Tech Tip: Driver Bit Sizes
Square Drive (and “Combo” Square Drive) screws are designed so that the driver bits fit snugly in the recess. If they don’t, you are probably using the wrong driver bit.
As a guide, our Square Drive screws use the following driver bit sizes, except as noted within the price list. (In special cases a non-standard recess is used. For instance, #7 and #8 trim head screws normally have a #1 recess in order to avoid breakage problems with the undersized head).
Those color bars you see in the driver bit guide below are repeated in the screw price list so it’s easy to match the driver bit to the screw.
Finally, there are really only two sizes of driver bits in common usage: #1 and #2 Square. They will fit 90% of the screws you are likely to use – screw sizes #6, 8 and 10. Other bits fit screws designed for rather specialized applications. In fact, the #4 driver bit is such a rare beast that it is virtually manufactured to order. We don’t carry screws to fit the bit, but we do carry the bit!
| Driver Bit Color Code |
| Screw Size |
Driver Size |
Hand Driver Color (Normally) |
| #4 |
#0 Bit |
Light Yellow |
| #5, 6, 7 |
#1 Bit |
Medium Green |
| #8, 9, 10 |
#2 Bit |
Red |
| #12, 14 |
#3 Bit |
Black |
| 5/16” & up |
#4 Bit |
Un-coded |
| Bit Tip Dimensions |
 |
| Bit Size |
Max |
Min |
Fraction |
| #0 |
0.071 |
.0696 |
1/16+ |
| #1 |
0.091 |
.090 |
3/32- |
| #2 |
0.1126 |
.111 |
7/64+ |
| #3 |
0.133 |
0.1315 |
1/8+ |
| #4 |
0.191 |
0.1895 |
3/16+ |