13 Fundamentals on wo rking with the machine
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13.6. Clamping in the lathe chuck
Caution!
Please comply with the enclosed operating instructions of
the chuck manufacturer as necessary!
Caution!
If work pieces are only clamped in the lathe chuck
without counter-bracket by the tailstock, the projection
may not be greater than the three-fold diameter of the
material (L = 3 x D), see figure at right.
13.7. Determining the correct spindle speed
The cutting speed is a decisive parameter during machining. Too high or too low cutting
speeds affect the good end result, so the choice of spindle speed – which is decisive for
the cutting speed – is very important for a good surface and clean metal removal.
Another determining factor is the diameter of the work piece: the greater it is, the greater
the relative speed is at the circumference at constant speed. The relation is
characterised by the following equation:
n = Vc * 1000/ (D * 3.14)
whereby:
n: Rotational speed
Vc: Cutting speed
D: Diameter
The table on the gear case of the machine offers help in choosing the right cutting
speed. For known cutting speed "Vc" and known work piece diameter "D", the necessary
spindle speed "n" can be calculated.
An example:
An aluminium work piece with a 30mm diameter will be machined. The necessary
cutting speed according to the table is 100–180m/min. We will calculate 132m/min.
n = 132 x 1000/ (30 x 3.14) = 1400 rev/min
This result can be read directly in the table on the gear case.
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