The milling inserts are one of the significant components of a milling machine. Just like the name, the cutting tool is responsible for scraping material off the workpiece. It consists of every milling machine.

Please visit our website for more information on this topic.

It is required for a very high removal rate of material, in severe conditions and works on wet as well as dry machining.

In this topic, you will know what is the milling insert, what types of milling inserts are available, what material it is made up of, and what are some of the well-known milling insert models. So let's dive in.

WHAT IS A MILLING INSERT?

These are replaceable bits for machining the toughest materials like cast iron, stainless steel, titanium, plastic, etc. They are usually made out of carbide which is why they give maximum durability and also work under extreme temperature conditions. They make holes, are used for drilling and finishing, etc.

Previously they were available in limited shapes but now you can buy one of these in shapes like helical, frustum and elliptical, etc. While the milling process, they move at 90 degrees to its axis which allows them to remove material around the insert's perimeter.

TYPES OF MILLING INSERTS

Following are various types of milling inserts available that perform different tasks:

END MILLING inserts

The end milling insert has teeth on both sides and is beneficial for drilling purposes. The terminology 'end mil' is usually known for flat bottom cutters.

• ROUGHING END MILLING INSERT

Also known as 'Pippa' cutters, these are used to remove a huge amount of material from the workpiece. They perform under extreme operating conditions. These inserts have wavy teeth that give a rough finished surface.

• PERIPHERY MILLING INSERT

The teeth present in this type of insert are at the circumference of the circular disc which is why they are known as periphery milling inserts. They only work in milling machines with a horizontal axis.

• SIDE MILLING INSERT

This type of insert has teeth on both face/end and periphery which is why it is used to make narrow slots or cut slots and is used for strand milling and face milling operations.

• FACE MILLING INSERT

They have a cutter body with a large diameter where many insertion tools are fastened. Material is removed from them by axially narrow and radially deep cuts. The diameter of the face milling insert depends upon the body of the cutter and workpiece length. It is mostly used for down milling.

• GANG MILLING INSERT

The gang milling insert is where periphery milling cutters with varying sizes are used to remove and cut material from the workpiece.

• STAGGERED MILLING INSERT

These milling inserts are staggered around the periphery having the option of left or right-hand helix angles.

• CONCAVE MILLING INSERT

It is a kind of formed insert and is designed with a specific shape for a particular workpiece. Its main use is to match a circular contour having a convex surface.

• CYLINDRICAL MILLING INSERT

It has a cylindrical shape and also consists of teeth on its perimeter.

• HOLLOW MILLING CUTTER

It is similar to a pipe and consists of thick walls. It has bites inside the hollow surface and is used in screw machines.

MATERIAL OF MILLING INSERT

They are made of two types of materials; steel (FSS and HSS), and carbide. Following are the details:

STEEL (FSS, HSS)

The milling inserts made out of HSS perform better against wear response and heat as compared to ordinary carbon steel. It further breaks down into special and general purposes HSS and consists of characteristics like hardness HRC62-70, great cutting edge strength, great vibration resistance, etc.

With the use of this type of steel, it has comparably great forging, machining, and sharpness features. But in comparison carbide-made milling inserts, it has low hardness and wears resistance.

CARBIDE

These are tougher than HSS but do not have good strength. Their high stiffness properties make them good wear-resistant but their lower strength makes them prone to peeling and crack.

BEST MILLING INSERT MODELS

Following are the well-known milling inserts with basic specifications:

Carbide Inserts APKT TiAlN Coated Indexable Milling Inserts APKT Style Used for end milling, indexable face milling, slotting etc. Carbide made, TiAN finished, Square end cut type, 85 degrees parallelogram, relif angle 11 degrees, 4-7 times faster cutting speed than generic steel Carbide Milling Insert RPMT Round Feasible to mill stainless steel and mild steel. Milling insert with groove, made with hard alloy casting, high toughness, 4.40 mm bore diameter, 4.80 mm thickness, weight 2.26 ounce Carbide Inserts for Aluminum SEKTAFFN-LH2 Feasible for roughing and finishing process on copper, brass, wood, aluminum etc. 12.7mm size, 4.76mm thick, 5.5mm diameter, 16mm length, 0.8mm radius. PDN-HQ-M IC28 Carbide Milling Inserts CNC Mainly used for aluminum milling on medium cutting speed and large chip section. Very sharp cutting edge 10.35mm cutting edge length, 4.48mm insert thickness, 0.4mm corner radius, 10.35mm inscribed circle diameter Carbide Insert milling Inserts APMTPDER Used for stainless steel and iron etc. milling. Made with 12.9 grade alloy steel, good cushioning and 90 degree cutting angle 11.18mm length, 3.5mm thickness, 0.8mm edge radius SEHT 43 AFSN Carbide Insert Face Mill Can mill at different angles or rough turning. Grooved design removes chips faster, and gives smooth finish. Best for milling aluminum alloy 5.50 mm bore dia, X83 chip breaker type, 0.50 mm thick, 0.50mm wide, 0.19 mm long, 0.13 pound weight

CONCLUSION

The milling inserts are used for milling extreme tough materials like stainless steel, cast iron, etc. and used to drill and finish these materials. They can mill and horizontal, vertical and inclined angles and can remove the chips extremely fast from the workpiece.

