Flashcards
1 of 35
Machining | Definitions
Deck complete
You’ve reviewed 35 terms. Keep up the good work!
tap to flip
Print
Machining | Definitions
Tolerance
The extent by which a dimension is allowed to deviate from the nominal or basic size.
Allowance
Allowance is the planned distance between two parts that assemble together. Allowance between parts that are assembled is very important.
Fit
Fit is the degree of tightness or looseness between two parts that assemble. The three main types of fit are clearance fit, interference fit and transition fit. When parts need to fit together you must take the tolerances of both parts into account.
Selective Assembly
Selective assembly is used to create tighter fits without having to pay more for small-tolerance manufacturing. Parts are manufactured cheaply to large tolerances (often transition fits). Manufactured parts are then graded into different-sized groups. Parts from similar-sized groups are tested and matched for fit.
Reamer
A type of rotary cutting tool used to enlarge the size of a previously formed hole by a small amount with a high degree of accuracy.
Forming
When the surface produced is a copy of the tool producing it. Form tools are customised to the profile of the part. A single plunge can machine a complex shape.
Generating
The use of a single-point cutting tool to machine a complex shape. The tool moves in various directions until the required surface is machined.
Gang Milling
When milling cutters are mounted side by side on the arbor. This may be used to mill a complex shape in one pass. The cutting profile is generated by the size and shape of the cutter.
Straddle Milling
The milling cutters are mounted on the arbor and are separated by a spacing cutter. This is used to mill two surfaces that are parallel to each other.
Plain Milling
The milling of a flat surface with the axis of the cutter parallel to the machining surface.
End Milling
The milling of a flat surface with the axis of the cutter perpendicular to the machining surface.
Up Cut Milling
When the cutter rotates in a direction opposite to the table feed.
Down Cut Milling
When the cutter rotates in the same direction as the table feed. This is also known as climb milling.
Plug Gauge
Used to accurately determine if a hole is within a specific range of limits.
Snap Gauge
Sometimes called a gap gauge, it is used to accurately check if an external diameter is within a specific range of limits.
Telescopic Gauge
Used to measure a gap or internal diameter that may be hard to reach with a conventional device.
Slip Gauges
Small blocks of alloy steel or tungsten carbide that are manufactured in a variety of precise sizes. They can be stacked to a specific size and can be used to check for accuracy or to calibrate instruments. The blocks are joined together by a sliding process called 'wringing'.
Clearance Fit
The shaft is smaller than the part it fits into. There is a space to allow the parts to fit together easily.
Interference Fit
The shaft is larger than the part it is intended to fit. The parts will have to be forced together.
Transition Fits
This is a range of fits that can be either clearance or interference. The tolerance areas overlap.
Countersinking
Enlarging the mouth of a hole to allow countersink screw heads to sit flush with the surface of the piece.
Counterboring
Increasing the diameter of the hole to a certain depth to allow a cheese head screw to lie flush with the surface of the piece.
Pilot Hole
A hole is drilled before a larger hole is drilled, giving the larger hole a centre to start.
Tapping Size Hole
A hole drilled prior to threading. The hole is always smaller than the tap to be used. The pitch of the thread will determine the size of the tapping size hole.
Rake Angle
The angle of the cutting face relative to the workpiece. It facilitates the lifting of the chip during cutting and can be positive, negative or zero.
Clearance Angle
Formed to allow one point of the cutting tool to contact the workpiece.
Lubricant
Reduces/eliminates heat caused due to friction.
Cutting Fluid
Used to cool and lubricate the cutting region while machining as well as carrying away the chips produced. The use of cutting fluids improves surface finish and reduces tool wear.
Rancidity
The cutting fluid can become rancid by dirt, bacteria and other microscopic organisms growing, eventually causing bad odours to form.
Surface Grinding
A metal cutting process in which flat and extremely smooth surfaces are produced.
Loading
In relation to the grinding wheel, this is when small particles of grinding debris become trapped in the space between the abrasive grains and the wheel.
Glazing
When a grinding wheel has a shiny appearance due to the abrasive particles having lost their edge and failed to break away from the wheel.
Dressing
In the grinding process, wheel dressing restores the cutting surface. The dressing tool creates a new cutting surface by dislodging debris and worn grains and exposing new fresh cutting grains. It also makes the wheel concentric (fully round) which improves surface finish and reduces vibrations.
Fixed Steady
In lathe work, this provides support for lengthy work which needs an intermediate support to prevent whip or wobble. This is useful where long lengths of bar are being machined at either end and need to be securely supported.
Vee Block and Clamp
Precision metalworking jigs typically used to hold round metal rods or pipes for performing drilling or milling operations.
