Cutting Tools Reference Library · Technical Reference

Spiral Point vs Spiral Flute vs Straight Flute Taps

Tap flute style decides where the chips go. Spiral point taps push chips ahead for through holes, spiral flute taps pull chips back out of blind holes, and straight flute taps hold chips in the flutes for short-chipping materials.

Ref CT-0017ASME B94.9

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Every cutting tap has flutes that make room for chips and carry cutting fluid. The three common styles are straight flute (hand taps), spiral point (also called gun taps) and spiral flute. They can all cut the same thread. The difference is how they handle chips, and that depends on the hole type and the material.

How to identify

Straight flute: flutes run straight along the tap, parallel to the axis. This is the classic hand tap.
Spiral point: flutes are straight, but the first few threads have an angled grind at the front that looks like a twisted cut. That grind shears chips and shoots them forward.
Spiral flute: flutes wrap around the tap like a drill. Low-helix and high-helix versions are made for different materials.

Flute style selection

Flute style	Chip direction	Best hole type	Typical materials	Notes
Straight flute	Chips stay in flutes	Through or blind, short depths	Cast iron, brass, short-chipping metals	Must back out to clear chips
Spiral point	Forward, ahead of tap	Through holes	Steels, aluminum, most stringy metals	Strong tap, good for machine tapping
Spiral flute	Backward, out of hole	Blind holes	Steels, aluminum, stainless, soft stringy metals	Use bottoming or semi-bottoming chamfer

Key points

Spiral point taps need room for chips below the hole. In a blind hole they pack chips at the bottom and can break.
Spiral flute taps lift chips up and out, which is why they are the usual choice for blind holes in machine tapping.
Higher helix flutes lift chips better in soft, gummy material. Lower helix flutes are stronger for harder material.
Straight flute taps are the general-purpose choice for hand tapping and for materials that break into small chips.
Chamfer style matters as much as flute style. See the tap chamfers sheet for taper, plug and bottoming.
Thread-forming taps have no flutes for chips at all. See the thread-forming (roll) taps sheet.

Common mistakes

Using a spiral point tap in a blind hole with little drill depth below the thread.
Choosing spiral flute taps for cast iron, where powdery chips do not need lifting.
Ignoring the tap drill size. See the tap drill chart for drill sizes.
Running a spiral flute tap without enough drill depth below the last full thread.

Governing standards: ASME B94.9 (taps, ground and cut threads). Tap maker's catalog for flute and chamfer options by material.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

More in Technical Reference

← All Cutting Tools sheets