These British manufactured High Speed Steel Ground Threading Dies have a machined lead-in for ease of use and accurate thread cutting. These Dies are also split to facilitate the fine adjustment of core diameter.

Die O.D.        Size Range

13/16"         (3/16" - 1/4")
1"             (3/16" - 1/2")
1-5/16"        (1/4" - 9/16")
1-1/2"         (3/8" - 3/4")
2"             (9/16" - 1")
3"             (1-1/8" - 1-1/2")

B.S.F. H.S.S. Split Dies (5/8"- 1-1/2")

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  • Tap Types: First Taper (or Taper Tap) A Taper Tap has a pronounced taper to the cutting edges. This feature gives the taper tap a very gradual cutting action that is less aggressive than that of the plug tap. The number of tapered threads typically ranges from 8 to 10. A taper tap is most often used when the material to be tapped is difficult to work (e.g., alloy steel) or the tap is of a very small diameter and thus prone to breakage. Second Taper (or Intermediate Taper) A Second Taper tap has tapered cutting edges, which assist in aligning and starting the tap into an untapped hole. The number of tapered threads typically ranges from 3 to 5 and is the most common type of threading tap used. Plug/Cleaning Tap (or Bottom Tap) A Plug tap has a continuous cutting edge with almost no taper — between 1 and 1.5 threads of taper. This feature enables a bottoming tap to cut threads to the bottom of a blind hole. A bottoming tap is usually used to cut threads in a hole that has already been partially threaded using one of the more tapered types of tap or for cleaning out dirty threads; the tapered end of a plug tap is too short to successfully start and cut new threads in an unthreaded hole.