CUTTING TAPS OVERVIEW

Cutting Taps

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Cutting Taps are used to cut screw threads in pre-drilled or punched holes. The cutting edges of the tap remove material from the workpiece, pushing the chips either in front of the tap, or drawing them up the flutes, depending on the type of tap.
There are two primary characteristics to consider when choosing the right cutting tap for the job: Cutting Angle and Chamfer Length.
There are three primary choices for each of these characteristics.

TECHNICAL DETAILS
CUTTING ANGLE

Cutting Angles come in various styles, and the style is always included in the tap name. The cutting angle determines whether the chips are pushed in front of the tap and into the hole, or drawn up the flutes and out of the hole. 

STRAIGHT FLUTE

SPIRAL FLUTE

SPIRAL POINT

Spiral Flute taps have a positive rake cutting angle, and they pull the chips up the flutes and out of the hole as they are cut. These taps work very well tapping blind holes in “long chipping” materials, like aluminum and steels.

Spiral Point taps have a negative rake cutting angle, and push the chips into the hole as they are cut. It is best to use this type of tap on through-holes, so the chips can exit the hole through the bottom. If used on blind holes, make sure the hole is drilled deep enough to leave space for the chips to go, to prevent breaking the tap. Spiral Point taps will have trouble with some “long chipping” materials, like aluminum, stainless steel, and some softer steels, when tapping blind holes.  

Straight Flute taps have a neutral rake cutting angle, which can cause the chips to go either way, depending on material and cutting conditions. These taps are primarily used on “short chipping” materials like cast iron. They can be used on blind holes or through-holes, and are a good choice for hand tapping.

CHAMFER LENGTH

Chamfer Length is the second characteristic to consider when buying taps. There are three primary types of chamfers: Taper, Plug, and Bottoming. You can purchase any cutting angle (Spiral Point, Spiral Flute, Straight Flute) tap in any of the chamfer types, but Plug and Bottoming are most commonly used in CNC machine applications.

Any of the cutting angles can be applied to any of the chamfer styles, but Haas Tooling carries the most popular combinations, including spiral point bottoming, spiral point plug, spiral flute bottoming, spiral flute plug, and straight flute bottoming.

Taper chamfers are usually 8 or 9 threads long. They require the least amount of torque and last the longest, because the cutting loads are spread over a greater number of threads. Taper chamfers are most often found on “hand taps” designed to manually tap a hole. The long chamfer helps get the tap started straight in a hole. The drawback to taper chamfer taps is that they will not produce full threads near the bottom of a hole. Typically, in hand-tapping operations, you will start with a chamfer tap, and then “chase” the threads with a bottoming tap to cut the threads to the bottom of the hole.

Plug chamfers are medium length, usually 4 to 5 threads. These are more common for CNC machining than Taper chamfers, and are the “workhorse” of taps. They require a little more torque to cut the threads, but spread the cutting load well across 4 or 5 chamfered threads.

Bottoming chamfers are only 1 or 2 threads in length, and are the best choice when you need to thread close to a shoulder, counterbore, or the bottom of a hole. Bottoming taps require the most cutting force, and also wear out faster than comparable plug taps, because all the cutting is done by the first 1 or 2 threads of chamfer.

TAPER             PLUG            BOTTOMING

Be aware that taper, plug, and bottoming taps will cut full threads to different depths when programmed to the same Z-depth. Carefully review your engineering drawing requirements before choosing which cutting tap to use in a particular application.

WEAKER CORE

Spiral Flute Bottoming taps should only be used for special cases, like reaching the bottom of blind holes. Blind holes with limited hole depth require a spiral flute bottoming tap to get chips out, and to produce full threads to the bottom of the hole. Also, spiral flute taps are typically weaker at their core than spiral point taps.

STRONGER CORE

Spiral Point Plug taps should be your first choice, when possible. They have a thicker core, and the plug chamfer spreads the load over more threads, requiring lower torque, and lasting longer than bottoming taps. Spiral point taps also have shallower flutes, so the core diameter is larger, making them stronger.

Roll/Form Taps

Roll/Form Taps

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Roll taps, or form taps, unlike conventional cutting taps, form threads through material deformation, rather than by cutting the material. As a result, no chips are produced in the process. Since there are no chips to interfere with the tapping process, roll taps produce stronger, cleaner threads, with excellent surface finish. And since there are no chips to clog flutes or collect in blind holes, there’s less chance of tap breakage.

Roll taps require a larger drill than a cutting tap of the same size, to allow room for the material to flow when creating the threads. The grain flow of the material follows the contour of the formed thread, creating a stronger thread, especially in materials that work harden, like steel and stainless. Generally, roll taps can be run at higher speeds and feeds than cutting taps, and have a significantly longer tool life. They are well suited for smaller holes and materials that require a stronger tap.

ROLL/FORM TAPS

Roll taps form threads through material deformation, so there are no chips to interfere with the tapping process.

CUT TAPS

Cut taps form threads by cutting the material, creating chips that can clog flutes or collect in blind holes.

Roll Tap Size Chart

Haas roll taps are constructed of HSS PM powder metal high-speed steel, with a high content of vanadium and cobalt, for high-speed tapping and excellent wear resistance. These taps feature a Titanium Carbonitride (TiCN) coating, which offers improved wear and resistance to built-up edge. TiCN has good adhesion, toughness, and resistance to chipping, and performs well where moderate temperatures are generated at the cutting edge. They are well suited for tapping in steel, stainless steel, and non-ferrous materials.

ISO MATERIAL TYPE

P - STEEL

M - STAINLESS STEEL

K - CAST IRON

N - NON-FERROUS

S - HIGH-TEMP ALLOYS

H - HARDENED METALS

 TiCN COATING

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COATINGS

Non-Coated/Bright

Used for cutting aluminum materials. Helps prevent the material from sticking/galling to the cutter, when used with mist or coolant.

Hardslick

Titanium Aluminum Nitride + Tungsten Carbide/Carbon, dark gray; excellent for reflecting the heat back into the chip and away from the workpiece. The Tungsten Carbide/Carbon (WC/C) coating significantly reduces friction and adhesion wear, and helps prevent galling and seizing. It works great on stainless steels, steels from 70 BHN to 340 BHN, and even nickel alloys and aluminum materials.

TiAlN

Titanium Aluminum Nitride, violet-bronze in color; forms a hard aluminum oxide layer in hot (800-degree C) dry-machining applications. This further reflects the heat back into the chip and away from the workpiece. Primary benefits are increased production levels at higher feeds and speeds, and longer tool life in high-heat applications. We feature this coating on our taps recommended for cast iron.

TiCN

Titanium Carbonitride, blue-gray in color; has a hard, smooth finish, which offers improved wear and resistance to built-up edge. TiCN has good adhesion, toughness, and resistance to chipping, and performs well where moderate temperatures are generated at the cutting edge. Provides very good results on a wide variety of abrasive materials, including high-silicon aluminum alloys, copper, and cast irons. Coolant must be used to control the temperature at the cutting edge, to prevent premature wear of the coated surface.

TiN

Titanium Nitride, gold color; the most popular general-purpose coating. TiN has the highest adhesion and ductility characteristics of any of the coatings offered. The excellent wear resistance, thermal stability, and low coefficient of friction reduce built-up edge, and improve thermal transfer of heat away from the tool. A good general-purpose coating for tapping.

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