Tap Drill Size Calculator

Tap drill size is crucial for creating threaded holes. It determines the hole diameter to accommodate the threads formed by the tap. The correct size ensures secure fastening. Consult tap drill charts or guidelines for specific sizes. Using a slightly smaller drill bit than the major thread diameter is a common rule of thumb.

Thread Size (Inches)	Tap Drill Size (Inches)
1/4-20	0.201
5/16-18	0.266
3/8-16	0.339
7/16-14	0.391
1/2-13	0.421
9/16-12	0.469
5/8-11	0.516
3/4-10	0.641
7/8-9	0.734
1-8	0.859

FAQs

How do you calculate tap drill size?

• The tap drill size is typically calculated by subtracting the pitch diameter of the desired thread from the nominal thread size. For example, for a 1/2-inch-20 tap, you’d calculate the tap drill size as approximately 0.473 inches (1/2 inch – 0.027 inch for the pitch diameter).

What size hole do you drill for a 1/2 tap?

• For a 1/2-inch-20 tap, you would drill a hole with a diameter of approximately 0.473 inches.

What size drill bit for a 7/8 tap?

• For a 7/8-inch-UNC tap, you would use a drill bit with a diameter of approximately 0.813 inches.

How deep do you drill for a tap?

• The depth you drill for a tap depends on the desired thread depth and the type of tap being used. Generally, you’d drill to a depth slightly greater than the length of the threaded portion of the tap, ensuring that there is room for chips and clearance.

What is a tap drill chart?

• A tap drill chart is a reference chart that provides recommended drill bit sizes for various tap sizes and thread types. It helps users select the appropriate drill bit for tapping holes.

What is the rule of thumb for tap drill size?

• The rule of thumb is to use a drill bit that is slightly smaller in diameter than the major diameter of the thread. This allows for a snug fit while providing enough material for the threads to engage.

What size hole for a 1/2-20 tap?

• For a 1/2-20 tap, you would drill a hole with a diameter of approximately 0.464 inches.

Are all tap holes the same size?

• No, tap holes are not all the same size. The size of the tap hole depends on the specific thread size and type of tap being used.

What size drill bit used for a 1/2-28 tap?

• For a 1/2-28 tap, you would use a drill bit with a diameter of approximately 0.469 inches.

What drill bit to use with a 1/8 tap?

• For a 1/8-inch-27 tap, you would use a drill bit with a diameter of approximately 0.332 inches.

What size is a 3/8 tap drill?

• For a 3/8-inch-16 tap, you would use a drill bit with a diameter of approximately 0.339 inches.

How do you read a tap drill chart?

• To read a tap drill chart, locate the tap size and thread type you intend to use. The chart will provide the recommended drill bit size to use for creating the tap hole.

Do you drill or tap first?

• You typically drill the hole first and then tap it. Drilling creates the initial hole, and tapping adds the threads to the hole.

What is the rule of thumb for thread depth?

• The rule of thumb for thread depth is to ensure that the tapped threads are at least 1.5 times the nominal diameter of the screw or bolt being used.

What size is #7 drill bit?

• A #7 drill bit typically has a diameter of approximately 0.201 inches.

What is the difference between tap and tap drill?

• A tap is a cutting tool used to create threads inside a hole, while a tap drill is a drill bit used to create the initial hole before tapping.

What are the 3 sets of tap drill?

• The three sets of tap drills typically refer to taper, plug, and bottoming taps, each requiring a different drill size to accommodate their design and purpose.

What is the formula for tapping depth?

• The tapping depth is typically the total depth of the hole minus the length of the threaded portion of the tap.

Should the drilled hole be bigger or smaller than the bolt diameter for tapping?

• The drilled hole should be slightly smaller than the major diameter of the thread on the bolt to provide a secure fit.

What is the tolerance for tap holes?

• Tolerance for tap holes can vary depending on the specific application and requirements. Common tolerances range from a few thousandths of an inch to a few hundredths of an inch.

