Correct Answer - Option 1 : 318.4 RPM
Concept:
Drilling:
- Drilling is used for producing holes in the components by using a rotating multipoint cutting tool.
- During producing a hole, it is always recommended to use the smallest size of the drill bit first and enlarge the hole slowly by using different sizes of drill bit until the required size of the hole is produced.
- Drilling time is given by:
\({\bf{T}} = \frac{{\bf{nL}}}{{{\bf{f}} \times {\bf{N}}}}\)
\(N=\frac{v\times1000}{\pi D}\)
where, Tool travel (L) = CAP + AP + OR + t, n = number of holes
here, L = t only
Calculation:
Given:
D = 25 mm, v = 25 m/min
\(N=\frac{25\times1000}{\pi \times25}=318.4 ~rpm\)