Cut dotted horizontal lines. Fold vertical line.
Tolerance
The extent by which a dimension is allowed to deviate from the nominal or basic size.
Allowance
Allowance is the planned distance between two parts that assemble together. Allowance between parts that are assembled is very important.
Fit
Fit is the degree of tightness or looseness between two parts that assemble. The three main types of fit are clearance fit, interference fit and transition fit. When parts need to fit together you must take the tolerances of both parts into account.
Selective Assembly
Selective assembly is used to create tighter fits without having to pay more for small-tolerance manufacturing. Parts are manufactured cheaply to large tolerances (often transition fits). Manufactured parts are then graded into different-sized groups. Parts from similar-sized groups are tested and matched for fit.
Reamer
A type of rotary cutting tool used to enlarge the size of a previously formed hole by a small amount with a high degree of accuracy.
Forming
When the surface produced is a copy of the tool producing it. Form tools are customised to the profile of the part. A single plunge can machine a complex shape.
Generating
The use of a single-point cutting tool to machine a complex shape. The tool moves in various directions until the required surface is machined.
Gang Milling
When milling cutters are mounted side by side on the arbor. This may be used to mill a complex shape in one pass. The cutting profile is generated by the size and shape of the cutter.
Straddle Milling
The milling cutters are mounted on the arbor and are separated by a spacing cutter. This is used to mill two surfaces that are parallel to each other.
Plain Milling
The milling of a flat surface with the axis of the cutter parallel to the machining surface.
End Milling
The milling of a flat surface with the axis of the cutter perpendicular to the machining surface.
Up Cut Milling
When the cutter rotates in a direction opposite to the table feed.
Down Cut Milling
When the cutter rotates in the same direction as the table feed. This is also known as climb milling.
Plug Gauge
Used to accurately determine if a hole is within a specific range of limits.
Snap Gauge
Sometimes called a gap gauge, it is used to accurately check if an external diameter is within a specific range of limits.
Telescopic Gauge
Used to measure a gap or internal diameter that may be hard to reach with a conventional device.
Slip Gauges
Small blocks of alloy steel or tungsten carbide that are manufactured in a variety of precise sizes. They can be stacked to a specific size and can be used to check for accuracy or to calibrate instruments. The blocks are joined together by a sliding process called 'wringing'.
Clearance Fit
The shaft is smaller than the part it fits into. There is a space to allow the parts to fit together easily.
Interference Fit
The shaft is larger than the part it is intended to fit. The parts will have to be forced together.
Transition Fits
This is a range of fits that can be either clearance or interference. The tolerance areas overlap.
Countersinking
Enlarging the mouth of a hole to allow countersink screw heads to sit flush with the surface of the piece.
Counterboring
Increasing the diameter of the hole to a certain depth to allow a cheese head screw to lie flush with the surface of the piece.
Pilot Hole
A hole is drilled before a larger hole is drilled, giving the larger hole a centre to start.
Tapping Size Hole
A hole drilled prior to threading. The hole is always smaller than the tap to be used. The pitch of the thread will determine the size of the tapping size hole.
Rake Angle
The angle of the cutting face relative to the workpiece. It facilitates the lifting of the chip during cutting and can be positive, negative or zero.
Clearance Angle
Formed to allow one point of the cutting tool to contact the workpiece.
Lubricant
Reduces/eliminates heat caused due to friction.
Cutting Fluid
Used to cool and lubricate the cutting region while machining as well as carrying away the chips produced. The use of cutting fluids improves surface finish and reduces tool wear.
Rancidity
The cutting fluid can become rancid by dirt, bacteria and other microscopic organisms growing, eventually causing bad odours to form.
Surface Grinding
A metal cutting process in which flat and extremely smooth surfaces are produced.
Loading
In relation to the grinding wheel, this is when small particles of grinding debris become trapped in the space between the abrasive grains and the wheel.
Glazing
When a grinding wheel has a shiny appearance due to the abrasive particles having lost their edge and failed to break away from the wheel.
Dressing
In the grinding process, wheel dressing restores the cutting surface. The dressing tool creates a new cutting surface by dislodging debris and worn grains and exposing new fresh cutting grains. It also makes the wheel concentric (fully round) which improves surface finish and reduces vibrations.
Fixed Steady
In lathe work, this provides support for lengthy work which needs an intermediate support to prevent whip or wobble. This is useful where long lengths of bar are being machined at either end and need to be securely supported.
Vee Block and Clamp
Precision metalworking jigs typically used to hold round metal rods or pipes for performing drilling or milling operations.