The milling inserts are rotary tools having one or multiple teeth. During the milling process, each cutter tooth cuts the workpiece one by one. They are used mainly for making grooves, steps, milling planes, forming surfaces, etc.

Selecting the right milling requires considering various factors. In this article you will know what factors to look for:

WHICH TOOL IS SUITABLE FOR AN ORDINARY MILLING MACHINE OR CNC MACHINING CENTER?

If you are using solid carbide inserts, then you need to use them on CNC machining centers. This is because carbide inserts have the great abrasion resistance and thermal rigidity but they have low impact resistance because they are made from alloys like powder metallurgy. They have a hardness of about 90 HRA and thermal rigidity of about 900- degrees.

For using inserts with ordinary milling, go for white steel milling inserts. These inserts are softer in comparison, have good toughness, and are economic. But the strength is not good enough which is why they have low heat hardness and wear resistance. Their thermal rigidity is approximately 600 degrees and 65HRC of hardness.

DIAMETER OF MILLING TOOL

The diameter of inserts varies depending upon the product batch. The milling insert's diameter depends upon the equipment's specification as well as the workpiece processing size.

If you are looking for more details, kindly visit Guangzhou Ruiyi Technology Co., Ltd..

Following are examples of milling inserts with standard diameter specifications:

FACE MILLING INSERT

The consideration of diameter depends mainly on the size of the processing workpiece and the power required to work on that workpiece. The diameter of the insert can also be selected based on the insert's spindle. The typical diameter range is 40 mm ' 250 mm.

The typical formula for calculating diameter is D = 1.5d where d is the diameter of the spindle.

SLOTTING MILLING INSERT

The standard diameter for slotting milling inserts starts from 1.5 inches, 2 inches, 3 inches, etc.

END MILLING INSERT

For slot milling inserts with a small diameter, the maximum number of revolutions is considered if it can reach up to 60m/min cutting speed. The standard diameter ranges from 5 mm ' 10 mm.

MILLING TOOL BLADE

There are various types of blades for milling inserts. Choose a grinding blade for fine milling. It has good accuracy in dimension therefore the cutting edge is higher in milling and delivers good surface roughness.

To attain roughing, you should use a pressed blade because it can reduce the cost of processing. Its dimensional accuracy and sharpness are not good compared to grind blades but give great edge strength and also resist impact during roughing during the machining process. It also can bear high feeds and large cutting depth.

For viscous materials like stainless steel, you can select inserts with sharpened large rake angles. Because during the cutting action of the sharp blade, there is reduced friction between the workpiece and blade, and chips are easily escaped from the front of the blade.

If you want to achieve a better-finished surface, use a scraping blade to remove rough machining marks.

MILLING TOOL BODY

The higher the diameter of the milling tool, the costlier. For instance, a face milling inserts with a 100 mm diameter costs above $600. Therefore, careful selection is required:

Consider the number of teeth

Coarse-tooth milling insert with a 100 mm diameter has 6 teeth. But the dense teeth insert of the same 100 mm diameter has 8 teeth. The size of the pitch tool is determined by cutter teeth which affect the smoothing and cutting rate of the insert.

A coarse milling insert is usually for rough machining because it consists of a large chip flute. After all, a small chip flute, will create difficulty for chip curling and removing.

The load of the cutting tool of coarse-toothed milling is larger compared to the dense-tool milling tool.

NOSE RADIUS OF INSERTS

RE (nose radius of an insert is another crucial factor in the selection of inserts. It is available in different nose radii. Its selection depends on surface finish, depth of cut and feed, insert length, etc.

ENTERING ANGLE

The lead angle or entering angle is between the feed direction and the cutting edge. It is necessary to select the entering angle for a successful turning operation. It affects:

• Cutting force direction
• Cutting edge length in the cut
• Formation of chips

USES OF MILLING INSERTS

It is used since the late s and is used in the following sectors:

Surgical tools ' Doctors and surgeons rely heavily on accurate tools, therefore, inserts with the base of stainless steel or titanium are selected and the tip of the tool is manufactured with tungsten carbide.

Jewelry ' The inserts are used here for shaping the jewelry. Since the tungsten is second hardest material than diamond, it is perfect and economic for the shaping of jewelry rings, etc.

Nuclear industry ' The inserts made with tungsten carbide are the best neutron reflectors and are heavily used for investigation and research on nuclear chain reactions for weapons etc.

CONCLUSION

Choosing the right milling inserts requires careful selection from various factors like entering angle, machining requirements, tool diameter and blade, nose radius, etc. Selecting the wrong milling insert will not only increase your cost of production but also may damage your workpiece.

