Tap drills
M5 x 0.8 tap drill size
The tap drill for M5 x 0.8 is 4.2 mm, which is 0.1654 inches or 4.20 mm. That leaves about 92 percent thread engagement.
M5 x 0.8 tap drill, clearance and engagement
| Series | Metric coarse |
| Major diameter | 0.1969 in (5.00 mm) |
| Pitch | 0.8 mm |
| Tap drill | 4.2 mm (0.1654 in / 4.20 mm) |
| Thread engagement | 92% |
| Drill for 75% thread | 0.1713 in |
| Clearance, close fit | 5.3 mm (0.2087 in) |
| Nearest metric drill | 4.2 mm (0.1654 in) |
What M5 x 0.8 is used for
Bicycle bottle cages and accessory mounts, furniture fittings, appliance panels and general light metric assembly.
If you do not have that drill
4.3 mm reduces engagement from about 92 percent to around 79 percent, which is the sensible choice in stainless or in a blind hole.
How to tap a M5 x 0.8 thread
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Drill the hole
Use a 4.2 mm drill, 0.1654 inches or 4.20 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 M5 x 0.8 tap?
- The tap drill for M5 x 0.8 is 4.2 mm, which is 0.1654 inches or 4.20 mm. That leaves about 92 percent thread engagement. 4.3 mm reduces engagement from about 92 percent to around 79 percent, which is the sensible choice in stainless or in a blind hole.
What is the clearance hole for a M5 x 0.8 bolt?
- 5.3 mm, which is 0.2087 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 M5 x 0.8 tap drill worked out?
- Subtract the pitch from the major diameter: 0.1969 inches (5 mm) minus 0.8 mm gives 4.20 mm, and 4.2 mm is the nearest standard drill. This is the metric convention and it lands near 92 percent engagement, not the 75 percent an inch chart targets.
Can I use a metric drill for a M5 x 0.8 tap?
- The closest standard metric drill is 4.2 mm, which is 0.1654 inches against 0.1654 for 4.2 mm. That changes engagement to about 93 percent, so check that figure is acceptable for your material before substituting.