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.
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.
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 APKT1604 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 RPMT1204 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 SEKT1204AFFN-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.|
|100404PDN-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 APMT1135PDER||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|
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 900-1000 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.
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.
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 1920s 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.
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.