Cutting Fluids Part 2 potx

cutting fluid, although certain non-ferrous metals

may have a susceptibility to staining, so here, it is

prudent to discuss the problem with the cutting

fluid manufacturer,

• Water-supply compatibility – a water-soluble cut￾ting fluid should ‘ideally’ be capable of being diluted

with any water supply. Geographical locations can

create variations in water supply and its condition,

this latter factor is especially true for water hardness

(i.e see Fig. 199b), where its hardness can vary quite

considerably. Thus, the ‘ideal’ cutting fluid would

not cause the typical problems of: foaming in soft

waters; or forming insoluble soaps in hard waters,

• Freedom from tacky, or gummy deposits – as water

soluble fluids dry out on a machine, or component’s

surface, the water content evaporates to leave a resi￾due which is basically the product concentrate. This

residue should ideally be light and wet, allowing

it to be easily wiped-off. However, any gummy, or

tacky deposits collect swarf and debris, necessitat￾ing increased machine and component cleaning,

• ‘Tramp oil’ tolerance – is a lubricating, or hydraulic

oil which leaks from the machine tool and contam￾inates the cutting fluid. Most modern machines are

equipped with ‘total-loss’  slideway lubricating sys￾tems which can contaminate the cutting fluid with

up to a litre of oil per day – on a large machine tool.

The ‘ideal’ cutting fluid would be capable of toler￾ating this contamination without any detrimental

effects on its operating performance. Some cutting

fluids are formulated to emulsify the ‘tramp-oil’,

while other fluid formulations reject it, allowing

 ‘Total-loss’ fluid systems, are as their name implies in that they

purposely leak oil to the machine’s bearing surface, requiring

periodic tank replenishment. When this oil leaks-out of the

machine tool it is termed: ‘tramp-oil’, therefore the oil will

eventually end up in the machine tool’s coolant tank, where it

is either tolerated by the coolant product, or is separated-out,

requiring periodic ‘tramp-oil skimming’.

NB ‘Tramp-oil’ losses are invariably not accounted for in

many production shops, which invariably means their ‘eco￾nomic model’ for such losses are habitually not considered,

or not even thought about by the company. It has been re￾ported that on a quite ‘large-sized’ horizontal machining cen￾tre, it can lose up to 365 litres of ‘tramp-oil’ per annum, which

is an on-going cost that needs to be addressed. Multiply this

individual machine tool loss by the number of machines in

the manufacturing facility and this will represent considerable

unaccounted for expenditure!

the residual ‘tramp-oil’ to float to the surface for re￾moval by physical ‘skimming’,

• Cost-effectiveness – but what does this term mean?

There was a time when the cost-effectiveness was

simply judged in terms of the price per litre of the

product concentrate. Fortunately, there are only

few engineering companies who still take this view,

with most recognising that there are many inter￾related factors that contribute to cost-efficiency.

Some of these factors might be the: dilution ratio;

sump-life; material versatility; tool life; machined

component quality; health and safety aspects; plus

many others.

Having identified the ‘ideal’ cutting fluid features, one

must unfortunately face reality, as there is no such

product that encompasses all of these desirable charac￾teristics – at the optimum level in just one cutting fluid

product. However, all cutting fluids are not equal and

even apparently similar products may well perform in

quite different ways! Therefore, it is for the machine￾shop supervisors/managers – in conjunction with

other interested parties: purchasing; health and safety;

unions; etc., to select a reputable supplier who is pre￾pared to undertake the necessary survey and ‘trouble￾shooting’ exercise to recommend the best fluid(s) for a

particular manufacturing environment.

Today, there are many different types of cutting

fluids available they can be classified according to

widely varying criteria, although some unified system

of terminology exists in various countries guidelines

and Standards. This commonality of ‘language’ reflects

both the chemical and technical requirements of the

users. On the basis of the various countries publicised

cutting fluid literature, the following classification

is perhaps the most useful – from the user’s point of

view. Broadly speaking, it was previously shown in Fig.

197, that cutting fluid groups are of two main types,

either ‘oil-’, or ‘aqueous-based’. The ‘aqueous’ cutting

fluids can be divided into ‘emulsifiable’ and ‘water-sol￾uble’ types. As has already been mentioned, the former

‘oil-based’ cutting fluids are supplied as ready-for-use

products, while ‘aqueous’ types are normally found in

the form of a concentrate, which must be mixed with

water, prior to use. Once mixed with water, the ‘emulsi￾fiable’ cutting fluids form an emulsion, conversely, the

‘soluble’ variety forms a solution. In both of these cases,

the resultant cutting fluid product is termed: ‘water￾mixed’. In the following section, the various types of

cutting fluids currently available will be briefly men￾tioned.

Cutting Fluids 391