a factor also.
--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
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snip-

Chip load plays little to no role in power tap life, particularly with modern cutter geometry. Taps such as the spiral pointed variety cut beautiful threads and will do so for a much longer time than you might expect, particularly when they're run at proper speed with proper lubrication, in a tapping head. Material plays a role, but it always does, regardless of the nature of the tap. If you've ever tapped mild steel with a spiral pointed tap, using the old Tap Magic (1,1,1, trichlor.), you may have noticed the shiny surface of the thread flanks. That material is difficult to machine with a good finish, but those taps accomplish it well. There is nothing to be gained by using a taper tap under normal circumstances, and plenty to lose.
A taper tap would see more miles per thread, so, if anything, it would wear prematurely, especially considering you have to back the tap every quarter turn, and remove it from the hole to clear chips on a regular basis. Because the chip accumulates in the flute, where they ball up if you don't clear them often enough, occasionally resulting in a chipped tooth when you back the tap, and usually a degraded thread. Unless a thread is very shallow in depth (1/4 diameter or less), if you attempt power tapping with hand taps, the chip load usually fills the flute and results in torn threads, or a broken tap. It gets worse. Assuming you're using a taper tap, when you go back in the hole, even by hand, you run the risk of screwing up the threads. One shot tapping with the proper tap, run quickly and withdrawn even faster, has the potential to produce threads of exceedingly high quality.
If you've never tapped with power, none of this may make much sense, Roger. Hand tapping is a whole different world. Taper taps are very desirable in the hand craft world, but, like buggy whips, they've outlived their usefulness in the modern shop.
Harold
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Tap Magic hasn't smelled right in years. Now I know why.
Wes
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wrote:

Original Tap Magic, with trichlor, was still available a couple of years ago. I've got a pint or so of it in my shop now, bought from Scott Logan during one of his open houses.
Mike
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On Feb 14, 4:41 pm, snipped-for-privacy@lycos.com wrote:

I use spiral-point plug taps exclusively. I think hand-taps are a *complete* waste of time, even if taping by hand. Spiral-point taps do not require any reversing until the hole is completely threaded. I don't see any drawbacks other than taper hand taps are perhaps easier to square by hand than plug taps.
Regards,
Robin
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Simple.
If it is pre-tapped - use a plug. If there is a bottom hole issue - plug. If it is a new tap - use a taper and then a plug if needed. Tapers start nice.
Simple as that.
Then, there are different taps that have ? H(number) ? and that indicates the effective depth of cut or % of cut.....
More taps..
Martin Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
snipped-for-privacy@lycos.com wrote:

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I tried using plug taps without using taper taps first, it does not work well.
i
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Ignoramus30656 wrote:

IF the tap is not started perfectly straight to the hole, it will become increasingly hard to turn as it goes deeper into the hole. Unless the tap flexes. it will cut progressively deeper threads on one side of the hole until either the tap breaks or the tape self aligns in the hole.
A tapered tap is easier to start straight in the hole. If you start any tap straight it will be a lot easier to turn it and not break it off.
John
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Close-----but no cigar. If there's a bottom issue, use a bottom tap. That's what they're for. Almost no lead, and difficult to use, but effective for getting that last couple turns. It's nearly impossible to start a hole with one.

Only by hand--------and never, ever, power tap with hand taps unless the material in question is very thin. It's an instant recipe for a broken tap. There is no need for taper taps when power tapping.

No-----it indicates the theoretical pitch diameter of the tapped hole. Drill size dictates the depth of cut.
Harold
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wrote:

Possible terminology issue:-
Only in the US a second tap is a plug tap and a plug tap is a bottoming tap.
Mark Rand (not from the US :-) RTFM
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