A guide to guarding
Small machine tool used in machine workshops (3rd Edition)
Workshops are encountered in a diverse range of industrial, commercial, educational and other establishments, not just within the manufacturing industries. While some workshops contain a considerable number and variety of machines, others have little more than a drill, a press and a set of hand tools. In all cases, however, it is important to ensure that the machinery is adequately guarded, as machinery is frequently involved with accidents resulting in minor, serious and even fatal injuries. Statistics form the HSE underline the fact that the hazards often translate into real accidents. HSE statistics for 2009/10 show that contact with moving machinery was responsible for significant numbers of injuries and fatalities in the manufacturing industries alone. Not all of these will have involved workshop machinery, but the figures nevertheless highlight how dangerous machinery can be:
- 1542 out of 15,047 over-three-day injuries (10%)
- 599 out of 4,015 non-fatal major injuries (15%)
- 2 out of 23 fatalities (9%)
In fact, the number of non-fatal injuries is likely to be much higher than these figures suggest, as it is estimated that just over half of non-fatal injuries to employees are actually reported, with the self-employed reporting an even smaller proportion. Source: HSE statics for 2009/10 If the moral argument is not, in itself, a sufficient reason to guard machinery, it should be borne in mind there are also regulatory requirements relating to the safety of machinery and work equipment. Furthermore, the costs associated with an accident are likely to exceed by far the cost of providing guarding. Fortunately, the subject of machine guarding is well understood by specialist suppliers, so stakeholders need not worry that their guarding requirements will be difficult to meet; virtually all standard machine types have been equipped with suitable guarding at some time, and bespoke guards for non-standard machinery can be manufactured and installed very cost-effectively. This present guide is not intended to be a comprehensive treatise on health and safety in workshops; rather it provides advice and guidance relating to the safeguarding of the physical hazards presented by machine tools typically found in workshops within the UK. Note that special cases – such as woodworking machinery and power presses – are excluded, as are welding and cutting equipment, portable power tools, lifting equipment, and degreasing, painting and finishing equipment. Stakeholders are advised to assess health and safety issues relating to these too, as the hazards can be at least as severe as those relating to basic machine tools.
Guarding: Costs and Benefits
Where, for example, guarding has been removed for machine maintenance and not replaced, rectifying this situation is straightforward and costs almost nothing. However, it is inevitable that most machinery that is inadequately guarded will need money to be spent in order to bring it up to an acceptable standard. Spending on health and safety is occasionally viewed as an investment that gives little or no returns, but working out what the cost of an accident would be can show the opposite to be true: accidents are extremely costly in terms of lost time, lost production, sick leave, fines, legal costs, increased insurance premiums, and so on. These costs alone could easily amount to tens of thousands of pounds.
A company was fined £500 and ordered to pay costs of £2,287.76 after an employee’s little finger was amputated in the unguarded rotating part of the pedestal drill. The employee was using the machine to de-burr holes when his cotton glove became caught in the tool. The HSE brought a charge against the company under Regulation 11(1) of the Provision and Use of Work Equipment Regulation 1998 and the court found that the company had failed to ensure that effective measures were taken in order to present access to dangerous parts of machinery during the de-burring task.
Regulation and Legislation
Safeguarding of workshop machinery is covered in various ways by the following:
- The Health and Safety at Work etc Act 1974
- The Supply of Machinery (Safety) Regulations 2008
- The Provision and Use of Work Equipment Regulations 1998
- The Management of Health and Safety at Work Regulations 1999
In addition, residual risks are often managed using PPE (Personal Protective Equipment), which is covered by The Personal Protective Equipment at Work Regulations 1992. (as amended) Machinery almost always generates noise; while emissions from individual machines are covered by The Supply of Machinery (Safety) Regulations, noise in working environments is additionally covered by The Noise at Work Regulations 1989. Numerous British, European and International standards provide information about safeguarding machinery (see below). While compliance with the standards is not compulsory, doing so will normally be sufficient to satisfy the necessary legal requirements. There are also official guidance documents and codes of practice that should be consulted and complied with as appropriate.
