Different Types of Thread Taps-Comprehensive Guide

2, Carbide Taps

Cemented carbide is much denser than high-speed steel and has high friction and heat resistance.

Although resistant to abrasives, solid carbide, like other tap materials, tends to become brittle and cannot withstand vibration. Therefore, solid carbide taps should only be used with modern high-speed cutting equipment with minimal vibration during operation.

Solid carbide taps can process many different materials, such as tapping threads in alloy steel, aluminum, brass, carbon steel, cast iron, copper, Hardened steel, Inconel, Nickel (and other cemented carbide), Sintered material, stainless steel, and titanium.

3, Carbide taps vs. HSS taps

• Solid carbide tap is more expensive than high-speed steel tap,
• Cemented carbide taps have super durability.
• The sharp cutting edge of carbide taps is longer than HSS taps.
• Using solid carbide taps means you will need fewer taps and spend less time to replace thread taps.
• Withstand much higher temperatures than HSS.
• It runs at a higher cutting speed than HSS.
• Produces cleaner and smoother edges than HSS.

Thread Tap size 

The thread tap size specifications include metric taps and inch taps. For example, metric taps M8*1.2, where M is the triangular thread code, 8 represents the tap’s diameter, and 1.2 means the tap’s pitch in mm. For example, for the inch tap 5/16-18, the tap’s diameter is 5/16 inches, and the 18 behind it means there are 18 threads in 1 inch.

You can find more thread tap size chart:

Thread Tap Tolerance Chart

The machine taps are marked with the code of the tolerance zone of the pitch diameter: H1, H2, and H3 respectively indicate the different positions of the tolerance zone, but the tolerance values are equal. The tolerance zone code of hand taps is H4, the tolerance value, pitch, and angle error are larger than machine taps, and the material, heat treatment, and production process are not as good as machine taps. H4 may not be marked as required. The internal thread tolerance zone grades that can be processed by the tap pitch tolerance zone are as follows:

The tap tolerance zone code applies to the internal thread tolerance zone grade:

Tap tolerance chart

Thread Tap Coatings 

Most of the thread tap manufacturers provide coated taps, which have greatly improved the service life and cut uncoated taps. The taps of unequal diameter design have reasonable cutting load distribution, high processing quality, but high manufacturing cost.

The tap’s geometry mentioned above, coupled with a unique coating surface (like TiN, TiCN, CrN, or TiAlN), can significantly increase the tap’s life. These heat-resistant, smooth coatings reduce cutting forces and allow tapping at higher cutting speeds. The development of newer high-performance taps has dramatically promoted the increase in machine tool spindles’ speed and power.

1, TiCN (Titanium Carbon Nitride)-blue-gray, PVD coating process, multilayer coating with a layered structure. TiCN-coated thread taps are generally used for tapping difficult-to-process materials, such as tapping threads in quenched and tempered steel, wear-resistant steel, etc.

2, TiAlN (Titanium Aluminum Nitride)-The appearance is purple and black. It also uses PVD technology. TiAlN coated taps are mainly used to tapping metal threads in castings, such as tapping threads in cast iron and cast aluminum wear-resistant materials and high temperature and high-speed cutting general cooling performance is not good. This coating is the first choice;

3, TiN (Titanium Nitride)-golden appearance, using PVD coating process, easy to produce, low cost, wide application range, generally can increase the tap’s life by about 300%. TiN Thread taps also provide additional resistance to heat damage and reduces friction in the tap head, which offers high lubricity and increases chip flow in softer materials.

4, Vap (Vaporized)-high-temperature oxidation treatment, that is, the tap is placed in 530℃ high-temperature water vapor to generate black Fe3O4 on the surface of the tap. The primary function is to absorb cutting fluid to increase lubrication performance and inhibit cutting. The generation and adhesion of nodules have a wide range of applications, especially in the tapping of medium and low-strength steels. The effect is particularly significant;

5, CH (Amorphous Carbon)-Amorphous carbon similar to diamond. The appearance is dark gray. Using the PVD process, the coating thickness is 1-2μm, and the hardness is about 2500HV. Mainly used for tapping of non-ferrous metals and aluminum and its alloy materials.

How to maintain thread taps well?

1. When tapping, the end hole should be chamfered; the tap should be coaxial with the workpiece’s hole; axial pressure should be applied at the beginning of tapping to make the tap cut in. After a few turns, no axial force is needed.

2. After the calibrated part of the tap enters the screw hole. It will return 1/4 or 1/2 turn every half turn to one turn so that the chips will be broken and then tap down; when tapping the through-hole, it must be withdrawn frequently Tap for chip removal.

3. When tapping on steel workpieces, add cutting fluid. When tapping on cast iron workpieces, add a little kerosene; after using the first tap, the tap must be screwed into the screw hole when using the second or third tap.

4. When threading, the end of the workpiece should be chamfered, and the end face of the threading should be perpendicular to the axis of the workpiece; the axial pressure should be applied at the beginning of the threading, and the rotating force should be correspondingly larger; when the threading is cutting the thread on the workpiece, Don’t put more pressure.

5. To break the chips and discharge them when threading, the teeth should be turned frequently.

6. The workpiece should be firmly fixed on the clamps and fixtures; when the tap is broken, do not touch the broken place with your hands, use a clamp or punch to remove it, and wear protective goggles when the wire is broken.