5. Setting of the tools

At bench-type and upright drilling machines, the ‘rotational speed’ and - with modern types - the ‘cutting speed’ and ‘feed’ must be set.

The rates of ‘rotational speed’, ‘cutting speed’ and ‘feed’ depend on the material to be drilled and the diameter of the drill.

To automatic feeds the following rules apply:

Low feed rate - with high rotational speed and hard material
High feed rate - with low rotational speed and soft material

The automatic feed is not required for making smaller bore holes (up to 12 mm dia.)

The cutting speed for drilling without automatic feed can be fixed at 22 m/min. Thus, the following rotational speeds apply:

Materials	Diameter of the drill in mm (Range)
	1 - 3	3 - 5	5 - 8	8 - 10	10 - 12	12 - 16
Soft materials (aluminium, copper)	7100 to 4500	5600 to 3500	3500 to 2200	2800 to 1800	2200 to 1400	1800 to 1100
Medium hard steels cast steel	2800 to 1800	2200 to 1400	1400 to 900	1100 to 700	900 to 560	710 to 450
hard materials (chromium-nickel alloys)	350	350	350	350	280	220

The following rule applies to the setting of the rotational speed:

Low rotational speed - with hard materials and great drill diameters
High rotational speed - with soft materials and small drill diameters

The rotational speed can be calculated with the help of the following formula:

n = rotational speed (in r.p.m.)
v = cutting speed (in m/min)
d = diameter of the rotating piece (in mm)
p = 3.14

Calculating example

What rotational speed has to be set if a bore hole of 10 mm shall be drilled into a workplace of steel on a bench-type drilling machine with feed by hand?

Exercise

What rotational speed has to be set if a bore hole of 5 mm dia. shall be drilled into a workpiece of steel by a bench-type drilling machine with hand feed?
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Compare the result with the value of the table:

Calculated value	Value indicated in the table