Spiral Point vs Spiral Flute Taps: Which to Use, When, and Why

Published by Cutronix | CNC Tooling Specialists | Australia-Wide

Choosing the right tap is one of the most common — and most costly — decisions on the shop floor. Pick the wrong style and you get chip clogging, broken taps, poor thread quality, or a scrapped part. Pick the right one and tapping becomes the reliable, repeatable operation it should be.

This guide breaks down the three main tap geometries — spiral point, spiral flute, and forming taps — explaining where each belongs and why. It then compares HSS versus solid carbide tap materials so you can match not just the geometry, but the substrate, to your job.

First Principle: It's All About the Chip (Except When There Isn't One)

Every cutting tap has to deal with one problem: what happens to the chip. As the tap cuts the thread, it generates a chip that has to go somewhere. Where that chip needs to travel — forward, backward, or nowhere at all — is what determines which tap you should use.

• Through hole? The chip can exit out the bottom → push it forward.
• Blind hole? The chip has nowhere to go at the bottom → pull it back out.
• Ductile material? You can avoid making a chip entirely → form the thread instead of cutting it.

Keep that principle in mind and tap selection becomes logical rather than confusing.

Spiral Point Taps (Gun Taps)

A spiral point tap — also called a "gun tap" — has a small angled grind at the cutting point that pushes chips forward, ahead of the tap. The flutes themselves are straight or nearly straight; they don't carry chips back. Their job is simply to deliver coolant and let the pushed-forward chips clear out the bottom of the hole.

Typical Application Area

Through holes. This is their home. Because the chip is driven forward and out the far side of the hole, spiral point taps are the fastest, most reliable choice for tapping all the way through a component.

• Through-hole tapping in steel, stainless, cast iron and non-ferrous materials
• High-speed CNC production tapping where cycle time matters
• Rigid tapping on machining centres

Why they work

The forward-push design means chips never pack into the flutes, so there's no clogging and no chip re-cutting. This gives spiral point taps excellent stability at high speed — they're the productivity choice for through-hole work.

Where NOT to use them

Never in a blind hole. The chips get pushed to the bottom of the hole with nowhere to go. They pack up, the tap jams, and you break the tap or ruin the thread. If the hole is closed at the bottom, choose a spiral flute tap instead.

Cutronix range: YG-1 TRG15 (general-purpose, all materials) and TL231 (Ti-N coated, superalloys) spiral point series.

Spiral Flute Taps

A spiral flute tap has deep, helically-twisted flutes — like a corkscrew or a drill's flutes. As the tap cuts, these spiral flutes pull the chip back up and out of the hole, in the opposite direction to the cut.

Typical Application Area

Blind holes. This is exactly where spiral point taps fail. Because the flutes evacuate chips upward and out, there's no chip accumulation at the bottom of a closed hole.

• Blind-hole tapping in all materials
• Tough, stringy materials (stainless, low-carbon steel) that produce long chips
• Deep threads where chip evacuation over distance is critical

Why they work

The helical flute acts like an auger, continuously lifting swarf clear of the cutting zone. This prevents the chip packing that destroys taps in blind holes, and keeps thread quality consistent even in gummy materials.

The spiral angle matters

• Slow spiral (15°–30°) — for short-chipping materials like cast iron and some steels
• Fast spiral (40°–45°) — for long-chipping, stringy materials like stainless steel and aluminium, where aggressive chip lifting is needed

Cutronix range: YG-1 TC163 spiral flute series (optimised for aluminium and non-ferrous, with large chip gullets).

Forming Taps (Roll Taps / Fluteless Taps)

A forming tap doesn't cut at all — it has no flutes and produces no chip. Instead, it displaces material, cold-forming the thread by pressure as it's driven in. Think of it as pressing the thread into the metal rather than carving it out.

Typical Application Area

Ductile materials that can flow rather than shear.

