The tap drill for 7/16-14 UNC is U (0.3680 in, 9.35 mm), which gives about 75% of full thread depth. The exact 75% hole is 0.3679 in (9.34 mm). The table lists every number, letter, fractional and metric drill that gives between 55% and 90% thread, so you can work from the bits you own.
| Drill | Type | in | mm | Thread | Note |
|---|---|---|---|---|---|
| T | letter | 0.3580 | 9.09 | 86% | deep, hard to tap |
| 9.1 mm | metric | 0.3583 | 9.10 | 85% | deep, hard to tap |
| 23/64" | fraction | 0.3594 | 9.13 | 84% | deep, hard to tap |
| 9.2 mm | metric | 0.3622 | 9.20 | 81% | deep, hard to tap |
| 9.3 mm | metric | 0.3661 | 9.30 | 77% | |
| U | letter | 0.3680 | 9.35 | 75% | chart drill |
| 9.4 mm | metric | 0.3701 | 9.40 | 73% | |
| 9.5 mm | metric | 0.3740 | 9.50 | 68% | |
| 3/8" | fraction | 0.3750 | 9.52 | 67% | easier to tap |
| V | letter | 0.3770 | 9.58 | 65% | easier to tap |
| W | letter | 0.3860 | 9.80 | 56% | easier to tap |
About the 7/16-14 thread
7/16-14 is the coarse 7/16 in thread, a size between 3/8 and 1/2 in that hardware stores stock less often but that is standard in machinery and in older American vehicles and equipment. Because it is uncommon, a 7/16 in bolt pulled from a machine is easily mistaken for 3/8 or 1/2 in. Measure the diameter (0.4375 in) and count the threads before buying a tap.
U (0.368 in) is the chart drill and gives almost exactly 75% thread. 3/8 in (0.375 in), which every fractional set has, gives about 67% and is a sensible choice when tapping by hand. T and 23/64 in are deeper, at about 85%, and make the tap work much harder.
7/16-14 thread dimensions
| Dimension | Value | Also |
|---|---|---|
| Nominal diameter | 0.4375 in | 11.11 mm |
| Threads per inch | 14 | pitch 0.0714 in (1.814 mm) |
| Basic pitch diameter | 0.3911 in | 9.934 mm |
| Basic minor diameter (nut) | 0.3602 in | 9.148 mm |
| Tensile stress area | 0.1063 in² | 68.59 mm² |
| 7/16-20 UNF (same diameter): tap drill | 25/64" (0.3906 in) | 72% thread |
Clearance hole for 7/16
The tapped hole is in the part that holds the thread; the part being clamped gets a clearance hole the bolt passes through. For 7/16 a normal fit is 15/32" (0.4688 in). Never drill the clearance part with the tap drill: the screw will not pass.
| Fit | Drill | Diameter |
|---|---|---|
| Close fit | 29/64" | 0.4531 in |
| Normal fit | 15/32" | 0.4688 in |
| Loose fit | 1/2" | 0.5000 in |
How deep to drill a blind 7/16-14 hole
| Part material | Full thread wanted | Drill depth (full diameter) | Depth to drill tip (118°) |
|---|---|---|---|
| Steel or cast iron (1 × diameter) | 0.438 in | 0.938 in (about 15/16″) | 1.048 in (about 1-1/16″) |
| Aluminium or brass (2 × diameter) | 0.875 in | 1.375 in (about 1-3/8″) | 1.486 in (about 1-1/2″) |
Wrench size and torque for 7/16
- Hex cap screw: 5/8 in wrench
- Socket head cap screw: 3/8 in hex key
| Bolt grade | Dry | Lubricated |
|---|---|---|
| Grade 2 | 32 ft-lb | 24 ft-lb |
| Grade 5 | 49 ft-lb | 37 ft-lb |
| Grade 8 | 70 ft-lb | 52 ft-lb |
Threads easily mistaken for 7/16-14
| Thread | Diameter (in) | Diameter (mm) | Pitch |
|---|---|---|---|
| 7/16-14 UNC (this page) | 0.4375 | 11.11 | 14 TPI (1.81 mm) |
| 7/16-20 UNF | 0.4375 | 11.11 | 20 TPI (1.27 mm) |
Tips for tapping 7/16-14
- Calipers settle the size at once: 7/16 in is 0.4375 in, 3/8 in is 0.375 in and 1/2 in is 0.500 in.
- The fine thread at this size is 7/16-20 UNF; its tap drill is in the dimensions table above. Check which you have before tapping.
- In aluminium, aim for at least 7/8 in of engagement (2 x diameter).
- Hex cap screws of this size take a 5/8 in wrench.
Frequently asked questions
What size drill bit for a 7/16-14 tap?
U (0.3680 in), which gives about 75% thread. The exact 75% size is 0.3679 in (9.34 mm).
How deep should a blind 7/16-14 hole be?
For a full thread of 1 × diameter in steel, drill about 0.938 in (about 15/16″) at full diameter with a plug tap, or 1.048 in (about 1-1/16″) to the drill tip; in aluminium, about 1.375 in (about 1-3/8″).
What is the 7/16-14 tap drill in mm?
9.3 mm is the nearest 0.1 mm drill to the 75% size and gives 77% thread.
Can I use a 3/8 drill for a 7/16-14 tap?
Yes. 3/8 in (0.375 in) gives about 67% thread, a little shallower than the U drill (0.368 in, about 75%) but easier to tap and strong enough for most uses.
What wrench fits a 7/16 bolt?
A 7/16 in hex cap screw takes a 5/8 in wrench. A 7/16 in wrench fits 1/4 in hex bolts, a common source of confusion.
Sources and method
Every dimension and percentage on this page is computed from the formulas listed, not copied from another chart. Values are basic (nominal); real parts are made to tolerance classes (2A/2B for inch, 6g/6H for metric).
- ASME B1.1 and FED-STD-H28/2B (Unified inch), ISO 68-1 and ISO 261 (metric): basic thread profile and stress area formulas.
- Machinery’s Handbook (Industrial Press): percentage-of-thread relation used by our tap drill size calculator.
- ASME B94.11M twist drill series (number, letter, fractional); 0.1 mm metric drill steps.
- ISO 273 metric clearance holes; inch close, normal and loose fits as published in the ASME B18.2.8 clearance classes.
- SAE J429 and ISO 898-1 proof strengths; T = K × D × F torque relation (see our bolt torque chart for the full method).
- Wrench and hex key sizes: ASME B18.2.1, ASME B18.3, ASME B18.6.3, ISO 4014/4017, DIN 933 and ISO 4762 values as widely published.
More thread and fastener tools
- All thread and fastener charts
- UNC and UNF thread chart
- Metric thread pitch chart
- Tap drill chart (inch and metric)
- Clearance hole chart
- Nail size chart
- Wood screw size chart
- Lag screw pilot hole chart
- Bolt torque chart
- Wrench size chart
- Drill bit size chart
- Thread engagement chart
- Nail gun nail sizes by gauge
- Screw and nail size calculator
- Tap drill size calculator
- Clearance hole size calculator
- Tapped hole depth calculator
Last reviewed: 24 October 2026. How we build and check our data: methodology and corrections. Spotted an error? Please let us know.