How are clearance holes calculated?
The LMC clearance hole also can be calculated by adding the diameter of the fastener and the diameter of the fastener head and then dividing the sum by two. This method of selecting the LMC clearance hole size is a rule of thumb that will yield the largest hole that will fit under the head of the fastener.
When would you need to drill a clearance hole?
Usually you need a clearance hole so that the screw literally clears the first piece of wood and doesn’t hold on to it. This is to prevent a problem called bridging where the screw acts like a bridge between the two pieces of wood, holding them apart.
What size hole do you drill for a 1/4 bolt?
| Screw Size-TPI | Recommended Hole Diameter | Drill Bit Size |
|---|---|---|
| 1/4-20 | 0.2280″ | #1 |
| 5/16-18 | 0.2900″ | L |
| 3/8-16 | 0.3580″ | T |
| 1/2-13 | 0.4531″ | 29/64″ |
What size bolt fits in a 1/4 hole?
Suggested pilot holes & drill sizes.
| Screw Size | Threads Per Inch | Recommended Hole Diameter for Material with Flexural Modulus of Over to 200,000 P.S.I. |
|---|---|---|
| #10 | 16 | 0.144″ |
| #12 | 16 | 0.166″ |
| #14 / 1/4″ | 15 | 0.201″ |
| 5/16″ | 14 | 0.250″ |
What size drill do I need for a quarter inch to tap for?
The best overall size drill bit for 1/4″ 20 UNC tap thread is a #7 drill bit, the measurement being 13/64” (0.203″diameter).
What size drill bit do you use for a 1/4 tap?
What size drill bit do I need for a 1/4 NPT tap?
7/16″
NPT Tap Drill Chart
| Tap Size | Drill Size | Tap and Drill Set |
|---|---|---|
| 1/4″ NPT Tap | 7/16″ Drill Bit | 1/4″ NPT Tap and Drill Set |
| 3/8″ NPT Tap | 37/64″ Drill Bit | 3/8″ NPT Tap and Drill Set |
| 1/2″ NPT Tap | 23/32″ Drill Bit | 1/2″ NPT Tap and Drill Set |
| 3/4″ NPT Tap | 59/64″ Drill Bit | 3/4″ NPT Tap and Drill Set |
What size is a clearance hole for 1/4 20?
0.2500
Tap and Clearance Drill Sizes
| Screw | O.D. | Close Fit |
|---|---|---|
| 10-32 | 0.1900 | 9 |
| 1/4-20 | 0.2500 | F |
| 1/4-28 | 0.2500 | F |
| 5/16-18 | 0.3125 | P |
What size hole do I drill for a 1/4 bolt?
Even sharp pointed screws such as Type A or Type AB Self-Tapping Screws can split wood or distort metal as they’re driven if they don’t have a properly sized pilot hole….
| Screw Size-TPI | Recommended Hole Diameter | Drill Bit Size |
|---|---|---|
| 1/4-20 | 0.2280″ | #1 |
| 5/16-18 | 0.2900″ | L |
| 3/8-16 | 0.3580″ | T |
| 1/2-13 | 0.4531″ | 29/64″ |