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American UN-8 thread

Hand taps for UN-8, Unified constant-pitch thread

Eight threads per inch across all diameters — the series for large threads where a proportional pitch would come out too coarse. Hand taps are turned by hand in a tap wrench. The thread is cut in several passes, because the work is shared between taper, second and bottoming tap.

VÖLKEL offers 64 versions to ISO 529, in HSS-G, from UN 1.1/8 x 8 to UN 4" x 8. Lead forms A, C and D cover through holes and blind holes.

All sizes at a glance

64 articles in 1 series. The article number links straight to the tool.

Hand Tap ISO 529 HSS-G

Threadnominal sizeTapping drillØ in mmset of 3 piecesTaper Form ABottoming Form CSecond Form D
UN 1.1/8 x 825.58294082940-182940-382940-2
UN 1.1/4 x 828.758294282942-182942-382942-2
UN 1.3/8 x 831.758294482944-182944-382944-2
UN 1.1/2 x 8358294682946-182946-382946-2
UN 1.5/8 x 8388294782947-182947-382947-2
UN 1.3/4 x 841.58294882948-182948-382948-2
UN 1.7/8 x 844.58294982949-182949-382949-2
UN 2" x 847.758295082950-182950-382950-2
UN 2.1/8 x 850.98295182951-182951-382951-2
UN 2.1/4 x 8548295282952-182952-382952-2
UN 2.3/8 x 8–8295382953-182953-382953-2
UN 2.1/2 x 860.48295482954-182954-382954-2
UN 2.3/4 x 866.78295682956-182956-382956-2
UN 3" x 873.18295882958-182958-382958-2
UN 3.1/2 x 885.88296082960-182960-382960-2
UN 4" x 898.58296282962-182962-382962-2

Tapping drill: drill diameter recommended by VÖLKEL (Technical Information “Tapping drill sizes”).

Application advice for VÖLKEL threading tools
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