Center Drills and Center Drill Dimensions

Center Drill Dimensions

Center drills are used to make a dimple to ensure that a drill doesn’t “walk” when it first contacts the flat face of a piece of metal.  We also use them to drill the end of a cylindrical part we will be turning with a lathe.

SizeBody Dia (A)Drill Dia (D)Drill Length (C)OAL (L)
001/80.0250.0301 1/8
01/81/320.0381 1/8
11/83/643/641 1/4
23/165/645/641 7/8
31/47/647/642
45/161/81/82 1/8
57/163/163/162 3/4
61/27/327/323
75/81/41/43 1/4
83/45/165/163 1/2

Bell Type Dimensions

SizeBody Dia (A)Drill Dia (D)Bell Dia (E)Drill Length (C)OAL (L)
111/83/640.13/641 1/4
123/161/160.151/161 7/8
131/43/320.23/322
145/167/640.257/642 1/8
157/165/320.355/322 3/4
161/23/160.43/163
175/87/320.57/323 1/4
183/41/40.61/43 1/2