Page 49 - CITS - Fitter - Trade Theory

FITTER - CITS

Calculations of spindle speed rpm, examples
At what should a 20mm dia. Drill be run cutting, steel at 25 m./min. Surface speed? Sol: cutting speed 25 =
πdn/1000
N = 25×1000/π20
N = 398 rpm
Definition of feed

Feed is the distance (X) a drill advances into the work in one complete rotation.
Feed is expressed in hundredths of a millimeter.
Feed rate: The overall rate at which the cutting tool moves along or into the workpiece. It is a combination of both
axial and radial feeds.
The rate of feed is dependent up on a number of factors.
• The finish required

• Type of drill (drill material)
• Material to be drilled

Factors like rigidity of the machine, holding of the workpiece and the drill, will also have to be considered while
determining the feed rate. If these are not to the required standard, the feed rate will have to be decreased.

It is not possible to suggest a particular feed rate taking all the factors into account.

Drill diameter (mm) H.S.S Rate of feed (mm/rev)
1.0-2.5 0.040-0.060

2.6-4.5 0.050-0.100
4.6-6.0 0.075-0.150
6.1-9.0 0.100 -0.200
9.1 - 12.0 0.150-0.250

12.1 - 15.0 0.200 -0.300
15.1-18.0 0.230-0.330
18.1-21.0 0.260-0.360
21.1 - 25.0 0.280 -0.380

Definition of depth of cut
Axial Feed (or Depth of Cut): This refers to the distance the cutting tool penetrates into the work piece along its
axial direction.
It influences the depth of the cut and, in turning or milling operations, is often associated with the term “depth of
cut.”
Depth of cut
The drill diameter is 40mm and find the depth of for the job? Sol. Depth of cut = dia.of hole /2 40/2=20mm

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CITS : CG & M - Fitter - Lesson 5