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What are the five most common types of lubrication failure?
daubing, galling, scratching, fretting & seizure |
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What is the difference between water soluble cutting fluid and neat cutting oil?
(a) Comparing with neat cutting oil, water soluble cutting fluid offers better heat dispersing ability and is easier to clean up.
(b) Comparing with water soluble cutting fluid, neat cutting oil has better lubricity and provide better surface finish. |
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Why does water soluble cutting fluid will become rancid when not in use?
This can be attributed to the presence of contaminants, such as tramp oil, light oil or residue on the surface. Non-circulation of fluid will cause rancidity because anaerobic bacteria will grow rapidly in the absence of air. |
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Why do some neat cutting oils induce colour change on non-ferrous metals?
Certain neat cutting oils contain active lubricant additives which cause colour change in machining non-ferrous metals. Therefore, it is advisable to use straight oils without active lubricant additives to cut non-ferrous metals. |
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Why do some neat cutting oils contain active sulphurised additive?
Active sulphurised additive could improve lubricity in machining and prolong tool life. However, it may affect some non-ferrous metals. |
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How do we choose a suitable cutting oil for high speed CNC machines?
A. (a) types of material, (b) feed rates, (C) cutting feeds & (d) spindle speeds |
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Under what conditions shall we use fire resistant hydraulic oil?
If there is a possibility of hydraulic oil leakage which leads to fire hazard, such as die casting machines or any other equipment subject to high temperature operating environment¡Mfire resistant hydraulic oil shall be used. It possesses high ignition point and non-flammable characteristics |
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What does the viscosity of hydraulic oil mean?
Viscosity indicates the speed of oil movement under certain temperature. |
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When the pressure in the mechanical system is not high enough, shall we use another hydraulic oil with higher viscosity to solve the problem?
No. Increasing the viscosity can increase the pressure in a short time. However, it will induce detrimental effect to the machinery. Almost all new equipment has specified the requirements of hydraulic oil for its operating system. If do so, it will cause damage to the pumps and shorten the working life of entire system. |
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Shall we use kerosene instead of EDM oil for electro-discharge machining?
No. The flash point of kerosene is extremely low and it is very easy to burn. The flash point of typical EDM oil must be above 100¢J. |
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Even though the work piece has been coated with rust inhibitor, the material still rust. Why?
It may be due to wrong use of rust inhibitor. If the surface of work piece is not clean enough and completely dry, coating of rust inhibitor will just trap the contaminants and moisture which in turn promote rusting. |
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What is the difference between silicone and non-silicone mould release agents?
Silicone based mould release agent is not suitable for processes involving secondary treatment work such as galvanizing, painting or silk-screening, etc. In these cases, non-silicone mould release agent shall be applied. |
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Under what circumstances shall hydraulic oil be changed?
It depends on whether (a) the pressure of the system becomes lower (without leakage), (b) the viscosity of hydraulic oil changes significantly, (c) the oil emits rancidity, (d) the oil has been emulsified. |
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What is the difference between synthetic and mineral base oils?
Synthetic base oil is made by chemical synthesis process while mineral base oil is refined from mineral oil. Synthetic base oil incurs higher production cost but it has a wide temperature range. Mineral base oil is cheaper to produce but it has a narrow temperature range and difficult to clean up. |
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Why do some metalworking fluids need an extreme pressure additive package?
Extreme pressure additives could improve load carrying capability, improve surface finish and reduce tool wear. |
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What is GREASE?
Grease is a lubricant which is a conglomerate of thickener and base oil in either stable solid or semi-solid form. It is used to provide lubrication, resistance to high load, cushioning effect and sealing, etc. It can be applied to some occasions where lubrication may not be possible or not so convenient, such as bearings and gears. |
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What contribute to the "slip-stick" phenomenon in slideway mechanism?
Except for the mechanical failure, usually it is caused by the lack of lubrication. A high quality lubricant is recommended in this situation. |
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Why do we need multi-grade oil for generator?
The viscosity of multi-grade oil does not change substantially at either high or low temperature. It ensures smooth start-up at low temperature while maintains sufficient lubrication at high temperature. |
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Why does the copper wire drawing lube change to blue colour after a long period of usage?
In the course of continuous production, the copper ion gradually dissolves into the drawing oil. Copper ion is blue in colour and then turns the oil into blue as well. This phenomenon is normal. |
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Why does water soluble cutting fluid sometimes not dissolve in water?
It may be due to the presence of some tramp oils or light oils, or the sump has not been cleaned up thoroughly. |
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