# What diameter hole should you drill in order tap a 3/8 NPT thread?

## What diameter hole should you drill in order tap a 3/8 NPT thread?

37/64
Commonly used sizes are 1/⁄ 8 , 1/4 , 3/⁄ 8 , 1/2 , 3/4 , 1, 1 1/⁄ 4 , 1 1/2 , and 2 inch, appearing on pipes and fittings by most U.S. suppliers….

TAPER PIPE SIZES – NPT
TAP SIZE DRILL SIZE
1/4-18 7/16
3/8-18 37/64
1/2-14 23/32

## What drill bit do I use for a 3/8 tap?

3/8-24 .3320 ‘Q’
7/16-20 .3906 25/64
1/2-20 .4531 29/64
9/16-18 .5156 33/64

What is the diameter of 3/8 NPT?

0.675
Basic Dimensions, American National Standard Taper Pipe Threads, NPT, (ANSI B2. 1-1968)

Nominal Pipe Size Outside Diameter of Pipe Wrench Makeup Length for Internal Thread
1/4 0.540 0.1667
3/8 0.675 0.1667
1/2 0.840 0.2143
3/4 1.050 0.2143

### How do you calculate NPT Drill size?

As a rule of thumb, for Metric threads, the tapping drill can be calculated by subtracting the pitch from the diameter of the thread. eg for an M5x0. 75 thread the tapping drill is 5-0.75mm = 4.25mm. For Imperial (inch) threads the tapping drill size is calculated in the same way, diameter minus pitch.

### How many mm is a 3/8 drill bit?

Drill Bit Hole Diameters
Metric Size Fractional Size
15 mm .5906 3/8
16 mm .6299 25/64
17 mm .6693 13/32

What size hole should I drill for a 3/8 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.

## What is NPT thread size?

NPT is defined by ANSI/ASME standard B1. 20.1. The taper rate for all NPT threads is 1 inch of diameter in 16 inches of length ( 3⁄4 inch per foot or 62.5 millimeters per meter) measured by the change of diameter (of the pipe thread) over distance of thread.

## What size hole do I drill for a 3/8 lag bolt?

Lag Screw Pilot Hole Diameters

Nominal Diameter of Lag Bolt, inches Shank (Unthreaded) Portion, inches Diameter of Pilot Hole, inches (Thread Portion)
3⁄8 3⁄8 15⁄64
7⁄16 7⁄16 9⁄32
1⁄2 1⁄2 5⁄16
9⁄16 9⁄16 23⁄64

What are the standard drill sizes?

Metric drill bit sizes. Metric drill set,1.0–6.0 mm by 0.1 mm,jobber length.

• Fractional-inch drill bit sizes.
• Number and letter gauge drill bit sizes.
• Drill bit conversion table
• Screw-machine-length drill.
• Jobber-length drill.
• Aircraft-length drill.
• Center drill bit sizes.
• Spotting drill bit sizes.
• ### How to match a drill to thread tap size?

A good tap drill is 85% (± 2 pp) of major diameter for coarse threads,and

• A good tap drill is 90% (± 2 pp) of major diameter for fine threads.
• For metric V threads,the concept of major minus pitch (i.e.,the major or widest diameter of the intended screw in millimeters minus the pitch of the threads of that
• ### How do you calculate tap drill size?

Only enter numbers in the fields.

• Do not enter any units of measurement.
• You can enter fractions. (i.e. 1/4)
• If you don’t know the %,just enter 70 Example: 1/2 – 20 Thread
• 1/2 = Major diameter