TAPS - Technical information

Taper tap Second taps Bottoming Plug tap technical information by The Tap & Die Company and how to choose and use correct taps

STRAIGHT FLUTE TAPS: Our taps can be used for both machine or hand tapping. They are most economical for use on production runs. Best used on material that produce chips or where swarf breaks readily. 
 Hand (or machine) taps can be supplied in sets of 3 pieces: TAPER,  SECOND & BOTTOM leads
   TAPER (T) TAPS: have a chamfer (lead) of 6 to 8 threads, the angle of the lead being around 4-5 degrees per side. The taper lead distributes the cutting force over a large area AND the taper-shape at the end of the thread helps the thread to start. They can therefore be used to start a thread prior to use of the Second or Bottom leads or used for ‘through’ holes
  SECOND (S) TAPS: have a chamfer (lead) of 3 to 6 threads, the angle of the lead being around 8 degrees per side. They are most popular and can be used for ‘through’ holes or even ‘blind’ holes where the thread does not need to go right to the bottom of the hole
   BOTTOM (B) TAPS: have a chamfer (lead) of 1.1/2 to 2.1/2 threads, the angle of the lead being around 18 degrees per side. They are used to produce threads close to the bottom of ‘blind’ holes
  Notes: The name PLUG is commonly used to indicate a Bottom tap. - However, in America it is used to indicate a Second tap. - To avoid confusion the terminology that should correctly be used, as stated by British Standard 949, 1979 is:  BOTTOM tap or BOTTOMING tap
Also a variation is that SECOND taps are sometimes called ‘intermediate’ and TAPER taps called ‘first’

 Tolerance:   Taps: General Dimensions to BSS 949 & American series NC NF NS to ASA standard -
                       Dies circular: Basic dimensions to BSS 1127 

 USING TAPS TO MINIMISE TAPPING PROBLEMS & TROUBLE-SHOOTING:
  - To minimise problems during tapping follow these rules:-
. Use the correct tap for the job
. Use the correct tapping drill
. Keep taps sharp - do not use blunt taps
. Choose correct speeds and feeds
. Ensure accurate alignment
. Never let a tap hit the bottom of a blind hole
. Choose correct lubricant
. Use a pitch controlled tapping attachment
  - Listed below are common problems customers may find with probable causes:
  Poor Thread Finish:
Chips/swarf not being cleared properly
Misalignment of tap & wrok piece
Incorrect feed rate
Tapping device or machine faulty
Insufficient or incorrect lubricant
Blunt tap or incorrectly ground tap
  Excessive Tap Wear:
Blunt tap or incorrectly sharpened tap
Wrong tap selection
  Taps Breaking:
Tap hits the bottom of the hole
Incorrect tapping Drill
Tapping speed too high
Hole work hardened
Blunt tap or incorrectly sharpened tap
Insufficient chip or swarf removal
Incorrect or insufficient lubricant
Machine or tapping device faulty
Wrong tap selection
  Tap Teeth Chipping:
Tap hits bottom of hole
Blunt tap or incorrectly sharpened tap
Machine or tapping device faulty
  Oversize / Bell Mouthed:
Incorrect feed rate
Misalignment
Incorrect tapping drill
Tapping device or machine faulty
Insufficient or incorrect lubricant
Incorrectly ground or eccentric tap
Wrong tap selection
  Cold Welding:
Wrong material composition
Blunt or incorrectly sharpened tap
Insufficient or incorrect lubricant
Tapping speed too high
Hole work hardened

The Tap and Die Company website has a lot of other very useful 'Technical’ Data & Information for you to view