Tap Drill Size Chart

M33 x 3.5 Tap Drill Size

Tap drill

29.5 mm 1.1614 in

Use a 29.5 mm drill (1.1614 in) for 77.0% thread.

Fine thread M33 x 2? Use 31 mm. (1.2205 in, 77.0% thread)

The drill size for a M33 x 3.5 tap is 29.5 mm (1.1614 in). If you are wondering what size drill bit a M33 x 3.5 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 M33 x 3.5

Tap drills and clearance drills for M33 x 3.5 (Metric coarse, 3.5 mm pitch). Percent of thread is the figure stored for each drill, which reproduces from the major diameter and pitch of M33 x 3.5.
Use Drill Decimal in mm % thread
Standard tap drill Cut tap, general use (D - P) 29.5 mm 1.1614 29.50 77.0%
Inch substitute Closest inch drill if you have no metric set 1-5/32″ 1.1562 29.37 79.9%
Hard material Stainless, tool steel, anything that fights the tap 30.5 mm 1.2008 30.50 55.0%
Form (roll) tap Theoretical 31.45 mm - starting point, check your tap maker's chart 31.5 mm 1.2402 31.50 —

Clearance holes for a M33 x 3.5 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 M33 x 3.5 per ISO 273. Clearance depends on the bolt diameter alone, so every M33 thread shares these figures.
Fit Hole mm Hole in
Fine 34.00 1.3386
Medium 36.00 1.4173
Coarse 38.00 1.4961

M33 x 3.5 dimensions

Nominal dimensions for M33 x 3.5. 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 1.2992 33.00
Basic internal minor diameter 1.150 29.21
Pitch 0.1378 3.50
Thread designation M33 x 3.5

What the hole looks like

Cross-section of a M33 x 3.5 tapped hole, drawn to scale The drilled hole is 29.5 mm, 1.1614 inches or 29.50 millimetres across. The tap cuts outward from that wall to the major diameter of 1.2992 inches. A 100 percent thread would reach in to the basic minor diameter of 1.150 inches, shown as a dashed line; the difference is why this drill gives 77.0% of thread. major 33 mm drill 29.5 mm · 29.5 mm dashed = 100% thread at 29.21 mm
M33 x 3.5 in section, to scale. The accent line is the thread the tap cuts from a 29.5 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 M33 x 3.5

Pre-filled with M33 x 3.5. 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

1-11/64″1.1719 in29.77 mm71.1% thread

Theoretical hole 29.82 mm

One size down, deeper thread29.5 mm 1.1614 in · 77.0%

One size up, easier tapping30 mm 1.1811 in · 66.0%

For comparison, the published chart drill for M33 x 3.5 is 29.5 mm at 77.0% thread.

Notes on M33 x 3.5

Coarse pitch
M33 x 3.5 is the coarse pitch at 33 mm. It is the usual choice for general work, and it tolerates a slightly off-size hole better than the finer pitches do. Finer options at the same diameter: M33 x 2.
What the standard drill gives you
29.5 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
30.5 mm opens the hole to 55.0% 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: 31.5 mm, against a theoretical 31.45 mm. Treat that as a starting point and check your tap maker's chart.
Closest inch size
1-1/4-7 is the nearest inch thread by diameter (31.75 mm against 33 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

Same diameter, different pitch

Next size up and down

Closest inch size

1-1/4-7 1-7/64″ · 1.1094 in · 28.18 mm · 75.8% 31.75 mm major against 33 mm

Not interchangeable. 1-1/4-7 is the nearest size by diameter, nothing more. The pitches differ, so a 1-1/4-7 fastener will not run into a M33 x 3.5 hole and forcing one will strip both.

Guides for tapping M33 x 3.5

Longer reads on the decisions behind the numbers above.

All guides →

M33 x 3.5 tap drill: common questions

What size drill bit do I need for a M33 x 3.5 tap?
A 29.5 mm drill, 1.1614 in. That leaves 77.0% of thread, which is the standard chart figure for M33 x 3.5.
What is the drill size for a M33 x 3.5 tap in inches?
The 29.5 mm tap drill measures 1.1614 in. If you only have inch drills, 1-5/32 in (1.1562 in) is the closest, giving 79.9% thread.
What drill should I use for M33 x 3.5 in stainless steel?
Use 30.5 mm instead of 29.5 mm. It leaves 55.0% of thread rather than 77.0%, so there is less material for the tap to cut and less chance of snapping it.
Is M33 x 3.5 the same as M33 x 2?
No. Both are 33 mm threads, but the pitch differs, so the drills differ: 29.5 mm for M33 x 3.5 and 31 mm for M33 x 2. The taps and the fasteners are not interchangeable.
What is the clearance hole for an M33 x 3.5 bolt?
For a medium fit, 36 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.