MECHANICAL INSTRUMENTS, GAUGES AND TOOLS
VERNIER CALIPER:
Parts of a vernier caliper:
1. Outside jaws: used to measure external diameter or width of an o bject 2. Inside jaws: used to measure internal diameter of an object o bject 3. Depth probe: used to measure depths of an object o bject or a hole 4. Main scale: scale marked every mm 5. Main scale: scale marked in inches and fractions 6. Vernier gives interpolated measurements to 1/10 mm or better 7. Vernier gives interpolated measurements in fractions of an inch 8. Retainer: used to block movable part to allow the easy transferring o f a measurement The vernier, dial, and digital calipers give a direct reading of the distance measured to high accuracy. They are functionally identical, with different ways of reading the result. These calipers comprise a calibrated scale with a fixed jaw, and another jaw, with a pointer, that slides along the scale. The distance between the jaws is then read in different ways for the three types. The simplest method is to read the position of the pointer directly on the scale. When the pointer po inter is between two t wo markings, the user u ser can mentally interpolate to improve the precision of the reading. This would be a simple calibrated caliper; but the addition of
avernier scale allows more accurate accurat e interpolation, and is the universal pract ice; this is the vernier caliper. Vernier, dial, and digital calipers can measure internal dimensions (using the uppermost jaws in the picture at right), external dimensions using the pictured lower jaws, and in many cases depth by the use of a probe that is attached to the movable head and slides along the centre of the body. This probe is slender and can get into deep grooves that may prove difficult for other ot her measuring tools. The vernier scales may include metric measurements on the lower part of the scale and inch measurements on the upper, or vice versa, in countries that use inches. Vernier calipers commonly used in industry provide a precision to a hundredth of a millimetre (10 micrometres), or one thousandth of an inch. They are available in sizes that can measure up to 72 in (1,800 mm).
MICROMETER:
Outside, inside, and depth micrometers
A micrometer, sometimes known as a micrometer screw gauge, is a device incorporating a calibrated screw used widely for precise measurement of small distances in mechanical
engineering and machining as well as most mechanical trades, along with other metrological instruments such as dial, vernier, and digital calipers. Micrometers are often, but not always, in the form of calipers.
DIAL INDICATOR:
Dial indicato rs, also also known as a s dial gauges gauge s and probe indicators, are instruments used to accurately measure small linear distances, and are frequently used in industrial and mechanical processes. They are named so because the measurement results are displayed in a magnified way by means of a dial. A special variety of o f the dial indicator indicato r is the dial test indicator (DTI) which is primarily used in machine setups. The DTI measures displacement at an angle of a lever or plunger perpendicular to the axis of the indicator. A regular dial indicator measures linear displacement along that axis. Dial indicators may be used to check the variation in tolerance during the inspection process of a machined part, measure the deflection of a beam or ring under laboratory conditions, as well as many other situations where a small measurement needs to be
registered or indicated. Dial indicators typically measure ranges from 0.25 mm to 300 mm (0.015 in to 12.0 in), with graduations of 0.001 mm to 0.01 mm (metric) or 0.00005 in to 0.001 in (imperial ( imperial). ).
SINE BAR:
A sine bar is a tool used to t o measure angles in metalworking. It consists of a hardened, precision ground body with two precision ground cylinders fixed at the ends. The distance between the centers of the cylinders is precisely controlled, and the top of the bar is parallel to a line through the centers of the two rollers. The dimension between the two rollers is chosen to be a whole number (for ease of later calculations) and forms the hypotenuse of a triangle when in use. The image shows a 10 inch and a 100 mm sine bar, however, in the U.S., 5 inch sine bars are the most commonly used. When a sine bar is placed on a level surface the top edge will be parallel to that surface. If one roller is raised by a known distance, usually using gauge blocks, then the top edge of the bar will be tilted by the same amount forming an angle that may be calculated by the application of the sine rule.
The hypotenuse hypot enuse is a constant d imension imension ² (100 (1 00 mm or 10 inches in the examples shown).
The height is obtained from the dimension between the bottom of one roller and the table's surface.
