Steel is a material that we are all familiar with… and for good reason. It’s versatile, fairly easy to work with, and less expensive than materials of similar hardness. That being said, steel can be scary to cut, especially with a low-horsepower machine, but it doesn’t have to be!
Steel isn’t a sticky metal (like aluminum), which means you are best off having more flutes on your cutter. Usually four or five flute end mills are best because having more teeth that create smaller chips. Smaller chips means the teeth are engaged more often, leading to more cutting from every tooth, which means more efficient cutting.
To that end, having more teeth also helps make your cutter more rigid. Think of it like a roof with five trusses instead of two… more trusses means it can support more weight. The same concept can apply to an end mill with more flutes.
You can use old-school, uncoated end mills to make chips with steel, but there are a number of benefits to using coated end mills. Titanium nitride coatings work really well for steel, but if you want to use some high-end tooling, Helical’s Aplus and Tplus coatings are great for steel work. According to Helical, Aplus coatings are designed to resist high temperatures, while also reducing tool wear. Tplus coatings are designed for wear resistance as well, but are meant for even harder materials… it might be a little overkill for mild steel, but it works great with stainless and titanium, so it’s versatile.
Just because steel isn’t as gummy as aluminum doesn’t mean you don’t want coolant. Cutting harder materials means more friction between your cutter and the stock. Friction means heat. And heat can cause steel to get even harder.
Hardened steel can be difficult and temperamental to machine. NYC CNC even created a special ProvenCut Recipe for hardened steel because it can be challenging.
Coolant does exactly what its name implies - it cools things down - but it also acts as a lubricant to lower the friction during the process.
Insert End Mills
Shell mills or face mills use replaceable inserts. This means that they can be more economical and diverse than traditional end mills. While inserted end mills are more expensive up front, over the long run, they are generally less expensive than traditional end mills.
Cutters like the Tormach Face Mill can utilize a variety of inserts, so it can be used for more than just steel… but it can really make some chips in steel, if you need it to.
The DIJET QM Mini Modular insert end mill is built to make chips out of steel. If you’re familiar with the Shear-Hog in aluminum, this is its steel-hungry brother.
This cutter is known as an insert end mill because rather than replacing the entire end mill, you simply replace the inserts as they wear. This is great for high feed operations because it can really make chips fly, but it also leaves a stellar finish on flat parts.
Whether you’re hogging out material or looking to put a nice finish on flat material, this cutter is a must-have for the Tormach machinists.
Steel can be intimidating, especially when you’re just getting started with machining, but having the right tools can help make the process easier to learn. You will scrap some parts and break some tools, but if you take it slow, steel can be as simple to cut as aluminum.