What size drill bit do you use for a 1/2-20 tap?

• For a 1/2-20 tap, you would use a drill bit with a diameter of approximately 0.464 inches.

What size drill bit do I use for a 1/4-20 tap?

• For a 1/4-20 tap, you would use a drill bit with a diameter of approximately 0.201 inches.

What drill to use for 1/4-20 tap?

• You would use a drill bit with a diameter of approximately 0.201 inches for a 1/4-20 tap.

Is there a standard tap size?

• Yes, there are standard tap sizes for common thread types and diameters, such as UNC, UNF, and NPT threads.

What size is a standard kitchen tap?

• A standard kitchen tap, referring to a faucet, typically has a threaded inlet of 1/2 inch or 3/8 inch, depending on the plumbing configuration.

What is the difference between a threaded hole and a tapped hole?

• A threaded hole and a tapped hole are essentially the same thing. Both refer to a hole with internal threads created using a tap.

What drill is used to tap a 1/2-14 NPT hole?

• For a 1/2-14 NPT tap, you would typically use a drill bit suitable for NPT threads, which may have a specific size, such as 37/64 inch.

What can I use if I don’t have a 1/2 drill bit?

• If you don’t have a 1/2 drill bit, you can use a drill bit slightly smaller in diameter, such as 15/32 inch, but be cautious to achieve the correct tap hole size.

Can you use a 1/2 bit in a 3/8 drill?

• No, you cannot use a 1/2-inch bit in a 3/8-inch drill chuck unless you have a suitable adapter. The bit must match the chuck size.

What drill bit to use for 1/8-27 tap?

• For a 1/8-27 tap, you would use a drill bit with a diameter of approximately 0.332 inches.

What is the diameter of 1/8 NPT?

• The nominal major diameter of a 1/8 NPT (National Pipe Taper) thread is approximately 0.405 inches.

What size bit for an 8-32 tap?

• For an 8-32 tap, you would use a drill bit with a diameter of approximately 0.159 inches.

What is a 3/8 drill used for?

• A 3/8 drill, referring to a drill bit with a 3/8-inch diameter, can be used for various drilling applications in woodworking, metalworking, and general construction.

What does 3/8 inch drill mean?

• A 3/8 inch drill typically refers to the size of the drill bit’s diameter, which is 3/8 of an inch or approximately 0.375 inches.

What size drill bit for a 3/8 self-tapping bolt?

• The size of the drill bit for a 3/8 self-tapping bolt may vary depending on the specific bolt design, but it’s generally close to 3/8 inch in diameter.

What are drill numbers?

• Drill numbers are a numerical system used to label drill bits in ascending order of size. Each number corresponds to a specific drill bit diameter.

How do you find the right drill?

• To find the right drill for a specific task, you should consider the material you’re drilling into, the desired hole size, and the type of drill bit (e.g., twist, spade, hole saw) that suits the application.

What size drill for a 1/4-inch tap?

• For a 1/4-20 tap, you would use a drill bit with a diameter of approximately 0.201 inches.

Why do you drill backwards first?

• Drilling in reverse (counterclockwise) initially helps create a small pilot dimple and prevents the drill bit from wandering before drilling forward. This technique is called “center punching.”

How do you know which drill bit to use when tapping threads?

• You select the drill bit based on the desired tap size and thread type. Refer to tap drill charts or guidelines to choose the appropriate drill bit.

Do you have to push a drill?

• Yes, you typically need to apply forward pressure or push when using a drill to create a hole. The drill bit’s rotation, combined with pressure, helps cut into the material.

Why is it necessary to drill the correct tapping size?

• Drilling the correct tapping size ensures that the threads created by the tap will fit properly and securely in the hole, preventing issues with thread engagement and strength.

Can you tap an undersized hole?

• Tapping an undersized hole is possible, but it may result in weak or incomplete threads. It’s generally better to use the correct tap drill size for optimal thread quality.

How do you drill and tap straight?