Machine Workshops in Schools and Colleges
Machine workshops in schools and colleges present a particular challenge due to the young, inexperienced and occasionally foolish nature of the students using or observing operations. BSI has therefore published BS 4163:2007, Health and Safety for design and technology in schools and similar establishments – Code of practice. This covers the full spectrum of health and safety, including machine guarding. Machines in educational establishments are typically not used as much as their equivalents in production environments, so older machines may continue to be used for longer. If still fitted with their original guards and safety-related control systems – or even if they have been upgraded – older machines might, therefore, have safeguards that are not up to the current standards. Establishments with older machinery should, therefore, take note of BS 4163 subclause 2.3, which states that the phrases ‘as far as reasonably practicable’ and ‘adequate control’ should be understood to mean that up-to-date good practice is applied as appropriate. Fortunately, subclause 2.3 also goes on to clarify how far establishments should go in applying control measures. Schools, colleges and similar establishments fall within the scope of the Health and Safety at Work etc Act 1974, the Management of Health and Safety at Work Regulations 1999 and the Provision and Use of Work Equipment Regulations 1992. Although there is no legal requirement to comply with the Code of practice BS 4163, doing so demonstrates that reasonably practicable steps have been taken to minimise the risks from machinery and other hazards.
General Requirements for Machine Guards
Most machine-related accidents involve operators loading or unloading components, removing swarf, taking measurements or making adjustments (e.g to the coolant supply). On manually-operated machines, operators are typically injured by the moving tool. Automatic and CNC machines also present hazards through movement of machine elements. Injuries range from minor cuts and abrasions through to eye injuries, broken bones, dislocations and amputations (fingers and hands are not infrequently lost). Fatalities can also occur, often arising from hair or loose clothing becoming entangled with moving machinery. Many of these incidents can be prevented by means of fixed guards, often in conjunction with jigs and fixtures (to make loading and unloading of components safer), and safe means of setting up, removing swarf, taking measurements and making adjustments. Note that measures can either prevent access to dangerous parts or prevent access until such time as the parts are no longer dangerous (e.g on machinery that has a run-down time). Regulation 11(2) of PUWER 98 specifies the measures that should be taken to prevent access to dangerous parts of machinery. These measures should be adopted, where practicable, in the following order: (a) fixed enclosing guards; (b) other guards or protection devices such as interlocked guards and pressure mats; (c) protection appliances such as jigs, holders and push-sticks; and (d) the provision of information, instruction, training and supervision. If a workshop contains machinery that is known or suspected of having inadequate guarding, then this should be addressed as a priority. And although all workshops should by now have undertaken a PUWER assessment, with the risks assessed and recorded for each item of machinery and work equipment, it is possible that the assessments have not been kept up to date or were never performed at all. When looking at machinery, bear in mind that older machines might have their original guards in place but these might not meet today’s standards – especially if the machinery was built prior to 1992 (when PUWER was first introduced) or 1995 (when the Machinery Directive was first introduced). Beware of machinery that has had safety-related modifications carried out in the past, as the state of the art may have evolved further since the time of the modifications. In addition, pay particular attention to machinery that has been bought second-hand, either as an item of equipment in its own right or as an asset of a business that has been required. Look closely at all machinery to see whether guards have been damaged or discarded a not repaired or replaced. If the original guards are reinstated or new guarding installed, check that all controls can still be accessed and that the lighting is adequate for the machinery as it is currently being used. Just because a machine has, say, a safety interlock on a movable guard, do not assume that this provides adequate safety. Some interlocks are easier to override or bypass than others, so both the type of interlock and the associated safety circuits need to be checked. Machinery that has been upgraded – such as with CNC – warrants close attention, and do not neglect non-powered equipment such as fly presses, treadle guillotines and hand-operated folding machines. In addition, assess all of the machinery that is located outside the workshop (e.g in a research laboratory, assembly area or tool room). Guards must be well designed so that provide good visibility, access to controls, and do not hinder operation, setting or maintenance of the machine. Applying these principles will minimise the temptation to override or bypass guards and interlocks. Note that retrofitted guards should not introduce new hazards (unless those hazards are very minor in comparison with the hazards being safeguarded). Before carrying out any work on machinery guarding or safety measures, perform a risk assessment and ensure that the following are taking into account: the intended use of the machinery; how the machine is likely to be used; how the machine might be misused; the people likely to use the machine, and their skills. For more information about risk assessments, see the Risk Assessment Calculator. Finally to the general requirements outlined above, the following notes will help to ensure that guarding is adequate on specific types of machine likely to be found in workshops.