The angle is calculated by using the sine rule. Some engineering and metalworking reference books contain tables showing the dimension required to obtain an angle from 090 degrees, incremented by 1 minute intervals.
GO/NO GO GAUGE: A Go-NoGo gauge (or Go/no go) refers to an inspection tool used to check a workpiece against its allowed tolerances. Its name derives from its use: the gauge has two tests; the check involves the workpiece having to pass one test (Go) and fail the other (No Go). It is an integral part of the quality process that is used in the manufacturing industry to ensure interchangeability of parts between processes, or even between different manufacturers. A Go NoGo gauge is a measuring tool that does not return a size in the conventional sense, but instead returns a state. The state is either acceptable (the part is within tolerance and may be used) or it is unacceptable (and must be rejected). They are well suited for use in the production area of the factory as they require little skill or interpretation to use effectively and have few, if any, moving parts to be damaged in the often hostile production environment.
PLUG GAUGE:
Hardened and ground plug gauge
Replaceable thread and plug gauges
These gauges are referred to as plug gauges; they are used in the manner of a plug. They are generally assembled from standard parts where the gauge portion is interchangeable with other gauge pieces (obtained from a set o f pin type gauge blocks) and a body that uses the collet principle to hold the gauges firmly. To use this style of gauge, one end is inserted into the part first and depending on o n the result of that test, the other ot her end is tried. In the right hand image, the top gauge is a thread gauge that is screwed into the part to be tested, the labeled GO end will enter into the part fully, the NOT GO end should not. The lower image is a plain plug gauge used to check the size of a hole, the green end is the GO, red is the NO GO. The tolerance of the part this gauge checks is 0.30mm where the lower size of the hole is 12.60mm and the upper size is 12.90mm, every size outside this range is out of tolerance. This may be initially expressed on the parts drawing in a number of styles, three possibilities may be:
12.75mm +/- 0.15mm
12.60mm +0.30 -0.00
12.90mm +0.00 -0.30
SNAP GAUGE:
Snap go/no go gauge for the OD of a cylindrical workpiece
Thread snap gauge
Snap gauges are oftentimes used when a large quantity of workpieces must be inspected. The snap gauge has fouranvils or jaws, the first one or pair (outermost) are set using the upper limit (tolerance) of the part and the inner set adjusted to the lower limit of the part. A correctly machined part will pass the first set of jaws and stop at the second ² end of test. In this manner a part may be checked in one action, unlike the plug gauge that needs to be used twice and flipped to access the second gauge.
THREAD PITCH GAUGE:
Three different sets of threading gauges
Threading gauges, pictured on the right, are also referred to as pitch gauges and are used to measure the pitch or lead of screw threads. The uppermost gauge in the image is an ISO metric pitch gauge, the larger gauge in the center is for measuring the Acme Thread Form, and the lower gauge is for imperial screws. Thread pitch gauges are used as a reference tool in determining the pitch of a thread that is on a screw or in a tapped hole. This tool is not used as a precision measuring instrument. This device allows the user to determine the profile of the given thread and quickly categorize the thread by shape and pitch. This device also saves time, in that it removes the need for the user to measure and calculate the t he thread pitch of the threaded item. SCREW GUN:
A DeWalt screw gun powered by mains.
A screw gun is a tool used to install sheetrock, also known as drywall. Screw guns look like a normal drill although they have a "nose" as opposed opp osed to a chuck. The nose holds ho lds an
interchangeable 0.25 inches (6 mm) shank bit, commonly known as a tip. Most commonly used is a 1 inch (25 mm) #2 phillips. The nose can be adjusted to countersink screws to desired depth. Pressure must be applied to the bit in order to engage the clutch and drive the screws. Some screw gun users like to keep their motor running constantly, and this practice is recommended by manufacturers. There are screw guns which auto-feed screws from a clip. Decking screw guns have a long handle so the tradesman does not have to bend over.