Have you ever tried a button cutter for milling? If so, you'll know that these versatile tools can really do a good job for you. They're commonly used for pocketing, die/mold roughing, face milling, slotting, step milling, and even helical interpolation of holes. There's a lot to recommend round inserts as they have a number of properties that contribute to their success. If you've used one turning, you know that their large radius can yield some very nice surface finishes. They can leave a good finish when milling too, but they have a number of other advantages. Their round shape makes them particularly strong as they have no weak corners that can chip. If you do wear or chip one, they can be rotated to expose a fresh edge. They're advantageous for lighter machines too. When operating at heavier depths of cut, they create cutting forces that are more radial. But, by taking a lighter depth of cut, they transition to behave more like high-feed machining tools. This means most of the cutting forces are directed straight up the spindle, which is the strongest rigidity on any machine. That's one reason plunge milling is so advantageous on light machines. Button cutters provide an alternative. It seems that for whatever reason, the physics of cutting favors circles. HSM toolpaths do better than conventional paths by adopting loops rather than sharp corners. And button cutters do well because corners on inserts are a weak point that can chip or break off. You can load up a button cutter pretty hard and they'll hang in there. If you do manage to chip one, just rotate the insert until the chipped portion is not being used and keep going.

In the most demanding applications, button cutters compete with high-feed cutters. For many shops, a high-feed cutter is a direct replacement of their button cutter that allows them to crank up the feeds and speeds. For this reason, some have said button cutters are on their way out.  But, there are cases where the button cutter still makes better economic sense:

• On older or lighter machines that can achieve the performance needed by high-feed cutters.
• With extremely tough materials where the ability to rotate a worn insert and keep going gives button cutters an edge.
• In re-roughing applications and applications with extremely hard materials where a button cutter's round inserts are just stronger and tougher, so they last longer.  Machining of welded parts is particularly well suited since the button cutter handles the hardened welds so well.

The physics of button cutters mean that some very special calculations have to be done when figuring their feeds and speeds. There are several important issues to consider:

1. Cuts should be made with a depth of cut less than the radius of the insert. That means the diameter of the tool is a function of the depth of cut because of the radius that is the edge of the cutter, just like a ball nose end mill.
2. Toroidal cutters are subject to chip thinning in two dimensions. Like any rotary cutter, if the width of the cut is less than half the diameter, chip thinning occurs. There's a diagram showing how this geometry works as part of our speeds and feeds tutorial. It's very important to consider chip thinning or your actual chipload may be lower than you expect and the tool can start rubbing, which will dramatically reduce cutter life. However, when you not only have a rotating tool but one with round inserts, you get chip thinning in both the radial and axial planes.
3. Because of their unique design, toroidal cutters can tolerate quite a bit more chipload than most other kinds of indexable cutter. There's no corner weak point that can be easily damaged by cuts that are too aggressive.  This is also true to a certain extent for bull nose end mills, which are just end mills whose bottom edge has been given a radius.  Think of them as button cutters whose round inserts have a really tiny radius.
4. While the cutter pictured doesn't do so, more exotic designs may also 'lay down' the round insert slightly, introducing a lead angle on top of everything else that is going on with the geometry.

Suffice it to say that simple tables are not going to yield the best results. You need to be prepared to do some extra calculating, or to use a calculator like my G-Wizard Software that does all that for you. There is a lot else to recommend button cutters. For example, they make great tools for helical interpolation of holes. And, they tend to convert a lot more of the cutting force to the axial direction, which is the stiffest direction for most machines. The lower the depth of cut, the more of the force is translated axially. Lastly, when roughing out steps, you get a smooth scallop instead of a shoulder with a corner. This can make life easier for your finishing cutter. Before we leave the topic, let's consider a few basics in terms of how to operate a button cutter: 1.  Try to keep at least a 75% stepover so the inserts spend a lot of their time in the cut.  This minimizes the chip thinning in one direction, but it's okay since round inserts get chip thinning in the other direction. The reason to maximize the stepover is that most of the wear and tear on the inserts is on entry into the cut. 2.  Speaking of entry into the cut, arcing in and helixing in are far preferably to plunging in. Try my Conversational CNC Surfacing Wizard and Hole Wizard for some gentle tool paths when using one of the cutters for face milling or helical interpolating holes. 3.  Keep the depth of cut below the cutter radius. 4.  As you're considering the best depth of cut, try to keep the width of cut relatively high (about 75% as mentioned in #1). Keep depth of cut less than the insert radius. In fact less is more with these cutters, so drop it down as far as you can while keeping acceptible Material Removal Rates. You can play with these tradeoffs using G-Wizard Calculator to find the sweet spot. Setting Up G-Wizard Calculator for a Button Cutter Setting up a Button Cutter in G-Wizard is pretty simple. We'll use Tormach's 25mm cutter as the example.  As mentioned, it has a 25mm diameter. It uses a round insert with a 10mm radius. So, choose an Indexable end or face mill tool type, tell it how many inserts (3 for the Tormach) or flutes, and click the 'Geometry' button. Set it up as shown: