Understanding Bolt Hole Diameter Increase

When using bolts for fastening components together, the hole drilled or punched in the material needs to be slightly larger than the nominal diameter of the bolt. This extra space is called clearance, and it is essential for several reasons:

• It allows for easier insertion of the bolt during assembly.
• It accommodates slight misalignments between holes in different parts.
• It prevents binding or jamming of the bolt.

The amount of clearance added to the nominal bolt diameter depends on engineering standards and the specific application. Common standards provide recommended hole sizes based on the bolt's nominal diameter.

Calculating Bolt Hole Diameter for a 14 mm Bolt

The question specifies a bolt with a nominal diameter of 14 mm. We need to determine by how much the bolt hole diameter increases compared to this nominal size.

According to standard engineering practices (like those defined by ISO or relevant national standards), the standard clearance for bolts in this size range (typically up to 20 mm) is usually 1 mm.

This means:

• Nominal bolt diameter = 14 mm
• Standard clearance = 1 mm
• Standard bolt hole diameter = Nominal bolt diameter + Clearance
• Standard bolt hole diameter = $$14 \text{ mm} + 1 \text{ mm} = 15 \text{ mm}$$

The question asks for the amount by which the bolt hole diameter increases. This increase is precisely the clearance value.

Therefore, the increase in the diameter of the bolt hole for a nominal 14 mm bolt is 1.0 mm.

Standard Bolt Hole Clearances

Here is a general guide for standard bolt hole clearances for common bolt sizes:

Based on this table, for a nominal bolt diameter of 14 mm (which is > 6 mm up to 16 mm), the standard clearance is indeed 1.0 mm. This matches the calculation and explanation above.

Conclusion on Bolt Hole Increase

For a bolt with a nominal diameter of 14 mm, the standard practice is to provide a 1.0 mm clearance in the bolt hole. This means the bolt hole diameter will typically be 15 mm.

The increase in the diameter of the bolt hole is equal to the standard clearance, which is 1.0 mm.

Revision Table: Bolt Hole Diameter Calculation

Additional Information on Bolt Clearances

While 1.0 mm is the standard clearance for a 14 mm bolt hole, other types of clearances exist depending on the application requirements:

• Oversize Holes: These provide even more clearance, useful for applications where significant adjustment or misalignment is expected. The increase might be 2 mm or more.
• Short Slotted Holes: These are elongated holes used to allow for movement in one direction, while restraining movement in the other.
• Long Slotted Holes: These provide greater allowance for movement or adjustment along the slot axis.

The choice of hole type and clearance is a design consideration based on factors like load transfer, assembly method, thermal expansion, and potential for fabrication errors.