U drills: what 2D, 3D and 4D mean
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A U drill is an indexable-insert drill. It uses replaceable inserts instead of a ground cutting edge. The D in 2D, 3D and 4D stands for the drill diameter.
What the number means
The number is the drilling depth as a multiple of the diameter. 2D means a depth of about two times the diameter, 3D about three times, and 4D about four times.
| Diameter | 2D | 3D | 4D |
|---|---|---|---|
| U drill 13 mm | about 26 mm | about 39 mm | about 52 mm |
| U drill 20 mm | about 40 mm | about 60 mm | about 80 mm |
| U drill 50 mm | about 100 mm | about 150 mm | about 200 mm |
These figures are the drilling depth, not the overall length of the drill.
How to choose
Work out the depth of your deepest hole first. Choose the shortest length that reaches it with a little margin, because the figure is the maximum drilling depth. A longer drill sticks out further and is less rigid.
Do not buy a longer drill just in case. If most holes are shallow and one is deep, buy for the common job.
What else to match
- Diameter: pick the size of the finished hole.
- Shank: it must fit your holder or machine. Check the shank on the listing before you order.
- Insert: the drill takes a specific insert. Our U drill listings state SPMG type. Check the insert code on the product page, and order inserts to match.
Which should I buy?
- Shallow holes (up to about 2 times the diameter): 2D.
- Holes up to about 3 times the diameter: 3D.
- Deeper holes, up to about 4 times: 4D. Check that your machine and holder can support the longer drill.
Our U drills run from 13 mm to 50 mm in diameter. Pick the length option on each product page.