Let's determine the correct bolt hole diameter for a 12 mm diameter bolt as per the guidelines provided in IS 800-2007, which is the Indian Standard Code of Practice for General Construction in Steel.

IS 800-2007 specifies the standard nominal clearances that should be provided around bolts in bolted connections to facilitate easy assembly and account for minor misalignments. This clearance is added to the nominal bolt diameter to get the required bolt hole diameter.

Understanding Bolt Hole Diameter and Clearance in IS 800-2007

The standard clearance for bolt holes is defined in Clause 5.2.2.2 of IS 800-2007. This clause provides a table or rule for determining the appropriate clearance based on the nominal diameter of the bolt. The standard classifies the holes primarily as 'Standard Clear Holes'.

Calculating Bolt Hole Diameter for 12 mm Bolt

According to IS 800-2007, the standard clearance depends on the bolt's nominal diameter. For bolts with a nominal diameter up to and including 12 mm, the standard clearance is 1 mm.

The bolt hole diameter is calculated by adding the standard clearance to the nominal bolt diameter:

\(\text{Bolt Hole Diameter} = \text{Nominal Bolt Diameter} + \text{Standard Clearance}\)

Given the nominal bolt diameter is 12 mm, and the standard clearance for a 12 mm bolt is 1 mm, the bolt hole diameter is:

\(\text{Bolt Hole Diameter} = 12 \text{ mm} + 1 \text{ mm}\)

\(\text{Bolt Hole Diameter} = 13 \text{ mm}\)

Therefore, as per IS 800-2007, the value of the bolt hole diameter for a 12 mm diameter bolt is 13 mm.

Standard Clearances for Bolt Holes (IS 800-2007)

Here is a summary of standard clearances as per IS 800-2007:

Based on this table, for a 12 mm bolt (which falls into the "Up to 12 mm" category), the standard clearance is 1 mm, resulting in a standard hole diameter of 12 mm + 1 mm = 13 mm.

Revision Table: IS 800-2007 Bolt Hole Sizes

Key details regarding bolt hole diameters in IS 800-2007:

• The standard aims to ensure proper fit and assembly.
• Different clearances are specified for different bolt size ranges.
• 1 mm clearance is used for smaller diameter bolts, up to 12 mm.
• Larger bolts get larger clearances (2 mm or 3 mm).
• This question specifically deals with the 12 mm size, which is the upper limit for the 1 mm clearance range.

Additional Information: Types of Bolt Holes

IS 800-2007 also mentions other types of holes besides standard clear holes, although standard clear holes are most common for general bolted connections:

• Oversize holes: These have larger clearances than standard clear holes and might be used in specific situations like allowing for thermal expansion or facilitating erection, but require washers. Their sizes are also specified in the code.
• Short slotted holes: These are elongated holes that allow for movement in one direction.
• Long slotted holes: These are even longer elongated holes allowing more movement.

The question specifically asks for the standard hole diameter, which refers to the standard clear hole based on the nominal bolt diameter and the standard clearance as discussed above.