{"id":3796,"date":"2024-03-19T00:01:00","date_gmt":"2024-03-19T04:01:00","guid":{"rendered":"https:\/\/therabbithoel.com\/?p=3796"},"modified":"2024-03-18T20:36:42","modified_gmt":"2024-03-19T00:36:42","slug":"spinning-blades-of-death-an-intro-to-end-mills","status":"publish","type":"post","link":"https:\/\/therabbithoel.com\/?p=3796","title":{"rendered":"Spinning Blades Of Death! An Intro To End Mills"},"content":{"rendered":"\n

Awhile back I made a post about my milling machine<\/a>. In that post I promised to talk further about end mills and other milling cutters. Well, today’s that dreaded<\/s> your lucky day!<\/p>\n\n\n\n\n\n\n\n

End Mill Basics<\/h2>\n\n\n\n

Milling machines rotate a spindle, which holds a cutter while you push the work past the cutter. On my machine the spindle, and therefore the cutter, is held vertically, much like a drill press. The cutter is sharp on the end, and is called an end mill<\/strong><\/em>. There are other types of milling machines, and other types of cutters, but those are generally for big industrial use, not home shops.<\/p>\n\n\n

\n
\"An
An assortment of end mills<\/figcaption><\/figure>\n<\/div>\n\n\n

They Aren’t Drill Bits<\/h2>\n\n\n\n

Some end mills look a lot like a drill bit, but they’re different in many ways. Firstly, drills have a sharp point to cut straight down, but the flutes have a different purpose than the flutes on an end mill. On a drill, the flutes pull loose cuttings out of the hole so they don’t interfere with the drilling. The edges of drill flutes are quite sharp, but those edges don’t stick out from the main diameter of the drill, so they can’t cut sideways.<\/p>\n\n\n\n

End mills, by contrast, have no problem cutting sideways. In fact, that’s what they’re designed for. The edges of the flutes protrude further out than a drill, and they’re sharpened in such a way as to allow side cutting. The flutes still pull cuttings out of slots and holes though, just like a drill bit.<\/p>\n\n\n\n

Drill bits and end mills differ in other ways too. The shanks of drills are soft steel. That way, if the shank slips in the drill chuck, the drill bit might be damaged but the drill chuck won’t be. Drill chucks cost a lot more than drill bits, so it makes sense.<\/p>\n\n\n\n

But end mill shanks are just as hard as the sharpened edges. They must be, or they would bend under the sideways forces of a milling cut. <\/p>\n\n\n\n

Getting a Grip<\/h2>\n\n\n\n

Unfortunately, a hard shank would likely slip in a drill chuck at the slightest provocation. So end mills are held in the mill spindle with a special holder. Some genius, in a burst of inspiration, named them end mill holders.<\/p>\n\n\n

\n
\"End
The two things on the left are end mill holders. The one on the right is a drill chuck for holding drill bits.<\/figcaption><\/figure>\n<\/div>\n\n\n

These use a set screw (or two) to bear against a flat spot on the end mill. That prevents the cutter from rotating independently of the holder.<\/p>\n\n\n\n

You can’t adjust an end mill holder for different sizes, so you need to have a separate one for each size of end mill shank you wish to use. <\/p>\n\n\n

\n
\"Size
From left: 3\/16″, 3\/8″, 1\/2″, 5\/8″ and 3\/4″ shanks<\/figcaption><\/figure>\n<\/div>\n\n\n

Flutes, Coatings, and Other Nuances<\/h2>\n\n\n\n

Sharp-eyed readers will note that some of the mills in the picture have more flutes than others. It can get complicated, but in general an end mill with more flutes will produce a smoother surface than one with fewer. But a mill with fewer flutes can remove metal faster, and is less prone to clogging up. That can be really important with softer materials like aluminum.<\/p>\n\n\n

\n
\"Illustration
Two, three, four and six-flute end mills.<\/figcaption><\/figure>\n<\/div>\n\n\n

All of the end mills I own are made of high speed steel. Fancier cutters used in industry are made of more exotic materials like tungsten carbide. Industrial cutters are often coated with titanium nitride or other special coatings in order to reduce friction and prolong cutter life. Cutters like that cost many times the price of high speed steel, but they let machinists run their machines much faster. They make sense in commercial shops, but my machine isn’t powerful enough to go any faster.<\/p>\n\n\n\n

So Many Shapes and Sizes<\/h2>\n\n\n\n

End mills come in an astonishing variety of shapes, sizes, materials, and coatings. A look at the site for Travers Tool<\/a>, an industrial supplier I often buy from, gives you a feel for the breadth of the options. (Note: Not an affiliate link, I get no compensation for the link. I’m just a satisfied customer.)<\/p>\n\n\n

\n
\"The
My end mill drawer. These are just the ones I keep handy. I have spares too.<\/figcaption><\/figure>\n<\/div>\n\n
\n
\"Larger
These are too big for the other holder<\/figcaption><\/figure>\n<\/div>\n\n\n

There’s a lot more to talk about, but we’ll save the rest for another day. I hope this gave you a bit of insight into end mills. Thanks for reading!<\/p>\n","protected":false},"excerpt":{"rendered":"

Awhile back I made a post about my milling machine. In that post I promised to talk further about end mills and other milling cutters. 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