Tap drills
7/16-14 tap drill size
The tap drill for 7/16-14 is U, which is 0.3680 inches or 9.35 mm. That leaves about 75 percent thread engagement.
7/16-14 tap drill, clearance and engagement
| Series | UNC (coarse) |
| Major diameter | 0.4375 in (11.11 mm) |
| Threads per inch | 14 |
| Tap drill | U (0.3680 in / 9.35 mm) |
| Thread engagement | 75% |
| Drill for 75% thread | 0.3679 in |
| Clearance, close fit | 29/64 (0.4531 in) |
| Nearest metric drill | 9.5 mm (0.3740 in) |
What 7/16-14 is used for
An intermediate structural size, common in older American machinery, agricultural equipment and automotive chassis work.
If you do not have that drill
Letter U is 0.368 in. A 23/64 drill at 0.3594 tightens engagement to about 84 percent; letter V at 0.377 drops it to about 65 percent.
How to tap a 7/16-14 thread
-
Drill the hole
Use a U drill, 0.3680 inches or 9.35 mm. Drill square to the surface and clear the swarf on deep holes.
-
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.
-
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.
-
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 7/16-14 tap?
- The tap drill for 7/16-14 is U, which is 0.3680 inches or 9.35 mm. That leaves about 75 percent thread engagement. Letter U is 0.368 in. A 23/64 drill at 0.3594 tightens engagement to about 84 percent; letter V at 0.377 drops it to about 65 percent.
What is the clearance hole for a 7/16-14 bolt?
- 29/64, which is 0.4531 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 7/16-14 tap drill worked out?
- Take the major diameter and subtract the engagement fraction times 1.299 divided by threads per inch: 0.4375 minus 0.75 times 1.299 divided by 14 gives 0.3679 inches. The nearest standard drill is U at 0.3680 inches.
Can I use a metric drill for a 7/16-14 tap?
- The closest standard metric drill is 9.5 mm, which is 0.3740 inches against 0.3680 for U. That changes engagement to about 68 percent, so check that figure is acceptable for your material before substituting.