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USER GUIDE
GUNDRILLS Drilling Tolerances Obtainable In Deep Hole Drilling

Deep Drilling Tolerances
Gundrill configurations when used under recommended conditions can produce holes with tolerances of IT8-IT9.
When operating under optimal conditions, even better tolerances can be achieved.
Nonferrous materials
Aluminum
Tool steel
Cast iron
High alloy steel>800N/mm2 Machinability
of Metals
Hardened steel
Low alloy steel<800N/mm2
Carbon steel
Sintered steel
Drilling quality IT 13 12 11 10 9 8 7 6 5

Tolerance range under normal conditions Tolerance range under
optimal conditions
Surface Quality
Surface quality of 0.2 Ra can be achieved when using gundrills under recommended conditions.

N12 N11 N10 N9 N8 N7 N6 N5 N4 N3 N2 N1
Indexable Drills
Reaming
Honing
Deep drilling
Degree of roughness μ m 50 25 12.5 6.30 3.20 1.60 0.80 0.40 0.20 0.10 0.05 0.025
(Ra roughness index) μ in 2000 1000 500 250 125 63 32 16 8 4 2 1
Tolerance range under normal conditions Tolerance range under optimal conditions

Concentricity and Straightness Circularity
The resulting quality depends on different factors such as: The geometric quality of bores obtained from deep
• Drilling depth and diameter hole drill bits is clearly higher than that obtained
• Type of machining and cutting parameters with the use of twist drills. It is possible to obtain
• Quality and uniformity of the workpiece material precision with deviations of less than 4 µm.
• Machine tool conditions
• Gundrill support
mm
mm
1.0
0.05
0.84
0.04
0,66
0.03
0.5
0.02
0.33
0.01
0.16
250 500 750 mm
500 1000 mm
Drilling Depth Drilling Depth
Stationary workpiece – rotating tool
Rotating workpiece – stationary tool

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