For manually operated bench or pillar frills, telescopic guards are often a simple and cost-effective way of preventing access to the dangerous parts and also helping to contain swarf. When the drill is not operating, such guards provide good access to the chuck, drill bit and workpiece, which should normally be held securely by means of a vice or jig/fixture (serious injuries can result from loose workpieces that spin after the drill bit has become jammed or that ride up the drill when it breaks through). Note that most accidents with drilling machines occur at the drill tip when it is in its uppermost position and the operator is removing the workpiece or securing the next; guarding of the drill (in addition to the chuck and spindle) can therefore provide a high standard of protection without obstructing the view of the workpiece or otherwise interfering with production. Where practicable, guards should be used in preference to trip devices, as trip devices merely reduce the severity of the injury and do not prevent entanglement with the rotating parts of the drilling machine. Manually operated drilling machines may be used for producing various batch sizes. Depending on the batch size and the component dimensions, it might be appropriate to install a fixed guard, together with other measures to keep the operator’s hands away from the dangerous parts – such as a feed magazine and discharge slide. If the drill speed is altered by means of gears or an arrangement of pulleys and belts, the corresponding guard should be electrically interlocked to prevent the machine from starting while the guard is open. Radial arm drilling machines are often best safeguarded using fixed, adjustable guards. A vertical tripping device linked to DC injection braking may also be required, depending on the application and hazards. Some older types of radial drilling machines have horizontal and vertical shafts that transmit the drive to the drill, rather than the more modern arrangement of a motor built into the saddle. These exposed shafts should be protected using telescopic guards. Small CNC drilling machines are best protected using fixed guards and interlocked movable guards. If access to the moving machine is required during setting, then it should be equipped with a hold-to-run device and the movements should have their speed restricted to a safer level. Because of the nature of drilling work, operators are often tempted to wear gloves to protect against cuts and contact with cutting fluids. However, wearing gloves when drilling greatly increases the risk and severity of injuries; the HSE claims that nearly half of all accidents at drilling machines involve gloves becoming entangled. It is therefore recommended that other hand-care measures should be sued (such as carefully selected cutting fluids and the provision of barrier creams and after-work conditioning creams) or, if gloves are still felt to be necessary, particular care should be taken in designing and maintaining protective measures. In addition, gloves should be selected that are less likely to become entangled or, if they do, tear easily.
For manual horizontal milling machine, a combination of fixed guards and adjustable (using tools) fixed guards is likely to be the most appropriate safeguard. A false table can help to restrict access to the cutter. On horizontal and vertical milling machines used for one-off or batch production, a combination of fixed and interlocked moveable guards is likely to be the optimum safety measure. Alternatively, an adjustable table guard may be adequate. Either way, the guards should still give good process visibility when closed and clear access when opened. If the machine has a manual quill feed arm, the guard should provide access to this as well. CNC milling machines and machining centres are best equipped with fixed guards and interlocked moveable guards to prevent access to all dangerous parts (not just cutters). If access to the machine is required with the guards open (e.g during setting), then a hold-to-run control should be used to enable the machine to operate at safe slow speeds. If workpiece transfer devices, automated tool changers or swarf collection/removal systems operate in conjunction with the milling machine or machining centre, then these must be adequately guarded too.
Vertical Boring Machines
In many respects, vertical boring machines are similar to milling machines, as borne out by the fact that both are covered by the same machinery safety standard, BS EN 13218 (see the table of standards below). As with milling machines, the safeguards tend to be very different, depending on whether the machine is operated manually or automatically by means of NC or CNC. Typically manual machines require close-fitting guards that do not hinder access to the controls, while NC / CNC machines are fully enclosed. Additional safeguards may also be necessary for other hazardous parts of the machine such as swarf conveyors and automatic tool changers.
The optimum safeguards for lathes depend on the model size of a lathe, as well as the type and size of chuck and workpiece. In most cases, a fixed guard will be required at the rear of the machine, plus there will need to be a means of guarding the chuck and feed dead screws. Guards can be mounted on the headstock or saddle, and they are usually interlocked so as to stop the lathe in the event of the guard being opened In addition, protective screens (something referred to as chip guards) can prevent swarf and coolant being ejected out of the machine. If equipped with a magnetic base and adjustable support, this type of protective screen can be located easily in the optimum position. CNC lathes normally benefit from a combination of fixed guards and sliding interlocked guards. If access to the lathe is necessary with the guards to open, it should be equipped with a hold-to-run device that enables safe, slow-speed operation. Note that it is also important to guard any stock bar projecting beyond the headstock.
