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Spiral Point vs Spiral Flute Taps
Guide · Updated October 28, 2026
Spiral point (gun) taps shoot chips ahead of the tap, so they suit through holes. Spiral flute taps pull chips back out of the hole, so they suit blind holes. Straight flute hand taps hold chips in the flutes; forming taps make no chips at all.
Check the hole size
Forming taps need a larger drill than cutting taps. Check the hole. The free Gage Block Calculator builds the stack.
Step by step
- Identify the hole: Through or blind.
- Through hole: Use a spiral point tap; chips exit the far side.
- Blind hole: Use a spiral flute tap; chips come back up the flutes.
- Short-chipping materials: Cast iron and brass often tap well with straight flutes.
- Consider forming: Forming taps suit ductile materials and need their own drill size.
- Set speed: Use the maker's speed.
- Check: Check threads with a plug gage.
Worked example: blind hole with spiral flute
Tapping 3/8-16 in a blind hole that needs 0.500 in full thread with a plug-chamfer spiral flute tap (3–5 threads). P = 0.0625 in; a 4-thread chamfer is 0.250 in. Tap depth to the tip = 0.500 + 0.250 = 0.750 in. Drill at least that plus a chip margin and the drill point, about 0.85–0.90 in to the full diameter.
Why the direction matters
Fastenal: spiral point taps reduce clogging by pushing chips ahead; spiral flute taps draw chips out where chip control is an issue. Running a spiral point tap into a blind hole packs chips at the bottom and breaks taps.
Strength
Spiral point taps have shallower flutes and a stronger core, so they tolerate higher speeds in through holes.
Common problems
Broken tap in a blind hole: spiral point used, chips packed. Bird-nesting chips: spiral flute in a long-chipping material at low speed. Oversize threads: worn tap or misalignment.
Worked example: through hole with a spiral point
A 1/4-20 through hole in a 0.500 in plate with a spiral point plug tap (3–5 thread chamfer, about 0.200 in). Run the tap until the full threads clear the far side: 0.500 + 0.200 = 0.700 in of travel, plus a little margin. Make sure there is clearance below the part, because the chips are pushed out the bottom.
More common problems
Spiral flute tap breaking in hard steel: the helix flutes weaken the tap; a straight flute or spiral point with lower speed may suit better. Chips wrapping around the tap shank: increase speed slightly or use a chip-breaker coolant. Torn first threads: dull chamfer.
Tips
- Set: taper, plug and bottoming taps.
- Power: power tapper.
- Speeds: tapping speeds.
FAQ
Which tap for through holes?
Spiral point.
Which tap for blind holes?
Spiral flute.
Can I hand tap with spiral point?
Yes, in through holes.
What is a forming tap?
A tap that forms threads without chips.
Do forming taps use the same drill?
No, a larger drill.
Related guides and calculators
- Taper, Plug and Bottoming Taps: How to Use a Hand Tap Set
- How to Use a Power Tapper
- Tapping Speeds and Feeds
- Tap Drill Chart Explained
- How to Tap on a Mill
- How to Use a Rotary Broach
- All free machinist calculators
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