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Goldcrest Oil Ltd

     Working with Chevron - Authorised distributors for Texaco Lubricants

NEAT CUTTING OILS

Please download our extensive Neat Cutting Oil portfolio incorporating the basic physiochemical characteristics of each grade enabling you to select the appropriate grade.



In addition we supply Petrofer’s Superfin HM a very specialised non cobalt leaching oil allow you to grind and hone tungsten carbide safety


We recommended you read the information below to aid your selection

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A number of factors need to be  taken into consideration when selecting the appropriate Neat Cutting Oils, namely:


Type of Material being machined (e.g. Metals, Plastics Composites, Graphites etc.)

Machining Process (e.g. Drilling, Grinding, Milling, Broaching etc.)

Component Finish

Permissible Extreme Pressure Additives (Sulphur, Chlorine, Phosphorous, Esters)

Major Company Approvals (Aerospace, Electronic, Food and Medical Companies)

Customers Preference for  Colour and Odour

Need for: Corrosion Inhibitors/Passivator etc.

Customer’s Fluid Management Practices

Sump Life Expectations

Cutting Tools/Inserts Employed e.g. Carbon Tool, Steel High Speed Steel, Tungsten Carbide, Diamonds & Ceramics.


With so many parameters to take into account the selection of the best neat oil to use is not simply a £/Litre decision.  


Understanding the Metal Machining - the cutting process


The Primary function of metal cutting is the removal of metal and thereby producing an object of precise shape and dimensions - from the initial rough forging to the finished form. A machine tool removes material by using power to force one or more precisely shaped cutting tools into the work piece, this forces the base material to part creating a ‘chip’.


All the different metal removal techniques are in principle to be regarded the same as that of single point cutting - although in the case of grinding, multiples of these single points are employed at any one time.


Chip Formation and Movement -


As the cutting tool advances through the work piece, the metal ahead of the cutting tool edge is compressed resulting in temperatures high enough to permit plastic flow (shear) of the material in the form of a chip, this is then removed via the flow action to create what is commonly termed ‘swarf’. The swarf then escapes by sliding over the tool face, in the process creating strong frictional resistance - heat generation.


It is this friction resistance and heat generated that would normally necessitate the use of cutting fluids.


Basic Types of Chip Formation

Discontinuous chip Formation


When brittle metals (Cast Iron, Brass etc.) are machined, or when certain ductile metals are cut at low surface speeds, the metal may rupture ahead of the tool resulting in a discontinuous or segmented chip formation. This shearing action may generate high chip temperatures and shock to the tool face creating wear.



‘Ideal’ Continuous Chip


This type of chip is formed when the metal is removed continuously without rupture and flows smoothly over the tool face. This formation is most desirable from the standpoint of surface finish and tool life - being associated with relatively low friction between the chip and tool. Caution must however be taken, as long continuous strands of razor sharp swarf can prove to be a hazard, to this end ‘chip breakers’ are often employed on tool faces to break these continuous strands into more manageable formations.


Continuous Chip with built up edge


At the point of contact between chip and tool, extremes of temperature up to 1300ºC and pressures of up to 35,000 Kg/cm create ideal pressure-welding conditions. Under such circumstances high frictional resistance is encountered as the chip is formed and moves up the tool face. This action causes small particles of the chip to become welded to the tool and form the ‘built-up-edge’. This is most undesirable as it will rapidly lead to tool failures, machining difficulties, energy losses, all contributing to increased production costs.


Cutting Tool Materials


Cutting tools by nature must be harder than the material being machined in order to cut efficiently for an economical service life.


Principal materials used in cutting tools are described below:


High Carbon Steel (and cast alloy steel)


Application - Very slow cutting speeds and light duty operations.


The main disadvantage of this material being that it softens at temperatures above 250°C.


High Speed Steel


Application - Slow cutting speeds and light duty intermittent cut operations.


Limited to speeds and feeds that do not develop temperatures above 600°C.


Stellite (Cast non-ferrous alloys)


Application - Medium cutting speeds and heavy duty intermittent cutting.


This alloy is very heat resistant at temperatures above 600°C.


