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Dunc
02-20-2013, 01:41 PM
I have been slowly converting from carbon steel to high speed.

There have been posts (tried search but no results) about the efficiencies from using spiral taps. Looking online I have found references to spiral point, spiral flute and gun taps. Are these the same or different? If the latter, which one is preferred? Where would the others be preferred?

I have also found references to "starting, intermediate & finishing" (my terminology) where they are used sequentially to cut the thread to full depth in a fashion similar to multi-pass thread cutting on a lathe - as distinct from a taper, plug, bottoming series that allows threading to the base of a blind hole. I imagine these are special purpose, but what?

Would any of these be suitable for threading under power on a lathe? Or, am I merely guaranteeing that I will break the tap?

Carld
02-20-2013, 01:59 PM
Spiral taps and gun taps are the same. Spiral flute taps are different from spiral or gun taps. Look them up in the online MSC catalog. Gun taps cause the continuous chip to be in front of the tap as it advances in the hole that is being tapped and does better in a through hole rather than a blind hole.

Taper, plug and bottom taps are most always four fluted and used with hand tapping. Since they are four flutes the don't hold up well under power tapping as the gun taps do. The taper, plug and bottom taps work well in blind holes but have to be removed and the chips removed from the holes often or the tap will bind up and chip or break.

Cleveland company used to put out a booklet on drilling and tapping that is helpful. I can't find that listed on their site but if you email them they may have something. There may be other help aids online from other companies.

becksmachine
02-20-2013, 04:00 PM
Spiral taps and gun taps are the same.


Spiral POINT taps are the same as gun taps.

Dave

Dr Stan
02-20-2013, 04:22 PM
I have also found references to "starting, intermediate & finishing" (my terminology) where they are used sequentially to cut the thread to full depth in a fashion similar to multi-pass thread cutting on a lathe - as distinct from a taper, plug, bottoming series that allows threading to the base of a blind hole. I imagine these are special purpose, but what?

That typically refers to larger Acme taps (1" +) making it much easier to cut the thread and reducing the likely hood of tap breakage.

goose
02-20-2013, 04:28 PM
And donít forget forming taps, to add to the confusion;)


As said, spiral point (often called gun taps) will push the chip in front of it, while spiral flute will move the chips back as it cuts. Spiral flute are the taps that look like woolly caterpillars.

I have used all varieties power tapping on the lathe. The issue is to allow the tap to slip when meeting resistance, like when bottoming out. A Jacobs style keyed chuck will allow it to slip while a keyless chuck wonít.

sbmathias
02-21-2013, 12:49 AM
I also found a catalog with tap info (starting at page 37) at
http://www.gfii.com/site/wp-content/uploads/2011/08/VTD2010_VERMONT-CATALOG.pdf

Georgineer
02-21-2013, 05:18 AM
While on the subject of terminology, readers might like to note that the US plug tap is the UK second, and the US bottoming tap is the UK plug... two nations separated by a common language!

George

J Tiers
02-21-2013, 08:15 AM
I have never had much success with "spiral flute" taps.....

I am sure there is a good reason for them to exist, but I never have found it. For sure you cannot use them by hand... break every time. Since I do mostly hand tapping, that may explain it..... but machine tapping seems no better.

One way, the spiral flute tap is EXPANDED by friction against the hole, the other way it CONTRACTS.... Seems that it either will cut undersize and lock up on the way out, OR cut oversize, and come out easier. The ones I had (past tense intended) were all of the first type, and most didn't survive coming out of the hole.... swarf jammed them, they expanded, and broke off.

Maybe one o the egg-spurts can explain the need for the ^%$#@! things.

meanwhile, spiral POINT taps purely rule.

johnnyd
02-21-2013, 11:08 AM
The "start,intermediate,finish" taps that you refer to,are generally known as "serial taps" & are usually sold in sets.
To add to the confusion, they also have taper,plug,& bottoming configurations.
They are made to be used as hand taps & for hard to tap materials.
In the USA they are available online from E-Taps....(google it)

If you'll PM me your e-dress, I'll send you a close up of a set & maybe we can get it posted here.

chipmaker4130
02-21-2013, 11:27 AM
. . .I am sure there is a good reason for them to exist, but I never have found it. . . .
I was told they are used when tapping a hole with an intersecting hole or slot, thereby avoiding a flute snag.

Toolguy
02-21-2013, 12:03 PM
Spiral flute taps are really good for blind holes as they push the chips up out of the hole instead of to the bottom. They do break a lot easier than straight flute taps. One of the secrets to not breaking fragile taps like spiral flute and small diameter is to not put any side pressure on them. That is almost impossible to do when hand tapping, even being careful. That means they should be held in the machine even if turned by hand. Another thing is to reduce the amount of force it takes to turn them. You can do this by: drilling the hole a few thou. bigger than normal, never using a dull tap, using the correct cutting fluid for the material. Spiral point taps are the best for through holes. They push the chips ahead of the tap out the bottom.

becksmachine
02-22-2013, 04:56 PM
I am sure there is a good reason for them to exist, but I never have found it. For sure you cannot use them by hand... break every time. Since I do mostly hand tapping, that may explain it..... but machine tapping seems no better.


A spiral flute tap, in all it's glorious, curly shaving splendor!! :o

This is a recurring job, nothing dramatic or particularly fussy, just need a 3/8-16 tapped hole in the end of these pins.

Here the drilled hole is ≈1" deep, full threads ≈3/4" deep, tap speed probably about 300 rpm. I would guess this tap has been in 300 holes at this point.

Note the external center on the end of the tap has been ground away. No one will ever use that part of the tap again and it does allow full threads to come much closer to the bottom of the hole.

I would also agree that a spiral flute tap is really only usable in a machine tapping setup. They are weaker than any other tap style and trying to get one started straight using a manual tap handle is just not going to happen.

Dave
http://i1042.photobucket.com/albums/b422/becksmachine/Spiral%20flute%20tap/th_IMG_1746.jpg (http://s1042.beta.photobucket.com/user/becksmachine/media/Spiral%20flute%20tap/IMG_1746.jpg.html)http://i1042.photobucket.com/albums/b422/becksmachine/Spiral%20flute%20tap/th_IMG_1750.jpg (http://s1042.beta.photobucket.com/user/becksmachine/media/Spiral%20flute%20tap/IMG_1750.jpg.html)http://i1042.photobucket.com/albums/b422/becksmachine/Spiral%20flute%20tap/th_IMG_1755.jpg (http://s1042.beta.photobucket.com/user/becksmachine/media/Spiral%20flute%20tap/IMG_1755.jpg.html)