Mechanical Engineering - Workshop Technology - Discussion

The correct answer is 1 to 3° (approximately 2 to 5 mm/m).

The draft or taper allowance on casting is the slight taper or angle provided on the vertical surfaces of the pattern to facilitate easy removal from the mould. This allowance is typically:

- 1 to 3° (approximately 2 to 5 mm/m) for small castings
- 2 to 5° (approximately 5 to 10 mm/m) for medium-sized castings
- 3 to 5° (approximately 10 to 15 mm/m) for large castings

The draft allowance depends on the:
- Size and complexity of the casting
- Type of moulding material (sand, investment, etc.)
- Casting material (aluminium, steel, etc.)

The draft allowance ensures that the casting can be removed from the mould without damage or excessive force, which could lead to mould breakage or casting defects.

=> The exact draft allowance may vary depending on the specific casting process and application.

The amount of draft depends upon the length of Vertical side of the pattern to be extracted, the intricacy(Complexity) of the pattern, the method of molding and pattern material.

Which means tapper section is provided only perpendicular face with parting line?

The amount of draft recommended on external surfaces varies from 10 to 20 mm/m.

As per my knowledge, 10-20mm external and 30-40 internal taper allowance.

In, Rs Khurmi 1 to 2 but RK Jain 10 to 15.

Which is the correct answer?

I think 1to 2 mm is correct.

10-15 mm/m is an allowance for shrinkage.

Provided draft allowance 10-15mm/mtr on casting vertical sides.

Answer is C.

Outer taper is 10 to 25.
Inner taper is 40 to 65.

Please explain this answer to get it.