Bottoming tap

[Jim]

Reading a tutorial, it keeps mentioning a Bottoming tap, what is a Bottoming tap?? Is it an American saying?

 

[Phil Dart]

Imodium?

 

[Grump]

One where the thread goes all the way down.
A full set of 3 taps same diameter the first is a leader tap tapered to start the thread.
Second has less taper to thread deeper and the third has no taper thread to the bottom.
Only applicable on shallow holes that need threading to bottom out.
If your hole goes all the way the material a plug tap (second one) will suffice, this is whats usually supplied with the cheaper sets that have only one tap of each size.
There will be arguments but thus is a laymen's explanation.

 

[GeordieB]

What Grump said

 

[ni9eofse7en]

One where the thread goes all the way down.
A full set of 3 taps same diameter the first is a leader tap tapered to start the thread.
Second has less taper to thread deeper and the third has no taper thread to the bottom.
Only applicable on shallow holes that need threading to bottom out.
If your hole goes all the way the material a plug tap (second one) will suffice, this is whats usually supplied with the cheaper sets that have only one tap of each size.
There will be arguments but thus is a laymen's explanation.

I think you know too much......

https://www.youtube.com/watch?v=HMagY_CQopA

 

[Bigblackdog]

I think the terms are sometimes mixed with the bottom tap sometimes called the plug, as well as the 2nd tap also called the plug or intermediate.

 

[paulm]

Yeah, I was going to say the same as Brian... probably

 

[Grump]

I think the terms are sometimes mixed with the bottom tap sometimes called the plug, as well as the 2nd tap also called the plug or intermediate.

I knew there would be arguments but yes you are very right the term ids often used for both.
Like some cheap sets only contain bottoming taps and people wonder why they break so easily.
Not because they are cheap but because of the undue strain being put on them by not using the previous two.
Lubricate you tap to cool it there is a lot of friction in this process.

Just looked at the wiki and that refers to both taps as plugs, can't win init?

 

[EStreet]

This is the key difference in a taper (first), plug (second) and bottom (third) tap.

The taper tap (1st tap) starts forming the threads and is the least aggressive, meaning the more delicate the material is the less stress is caused and also the more work needed.

The plug tap (2nd tap) is designed to make plugs, nuts and similar items. Short sections that is threaded from end to end. This tap is the most common tap in use. It provides a trade off between delicate/difficult materials and aggressiveness.

The bottom tap (3rd tap, final tap), also called a blind hole tap, is designed to reach the bottom corner of the hole and provide the most threads possible. Otherwise as you get towards the end of the threading it will get hard to turn and cause problems.

There are a hefty number of types of bottom taps, i.e. semi-modified bottom tap for specific needs.

 

[Penpal]

The Dorathy questions regarding threads are summed up as terms for the cutting of internal threads using a Tap or external threads using a Die. Taps come in three types self explaining Taper. Intermediate half full thread, and the bottoming in that they have full thread enabling them to reach the bottom of the hole (most difficult to use in a blind hole as they tend to be pushed too far in locking and breaking common causes. All holes for tapping benefit from a shamfer at the beginning or top of the hole and external threads benefit from a chamfer that allows an easier unstressed start. As in all phases of use there are countless instructions written that cover the nature (type of steel etc) of the threading devices and their use in all metals and timbers. Thanks Ed Street for the pics the term plug is different over here naturally the fact also America has not become metric.

Peter.

 

[EStreet]

In a nut shell.

Taper taps: 7 to 10 threads chamfer (not full threads but they taper)
Plug taps: 4 to 7 threads chamfer
Bottom taps: 1 - 2 threads chamfer

 

[Vic Perrin]

I have always known the 3rd Tap in a set to be the Plug or Bottoming Tap

Vic

 

[Terry]

I agree with Vic. 1. Taper 2. Second. 3. Plug

 

[Walter]

As with so many things the USA and UK terminology differs.

UK = First (or taper), second and plug (as Brian and Terry said) Metric Taps and Dies

USA = taper, plug and bottom (or bottoming) (as Ed said) Regular Tap Sets On Tapco Cutting Tools Inc.

See also bushes = bushings

potato potarto tomayto tomato

 

[paulm]

Well I didn't have a clue about any of this and its very interesting, is it the same for dies?

 

[Walter]

Nope

(Good quality) dies are split and adjustable. Cut female thread first then cut male thread with split die, adjusting gradually until fit is correct.

Tightening the middle screw forces the die to spread and increases the diameter of the thread for the first pass. Loosening the middle screw and tightening the outer ones reduces the thread diameter for second and additional passes.

 

[Jim]

Nope

(Good quality) dies are split and adjustable. Cut female thread first then cut male thread with split die, adjusting gradually until fit is correct.

Tightening the middle screw forces the die to spread and increases the diameter of the thread for the first pass. Loosening the middle screw and tightening the outer ones reduces the thread diameter for second and additional passes.

The dies i have, do have these grub screws on Walter, is it necessary to do this or just when needed?

 

[Terry]

The dies i have, do have these grub screws on Walter, is it necessary to do this or just when needed?

You should use them Jim so as to get a clean thread. If you don't you run the risk of chipping the thread by taking too much stock off in one go!!!!

 

[Walter]

The dies i have, do have these grub screws on Walter, is it necessary to do this or just when needed?

What Terry said.

 

[Terry Q]

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