Ordering Cutting Taps
It is highly recommended that a drawing with the thread information be supplied whenever possible. This will assist engineering staff in providing the right cutting taps for the job and avoiding long delays and costly problems in manufacturing.
Critical information required to supply the correct cutting taps are as follows:
- Nominal Size, TPI or Thread Per Inch, Thread Form, and if the thread is a multiple start.
- Class of thread to be manufactured – 2B or 3B.
- Right hand or Left hand thread. Right hand is always assumed if not specified.
- Material to be tapped.
- Nature of hole to be tapped.
- Drilled, punched, or cast.
- Tap drill or hole size.
- Depth of hole.
- Through hole or blind hole.
- Required length of full threads.
- Style of cutting taps required – Taper, plug, bottoming, gun tap, and spiral fluted tap.
- Our manufacturing engineer will determine this based on the information supplied.
Any additional information concerning the type and condition of the machine or equipment being used can be helpful in manufacturing the best design of cutting taps for the job.
Trouble Shooting Checklist For Tapping
- Using an incorrect style or design for the job.
- Using an incorrect tap limit size for the class of thread.
- Using dull cutting taps, cutting dies, and cutting tools that require re-sharpening.
- Using poorly re-sharpened cutting taps, cutting dies, and cutting tools.
- The part material is too hard or too soft.
- The part material is of poor quality and not uniform in structure or analysis.
- The part material is galled on the tap threads.
- Over packing of chips in the flutes.
- Tapping machine is too heavy or too light for job.
- Tapping machine lacking a quality lead screw.
- Speed range of tapping machine is too limited.
- Table of tapping machine or work piece not perpendicular to the tap.
- CNC machine not properly programmed.
- Adverse pre-tap hole conditions ( size, depth, straightness, roundness, glazed or work hardened surface, chips in the bottom ).
- Tap and prepared hole are not aligned.
- Work piece and fixture lifting on reversal when tapping vertically.
- Lack of proper lubrication on application.
Measuring Cutting Taps
The major diameter and pitch diameter are two critical measurements on cutting taps. It is important to monitor the wear on these dimensions as they will eventually wear with prolonged use. Back taper, thread relief, and built up major diameter are three factors in the design of cutting taps, cutting dies, and cutting tools that should be taken into consideration when making measurements on the major diameter and pitch diameter of cutting taps, cutting dies, and cutting tools.
Back taper is a gradual decrease in the thread diameter towards the shank. This is usually about .001" in the diameter per one inch of length. Thread relief gradually decreases the thread diameter towards the heel of the land and as a rule covers about two thirds of the land width although in certain cases it may cover the entire width. The function of the back taper and thread relief is to provide easier cutting action and reduce friction. Measurements for size should always be taken across the full threads immediately behind the chamfer and as near the cutting face of the land as possible. Cutting taps, cutting dies, and cutting tools are always made larger than basic on the major diameter to allow for wear, and to provide major diameter clearance in the tapped hole.
A basic micrometer can be used to measure the major diameter of cutting taps. The micrometer anvil should contact the teeth at the cutting taps and cutting dies face. The pitch diameter can be measured by use of the Three Wire Method Thread Measuring System.