Guide · Bits and fit
3/32 vs 2.35 mm nail drill bits
3/32 inch is exactly 2.38 mm, not 2.35 mm. Why the labels differ, what KUPA, Medicool and MelodySusie specify, and how to buy bits your handpiece takes.
Short answer
3/32 inch is exactly 2.38125 mm, or about 2.38 mm, because the inch is defined as exactly 25.4 mm.[1] A bit labeled 2.35 mm is therefore a different number, not a metric spelling of 3/32. We found no maker statement that says bits under the two labels are interchangeable, so follow the shank size your handpiece maker states. KUPA, Medicool and MelodySusie all specify 3/32 inch.
The arithmetic
| Label | In millimeters | In inches |
|---|---|---|
| 3/32 inch | 2.38125 mm (about 2.38 mm)[1] | 0.09375 in |
| 2.35 mm | 2.35 mm | About 0.0925 in |
The gap is about 0.03 mm. That sounds tiny, and in many chucks it may not matter. But "may not matter" is not the same as a maker saying it fits, and a chuck grips a spinning bit at tens of thousands of RPM.
If a listing gives 2.35 mm as the metric version of 3/32 inch, it has rounded differently from the exact figure. Treat the 3/32-inch label as the one that counts and check it against your handpiece.
What the makers specify
Every drill and bit maker we read states 3/32 inch:
| Maker | What it says |
|---|---|
| KUPA | KP-55 handpiece and Passport NEXT kit take standard 3/32-inch bits in a locking chuck[2][3] |
| KUPA | Its diamond small barrel bit can be used with any 3/32-inch e-file handpiece[4] |
| Medicool | Pro Power 35K Portable has a twist-lock chuck for standard 3/32-inch bits[5] |
| Medicool | All Medicool Pro Bits use a standard 3/32-inch shank and fit all Medicool drills and most professional nail drills[6] |
| MelodySusie | All its nail drill bits are 3/32 inch, which it calls the industry-standard size[7] |
None of these pages mentions 2.35 mm. KUPA's statement about its diamond bit covers 3/32-inch handpieces only; it does not cover chucks labeled 2.35 mm.
Why the 2.35 mm label exists
The two labels come from different measuring systems: 2.35 mm is a metric size, while 3/32 inch is the size the nail drill makers we read state. We found no maker explaining why some nail bits carry the metric label. Both labels describe a nominal size, the size a part is made to, not a measurement of the bit in your hand.
How to buy bits that fit
- Find your handpiece's stated shank size in the manual or on the maker's page.
- Buy bits labeled with that size. If your handpiece says 3/32 inch, buy 3/32-inch bits.
- Be wary of mixed labels. A bit listed only as 2.35 mm, or as "3/32 (2.35 mm)", has not been confirmed to match a 3/32-inch chuck by the drill maker.
- Check the machine exceptions. Even true 3/32-inch bits do not fit every machine. See do all nail drill bits fit all drills.
Next
Questions
Is 3/32 inch the same as 2.35 mm?
No. 3/32 inch is exactly 2.38125 mm because the inch is defined as exactly 25.4 mm. 2.35 mm is about 0.03 mm smaller.[1]
Will 2.35 mm bits fit my 3/32 nail drill?
We found no maker statement that says so. KUPA, Medicool and MelodySusie specify 3/32 inch only, so buy bits in the size your handpiece maker states.[2][6][7]
What shank size are most nail drill bits?
The makers we read all state 3/32 inch. MelodySusie calls it the industry-standard size, and Medicool says its bits fit most professional nail drills.[7][6]
What if my bit wobbles in the chuck?
Stop and do not run it. Check that the bit is the shank size your handpiece maker states and that it is fully seated and locked; if it still wobbles, contact the drill maker.