There are many different factors that go into the objects you can create with a CNC mill, but the biggest contributor is going to be your CNC end mills. At the most basic level, end mills are like drill bits but instead of only drilling vertically, they can also cut horizontally and have several form factors to get the cleanest cut for specific materials. Some are used only for plastics to keep from heating too much, some are designed to keep wood from chipping or tearing out, and some are designed for ultra-fine detail work. ;
Shape
From one end mill to the next, the most obvious difference you will find is that end mills come in many shapes and sizes. Some are thin and pointy, and others are wide and rounded. Some of the most common shapes you will find are fishtail (or flat), ball-nosed, and the bullnose, and each of these can be a straight cut or a tapered cut.
Size
Size is the biggest determination of what you can do with any given end mill. Large ones excel at grinding through a lot of material at once, but you don’t get a lot of detail out of your parts. With CNC milling, the radius of your end mill is the radius of any internal corner, so you will almost never have a perfectly square corner on the inside of a milled object. Smaller and smaller end mills can be used for each pass to clean up an edge and get the part to the final dimension and shape. ;
Straight vs. Tapered
There are generally two forms of end mills: straight and tapered. This is a choice based on the geometry of your finished part because a tapered end mill won’t be able to do all the same things as a straight end mill, and a straight end mill may not be the most efficient choice. By using a tapered end mill, the cross-sectional area is larger than a straight end mill of the same tip diameter, creating a much stronger end mill that is less likely to bend while milling. For perfectly vertical walls you will need to use a straight end mill as the taper just won’t reach. However for angled walls, using a straight end mill is not the most efficient, ideal choice.
Why Use a Single Flute End Mill?
There are a lot of strange beasts out there in the cutting tool world and a lot of physics that are not obvious. For example, many machinists will know that more flutes mean more productivity, but that certain materials, like aluminum, require fewer flutes–usually two or three. If that's the case, when would it ever make sense to use 1 flute end mill? Is there a time when the least number of flutes possible is a good idea?
Now let's take a CNC Router example. ; Say it's got a spindle capable of 24,000 rpm, but it will go no slower than 12,000 rpm. ; When cutting aluminum, the first thing we discover is we need carbide to run at those surface speeds–preferably a good coating is needed to up the limit even more. As we begin working through the feeds and speeds (hopefully using G-Wizard Calculator!), we discover we're going to need some pretty high feed rates at those RPMs too. ; For a 1/4″ endmill, it wants to run at 24000 rpm and a feed rate of about 255 IPM. ; ;Now depending on the machine, we may have discovered a problem. What do we do if our machine can't feed that fast?
The answer is to use a 1 flute endmill because it halves the necessary feed rates without rubbing. So there is one case wher it helps when the machine just can't feed fast enough to keep up with what the spindle is putting out and maintain adequate chip loads.
FINISHING END MILLS-2 FLUTE
Finishing End Mills are used in metalworking applications for removing material or burrs from a workpiece and leaving behind a smooth finish. 2 Flute End Mills ;are used for center cutting (plunge cut) operation and when chip removal in slots and grooves is a problem. A wide range of coatings such as Titanium Nitride (TiN), Titanium Carbon Nitride (TiCN), Titanium Aluminum Nitride (TiAlN or AlTiN), and Diamond finishes permit maximum performance and value for a particular application or material. Both standard and metric shank and cutting diameters are available.
Uncoated High Helix Single End Mills from TTC Production. These HP series of single-end mills are exclusively designed to work on aluminum workpieces. TTC's HP series are available in two-flute, spiral designs and come in regular, long, and extra-long lengths. The tool is made from high-speed steel and the center cutting makes it suitable for peripheral, ramping, helical, plunging, and slotting operations. The high helix angle wraps around the tool faster and provides excellent chip evacuation at high speeds. ;
3 Flute End Mills - Carbide, Cobalt & HSS
Three flute end mills ;are used for higher feed rates than two flute end mills and are often used in aluminum machining. ; They are commonly used in grooving operations wher the chip is crowded. ; They are also used in non-ferrous milling applications wher high feed rates are used. ; Three flute mills tend to reduce vibrations during the cutting operation. ;
PCB Corn Teeth End Mill
PCB Corn Teeth End Mill is suitable for printed circuit board (PCB), high-density fiberboard (HDF), super hardwood, carbon fiber, fiberglass, HDF composite board, bakelite plate, epoxy board, shell, or powder materials.
Features of ;PCB Corn Teeth End Mill
1. Special Cutting Edge: Special cutting edge can increase the cutting ability. The lifetime of tools and machines will be longer
2. Smooth And Wide Flute: Smooth and wide flute will remove the cuttings more easily
3. Heat-resistant Coating: With highly heat-resistant HELICAL coating, can be used for high-speed processing
4. Bronze Coating: Under bronze coating, any abrasion is easy to be recognized
5. High-Quality Raw Material: The raw material is used of high toughness, grain-sized carbon tungsten
6. Polished Surface Treatment: With high polished surface treatment, the friction coefficient could be reduced, the lathe efficiency could be improved, more production time could be saved
The Bits
Now when it comes to the actual engraving bits, there are an incredible amount of different types. However, in this article, we'll simplify things and go down to two basic ones - metal and Plexi.
For steel/aluminum engravings, I always use diamond bits since these give a great result and they are very durable. There are all kinds of different sizes but there are three basic bits that get you started in a good way.
When doing plexiglass engravings you can use the diamond bits, but I like to use a different kind of bit since I like to play around with different textures. Therefore, I use a cutting bit, instead. Since the Plexi is a lot softer than metal, you can do some very cool things indeed with cutting bits.
Drill Bits
Drill bits ;are grouped into two categories: roller cone and drag (Fig. 11). Roller cone bits are of two types: milled-tooth and insert. They are designed to drill rocks of various types and strengths. The milled-tooth bits are generally used when tooth wear is not a critical issue, wheras the insert bits with tungsten carbide inserts are used when tooth wear becomes the limiting factor in the life of the bit. Both the milled-tooth and insert bits have bearings wear that limits their operating lives. The rock-cutting mechanisms of roller cone bits use a shoveling (gouging) action in soft formations and a crushing (chiseling) action in hard formations. Drag bits are of two types as well: polycrystalline diamond cutters (PDCs) and diamond matrix bodies. The major differences from the roller cone bits are the rock-cutting mechanisms and a lack of bearings. The PDC bit cutting mechanism is rock shearing, wheras the diamond matrix is rock grinding. PDC bits are used in all nonabrasive rocks regardless of strength, wheras the diamond matrix bits are generally used in extremely hard abrasive formations. Drill bit selecion is based mainly on past bit performance records. Past experience and learning are key factors in selecting the right bit for the right hole interval to be drilled.
Choosing and Using the Right Router Bits for Woodworking
Walk into any fine woodworking supplier and you'll likely find a wall covered with hundreds of different router bits of different profiles, shank sizes, tip types, and more. A woodworking router bit is one of the most versatile woodworking tools you can own, but it's not the tool itself that brings versatility; it's the bits. Choosing the right router bit and using it properly involves selecting the right style and size of bit for the job as well as installing the bit correctly and using an appropriate tool speed.
Woodworking router bits come in a variety of sizes. To ensure safety and the best possible results from your routing, you must adjust the speed of the router to suit the diameter of the router bit. The general rule is the larger the bit, the slower the maximum allowable router speed.
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