Page 257 - Fanar

Technical Information i

8. TWIST DRILLS

8.1. Nomenclature of Twist Drills

A

F E D C
B

C1 D1 D2

B
C2
L2
L3 L4
L1

A
with no web with web thining
thining
C - channel supplying coolant H
D - chip flute J G
E - margin
F - rake face
G - primary clearance surface
H - secondary clearance surface
I - chamfer C3
J - chamfer edge I

L1 - total length
L2 - chip flutes length A-A
L3 - margin length G2
L4 - shank length D5
D1 - working part diameter G1
D2 - shank diameter D3
D3 - core diameter
D4 - spacing of cooling channels
D5 - diameter of cooling channels
C1 - point angle
C2 - Helix angle D4
C3 - chisel angle B
C4 - clearance angle
C5 - angle of primary clearance surface
C6 - angle of secondary clearance
G1 - margin width
G2 - lowering of margin
B - blade width
B-B
Types of Drill Clearance Surfaces
Four faced Conical (eccentric)

C6 C5 C4 11

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