• To drill and tap straight, use a center punch to mark the drilling location, use a drill press or guide to maintain alignment, and proceed with care to ensure the drill and tap are perpendicular to the workpiece.

What is the 2 thread rule?

• The 2 thread rule suggests that for effective thread engagement and strength, a minimum of two full threads should be inside the tapped hole.

What is the minimum depth for a tapped hole?

• The minimum depth for a tapped hole should allow for at least two full threads to be engaged. However, specific applications may require deeper threads for additional strength.

What is the minimum thread depth for tapped holes?

• The minimum thread depth for tapped holes should be at least equal to the length of engagement needed for the intended purpose, typically a minimum of two threads.

What size drill bit for a 5/8 tap?

• For a 5/8-18 tap, you would use a drill bit with a diameter of approximately 0.578 inches.

What size drill bit for a 5/16 tap?

• For a 5/16-18 tap, you would use a drill bit with a diameter of approximately 0.295 inches.

What size drill for a half-inch tap?

• For a 1/2-13 tap, you would use a drill bit with a diameter of approximately 0.421 inches.

What is the best rpm for tapping?

• The best RPM (revolutions per minute) for tapping depends on the tap size, material, and specific conditions. As an estimate, a common starting point is around 100 RPM, but adjustments may be needed.

Do plumbers drill tap holes?

• Plumbers may need to create tap holes when installing fixtures and pipes, but the specific tools and techniques they use can vary depending on the job.

What is needed to select the right size drill and tap?

• To select the right size drill and tap, you need to know the thread size and type, as well as the material you’re working with. Reference charts and guidelines can help in choosing the correct sizes.

Why do taps come in sets of 3?

• Taps often come in sets of three, including taper, plug, and bottoming taps, to provide versatility for different drilling and threading needs. Each tap type serves a specific purpose.

What is the ratio of drill bit to tap?

• The ratio of drill bit to tap is typically such that the drill bit diameter is slightly smaller than the major diameter of the thread created by the tap. This ensures a secure fit.

How deep should threads be?

• The depth of threads should be sufficient to provide secure engagement for the intended application. A common guideline is a minimum of two full threads.

How do you read a tapped hole size?

• To read a tapped hole size, you would measure the major and minor diameters of the internal threads using appropriate measuring tools.

Do you need to ream before tapping?

• Reaming is not always necessary before tapping, but it can help ensure precise hole dimensions and improve thread quality in certain cases.

What happens when a drilled hole is larger than needed for a tapping operation?

• If the drilled hole is larger than needed, the threads may not engage properly, resulting in a weaker connection. It’s essential to use the correct tap drill size.

What if you drill a hole too big?

• If you drill a hole too big for the intended tap, you may need to use a larger tap size or insert a thread insert to salvage the hole.

How much bigger should a drill bit be than the screw?

• The drill bit should be slightly smaller in diameter than the major diameter of the screw’s threads to ensure a secure fit.

How close to the edge can I tap a hole?

• The distance from the edge to tap a hole depends on the specific application and material. In general, it’s recommended to have at least one to two times the hole’s diameter from the edge for strength.

Should the hole to be tapped must be the same size as the tap, True or false?

• False. The hole to be tapped should not be the same size as the tap. It should be slightly smaller to allow for proper thread engagement.

What size drill bit do I use for a 1/4-20 tap?

• For a 1/4-20 tap, you would use a drill bit with a diameter of approximately 0.201 inches.

What size hole do I need to tap quarter-20?

• To tap a 1/4-20 thread, you would need to drill a hole with a diameter of approximately 0.201 inches.

What is the diameter of a 1/4-20 tapped hole?

• A 1/4-20 tapped hole would have a major diameter of approximately 0.250 inches.

How do you drill and tap a 1/4-20 hole?

• To drill and tap a 1/4-20 hole, first drill a hole with a 0.201-inch diameter drill bit. Then, use a 1/4-20 tap to create the threads in the hole by turning it clockwise with a tap wrench.