How to Choose a CNC Diamond Drill Bit for Stone

A bit with the wrong junction, length or type cannot be used on your machine or job. This guide walks through the choices in a practical order, using the data sheets of the KDRILLS stone line.

Start with the machine and the junction

The junction is the thread or fitting that joins the bit to the spindle or adapter. On the KDRILLS stone line it follows the machine type. Drill Bits for CNC Machines (series FFG and IFG) have a 1/2 inch gas junction and are listed for CNC work centers and bridge routers. Drill Bits for Hand Machines (series FG and IG) have a 5/8 inch UNC junction and are listed for hand drills. Drill Bits for Semi-Automatic Machines have their own page, and the junction is one of the things to confirm with us.

All the CNC bits can be requested with a left junction. If your machine turns the other way, or your adapter is threaded left, say so at the start.

Pick the diameter

The product page for the CNC bits lists diameters from 4 to 150 mm, and the data sheet tables run from 5 to 100 mm in roughly 1 mm steps (a few sizes are missing or repeated in the data sheet), each with its own code. The data sheet adds a note that decimal measures are rounded up to the next diameter, so if you need 17.5 mm, expect an 18 mm bit. Measure the hole you need, not the fixture that goes in it, and allow for the tolerance of your faucet or cooktop. Each diameter in the table has its own code, so quote the code when you reorder.

Check the length and working length

The CNC bits are 95 mm long with a 55 mm working length. The hand-machine bits are 80 mm long with a 55 mm working length. The working length is the part that carries the diamond, so it must be longer than the thickness of the slab you drill. Slabs of 20 and 30 mm are well inside it, but if you drill through a thick edge build-up, check the numbers before you order.

Decide: through or blind

A through hole goes all the way, which is what a faucet hole needs. A blind hole stops inside the slab. For that job the Blind Drill Bits (series FCI) are made. The data sheet lists them with a 55 mm working length, in two versions: a cylindrical 10 mm junction and a cylindrical 1/2 inch gas junction. The product page says they suit CNC work centers and hand machines.

Segmented drill bits

The Segmented Drill Bits (series FS) are a separate family from the standard CNC bits, with a 3 mm crown thickness and a 95 mm total height, and are listed for CNC work centers. If you are not sure which family suits your job, send us the details and we will check them against the listed tools.

Dekton drill bits

The KDRILLS stone line has a separate Dekton Tools family. It includes the Dekton Drill Bits for CNC Machines and the Dekton Drill Bits for Hand Machines, both series IFDK, with diameters from 4 to 100 mm; the CNC version has a stainless steel body. If you plan to use a standard bit on a sintered surface, ask us first.

Non-standard needs

Every bit family on the site is marked as available in non-standard options on the customer's request. That covers a different length, a different junction or a size outside the table. If your job repeats, for instance the same faucet hole on every kitchen, mention the quantity and the machine too, so we can see whether a made-to-order bit makes sense for your shop.

What to send us

For a quick, accurate quote, include these five points: the machine make and model, the junction, the diameter, through or blind, and the material with its thickness. Send them through the contact page or write to [email protected].