• Aluminium and aluminium alloys
• Copper, brass and softer non-ferrous metals
• Low-carbon and mild steels
• Any ductile material with at least ~5–10% elongation

Suitable for both blind and through holes — because there's no chip, the blind-vs-through problem disappears entirely.

Why they work

With no chip produced, there is:

• No chip clogging — ever, in any hole type
• No chip disposal or handling — cleaner operation
• Stronger threads — the cold-forming process work-hardens the thread and follows the grain of the material rather than cutting across it, producing a thread that is typically stronger than a cut thread
• Longer tool life — no cutting edges to wear or chip; forming taps often last far longer than cutting taps

The critical requirements

Forming taps have two non-negotiable conditions:

1. The material must be ductile enough to flow. Cast iron, hardened steel, and brittle materials cannot be form-tapped — they'll crack instead of flow.
2. The pre-drilled hole size is different. Because material is displaced rather than removed, forming taps require a larger tapping drill than cutting taps for the same thread. Using a cutting-tap drill size will break a forming tap. Always use the forming-tap drill chart.

Cutronix note: Forming taps are ideal for high-volume aluminium and mild-steel production where thread strength and tool life justify the process.

Quick Reference: Which Tap for Which Job

Situation	Best Tap	Why
Through hole, any material	Spiral Point	Pushes chip forward and out
Blind hole, any material	Spiral Flute	Pulls chip back and out
Ductile material (aluminium, mild steel, copper)	Forming Tap	No chip, stronger thread, longer life
Stringy stainless, blind hole	Spiral Flute (fast spiral)	Aggressive chip lifting
Cast iron, blind hole	Spiral Flute (slow spiral)	Short chip evacuation
High-volume aluminium	Forming Tap	No chip disposal, long tool life
Cast iron, through hole	Spiral Point or straight flute	Short chips exit easily
Hardened steel	Spiral Flute or Spiral Point (carbide)	Cannot form-tap hard material

HSS vs Solid Carbide Taps: The Material Question

Once you've chosen the geometry, you need to choose the substrate. This is a separate decision, and getting it right has a major impact on tool life, cutting speed, and cost per hole.

HSS and HSSCo (Cobalt HSS) Taps

High-Speed Steel is the industry standard tap material, and for good reason. Adding cobalt (HSSCo / HSS-E, typically 5–8% Co) increases hardness and heat resistance further.

Strengths:

• Tough and forgiving — HSS flexes rather than shatters. In less rigid setups, on manual machines, or where there's any misalignment or vibration, HSS survives conditions that would snap a carbide tap.
• Lower cost per tap — significantly cheaper upfront
• Wide material range — handles steel, stainless, cast iron and non-ferrous
• The safe default — for most general-purpose and lower-volume work, HSS/HSSCo is the correct, economical choice

Limitations:

• Lower maximum cutting speed than carbide
• Wears faster in abrasive materials and high-volume runs
• Not suitable for hardened materials above ~HRc 40

Use HSS/HSSCo when: general-purpose tapping, lower-to-medium volumes, less rigid or older machines, interrupted conditions, or where budget favours a lower tool cost. HSSCo specifically when you need a bit more heat and wear resistance than plain HSS — for stainless and tougher alloys.

Solid Carbide Taps

Solid carbide is far harder than HSS, holds its edge at much higher temperatures, and resists abrasion dramatically better. But it is also brittle — it doesn't flex, so under shock or misalignment it fractures instead of bending.

Strengths:

• Much higher cutting speeds — carbide can run 2–3× the speed of HSS, cutting cycle times
• Superior wear resistance — holds up in abrasive materials and long production runs, giving far more holes per tap
• Handles hardened materials — the only real choice for tapping hardened steel (HRc 45–60) and abrasive cast irons
• Excellent in high-volume automated production — where consistency over thousands of holes matters

Limitations:

• Brittle — requires rigid, well-aligned setups. On a machine with any runout, vibration, or flex, carbide taps break.
• Higher cost per tap — significantly more expensive upfront
• Demands rigid tapping — synchronised spindle-and-feed (rigid tapping) is essential; tension-compression holders and floppy setups will break them
• Less forgiving of error — a crash that an HSS tap might survive will shatter a carbide one

Use solid carbide when: high-volume production, hardened or highly abrasive materials, rigid modern CNC machines with synchronised tapping, or where the higher speed and longer life justify the cost across a large run.

