M16 Tap Drill Size
The tap drill for M16 x 2.0 is 14.0 mm (0.5512 in). That is the standard chart size and leaves about 77% thread.
Drill a 14.0 mm hole, then cut the thread with an M16 tap. The hole is 2.00 mm narrower than the screw, so the tap cuts 1.00 mm into each side.
A full-height thread would be 1.30 mm deep on each side. The 14.0 mm drill leaves 77% of that.
Try another material or drill
M16 tap drill size by material
| Material | Target thread | Drill | Size | Thread left |
|---|---|---|---|---|
| Aluminum, brass, plastics | 75% | 14.0 mm | 0.5512 in | 77% |
| Mild steel | 60% | 14.4 mm | 0.5669 in | 62% |
| Stainless, titanium | 50% | 14.7 mm | 0.5787 in | 50% |
The 75% row is the published chart drill. The 60% and 50% rows pick the biggest standard drill that still leaves close to that much thread.
Notes on M16
M16 x 2 and 5/8-11 are 0.13 mm apart in diameter, with pitches of 2.0 mm and 2.309 mm. The drills are 14.0 mm for M16 and 17/32 in for 5/8-11.
On M16 the drill steps of 0.1 mm are fine: one step changes the thread by only 3.8 points. Steel takes 14.4 mm (62%) and stainless 14.7 mm (50%).
How much thread do you need?
The chart prints one drill. The right amount of thread depends on the material, and the guides give slightly different ranges.
| Material | Texas Metalworks | ToolGrit | OSG (tap maker) | Drill for M16 |
|---|---|---|---|---|
| Aluminum | 70-75% | 60-65% | 65-70% | 14.0 mm (77%) to 14.4 mm (62%) |
| Brass | 70-75% | 70-75% | 65-70% | 14.0 mm (77%) |
| Plastic | not covered | 70-75% | not covered | 14.0 mm (77%) |
| Mild steel | 60-65% | 60-65% | 65-70% | 14.4 mm (62%) |
| Stainless steel | 50% | 55-60% | 60-70% | 14.4 mm (62%) to 14.7 mm (50%) |
| Titanium | 50% | 50-55% | not covered | 14.7 mm (50%) |
The three rows in the first table follow Texas Metalworks. OSG makes taps, and asks for more thread in stainless than either guide, so its range sits closer to our steel column. ToolGrit also suggests 50 to 55% for blind holes in stainless, titanium and hardened steel, and for small taps (#6 and below).
Why not a full thread?
A 100% thread is not possible in practice. The tap and the thread both have flat crests and roots (ToolGrit).
More thread also means more work for the tap: higher cutting force, more heat, poorer chip clearance and a bigger risk of breaking it (ToolGrit).
And it adds little strength. ToolGrit cites studies showing about 90% of a thread's shear strength at 60% thread. Texas Metalworks says going from 75% to 60% costs only about 5% of pull-out strength.
On M16, that step is from 14.0 mm to 14.4 mm. The two drills differ by 0.40 mm.
If you do not have the 14.0 mm drill
Here are the drills on either side, and the thread each one leaves.
| Drill | Size | Thread left | What changes |
|---|---|---|---|
| 13.8 mm | 0.5433 in | 85% | More thread, harder to tap |
| 13.9 mm | 0.5472 in | 81% | More thread, harder to tap |
| 14.0 mm | 0.5512 in | 77% | Standard size |
| 14.1 mm | 0.5551 in | 73% | Less thread, easier to tap |
| 14.2 mm | 0.5591 in | 69% | Less thread, easier to tap |
A bigger drill removes thread and makes the tap easier to turn. A smaller drill keeps more thread and puts more torque on the tap.
The check behind the 14.0 mm number: (16.00 - 14.00) / (1.299 x 2.00) = 77.0%.
What M16 means
- M16
- Metric thread. The 16 is the major diameter in mm (0.6299 in).
- x 2.0
- The pitch: 2.0 mm from one thread to the next. This is the coarse pitch for M16, so it is often left off.
The rest of the size, worked out from the major diameter and pitch:
| Property | Value |
|---|---|
| Major diameter | 16.000 mm (0.6299 in) |
| Pitch | 2.00 mm |
| Pitch diameter (basic) | 14.701 mm (0.5788 in) |
| Minor diameter, internal thread (basic) | 13.835 mm (0.5447 in) |
The pitch and minor diameters are for checking a thread with gauges. You can skip them if you only need the drill.
How long to make the M16 thread
Aim for a thread at least 1 to 1.5 times the diameter long. ToolGrit's strength figures assume that length.
| Thread length | In threads | Drill a blind hole at least |
|---|---|---|
| 1 x diameter: 16.0 mm | 8 | 24.0 mm |
| 1.5 x diameter: 24.0 mm | 12 | 32.0 mm |
The blind hole depth adds 4 threads (4 x 2.00 mm) so the tap has room to finish and the chips have somewhere to go.
How to tap an M16 hole
- Drill the hole with the 14.0 mm drill (0.5512 in).
