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What is the difference between entering angle and approach angle?
The entering angle is the angle between the bottom of the tool and the major cutting edge, which is an important angle that can distinguish the use of a milling cutter.
The sum of Entering angle and approach angle make 90°.
As an example, a cutter with an entering angle of 30° means the approach angle of the tool is 60°.
As the entering angle becomes smaller from 45°, it is effective for high-feed machining and as the entering angle approaches 90°, it is effective for machining that generates heavy cutting load.
What is the difference between shank type and cutter type in milling tools?
In order to fasten a milling tool to an arbor or chuck, it must have a shank or inner diameter for fastening.
The tool type with a cylindrical shank is called the shank type, and the tool type with an inner diameter is called the cutter type.
When the tool’s cutting diameter is small, the shank type is often used, and when the tool’s cutting diameter is large, the cutter type is often used.
What is a chip breaker?
It means a geometry or step design in the cutting edge of the insert for the purpose of chip control and cutting load reduction, and an unique model code is given according to the shape of the chip breakers.
Unlike turning which is mainly continuous machining, chip breaking occurs easily due to the characteristics of general milling machining.
Therefore, milling inserts’ chip breakers are designed to minimize the cutting load and to help smooth chip evacuation by reducing the radius of the chip curl .
What is the feed per tooth?
When the milling tool makes one revolution during machining, the moving distance is called feed per revolution,
and the value obtained by dividing feed per revolution by the number of teeth of the milling tool is called feed per tooth. It is easy to check the load on the insert by feed per tooth.
A higher feed per tooth increases the risk of insert chipping or breakage, and a lower feed per tooth leads to faster wear.
What are the pros and cons of wedge clamping type?
The advantage is that inserts can be exchanged by turning the clamping screw a little without removing it completely, making it easier to change inserts compared to the screw-on type.
The considerable factors are as follows; there is a wedge on the insert, so it is difficult to use when there is insufficient space for chip evacuation such as internal machining, and it requires to keep more inventory of fastening parts.
How often should the clamping screws of a milling inserts be replaced?
Screws are the consumables and it is recommended to have a standard lifetime. The regular replacement will help to prevent damage to the cutter and inserts.
If there are cases as the below, please replace screws as possible
. In case screw threads are damaged or warped
. If rust occurs due to long-term non-use
※ When replacing the screws, apply the grease included with the cutter to the threads of screws before tightening.
How to decide when to replace an insert?
It depends on the customer's machining process and machining environment generally.
It is safe to use 70~80% of the maximum tool life in normal machining as the replacement cycle.
If it is difficult to check the replacement cycle, it is recommended to replace the inserts in case of increased chattering or noise, worsened surface roughness of the workpiece, chipping or buit-up edge on the inserts.
What is the "Pitch" of the milling tools?
It is a gap between the cutting edges and it is divided into Coarse, Close and Extra Close pitch.
Coarse pitch has a large chip pocket and small number of teeth and it is used for steel's roughing and finishing machining, and in large vibration conditions.
Close pitch has a medium-sized chip pocket and medium number of teeth and it is generally used for medium machining of cast iron and steel.
Extra Close pitch has a small chip pocket and large number of teeth and as it achieves a high table feed, it is recommended for cast iron's interrupted and roughing machining, and steel's small depth of cut conditions.
What is the difference between roughing and finishing milling?
Roughing is one of the machining methods which roughens the surface of the workpiece quickly to obtain a sketchy figure before finishing, and finishing is a precise machining to meet the reuiqred specifications for the purpose of the workpiece.
For roughing, inserts with reinforced cutting edges are mainly used which do not easily occur chipping or breakage and for finishing, inserts with relatively sharpened cutting edges are used.
How to find an indexable milling cutter that is more efficient for machining?
When the application such as facing, shouldering, or etc. is decided according to the characteristics and shape of the workpiece, the cutter’s entering angle and diameter can be selected.
After confirming the specification of the fastening part, select a tool with an appropriate internal or shank diameter.
Select the number of cutter’s teeth by checking the maching type such as roughing, medium cutting, or finishing.
Select the suitable inserts’ chip breakers and grades for workpiece material and its hardness.