Tap nomenclature: US vs UK

[kquiggle]

On another forum I saw a post that stated that while in the US we call the three basic types of taps "taper, plug, and bottoming" in the UK it's "Taper, second, and plug/bottoming" - can anyone here confirm that this is correct information?

By the way, I think this statement is always correct: "Our name for it sounds right, your name for it sounds kind of funny."

 

[jmshep]

In my(UK) book on Metalwork Technology by G.H. Thomas, he uses the terms 'Taper tap, Second tap or Intermediate tap and Bottoming tap or Plug tap' to describe the three types of tap just as you say. Personally I have always known them as taper, second and plug.
Hope that helps.

 

[Swifty]

Being in Australia, have always called them taper, intermediate and plug. However generally use only 2 types now, gun tap and plug. The smaller sets of BA taps that I use on some models come in sets of 3.

Paul.

 

[Omnimill]

The supplier told me when I bought my very first tap (1/4" Whitworth) that it was First Taper, Second Taper and Plug (for Blind hole)

 

[fltenwheeler]

UK
The Tap & Die Co lists (taper, second, bottoming/plug)


USA
McMaster Carr shows the following:

Taper Chamfer—Has 7 to 10 chamfered threads. Use for starting threads and in through holes. Requires less torque than other chamfers.

Plug Chamfer—Has 3 to 5 chamfered threads. Use in through holes as well as in blind holes that have sufficient space at the bottom for chips to accumulate.

Bottoming Chamfer—Has 1 to 2 chamfered threads. Variations of the bottoming chamfer include semi-bottoming, which has 2 to 2 1/2 chamfered threads, and modified bottoming, which has 2 1/2 to 4 chamfered threads. Use in blind holes where threads must come as close to the hole's bottom as possible.

Victor Machinery Exchange, Inc. shows the following:

Taper tap: 5-6 lead threads ground. The easiest tap for starting to thread a hole.

Plug tap: 3-4 lead threads ground. The most common tap: a "middle ground" tap for threading.

Bottoming tap: 1-2 lead threads ground. Used for continuing to thread a blind hole close to the bottom of the hole. It's difficult to start threading a hole with this tap.

 

[gus]

UK
The Tap & Die Co lists (taper, second, bottoming/plug)


USA
McMaster Carr shows the following:

Taper Chamfer—Has 7 to 10 chamfered threads. Use for starting threads and in through holes. Requires less torque than other chamfers.

Plug Chamfer—Has 3 to 5 chamfered threads. Use in through holes as well as in blind holes that have sufficient space at the bottom for chips to accumulate.

Bottoming Chamfer—Has 1 to 2 chamfered threads. Variations of the bottoming chamfer include semi-bottoming, which has 2 to 2 1/2 chamfered threads, and modified bottoming, which has 2 1/2 to 4 chamfered threads. Use in blind holes where threads must come as close to the hole's bottom as possible.

Victor Machinery Exchange, Inc. shows the following:

Taper tap: 5-6 lead threads ground. The easiest tap for starting to thread a hole.

Plug tap: 3-4 lead threads ground. The most common tap: a "middle ground" tap for threading.

Bottoming tap: 1-2 lead threads ground. Used for continuing to thread a blind hole close to the bottom of the hole. It's difficult to start threading a hole with this tap.

Thanks for the enlightment. Here in Singapore,the hardware shops call it
No.1 No. 2 No. 3. Fortunately hand taps come in sets of three.

 

[kquiggle]

Just to add to the confusion, there are also "serial taps" referred to as 1, 2, 3 but these different from taper/plug/bottoming. The serial taps progressively cut a shallow to deep thread so that the tapping is more gradual - useful in hard materials and supposedly leaves a smoother final tap.