What is a thread forming tap

Basic Definition of Thread Forming Tap

A thread forming tap, also known as roll tap, fluteless tap or extrusion tap, is a special thread machining tool without chip flutes.

Different from traditional cutting taps that remove excess metal to form threads, thread forming taps use cold extrusion principle to squeeze and deform the inner wall of the pre-drilled bottom hole, so that the metal material flows to form complete internal threads.

It produces no metal chips during the whole tapping process, which is its most obvious feature.

2. Structure Features of Thread Forming Tap

• No chip grooves: No flutes design, integral smooth body
• Trilobular three-lobe structure: Most standard forming taps adopt triangular convex edge design, evenly distribute extrusion force
• Tapered lead chamfer: Gradual entry section for smooth positioning and gradual forming
• High precision thread tooth profile: Uniform tooth shape, high surface finish of formed threads
• High hardness substrate: Mostly made of HSS, HSS-Co cobalt high speed steel, with wear-resistant coating

3.  How Does a Thread Forming Tap Work?

• Drill a standard larger bottom hole in the workpiece in advance (the hole size is larger than cutting tap bottom hole)
• The forming tap vertically taps the bottom hole at constant speed
• The three convex edges of the tap continuously squeeze the hole wall metal
• The metal material is plastically deformed, flowing upward and filling the gap of tap thread profile
• After tapping is completed, dense and high-strength internal threads are formed on the inner wall of the hole
• No chips are generated throughout the process, and the metal fiber structure is completely retained

✅ Recommended Materials

• Aluminum alloy, pure aluminum
• Brass, copper alloy
• Mild steel, low carbon steel
• Stainless steel 304 / 316 (with cobalt coating & EP oil)
• Zinc alloy, magnesium alloy and other easy-to-form ductile metals

❌ Not Applicable Materials

• Cast iron, gray iron (brittle, easy to crack during extrusion)
• Hardened steel, high carbon steel
• Powder metallurgy parts with loose structure
• Hard plastic, fragile non-metal materials

6.   Main Application Scenarios

• Automobile parts, new energy vehicle fastener holes
• Electronic precision hardware, communication shell internal threads
• Hydraulic & pneumatic valve body thread holes (high sealing demand)
• Household appliances, sanitary ware metal thread processing
• Blind hole dense thread mass production

High-strength connecting thread occasions with vibration resistance requirements

7.   Thread Forming Tap vs Cutting Tap (Simple Comparison)

8.  Basic Usage Tips

• Choose dedicated bottom hole drill size strictly according to forming tap standard
• Use extreme pressure tapping oil, especially for stainless steel
• Control low and stable tapping speed, avoid fast speed causing overheating
• Keep the tap vertical to prevent thread deflection
• Do not reverse the tap frequently when exiting to avoid thread damage