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What is the next closest drill bit to 5 16?

Published in Drill Bit Sizing 3 mins read

The next closest drill bits to 5/16 (which is equivalent to 10/32) are 9/32 (the next smaller size) and 11/32 (the next larger size), assuming your drill bit set includes these common fractional increments.

Understanding Fractional Drill Bit Sizing

Drill bits are often measured in fractions of an inch, and understanding these increments is key to selecting the correct bit for a project. To easily compare sizes, it's helpful to convert them to a common denominator. For instance, 5/16 of an inch can be precisely converted to 10/32 of an inch. This common denominator makes it straightforward to identify the adjacent sizes within a standard set.

Closest Drill Bit Sizes to 5/16

When you need a bit that is just a hair off from 5/16, you're looking for the next increment up or down in the fractional system, typically in 32nds or 64ths of an inch. Given 5/16 as 10/32:

  • Next Smaller Size: The fractional drill bit immediately smaller than 10/32 is 9/32. This bit would create a slightly tighter hole, often used for pilot holes where a fastener needs to achieve maximum grip.
  • Next Larger Size: The fractional drill bit immediately larger than 10/32 is 11/32. This bit would create a slightly looser hole, commonly chosen for clearance holes or when a component needs to slide through freely.

When to Choose a Slightly Larger Bit

Choosing an 11/32 bit over 5/16 is beneficial in several scenarios:

  • Clearance Holes: For applications where a screw, bolt, or dowel needs to pass through one material without threading or catching, creating a clearance hole is essential. The slightly larger 11/32 bit ensures a free passage.
  • Easier Assembly: If you are assembling multiple components and need some tolerance for alignment, a slightly larger hole can make the parts fit together more easily.
  • Preventing Splitting: When drilling into softer woods or close to the edge of a workpiece, a marginally larger pilot hole can sometimes reduce the risk of the material splitting.

When to Choose a Slightly Smaller Bit

Opting for a 9/32 bit instead of 5/16 is ideal for:

  • Pilot Holes for Screws: A 9/32 bit can serve as a precise pilot hole for a 5/16-inch screw, ensuring that the screw threads have ample material to bite into for a strong, secure, and lasting connection.
  • Tight Fits: For components that require an interference fit or a very snug connection, such as for dowel pins or tight-fitting fasteners, an undersized hole maximizes contact and friction.
  • Hardwood Drilling: When working with dense hardwoods, a slightly smaller pilot hole may be necessary to allow screws to gain purchase without stripping the wood or the screw head due to excessive resistance.

Drill Bit Measurement Table

This table illustrates the relationship between 5/16 and its closest common fractional neighbors, including their decimal equivalents for easy comparison:

Description Fractional Size Decimal Equivalent (approx.)
Next Smaller Bit 9/32" 0.28125"
Target Bit 5/16" (10/32") 0.3125"
Next Larger Bit 11/32" 0.34375"

Selecting the appropriate drill bit size is crucial for successful drilling outcomes, ensuring precision, proper fastener seating, and the integrity of your materials.