Grinding machines are often installed in workshops for offhand grinding and tool sharpening. As well as protecting the operator from contact with the moving wheel, the guarding must also contain fragments in the event of the wheel bursting. Typically the guarding on a pedestal grinding machine will be upgraded by adding an adjustable protective screen with a clear viewing panel.
Manually-fed, pivoting-head circular saws can cause injuries when workpieces are fed into, adjusted in or retrieved from the saw. Guards should prevent access to the saw blade when the saw head is in the raised position, and minimise the amount of the blade that is exposed during cutting. Self-adjusting guards using mechanical linkages are preferred; blade guards that rely on gravity for their adjustment are not considered to be fully effective. If a mechanically linked guard cannot be installed, a hold-to-run control should be mounted on the operating handle so that when the handle is released to power to the saw blade is removed. Alternatively, if the saw is only used for one operation and rarely requires resetting, then fixed guards can be attached to the machine table.
Note: The following information applies on to hand- and foot-operated presses. Powered press is not covered here, as they are a special case with particular requirements due to the nature of the hazards they present. Where practicable, fixed guards or closed tools should be used to prevent access to dangerous parts, yet it must remain possible to feed the workpiece into and out of the press. As an alternative, devices can be used to restrict the maximum opening. If the measures outlined above are insufficient to prevent access to all dangerous parts, interlocked guards can be used to prevent the tool from closing unless the guard is closed. Should none of the above be practicable, other devices may be used; for example, sweep-away guards can be set so as to sweep across the area in front of the tool as the press operates, thereby either moving the operator’s (or other person’s fingers) out of the way or stopping the press.
Other Measures Relating to Machinery Safety
While this guide is focused on machinery guarding, it is pertinent to mention other machine-related issues to be aware of in workshops.
- Training, operating procedures and the availability of machine instructions
- Machine-generated noise
- Machine-generated vibration
- Coolants and other chemicals that can cause skin diseases
- Dusts and fumes that can cause respiratory and eye diseases
- Chips and swarf that can cause eye injuries
- Sharp tools, workpieces and swarf
- Hot tools and workpieces
- Lifting of heavy workpieces and tooling
- Maintenance and periodic inspection of safety-related equipment
- Warning signs
- Housekeeping (e.g clearing away spilt coolant or lubricants, and tidying trailing cables and other trip hazards)
- Working alone
There is an extensive range of British, European and International standards that may be applicable to machine guarding in workshops. This present guide cannot advise which standards apply in particular situations; it is the stakeholder’s duty to ensure the health and safety of employees and others in the workshop. Remember that compliance with standards is not mandatory, though doing so will usually be sufficient to meet the necessary legislative requirements. Download Free Guide to Machinery Guarding Standards.
All can be downloaded from www.machinesafety.co.uk/free-downloads/free-machine-safety-guides or email [email protected]
Free Risk Assessment Calculator Based on the requirements of BS EN ISO 12100 and designed to be simple to use.
Free Safety Distance Calculator Establishes machine guard safety distances and heights in accordance with BS EN ISO 13857.
Free Guide to the New Machinery Directive 2006/42/EC To help companies comply with the Directive that came into force on 29 December 2009.
Free White Paper: Machinery Directive and Fixings for Fixed Guards Explaining the amended requirements for Guard Fixings under the new Machinery Directive.
Free White Paper: CE Marking of Machine Guards Explaining the requirements relating to CE marking of guards under the Machinery Directive.
Free White Paper: EN 349, Minimum Gaps to Avoid Crushing Explaining the requirements of the standard for minimum gaps to prevent crushing.
Free White Paper: Differences Between BS EN 953 and BS EN ISO 14120 Explaining what changes have been introduced in BS EN ISO 14120, which replaces and supersedes BS EN 953.
Free White Paper: Conveyor Guarding Explaining the hazards associated with conveyors, regulations and standards, and how to safeguard conveyors without adversely affecting productivity.
Free White Paper: The 2014 Edition of PD 5304 Explaining the changes in the new edition of BSI’s Guidance on the safe use of machinery.
Free Guide to Work Shop Safety A guide to guarding small machine tools typically used in workshops.
Free Machine Accident Investigation Kit To help companies meet their statutory obligations and prevent future accidents.
Free Ergonomics Guidance European Commission publication Guidance on the application of the essential health and safety requirements on ergonomics. Download: http://eceuropa.eu/growth/sectors/mechanical-engineering/machinery/index_ex.htm