HSS vs Carbide at a Glance

Factor	HSS / HSSCo	Solid Carbide
Hardness	High	Very High
Toughness	High — flexes, forgiving	Low — brittle, fractures
Cutting speed	Lower	2–3× higher
Tool life (abrasive/high-vol)	Moderate	Excellent
Hardened materials (>HRc 40)	No	Yes
Machine rigidity needed	Moderate	High — rigid tapping essential
Cost per tap	Lower	Higher
Best for	General purpose, lower volume, less rigid setups	High volume, hard materials, rigid CNC

Putting It Together: A Selection Framework

Work through these three questions in order and you'll arrive at the right tap every time:

1. What's the hole?

• Through hole → Spiral Point
• Blind hole → Spiral Flute
• Ductile material (any hole) → consider Forming Tap

2. What's the material?

• Ductile (aluminium, mild steel, copper) → Forming tap is an option; if cutting, match spiral to chip type
• Hardened (>HRc 40) → must be carbide, cutting tap only (no forming)
• General steel/stainless/cast iron → geometry by hole type, substrate by volume

3. What's the volume and machine?

• Low-medium volume, general machine → HSS / HSSCo (economical, forgiving)
• High volume, rigid CNC, abrasive or hard material → Solid Carbide (speed, life)

Common Mistakes to Avoid

Using a spiral point tap in a blind hole. The single most common tapping failure. Chips pack at the bottom and break the tap. Blind hole = spiral flute, always.

Using a cutting-tap drill size for a forming tap. Forming taps need a larger pre-drill because they displace material. The wrong drill size will snap the tap immediately.

Trying to form-tap cast iron or hardened steel. Forming needs a ductile material that flows. Brittle materials crack. Cut, don't form.

Running solid carbide taps on a non-rigid setup. Carbide's brittleness demands rigid, synchronised tapping. Without it, you'll break expensive taps. If your machine can't rigid-tap, use HSS.

Defaulting to carbide for everything. Carbide isn't "better HSS" — it's a specialist for high volume, hard materials, and rigid machines. For general work on a standard machine, HSS is often the smarter, cheaper, more forgiving choice.

Summary

Tap geometry follows the chip: spiral point for through holes (chip forward), spiral flute for blind holes (chip back), and forming taps for ductile materials (no chip at all, with a stronger thread and longer tool life).

Tap material follows the job: HSS and HSSCo are the tough, forgiving, economical choice for general and lower-volume work on any machine. Solid carbide is the high-speed, long-life specialist for high-volume production, hardened materials, and rigid CNC machines — provided you can rigid-tap.

Match the geometry to the hole, the substrate to the volume and material, and tapping becomes the reliable operation it should be.

Get the Right Tap for Your Job — Browse Cutronix

Cutronix supplies genuine YG-1 taps across Australia — spiral point (TRG15, TL231), spiral flute (TC163), and forming taps, in HSS, HSSCo and solid carbide, for every material group.

Browse the range:

• YG-1 Threading Taps: /shop/category/cnc-cutting-tools-yg-1-hss-threading-taps-metric-25
• All YG-1 Cutting Tools: /shop/category/cnc-cutting-tools-yg-1-22

Not sure which tap suits your material, hole and machine? Contact the Cutronix team — we'll match the right geometry and substrate to your exact application.

Call: +61 8 7119 8959 | Email: sales@cutronix.com.au

Genuine YG-1 tooling. Expert advice. Fast dispatch — Australia-wide.