Y Drill Size
letter drill
Y 0.404 in 10.26 mm
A Y drill is the standard tap drill for 7/16-28.
What a Y drill taps
Every thread this drill cuts between 50% and 85% of thread, deepest first. Outside that band it is the wrong drill for the job, so nothing below that line is listed.
| Thread | % thread | Chart drill | Chart % |
|---|---|---|---|
| M12 x 1.75 | 76.5% | 10.2 mm | 79.2% |
| 7/16-28 chart drill | 72.2% | Y | 72.2% |
| 7/16-20 | 51.6% | 25/64″ | 72.2% |
Drills either side
Y drill: common questions
What size is a Y drill?
0.404 inches, which is 10.26 mm. It is a letter drill.
What can I tap with a Y drill?
3 threads: M12 x 1.75 at 76.5%, 7/16-28 at 72.2%, 7/16-20 at 51.6%.
Is a Y drill the standard tap drill for anything?
Yes, for 7/16-28 (72.2% thread). That is the size published tap and drill charts give.
What drill is next to a Y?
Down: 10.2 mm at 0.4016 in. Up: 10.3 mm at 0.4055 in.