New miniature milling cutters for small hole operations

Internal threading and chamfering in small holes simplified using CoroMill 326

Suitable for use in holes down to 6 mm diameter, CoroMill 326 benefits users through the application of three cutting edges for high metal removal rates when performing internal thread milling, chamfering and back-chamfering operations – all with a single tool. Furthermore, because the cutters utilize high precision ground profiles with sharp cutting edges, the resulting low cutting forces enable a smooth cutting action and repeatable accuracy.

Internal thread milling in small holes is growing in popularity because it overcomes the difficulties of chip control. Tapping in small holes can create a bird’s nest of swarf around the tap leading to oversize threads or broken taps inside the part. Conversely, thread mills that move in an upward, helical tool path inside a hole generate short, controllable chips that are readily evacuated out of blind or through-holes using coolant or an air blast.

Versatile and cost efficient, the success of the new CoroMill 326 cutters is based on the solid carbide grade GC1025 with a wear resistant PVD coating which increases the lifetime of the tools and allows the application of higher speeds and feeds. Standard threads and 45° chamfers can be produced, along with partial thread profiles to provide even greater flexibility for users.

Thread milling using CoroMill 326 offers many advantages over taps – a cutter is able to produce both blind and through-holes; right- and left-hand threads; and multiple thread sizes that share a common pitch. It is also able to machine complete threads very close to the bottom of a blind hole because the tools have flat undersides.

Suitable for the entire ISO material application area (ISO P, M, K, N, S, H), CoroMill 326 cutters are available down to 5.8 mm diameter, and with reach on the Weldon shank up to 35 mm. Sandvik Coromant recommends its Hydro-Grip® pencil chuck tool holders with cylindrical collets for optimum precision and stability.

The cutters are part of Sandvik Coromant’s family of productive thread milling and chamfer milling tools that includes the new CoroMill 327 and CoroMill 328 ranges, as well as CoroMill Plura.

Speed and feed selection should be based upon material tensile strength, hardness and elongation characteristics. Sandvik Coromant is happy to assist customers in thread mill selection, recommend speeds and feeds, and make cost savings and productivity improvements.