Tapping threads sounds simple—until you break a tap or end up with a crooked thread.
Whether you’re working with aluminum, stainless steel, or cast iron, using a thread tap correctly is essential for getting clean, accurate internal threads that fit and hold fasteners securely. But many machinists (especially beginners) make small mistakes that lead to tool breakage, poor fit, or damaged parts.
In this guide, we’ll walk you through how to properly use a thread tap, cover the different types of taps, and explain how to avoid the most common tapping problems.
A thread tap is a cutting tool used to create internal threads inside a pre-drilled hole. These threads allow bolts, screws, or threaded studs to fasten securely into metal, plastic, or other materials.
Taps come in several types:
Hand Taps (Taper, Plug, Bottoming): For manual threading
Spiral Point Taps: For through holes in CNC operations
Spiral Flute Taps: For blind holes and better chip removal
Forming Taps: For thread forming without cutting (ideal for ductile materials)
Before you tap, you need to drill a correctly sized hole. Too small, and the tap breaks; too big, and the threads won’t hold.
Use a tap drill chart or formula:
Tap Drill Size = Major Diameter – Thread Pitch
Example: For M6 × 1.0, the drill size = 6mm – 1.0mm = 5.0mm drill
Tip: Use a sharp drill bit and drill as straight as possible to avoid misalignment.
Clamping the part tightly prevents movement during tapping. For hand tapping, use a bench vise. In CNC or manual machines, ensure no play or vibration in the fixture.
For hand tapping:
Use a tap wrench that fits the square shank of your tap.
Start with a taper tap for the first cut—it’s easier to guide into the hole.
Use a plug or bottoming tap afterward if threading to full depth is required.
For machine tapping:
Use tapping holders with torque protection or floating compensation.
Use the right tapping fluid:
Aluminum: Use light oil or tapping fluid (e.g. WD-40)
Steel: Use heavy-duty cutting oil
Stainless steel: Use sulfur-based oils or high-pressure lubricants
Lubrication reduces cutting torque, prevents tap wear, and improves thread quality.
Turn the tap clockwise (right-hand tap) while applying gentle downward pressure.
Every 1–2 turns, reverse the tap a half-turn to break chips and prevent jamming—especially in blind holes.
Don’t force it—if the tap resists or squeaks, stop, reverse out, clean chips, and reapply lubricant.
Once done, back the tap out completely and blow the hole clean using air or brush. Check:
Are threads clean and continuous?
Is the tap damaged or dull?
Does the screw fit snugly without binding?
For production or critical parts, use a thread gauge to verify accuracy.
Wrong hole size → Causes tap breakage or loose threads
No lubrication → Leads to tool wear and poor finish
Tapping too fast → Increases heat and tap stress
Forcing the tap → Can break the tool and ruin the part
Using the wrong tap type → For example, using a hand tap in a CNC machine
Forming taps don’t cut—they displace the material. They work best in ductile materials like aluminum, copper, or soft steel.
Advantages:
Stronger threads
No chips (great for blind holes)
Longer tool life
Disadvantage: Requires tighter hole size tolerance and more torque.
Whether you're threading aluminum, steel, titanium, or plastics, we offer:
High-speed steel (HSS) and solid carbide taps
Spiral point, spiral flute, and forming taps
Coated taps (TiN, TiAlN, AlCrN) for tough materials
Metric and imperial sizes
OEM/custom branding available for bulk buyers
Contact us for technical advice, pricing, or to request samples for your workshop or production line.
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