Cemented (Sintered) Carbides (e.g. Tungsten Carbide)


Application - High speed and heavy duty operations.


Being used at 1000°C plus.


Ceramics


Application - Very high speed and heavy duty non-intermittent operations.


Ceramics are not suitable for intermittent or vibration effected cuts due to their brittleness.


Carbide Ceramics (cermets)


Application - Very high speed and heavy duty operations


Primarily used for cast iron and lower grade Nimonics.


Selecting the correct neat cutting oil


Cutting tools wear out inversely to the operating temperature, even relatively small increases in temperature can quickly shorten the life of a cutting tool.


Tool Life = Constant Wear

                   Temperature


The machining process produces friction and heat thus we require a lubricant that will increase Tool Life.


We aim to produce an ‘Ideal’ Continuous Chip


The neat cutting oil used must:



Low viscosity oils - can penetrate and ‘wet’ the metal rapidly, with the appropriate additives they are carried to the cutting zone more quickly. Being thinner, these low viscosity oils cool quicker and in certain instances can help increase the ‘bite’ of the cutting tool.


High viscosity oils - have larger molecules giving the oil better lubricating properties with greater ability to maintain separation between the metal surfaces, however they do not flow and cool so well as low viscosity oils.


To enhance their working abilities, a selection of additives are employed to give specific performance abilities - depending upon the tasks required.


Neat cutting fluid additives



Neat oil characteristics


Hydrodynamic (Physical)


In this type of lubrication, the lubricant physically separates the two interacting metal surfaces i.e. cutting tool and the workpiece.  


While mineral oil on its own can in practice be used for very light work, additives are needed for most metal cutting operations.


Boundary (polar)


In boundary lubrication, polar materials are added to the mineral oil to cause an organic film to bond chemically to the metal surfaces of both the cutting tool and the workpiece.


Fatty materials have long been used as additives.  Fatty additives used today include oleine, synthetic esters, stearin, rapeseed oil and their derivatives, these remain effective at cutting tip temperatures of 100°C to 200°C.


Extreme pressure (EP - chemical)


Most cutting operations develop tool tip temperatures higher than the boundary temperature range, requiring the use of additives which will form films with a higher melting point.  Such additives are the inorganics, with the two commonly used elements used being chlorine and sulphur, chlorides - 600°C, sulphur 1000°C.


When sulphur and chlorine additives are used, a chemical reaction takes place between the metal surface and the additives, this produces a separating effect similar to dry lubrication by forming a low friction film to prevent wear and welding. Sulphur and chlorine are known as extreme pressure (EP) additives with chlorine normally added in the form of chlorinated paraffin, while sulphur may be incorporated more commonly as sulphurised fat.


Sulphurised fat can be made so that it is either ‘active’ or ‘inactive’.

this simply means that the effect it has on copper will stain in the ‘active’ form since it is in the free or dissolved state, whereas an ‘inactive’ oil will not stain copper as the sulphur is fully combined with the fat. Sulphur can also be incorporated simply by dissolving it in mineral oil or fat, but these are extremely active and are called ‘sulphured’.





      






















Consideration of the operation when selecting the neat oil


















If the machining operation is not arduous, the material being machined is free machining and the operation is being carried out at low speeds use straight neat oil containing antifoam, antioxidants and anti-misting additives


Improve the surface finish by using the above but include a polar fatty additive.

Should more difficult materials need to machined or you want to speed up the process use a fatty formulation + Extreme Pressure additive.


Note Chlorinated Paraffinic additives exhibit both polar and Extreme Pressure characteristics.


When even more difficult materials are cut use a sulphurised EP additive.  Do not use the sulphurised products on Beryllium copper alloys because you will stain the copper component.


Use of Chlorinated and Sulphurised additives often has a symbiotic affect and you will be able to machine at higher temperatures.  It is a case of 1 + 1 = 3 and not 2.


N.B. Extreme Pressure additives are only activated when the system reaches the operational temperature, thus if a wide temperature range is being encountered a combination of Fatty additive plus sulphur-chlorinated extreme pressure additives will produce the best surface finish and prolong tool life.






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