The tap drill for an M16x2 thread is 14 mm (0.5512 inch). That is the ISO rule of major diameter minus pitch, 16 - 2 = 14 mm, which leaves roughly 77% of full thread depth.
Taps and dies for M16x2
Which drill gives which percentage of thread?
| Target thread | Ideal drill (in) | Nearest drill | Drill (in) | Actual thread |
|---|---|---|---|---|
| 60% | 0.5686 | 14.5 mm | 0.5709 | 58% |
| 65% | 0.5634 | 9/16" | 0.5625 | 66% |
| 70% | 0.5583 | 9/16" | 0.5625 | 66% |
| 75% | 0.5532 | 14.0 mm | 0.5512 | 77% |
| 80% | 0.5481 | 35/64" | 0.5469 | 81% |
What are the M16x2 thread dimensions?
| Series | ISO metric coarse pitch |
| Pitch | 2 mm pitch (12.70 TPI) |
| Major diameter | 0.6299" / 16.00 mm |
| Basic pitch diameter | 0.5788" / 14.70 mm |
| Basic minor diameter (external) | 0.5276" / 13.40 mm |
| Standard tap drill (about 75%) | 14 mm = 0.5512" |
| Clearance, close fit (rule of thumb) | 21/32" = 0.6563" |
| Clearance, free fit (rule of thumb) | 11/16" = 0.6875" |
How do you tap M16x2 cleanly?
A thread this size needs real torque to tap by hand. A T-handle wrench is too small; use a full-size bar tap wrench, start square with a tap guide or a center in the drill press or lathe tailstock, and use cutting oil throughout. In a lathe, a thread this size is often quicker and more accurate to single-point cut than to tap.
Other threads at this diameter: M16x1.5.
Drills and cutting fluid for tapping
Frequently asked questions
What size drill for a M16x2 tap?
The tap drill for an M16x2 thread is 14 mm (0.5512 inch). That is the ISO rule of major diameter minus pitch, 16 - 2 = 14 mm, which leaves roughly 77% of full thread depth. For hard or tough material a slightly larger drill giving about 65% thread taps much more easily; the table on this page lists it.
What size clearance hole for M16x2?
For a bolt to pass through, a close fit is about 21/32" (0.6563") and a looser free fit about 11/16" (0.6875"). These are rule-of-thumb sizes of about 3% and 8% over the 0.6299" major diameter; use the close fit where location matters and the free fit where parts must line up easily.
What is the minor diameter of M16x2?
The basic minor diameter of a M16x2 external thread is about 0.5276" (13.40 mm) and the basic pitch diameter about 0.5788" (14.70 mm). An internal thread's minor diameter is set by the tap drill, which is why the drill decides how much thread is cut.
Nearby thread sizes
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Tap drills per the standard 75% thread convention used by published charts. Clearance sizes are rules of thumb, not ASME B18.2.8 values. Not professional advice.