Four factors are crucial
When choosing a tool holder, the machining application, cutting edge strength and economy are all taken into consideration.
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Tool selection by lead angle
This image shows the lead angle and cutting edge for external turning.
The tool holder is chosen according to different machining methods such as external turning, facing and copying and the direction of traverse. The cutting method for which each tool holder and insert combination can be used is decided by the lead angle.
Generally, when 90° finishing is not necessary, choosing a tool holder with up to a 90° lead angle is economical because a square insert with four cutting edges per side can be used.
For back feed facing, please select a tool holder and an insert with a lead angle of 105° or greater for effective chip control. A lead angle of 95° or less is not recommended due to very poor chip control. A lead angle of 90° or less cannot be used for back feed facing. A negative end cutting edge angle is used only for facing.
Tool selection by lead angle
Tool holders and lead angles
Lever lock type (P) is the most common clamp method.
ISO prescribes clamping structures of indexable insert tool holders.
M type: Method to clamp the insert on top and in the hole.
(Multi clamp method)
P type: Method to clamp the insert in the hole.
(Pin lock method, lever lock method)
S type: Method to clamp the insert with a screw through the hole. (Screw-on method)
C type: Method to clamp the top of an insert that has no hole. (Clamp-on method)
* Clamping mechanisms in brackets are typical types. If any clamping types satisfy the points above, the clamping structure symbols can be used. However, unique symbols are now being used for some recent clamping methods to differentiate them from the original conventional methods.
Lever lock type (P)
A method used to clamp an insert with a hole by pushing it towards the insert seat walls using an L-shaped lever. Due to it's ease of use this is the most widely used clamping method and ensures the cutting edges positioning accuracy*. However, the clamping strength in the vertical direction is not so strong and therefore, not effective for heavy interrupted cutting.
Double clamp type (D)
A method used to clamp an insert with a hole by pulling it towards the body of the holder. The clamp bridge also exerts a downward force in addition to the side force that pulls it into the tool body and is therefore excellent for clamping even during heavy interrupted cutting.
The double clamp type does not have an assigned ISO identification, but is usually viewed as an M type classification. ISO M type often refers to multi clamp methods, a combination of a pin lock and clamp on method.
Wedge lock type (M)
(ISO M type is prescribed as a method that simultaneously clamps the top of the insert and hole. The actual mechanism is not specified, therefore there are various clamping mechanisms that can be used. The wedge lock type using a clamp bridge is introduced here.)
The wedge type system is a method of clamping an insert with a hole against the tool holder by simultaneously clamping the top and the side of the insert, or only the side of the insert by using a clamp bridge. One advantage of this method is high reliability clamping of one face when clamping a triangular insert. When trying to clamp a triangular insert with a two face clamping system, the end cutting edge has to be held and this can easily interfere with the workpiece making it unsuitable for copying. The wedge lock method can be used for copying. However, there is a disadvantage of poor cutting edge positioning accuracy because the clamping is carried out by pressing the insert against a pin.
Screw-on type (S)
The screw on method is used to clamp an insert with a tapered hole by using a screw. Because the system is simple and small inserts can be clamped, this method is widely used for small tool holders and boring bars, indexable insert type drills, end mills and in face milling cutters. The holes in the holder and insert are offset from each other and therefore enable the insert to be pushed against the wall of the insert pocket and clamped securely. Consequently, the cutting edge positioning is accurate with enough clamping strength to be used for holding positive inserts. One drawback is that the screw has to be completely removed to change or index the insert and therefore lowers workability.
Clamp-on type (C)
The clamp on method is used to secure inserts without a hole by clamping the insert on the top with a clamp bridge. Both negative and positive inserts can be clamped in this way and additionally has high clamping strength that makes it suitable for heavy interrupted machining. The insert is not pulled into the location face, but the cutting edge positioning accuracy is relatively high.
Cam lock type (E)
This method is for clamping an insert with a hole by pressing it against the locating wall with an eccentric pin. As there are only a few parts this method is inexpensive, but the cutting edge positioning accuracy is low. This method is not designated in ISO, but is broadly designated as a P type.