- For a blind hole, drill 24.0 mm deep if you need a 16.0 mm thread. That is 4 threads past the thread (ToolGrit).
- Put cutting fluid on the tap. Do not tap dry (ToolGrit, Wikipedia).
- Hold the tap in line with the hole.
- Turn the tap forward, then back it off now and then to break the chip (Wikipedia).
- Need threads right to the bottom of a blind hole? Finish with a bottoming tap (Wikipedia).
Taps usually break for one of these reasons (Wikipedia, ToolGrit):
- Chips clog the flutes.
- The tap is not in line with the hole.
- The tap is pushed too hard or too little.
- There is not enough cutting fluid.
- The drill was too small, so the tap works against too much thread.
Which tap to use for M16
The three common hand taps differ in how many threads at the tip are tapered (Wikipedia).
- Taper tap: 8 to 10 tapered threads, about 16.00 mm to 20.00 mm on M16. For hard materials and very small taps.
- Plug tap: 3 to 5 tapered threads, about 6.00 mm to 10.00 mm on M16. The most common tap, easy to start and keep straight.
- Bottoming tap: 1 to 1.5 tapered threads, about 2.00 mm to 3.00 mm on M16. Cuts threads to the bottom of a blind hole, usually after a plug tap.
Spiral-point taps are usually used in through holes so the chips can escape. Spiral-flute taps work well in blind holes (Wikipedia).
Forming (roll) taps only work in malleable metals such as mild steel and aluminum (Wikipedia). They use different drill sizes, which we do not cover yet.
Closest inch size
5/8-11 is close to M16, but it is not the same thread.
| Major diameter | Pitch | Standard drill | |
|---|---|---|---|
| M16 | 16.00 mm | 2.000 mm | 14.0 mm |
| 5/8-11 | 15.88 mm | 2.309 mm | 17/32 in |
The diameters differ by 0.13 mm and the pitches are not the same. Do not swap them.
FAQ
What is the tap drill size for M16?
The standard drill is 14.0 mm (0.5512 in). It leaves about 77% thread, which is the standard chart choice.
Can I use 14.1 mm instead of 14.0 mm for M16?
14.1 mm (0.5551 in) leaves about 73% thread instead of 77%. The tap cuts more easily and the thread is weaker. That is still at or above the 60% Texas Metalworks suggests for mild steel.
Is a 35/64 in drill the same as 14.0 mm?
It is very close. 35/64 in is 0.5469 in, 13.89 mm, against 0.5512 in for 14.0 mm. It leaves about 81% thread.
What drill size do I use for M16 in aluminum?
Use 14.0 mm (77%) or 14.4 mm (62%), depending on the guide. Texas Metalworks says 70 to 75% for soft aluminum, which is 14.0 mm. ToolGrit says 60 to 65% for aluminum alloys, which is 14.4 mm. Either is a normal choice. OSG, a tap maker, gives 65 to 70% for average work in aluminum, brass and mild steel.
What is the tap drill size for M16 in stainless steel?
14.7 mm (0.5787 in) leaves about 50% thread, close to the 50% Texas Metalworks recommends for stainless and titanium. ToolGrit gives 55 to 60% for 304 and 316 stainless, which is between 14.4 mm and 14.7 mm. The standard drill, 14.0 mm, puts more torque on the tap. OSG, a tap maker, asks for 60 to 70% in stainless for average work, which is closer to the steel drill, 14.4 mm.
Does a bigger drill make the M16 thread much weaker?
Not by much at first. ToolGrit cites studies showing about 90% of a thread's shear strength at 60% thread, if the thread is at least 1 to 1.5 times the diameter long. Texas Metalworks says going from 75% to 60% costs only about 5% of pull-out strength. For M16, the 60% drill is 14.4 mm.
How long should an M16 thread be?
Aim for at least 1 to 1.5 times the diameter, the length ToolGrit's strength figures assume. For M16 that is 16.0 mm to 24.0 mm, or about 8 to 12 threads.
How deep do I drill a blind M16 hole?
At least 4 threads deeper than the thread you need, says ToolGrit. A 16.0 mm thread needs a hole at least 24.0 mm deep.
Which tap do I use for a blind M16 hole?
Start with a plug tap, then finish with a bottoming tap if the thread has to reach the bottom. Wikipedia says a bottoming tap has 1 to 1.5 tapered threads, about 2.00 mm to 3.00 mm on M16.
What is M16 in inches?
M16 is 0.6299 in across, with a pitch of 2.0 mm.
Is M16 a coarse or fine thread?
M16 x 2.0 is the coarse pitch for M16.
Related sizes
Chart drill checked against the American Fastener tap and drill chart and the Fabworks tap drill chart. Diameters from Wikipedia: drill bit sizes. Thread percentages, thread length and blind-hole depth from Texas Metalworks and ToolGrit. The percentage formula is the one printed in the OSG tap drill chart, Vol 3 (2024). Tap types and tapping tips from Wikipedia. Last reviewed October 7, 2026.