Spiralock taps are furnished with ramp angles as shown here. This is referred to as style "BT" for bottom tapping. When tapping from the opposite end of a through hole, you must specify Spiralock style "TT" (top tapping), which has the ramp angle facing the opposite direction.
Specialized geometry for short-chipping materials such as cast iron and hardened alloy steels. The straight flutes do not provide chip transport, so these taps should not be used on deep blind holes unless tap is extracted mid-way to evacuate chips. TiN coating adds durability and lubricity. The T-10 tap range is intended for use on CNC machining centers.