Page 296 - Hartner

Precision

of single-fluted deep hole gun drills

Basic tolerances normal
conditions
The application of single-fluted gun drills can achieve a lower Achievable
tolerances
optimal
basic tolerance, as the cutting forces at the cutting edge are conditions
absorbed by the supporting strips, unlike twist drills where the Copper, nickel, zinc
slightest deviation of the two cutting edges causes a larger and their alloys
hole. Al-alloys
(acc. to Si-content)
Heat-treatable steels

Cast iron
Nitriding steels
Stainless steels

Structural steel
Case hardened steel

11 10 9 8 7 6 5
Basic tolerance grade IT

Surface quality Achievable
The forces at the cutting edge are absorbed by the support surface
bushes, which in return burnishes the surface. Lubrication bet- quality
ween the supporting strips and hole surface is therefore very
important. Twist drills
The better the lubricant, the better the surface quality.

Pilot holes

Reaming

Honing

Deep hole drilling
Average peak-to-valley 25 12,5 6,3 3,2 1,6 0,8 0,4 0,2

height R in µm
ª
Peak-to-valley N11 N10 N9 N8 N7 N6 N5 N4
height class N

290

04_TLB.indb 290 28.11.11 11:07