#1-64 tap drill size
#53
- Inches
- 0.0595
- Millimetres
- 1.51
- Thread
- 67%
Drill a #53 hole before cutting a #1-64 thread. That is the standard tap drill for about 75% thread.
#1-64 thread and hole sizes
| Thread | #1 diameter, 64 threads per inch, coarse (UNC) |
|---|---|
| Major diameter | 0.0730 in 1.85 mm |
| Pitch | 0.0156 in 0.397 mm |
| Tap drill, about 75% thread | #53 0.0595 in |
| Tap drill, about 50% thread | 1/16" 0.0625 in, for stainless and other hard materials |
| Clearance hole, close fit | #48 0.0760 in |
| Clearance hole, free fit | #46 0.0810 in |
| Nearest metric bit | 1.5 mm |
Why #53
A tap cuts threads into the wall of a hole, so the hole has to be smaller than the screw. For a #1-64 thread the hole that leaves exactly 75% thread is 0.0578 in. The closest standard bit is #53 at 0.0595 in, which leaves 67%.
More thread than that adds almost no strength and makes the tap much easier to break. In hard or tough material, go one step larger.
Tools for this job
- #1-64 tap
- #53 drill bit
- Tap and drill set
- Drill bit size gauge
- Thread pitch gauge
- Cutting oil for tapping
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