Tap drills
M12 x 1.75 tap drill size
The tap drill for M12 x 1.75 is 10.2 mm, which is 0.4016 inches or 10.20 mm. That leaves about 95 percent thread engagement.
M12 x 1.75 tap drill, clearance and engagement
| Series | Metric coarse |
| Major diameter | 0.4724 in (12.00 mm) |
| Pitch | 1.75 mm |
| Tap drill | 10.2 mm (0.4016 in / 10.20 mm) |
| Thread engagement | 95% |
| Drill for 75% thread | 0.4165 in |
| Clearance, close fit | 13.0 mm (0.5118 in) |
| Nearest metric drill | 10.2 mm (0.4016 in) |
What M12 x 1.75 is used for
Heavy structural metric fastening: machine bases, towing components, lifting eyes and chassis work.
If you do not have that drill
10.5 mm brings engagement from about 95 percent down to around 78 percent. At 10.2 mm this is the tightest standard metric tap drill on the chart and it is unforgiving in hard material.
How to tap a M12 x 1.75 thread
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Drill the hole
Use a 10.2 mm drill, 0.4016 inches or 10.20 mm. Drill square to the surface and clear the swarf on deep holes.
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Start the tap square
Start with a taper tap and check it is square in both axes within the first two turns. A tap started crooked will cut a crooked thread all the way down and cannot be corrected.
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Cut and break the chip
Turn forward about half a turn, then back a quarter turn to break the chip. Use cutting fluid on steel and stainless; aluminium and brass usually need none, though a wax stick helps in aluminium.
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Check the fit
Run the mating fastener in by hand. It should turn freely without side play. If it binds, the hole was undersized or the tap wandered.
Common questions
What size drill do I need for a M12 x 1.75 tap?
- The tap drill for M12 x 1.75 is 10.2 mm, which is 0.4016 inches or 10.20 mm. That leaves about 95 percent thread engagement. 10.5 mm brings engagement from about 95 percent down to around 78 percent. At 10.2 mm this is the tightest standard metric tap drill on the chart and it is unforgiving in hard material.
What is the clearance hole for a M12 x 1.75 bolt?
- 13.0 mm, which is 0.5118 inches. That is a close fit. A normal fit is one drill size larger and a loose fit two, and the looser classes are the sensible choice when the parts have to line up without reaming.
How is the M12 x 1.75 tap drill worked out?
- Subtract the pitch from the major diameter: 0.4724 inches (12 mm) minus 1.75 mm gives 10.25 mm, and 10.2 mm is the nearest standard drill. This is the metric convention and it lands near 95 percent engagement, not the 75 percent an inch chart targets.
Can I use a metric drill for a M12 x 1.75 tap?
- The closest standard metric drill is 10.2 mm, which is 0.4016 inches against 0.4016 for 10.2 mm. That changes engagement to about 95 percent, so check that figure is acceptable for your material before substituting.