90°, 45°, or High Feed? Choose the Right Milling Cutter

Have you guys ever wondered what type of milling cutter to use in your operations? My name is Justin Wilkes. I’m a technical sales engineer with KYOCERA Precision Tools. Today we’re going to talk about the differences between 45°, 90°, and high-feed milling cutters and when you should apply each in your operation.

Along with the three basic cutter types, those being 90°, 45°, and high-feed mills, I’d like to go over the 90° cutter systems first. There’s a lot of features and benefits to 90° cutters that I’d like to discuss. One of those is versatility. 90° cutters can be used for general-purpose facing, square-shoulder milling, slotting, ramping, hole enlargement, finishing, and roughing. They can be applied in many different types of machine tools, from heavy-duty to light-duty. Shoulder cutters can be applied in manual machines, CNC machines, small machines, larger machines, heavy-duty, and light-duty. They’re extremely versatile.

The cutter that I have in my hands right now is what’s called a tangential cutter. These typically have four cutting edges per insert. They offer a very robust seating surface. They’re very strong. They leave a very nice sidewall finish and a very nice face finish. This one in particular, our new MA90, does have the capability of ramping, so you can enter into a pocket, enlarge a hole, or slot without an entry hole.

Next up, we’re going to talk about 45° face mills. 45° face mills are the most common lead angle available for general-purpose face milling, but there are others, and we’d like to cover those in a separate topic in the future. Some of the advantages of a typical face mill, like this 45° face mill that we’re working with today, are increased economy due to each insert having multiple cutting edges, and a smooth workpiece finish because of the wiper flat width on each insert. They typically can be fed at higher feed rates than 90° cutters, which further increases economy over a 90° cutter, but can’t be fed quite as hard as a high-feed mill. They strike an ideal balance between metal removal rate and economy while still providing a great surface finish. While this 45° cutter is going to be our best option out of these three for general-purpose facing operations, it will not be the best option for reaching close to fixtures or areas where a 90° cutter or a high-feed mill would make more sense.

Let’s talk about high-feed mills next. High-feed mills are incredibly useful roughing tools, not necessarily used for finishing operations, and they’re really only useful in CNC machines. High-feed mills operate on the principle of a chip-thinning process, which is to say that each insert has a lead angle that can be fed extremely fast into the workpiece, which thins out the chip, allowing for a much higher feed rate. A few of the applications where you might want to apply a high-feed mill in your roughing operations are 3D surfacing, slotting, ramping, pocketing, cavity machining, plunging, and helical interpolation.

Moving on to the benefits of a high-feed mill: why use a high-feed mill versus a square-shoulder cutter if they can accomplish some of the same goals? A high-feed mill just does it a lot faster and a lot more rapidly to increase your metal removal rate and decrease your cycle time. Beyond that, they’re incredibly useful because of that chip-thinning angle on the insert. What that means is it directs the cutting forces—instead of 90° into the cutter, which can cause deflection at long overhangs—that lead angle of the inserts deflects your cutting forces up into the cutter and the head casting of the spindle. You can get a very long overhang out of a high-feed mill for cavity roughing, long-reach slotting, reaching around fixtures, and things like that.

If high-feed mills are so great, when would you not want to use one versus a square-shoulder cutter? Here’s one good reason: if your machine tool lacks the feed-rate capability that is needed by a high-feed mill to show value, then perhaps a square-shoulder cutter would be a better option for your needs.

In conclusion, 90° cutters are best for reaching in close to fixturing and general versatility. 45° face mills are going to offer the maximum amount of economy and the smoothest finish. High-feed mills are going to be awesome for general-purpose roughing, maximum metal removal rates, and minimizing chatter at long overhangs.

Just a reminder, everyone: this is just a brief overview of the topics that we’ve covered today. If you have any more specific questions, please feel free to reach out to your sales representative using the provided link. Like, comment, and subscribe for more Chips and Tips. Again, my name is Justin Wilkes with KYOCERA Precision Tools. Keep those chips flying.