Tap Type Guide

Data quality

• Dataset: Tapping & Threading tap types
• Projection: T3 Tapping Tap-Type Projection
• Tap types: 7
• Facts: 1 verified / 15 source-bound
• Verification: Mixed — see per-fact status below

How BoltLab classifies and verifies engineering data

Compare tap types

Each column reflects a directly-quoted fact from the classified evidence below, not a new claim. Where a cell shows "—", no fact in that category was recorded for this tap type.

Choosing between tap types

This comparison summarizes documented characteristics; it does not issue a universal recommendation. Match the chip-evacuation direction and hole suitability to your own job, and treat "typical application" facts as widely-corroborated observations rather than guarantees for every material or application.

Taper Tap

A tap with a gradually tapered chamfer at the point, typically engaging six to eight threads before reaching full thread form, used to start threads gradually and reduce cutting force per pass.

Manufacturing characteristics

• Chamfer length is approximately 7-10 threads/pitches, the longest of the three chamfer-length tap styles. — Source-bound, source: Cross-corroborated across multiple machining reference sources (Travers Tool, MisolTap, Rapmaf, AIMS Industrial)

Typical applications

• Long chamfer distributes cutting load gradually and makes the tap easier to start straight/square, but it cannot cut full-depth threads within roughly 7-10 pitches of the bottom of a blind hole. — Source-bound, source: Cross-corroborated across multiple machining reference sources

Plug Tap

A tap with a moderate chamfer length, shorter than a taper tap but longer than a bottoming tap, engaging approximately three to five threads before reaching full thread form.

Manufacturing characteristics

• Chamfer length is approximately 3-5 threads/pitches, shorter than a taper tap and longer than a bottoming tap. — Source-bound, source: Cross-corroborated across multiple machining reference sources

Typical applications

• General-purpose tap; commonly the sole tap used for through-hole tapping, and can start in an unthreaded hole (unlike a bottoming tap). — Source-bound, source: Cross-corroborated across multiple machining reference sources

Bottoming Tap

A tap with a short chamfer, typically engaging one to one and a half threads before reaching full thread form, designed to cut threads as close as practical to the bottom of a blind hole.

General taxonomy

• Incomplete internal threads are inherently present at the bottom of a tapped blind hole -- the physical reason bottoming taps exist as a distinct style. — Verified, source: NASA-STD-5020A section 4.7.5 [TFSR 25]: "Where blind holes are tapped, incomplete internal threads are present at the bottom of the hole."

Manufacturing characteristics

• Chamfer length is approximately 1-2 threads/pitches, the shortest of the three chamfer-length tap styles. — Source-bound, source: Cross-corroborated across multiple machining reference sources

Typical applications

• Cannot start in an unthreaded hole; used to extend threads to the base of a blind hole after a taper and/or plug tap has already established the thread. — Source-bound, source: Cross-corroborated across multiple machining reference sources

Spiral Point Tap

A tap with an angled point ground onto the flutes that pushes chips forward, ahead of the tap and out through the far side of the hole, commonly associated with through-hole applications.

Manufacturing characteristics

• Also called a gun tap or gun-nose tap; a forward-angled point ground onto the cutting chamfer drives chips forward, ahead of the tap. — Source-bound, source: Cross-corroborated across multiple machining reference sources (Cutwel, MisolTap, Slugger Tools)

Typical applications

• Suited to through-hole tapping only. In a blind hole the forward-pushed chips have nowhere to go, pack at the bottom, and can bind and break the tap. — Source-bound, source: Cross-corroborated across multiple machining reference sources; consistent with NASA-STD-5020A's confirmation that blind-hole tapped threads terminate at a closed bottom with no chip escape path

Spiral Flute Tap

A tap with helical (spiral) flutes that lift chips backward out of the hole entrance during cutting, commonly associated with blind-hole applications.

Manufacturing characteristics

• Helical (spiral) flutes lift chips backward, up and out of the hole entrance, opposite in direction to a spiral-point tap. — Source-bound, source: Cross-corroborated across multiple machining reference sources

Typical applications

• Suited to blind-hole tapping, where chips cannot be pushed forward out of a closed bottom. — Source-bound, source: Cross-corroborated across multiple machining reference sources

Forming Tap

A tap that forms threads by radially displacing material rather than cutting it, producing no chips; also referred to as a roll tap or fluteless tap.

Manufacturing characteristics

• Requires a larger pre-tap hole diameter than an equivalent cutting tap, since material is displaced outward rather than removed. — Source-bound, source: Cross-corroborated across multiple manufacturer technical guides

Typical applications

• Unsuitable for brittle materials such as cast iron, which can crack rather than flow under the forming pressure. — Source-bound, source: Cross-corroborated across multiple manufacturer technical guides
• Produces no chips, which removes chip-evacuation as a constraint on blind-hole use -- unlike cutting taps, hole geometry (blind vs. through) is not the limiting factor for this tap type; material ductility is. — Source-bound, source: Cross-corroborated across multiple manufacturer technical guides

Manufacturer-specific recommendations

• Requires a ductile workpiece material -- commonly cited minimum elongation of roughly 8% and maximum hardness of roughly Rc 30 -- because threads are formed by plastic displacement, not cutting. — Source-bound, source: Commonly cited across manufacturer/tooling technical guides (e.g. Harvey Performance, Jarvis Cutting Tools); not independently verified against a primary standard in this phase

Hand Tap

A tap designed for manual operation with a tap wrench, typically supplied as part of a set spanning taper, plug, and bottoming chamfer styles for a given thread size.

Typical applications

• Designed for manual operation with a tap wrench; commonly supplied as a taper/plug/bottoming set for progressive blind-hole tapping by hand. — Source-bound, source: Cross-corroborated across multiple machining reference sources

Browse tapping data

Compare verified and source-bound tap-drill data across metric, UNC, and UNF thread sizes in the Tapping Atlas.

Tapping & Threading Atlas

Download the tapping dataset (CSV)

Related references

• Tapping Evidence & Provenance — see the classification and source behind each fact above
• Tapping Workflow — a guided, step-by-step decision aid built on this same data
• Tapping & Threading Atlas
• Tap Drill Calculator
• Engineering Data Methodology

FAQ

What is the BoltLab Tap Type Guide?

A structured comparison of BoltLab's seven tap types -- taper, plug, bottoming, spiral-point, spiral-flute, forming, and hand -- built from the same verified knowledge layer as the Tapping & Threading Atlas, with every fact labeled by evidence kind and verification status.

How are tap types classified in this guide?

Each fact is tagged as general taxonomy (a settled, definitional fact), a manufacturing characteristic (a physical or structural trait), a typical application (a widely-corroborated but not universally guaranteed use case), or a manufacturer-specific recommendation (a vendor's own guidance, not a general industry fact).

Which tap type is verified against a primary standard?

Bottoming taps carry the one fact in this guide verified against a Tier 1 primary source: NASA-STD-5020A confirms that incomplete internal threads are present at the bottom of a tapped blind hole, which is the physical reason bottoming taps exist as a distinct style. Every other fact in this guide is source-bound rather than independently verified against a primary standard.

Can BoltLab tell me which tap type to use for my job?

This guide compares documented characteristics -- chamfer length, chip-evacuation direction, and blind/through-hole suitability -- so you can match them to your own job requirements. It does not issue a universal recommendation, since the underlying facts are typical-application observations rather than guaranteed rules for every material and application.

Where does this data come from?

Each fact traces to either a Tier 1 primary standard (NASA-STD-5020A, for the one verified fact) or cross-corroborated machining and manufacturer technical references (source-bound). See the BoltLab Data Methodology page for the full verification-tier system.