Union Butterfield® STI Tap, Spiral Point, Series: 1578, Measurement System: Imperial, #10-32 Thread, UNF Thread Standard, 1 in Thread Length, 2-1/2 in Overall Length, 2 Flutes, Plug Chamfer, Right Hand Cutting Direction, Class of Fit: 2B/3B/H2, 0.255 in Shank Diameter, #21 Tap Drill, 0.191 in Square, HSS, Bright

• Designed for use in aluminum, magnesium, and other nonferrous materials where taps of this type are most commonly used
• Taps suitable for other materials can be furnished on request
• STI taps are dimensionally oversize and utilize a larger tap drill size so that the thread they produce will accept a helical coil wire screw thread insert of the same nominal size and pitch
• For a particular size and pitch the lower H-Limit number is suggested for class 2B and 3B threads, while the higher H-Limit is suggested for class 2B
• Through hole

• https://externalassets.unilogcorp.com/ASSETS/DOCUMENTS/ITEMS/EN/Union_Butterfield_1010300_Catalog.pdf https://externalassets.unilogcorp.com/ASSETS/DOCUMENTS/ITEMS/EN/Union_Butterfield_1010300_Catalog.pdf