Operating grinding machines
Overview
This standard identifies the competences you need to carry out grinding operations, using machines such as horizontal or vertical surface grinding, external cylindrical, internal cylindrical, centreless, profile or thread grinding machines, in accordance with approved procedures. You will confirm with the machine setter that the machine is ready for the operations to be performed and that all the required components/materials and consumables are available. You will be expected to grind a range of components that combine a number of different features, such as parallel faces, flat faces, vertical faces, parallel, diameters, stepped diameters, tapered diameters, shoulders and faces, bores and counterbores, different thread forms and profiles.
You will be required to operate the machine in line with safe working practices and approved procedures, to continuously monitor the machining operations and, where necessary, make minor adjustments or seek the help of the setter to make the required adjustments, in order to ensure that the work output is to the required quality and accuracy. Meeting production targets will be an important issue, and your production records must show consistent and satisfactory performance.
Your responsibilities will require you to comply with organisational policy and procedures for the machining activities undertaken, and to report any problems with the machining activities that you cannot personally resolve, or are outside your permitted authority, to the relevant people. You will be expected to work to instructions, with a minimum of supervision, taking personal responsibility for your actions and for the quality and accuracy of the work that you produce.
Your underpinning knowledge will be sufficient to provide a sound basis for your work, and will enable you to adopt an informed approach to applying grinding procedures. You will have an understanding of the grinding machine used, the grinding process and its application, and will know about the equipment, materials and consumables in adequate depth to provide a sound background for carrying out the activities to the required specification.
You will understand the safety precautions required when working with the machine, its associated tools and equipment. You will be required to demonstrate safe working practices throughout, and will understand the responsibility you owe to yourself and others in the workplace.
Setting up of the machine, its tooling and associated workholding devices, is the subject of another standard and is the responsibility of the machine-tool setter.
Performance criteria
You must be able to:
- work safely at all times, complying with health and safety and other relevant regulations, directives and guidelines
- confirm that the machine is set up and ready for the machining activities to be carried out
- operate the machine tool controls safely and correctly in line with operational procedures
- produce ground components to the required quality and within the specified dimensional accuracy
- carry out quality sampling checks at suitable intervals
- deal promptly and effectively with problems within your control and report those that cannot be solved
- complete the required production documentation
- shut down the equipment to a safe condition on conclusion of the machining activities
Knowledge and Understanding
You need to know and understand:
- the safe working practices and procedures to be followed whilst operating grinding machines
- the safety mechanisms on the machine, and the procedure for checking that they function correctly
- operation of the machine controls in both hand and power modes
- how to stop the machine in both normal and emergency situations, and the procedure for restarting after an emergency
- the personal protective equipment (PPE) to be worn, and where this can be obtained
- the hazards associated with operating grinding machines and carrying out the grinding operations (such as moving machine parts, sparks/airborne particles, bursting grinding wheels, insecure workpiece), and how to minimise them and reduce any risks
- the importance of keeping the work area clean and tidy
- where to obtain the component drawings, specifications and/or job instructions required for the components to be machined
- how to extract and use information from engineering drawings and related specifications (to include symbols and conventions to appropriate BS, ISO or BSEN standards) in relation to work undertaken
- how to use imperial and metric systems of measurement
- the main features of the grinding machine, and the accessories that can be used
- the various grinding operations that can be performed, and the methods and equipment used
- the effects of backlash in machine slides and screws, and how this can be overcome
- the application of roughing and finishing cuts, and the effect on wheel life, surface finish and dimensional accuracy
- how to dress and reshape grinding wheels, and the equipment to be used
- the application of cutting fluids with regard to a range of different materials
- the effects of clamping the work piece in/on a chuck/work holding device, and how this can cause distortion in the finished components
- how to recognise machining faults and identify when wheels need dressing
- the quality control procedures used, inspection checks to be carried out, and the equipment that will need to be used
- the problems that can occur with the grinding activities, and how these can be overcome
- the extent of your own authority and to whom you should report if you have problems that you cannot resolve
Scope/range
Scope Performance
Apply all of the following during the machining activities:
- obtain and use the appropriate documentation (such as job instructions, drawings, quality control documentation)
- adhere to procedures or systems in place for risk assessment, COSHH, personal protective equipment and other relevant safety regulations and procedures to realise a safe system of work
- confirm with the machine setter that the machine is ready for production
- where appropriate, seek any necessary instruction/training on the operation of the machine
- ensure that machine guards are in place and are correctly adjusted
- hold components securely, without distortion
- follow the defined operating procedures and apply safe working practices and procedures at all times
- ensure that grinding wheels are maintained correctly dressed/formed and are in a usable condition
- ensure that machine settings are adjusted as and when required (either by yourself or the setter) to maintain the required accuracy
- ensure that the components produced meet the required specification for quality and accuracy
- leave the work area and machine in a safe and appropriate condition on completion of the activities
Operate one of the following types of grinding machine:
- horizontal surface
- external cylindrical
- universal
- thread grinding
- vertical surface
- internal cylindrical
- centreless
- profile grinding
Produce ground components which include three of the following features, as applicable to the type of machine used:
- flat faces
- parallel diameters
- other thread forms
- internal threads
- vertical faces
- tapered diameters
- vee-form threads
- external threads
- parallel faces
- counterbores
- left hand threads
- angular faces
- faces square to each other
- tapered bores
- right hand threads
- shoulders and faces
- parallel bores
- single start threads
- slots
- profile forms
- multi-start threads
Grind components made from one of the following types of material:
- ferrous
- non-ferrous
- non-metallic
Use appropriate gauges or instruments to carry out the necessary checks, during production, for accuracy of three of the following:
- dimensions
- profile
- surface texture
- parallelism
- concentricity
- angle/taper
- squareness
- thread form
- ovality/lobbing
Produce components with dimensional accuracy, form and surface texture within all the following standards as is applicable to the operations performed:
- tolerance to BS EN 20286 or BS 1916 Grade 5
- surface texture 8µin or 0.2µm
- angles within +/- 0.5 degree
- components to be free from false grinding cuts, burrs and sharp edges