A clearance hole is a hole through an object which is big enough to enable threads of a screw or bolt to pass through but not the head of the screw or bolt. It allows a screw to pass through it without the threads biting into the material.

What is a free fit clearance hole?

Each fit is toleranced so that a threaded object can pass through the hole while the head of the object will not. Free fit has a larger allowance while Close Fit has a tighter allowance.

What does clearance drill size mean?

Clearance holes: A clearance hole is large enough for the screw to slide through without being turned. Many tapping charts will have two types of clearance drills: tight and loose.

How deep is a pilot hole?

Pilot holes guarantee that your screw won’t break off and your wood won’t crack. For most hardwoods, the pilot hole should be at least as large as the screw’s minor diameter. If the screw has deep threads, or the wood is very hard, the pilot hole should be another 1/64-in.

What is the formula for tap drill size?

Tap-drill diameter equals nominal diameter minus thread pitch. For example, drill size for a 3/8-16 thread is 0.375 0.0625 (pitch) = 0.312 in. in diameter, and for a 10-32 thread, the drill diameter is 0.190 0.032 = 0.159 in. (a #21 drill).

Are bolt holes always clearance holes?

Most bolt holes are made with “standard” clearance and are considered a normal fit. A normal fit provides relatively accurate positioning of assembled components while still allowing for slight misalignment.

What is the clearance hole for a 3/8 bolt?

This table shows how to determine the clearance hole size for a bolt. For example, an 3/8″ bolt with a close fit would have a W (0.3860) clearance hole.

What size hole is required for a 3/8 inch bolt?

Most drill charts recommend a 5/16 drill for a 3/8-16 bolt. Cutting holes that are smaller will leave more material for the tap to cut out, risking tap breakage. Drilling larger holes will result in weaker threads, increasing the possibility of stripping them.