Purpose and effect
- Click on the links below to view a brief explanation of the results obtained by employing coolant when machining!
Using coolant serves three main purposes, cooling, lubrication and chip control. To prevent thermal cracks due to thermal shock during machining, it is important to apply plenty of coolant over the cutting edge.
The heat generated whilst machining is due to the impact of the cutting edge with the workpiece and the rubbing of the chips across the rake face of the insert. Generally up to 80% of the heat generated during a machining process is removed within the chips. The remaining 20% remains at the cutting edge.
Heat generated during machining softens the cutting edge and hastens tool wear, or causes dimensional change of the work due to thermal expansion. By applying coolant it prevents heat from gathering in the tool and the workpiece due to the cooling action. This results in prolonging tool life and maintaining machining accuracy.
For cutting thin, long boards, that are liable to warp due to heat, machining in a tank filled
with coolant is sometimes carried out.
70 ~ 80% of the heat
removed by chip
10% ~ 20% heat left
at the cutting edge
Coolant permeates, seeps, into the faces between the rake and flank face, and the work. This action provides cooling and lubricity. Another area where coolant permeates is into the shear plane, as the chip develops. When this occurs the shearing of the chips accelerates and improves machinability. This can be especially seen when machining of aluminium alloys.
made by coolant
If the chips developed slide across the surface of the rake face smoothly, then problems such as built-up edge and welding can eliminated and tool life can be prolonged. Additionally the dimensional accuracy of the machined part will also stabilize. By applying a coolant a lubricating film between the chips and the rake face develops. This film allows the chips to slide across the rake face with ease, protecting the cutting edge.
This flow action is one in which the force or pressure of the coolant flow is used to physically direct or to dispose of the chips as they are developed. When deep hole drilling using gun drills or gun reamers the coolants used need to have a moderate viscosity level.
Increase tool life
Increase surface accuracy
Maintain and increase