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What are these kind of taps called?

Posted: Mon Dec 24, 2018 7:13 pm
by ecdez
See the picture below. The add lists them as this

Thread Limit H3, 3 Flute, Oxide Finish Vanadium High Speed Steel Spiral Flute Tap
Modified Bottoming Chamfer, Right Hand Thread, Right Hand Flute, 2-1/2 OAL, 6.477mm Diam, Class 3B

No problem. Question is, the threads appear to taper off after the 4th or 5th thread in. Is there a specific name for that feature? All the other nomenclature in the listing seems to reference everything else. I'm having some trouble tapping 1" thick stock on the CNC with every other tap I can get my hands on. I think the coolant (mist) can't get down toward the bottom of the hole. I'm also thinking having only a few full size cutting threads will help keep things cool. Sure this is the one I can try buy knowing what that feature is called will help me locate them in the future or from another source.

Thanks in avance!

Image

Link to catalog listing.

https://www.mscdirect.com/product/details/62666789

Re: What are these kind of taps called?

Posted: Mon Dec 24, 2018 8:14 pm
by choprboy
Well... the are 3 basic tap thread taper/chamfer: Taper, Plug, and Bottoming. The more taper the easier it is to cut (less cutting force on each tooth), but the longer it takes and less efficient the cut.The tap in your description is a bottoming tap. The number threads in the taper varies a bit manufacturer, but tend to roughly be:
Taper - 7-10 threads - for thru-hole hand tapping
Plug - 3-6 threads (normally around 5) - for machine thru-hole tapping (though I normally hand tap with one)
Bottoming - 1-3 threads (normally about 2) - for machine tapping to the bottom of blind holes (possibly with a plug tap partially run to start)

If your are thru-hole tapping on a CNC, you probably want to use a spiral flute plug tap.

Re: What are these kind of taps called?

Posted: Mon Dec 24, 2018 8:31 pm
by John Hasler
For through-hole tapping you want a spiral point tap, also called a gun tap. It shoots the chips forward out through open hole. Spiral (helical, actually) flute taps are most suitable for blind holes because they pull the chips up and out.

Re: What are these kind of taps called?

Posted: Mon Dec 24, 2018 11:26 pm
by johnfreese
Most of my spiral flute taps have dimensions similar to a hand tap. I see the type pictured here in catalogs. They seem to be designed for machine tapping in a production environment. They have a short threaded portion with a reduced shank above the threads. I have no idea what the benefit of that configuration is. I hope there is a member that could educate me regarding that tap design.

Re: What are these kind of taps called?

Posted: Tue Dec 25, 2018 2:15 am
by neanderman
johnfreese wrote:
Mon Dec 24, 2018 11:26 pm
I hope there is a member that could educate me regarding that tap design.
Second that!

Re: What are these kind of taps called?

Posted: Tue Dec 25, 2018 5:07 am
by ecdez
Thanks for the responses thus far. I understand that it's a bottoming tap both by the general shape and by the number of tapered threads leading in. It's the tapered threads above the threaded portion that I thought would have special name and knowing that name might make it easier to locate. Perhaps I'm wrong.

I've used both a sprial flute and a gun tap and either will work fine for tapping 1/2" material but when I get to the 1" stuff they always break 2-3 holes into the project. EVERY TIME!!

This special tap may not be the solution to the problem but it's worth a try. That is, unless someone can offer another solution I hadn't thought of.

Thanks!

Re: What are these kind of taps called?

Posted: Tue Dec 25, 2018 5:39 am
by Harold_V
ecdez wrote:
Tue Dec 25, 2018 5:07 am
I've used both a sprial flute and a gun tap and either will work fine for tapping 1/2" material but when I get to the 1" stuff they always break 2-3 holes into the project. EVERY TIME!!
How do you drive the tap? If you're tapping by hand, or without some means to register the tap so it's dead vertical with the hole, yeah, you can expect breakage. A tap, once started crooked, suffers because it doesn't have the ability to straighten as it progresses in the hole. That condition is forgiving to some degree in thin material, but a death sentence in thick stuff. It typically leads to a broken tap as the chip load becomes so great on one side that the tap deflects until it breaks. Needless to say, taps, which are in excess of 60 Rc, don't bend.

Strange as it may sound, if you hope to tap without breaking taps, power drive them, but make damned sure you can stop the tap at the appropriate time, and that it is well lubricated with the proper lubrication for the material being tapped. The use of a tapping head is strongly advised, assuming you can justify one. They're not cheap. Using a drill chuck for tapping can be acceptable, although if the threads are inspected, pretty good chance they will be oversized. Drill chucks rarely run true enough to yield a tight thread. If nothing else, they'll usually start bell-mouthed.

The other concern might be if you're trying to power tap using a hand tap. If they're not reversed regularly, which breaks the chip and, hopefully, allows it to drop from the flute, the flutes will fill to the point of wedging the tap in the generated thread. That is usually followed by breakage. Don't power tap with a hand tap unless the material is quite thin.

Unfortunately for me, I left the machining field way back in '83, and made no attempt to stay current with technology. While I am aware of the grind of the "new" style taps, I am not aware of the benefits they offer, so I can't contribute anything to that conversation. Such taps were not on the market when I was actively machining.

H

Re: What are these kind of taps called?

Posted: Tue Dec 25, 2018 8:11 am
by ecdez
I'm tapping on a CNC mill with a tapping head. It's a tension/compression style so the motor reverses to get it out.

Re: What are these kind of taps called?

Posted: Tue Dec 25, 2018 9:06 am
by John Hasler
Here is a document that may be relevant:

https://www.natool.com/sites/default/fi ... 05-106.pdf

I think that "back taper" may be the term you are looking for.

Re: What are these kind of taps called?

Posted: Tue Dec 25, 2018 9:18 am
by ecdez
Could be! I didn't realize that it had a purpose. It says it gives a slight radial relief on the thread.

Re: What are these kind of taps called?

Posted: Tue Dec 25, 2018 1:37 pm
by GlennW
If you are tapping 1" deep, your mist coolant is most likely the problem, unless you are trying to tap blind holes that deep using spiral point or hand taps.

You need flood coolant or a good tapping fluid.

Re: What are these kind of taps called?

Posted: Tue Dec 25, 2018 5:03 pm
by Harold_V
ecdez wrote:
Tue Dec 25, 2018 9:18 am
Could be! I didn't realize that it had a purpose. It says it gives a slight radial relief on the thread.
Unbeknownst to many, many cutting tools have that same feature. The periphery of drills and reamers get smaller towards the shank, as an example. That's to lower friction of the tool in the hole. Woodruff cutters are hollow ground on the sides, for the same reason. It's very important that cutting tools make contact with material ONLY where they cut.

H