DRILL:
Drill scheme
A drill or drill motor is a tool fitted fitted with a rotating cutting tool, usually a drill bit, used for drillingholes in various materials. The cutting tool is gripped by a chuck at one end of the drill and rotated while pressed against the target material. The tip of the cutting tool does the work of cutting into the target material. This may be slicing off thin shavings (twist
drills or auger bits), grinding off small particles (oil drilling), crushing and removing pieces of the workpiece (SDS masonry drill),countersinking, co unterboring, or other operations. Drills are co mmonly used in woodworking, metalworking, construction and most "do it yourself" projects. Specially designed drills are also used in medicine, space missions and other applications.
REAMER:
A reamer is a metalworking tool used to create an accurate sized hole. The process is called reaming. They may be used as a hand tool or in a machine tool, such as a milling machine or drill press.
TAP:
Bottoming, plug and taper taps, from top to bottom, respectively.
A tap and "T" wrench
A tap cuts a thread on the inside surface of a hole, creating a female surface which functions like a nut. The three t hree taps in the image illustrate the basic types commonly used u sed by most machinists:
Bottoming
tap or plug tap: The tap illustrated in the top of the image has a continuous
cutting edge with almost no taper ² between 1 and 1.5 threads of taper is typical. This feature enables a bottoming tap to cut threads to the bottom of a blind hole. A bottoming tap is usually used to cut threads in a hole that has already been partially threaded using one of the more tapered types of tap; the tapered end ("tap chamfer") of a bottoming tap is too short to successfully start into an unthreaded hole. In the US they are commonly known as bottoming taps, but in Australia and Britain they are also known as p lug taps.
Intermediate tap, second tap, or plug tap: The tap illustrated in the middle of the image has tapered cutting edges, which assist in aligning and starting the tap into an untapped hole. The number of tapered threads typically ranges from 3 to 5. Plug taps are the most commonly used type of tap. In the US they are commonly known as plug taps, whereas in Australia and Britain they are commonly known as second taps.
Taper tap: The small tap illustrated at the bottom of the image is similar to a plug tap but has a more pronounced taper to the cutting edges. This feature gives the taper tap a very gradual cutting action that is less aggressive than that of the plug tap. The number of tapered threads typically ranges from 8 to 10. A taper tap is most often used when the
material to be tapped is difficult to work (e.g., alloy steel) or the tap is of a very small diameter and thus prone to breakage. HAMMER:
A modern claw hammer
A hammer is a tool meant to deliver an impact to an object. The most common uses are for driving nails, fitting parts, forging metal and a nd breaking up objects. Hammers are often designed for a specific purpose, and vary widely in their shape and structure. The usual features are a handle and a head, with most of the weight in the head. The basic design is hand-operated, but there are also many mechanically operated models for heavier uses. The hammer may be the oldest tool for which definite evidence exists. Stone hammers are known which are dated to 2,600,000 BCE. The hammer is a basic tool too l of many professions. By analogy, the name hammer has also been used for devices that are designed des igned to deliver blows, e.g. in the caplock mechanism of firearms.
SPANNER:
A set of chrome-vanadium metric wrenches, open at one end, box/ring at the other. This type is commonly known as a "combination" wrench.
A wrench or spanner is
a tool used
to
provide
grip
and mechanical
advantage in
applyingtorque applyingtorque to turn objects²usually rotary fasteners fasteners,, such as nuts and bolts and bolts ²or keep them from turning. In British
nglish,, English
spanner is the standard term. The most common shapes are called open-
ended spanner and ring r ing spanner. The term wrench refers to a type of adjustable spanner. In American English nglish,, wrench is the standard term. The most common shapes are calledopenend wrench and box-end wrench. In American
English,
spanner refers to a specialized
wrench with a series of pins or tabs around the circumference. (These pins or tabs fit into the holes or notches cut into the object to be turned.) In American commerce, such a wrench may be called a spanner wrench to t o distinguish it from the British sense of spanner. Higher quality wrenches are typically made from chromium chromium-- vanadium alloy tool steels and are often drop-forged drop-forged.. They are frequently chrome-plated to resist corrosion and ease cleaning. Hinged tools, such as pliers as pliers or tongs or tongs,, are not generally considered wrenches. C
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