Tap Drill Size Chart

M64 x 6 Tap Drill Size

Tap drill

58 mm 2.2835 in

Use a 58 mm drill (2.2835 in) for 77.0% thread.

The drill size for a M64 x 6 tap is 58 mm (2.2835 in). If you are wondering what size drill bit a M64 x 6 tap needs, that is the one: it leaves 77.0% of thread, which is the figure standard tap and drill charts are built around. Below are the other holes you might want for this size - a larger drill for tough material, the form-tap hole, and the clearance holes for the bolt that goes in.

Every drill for M64 x 6

Tap drills and clearance drills for M64 x 6 (Metric coarse, 6 mm pitch). Percent of thread is the figure stored for each drill, which reproduces from the major diameter and pitch of M64 x 6.
Use Drill Decimal in mm % thread
Standard tap drill Cut tap, general use (D - P) 58 mm 2.2835 58.00 77.0%
Inch substitute Closest inch drill if you have no metric set 2″ 2.000 50.80 169.4%
Hard material Stainless, tool steel, anything that fights the tap 59.5 mm 2.3425 59.50 57.7%
Form (roll) tap Theoretical 61.35 mm - starting point, check your tap maker's chart 60 mm 2.3622 60.00 —

Clearance holes for a M64 x 6 bolt

A clearance hole is not tapped. It is the hole in the part the bolt passes through, so it is always larger than the thread.

Clearance holes for M64 x 6 per ISO 273. Clearance depends on the bolt diameter alone, so every M64 thread shares these figures.
Fit Hole mm Hole in
Fine 66.00 2.5984
Medium 70.00 2.7559
Coarse 74.00 2.9134

M64 x 6 dimensions

Nominal dimensions for M64 x 6. The basic internal minor diameter is the hole a 100% thread would start from, which is why no tap drill is ever that small.
Dimension Inch mm
Major diameter 2.5197 64.00
Basic internal minor diameter 2.264 57.51
Pitch 0.2362 6.00
Thread designation M64 x 6

What the hole looks like

Cross-section of a M64 x 6 tapped hole, drawn to scale The drilled hole is 58 mm, 2.2835 inches or 58.00 millimetres across. The tap cuts outward from that wall to the major diameter of 2.5197 inches. A 100 percent thread would reach in to the basic minor diameter of 2.264 inches, shown as a dashed line; the difference is why this drill gives 77.0% of thread. major 64 mm drill 58 mm · 58 mm dashed = 100% thread at 57.51 mm
M64 x 6 in section, to scale. The accent line is the thread the tap cuts from a 58 mm hole; the dashed line is where the crest would sit at 100% thread. The gap between them is the 23.0% of thread this drill leaves behind.

Work out a different hole for M64 x 6

Pre-filled with M64 x 6. Change the material, the tap type, or which drills you actually own, and it picks the closest real drill and tells you the percent of thread you end up with. The tables above are the published figures and do not depend on this.

The general-purpose target

Tap type
Drills you have

Best drill you have, cut tap, 70% target

58.5 mm2.3031 in70.6% thread

Theoretical hole 58.54 mm

One size down, deeper thread58 mm 2.2835 in · 77.0%

One size up, easier tapping59 mm 2.3228 in · 64.2%

For comparison, the published chart drill for M64 x 6 is 58 mm at 77.0% thread.

Notes on M64 x 6

Only pitch in the data
M64 x 6 is the only pitch this chart lists at 64 mm, so there is no fine or coarse alternative to confuse it with.
What the standard drill gives you
58 mm leaves 77.0% of thread (D - P). That is in the normal 65-80% band most shop charts aim for.
Stainless, tool steel and other tough material
59.5 mm opens the hole to 57.7% engagement. Less material for the tap to cut means less torque and less heat, at the cost of some thread depth.
Using a form (roll) tap
A form tap displaces metal instead of cutting it, so it needs a larger hole: 60 mm, against a theoretical 61.35 mm. No twist drill in the standard sets reaches that size, so 60 mm is simply the largest there is rather than a 61.35 mm hole. Bore it to size instead. Treat that as a starting point and check your tap maker's chart.
This size is usually bored, not drilled
At 64 mm, holes this big are normally bored or thread-milled rather than drilled and tapped. The 58 mm figure is here so the numbers are complete and so you can check a hole you already have; on a machine you would single-point or thread-mill the thread and bore the hole to size.
Closest inch size
1-1/2-6 is the nearest inch thread by diameter (38.1 mm against 64 mm). It is a planning reference only. The two are not interchangeable: the pitches differ, and a bolt from one will not run into a hole tapped for the other.

Related sizes

Next size up and down

Closest inch size

1-1/2-6 1-11/32″ · 1.3438 in · 34.13 mm · 72.1% 38.1 mm major against 64 mm

Not interchangeable. 1-1/2-6 is the nearest size by diameter, nothing more. The pitches differ, so a 1-1/2-6 fastener will not run into a M64 x 6 hole and forcing one will strip both.

Guides for tapping M64 x 6

Longer reads on the decisions behind the numbers above.

All guides →

M64 x 6 tap drill: common questions

What size drill bit do I need for a M64 x 6 tap?
A 58 mm drill, 2.2835 in. That leaves 77.0% of thread, which is the standard chart figure for M64 x 6.
What is the drill size for a M64 x 6 tap in inches?
The 58 mm tap drill measures 2.2835 in. If you only have inch drills, 2 in (2.000 in) is the closest, giving 169.4% thread.
What drill should I use for M64 x 6 in stainless steel?
Use 59.5 mm instead of 58 mm. It leaves 57.7% of thread rather than 77.0%, so there is less material for the tap to cut and less chance of snapping it.
What is the clearance hole for an M64 x 6 bolt?
For a medium fit, 70 mm per ISO 273. A clearance hole is not tapped; the bolt passes straight through it.
A 4 × 6 in card with the drills for this size.