Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine. This can take two forms; the first type of lapping, involves rubbing a brittle material such as glass against a surface such as iron or glass itself with an abrasive such as aluminum oxide, jeweller's rouge, optician's rouge, silicon carbide, etc. between them. This produces microscopic conchoidal fractures as the abrasive rolls about between the two surfaces and removes material from both; the other form of lapping involves a softer material such as pitch or a ceramic for the lap, "charged" with the abrasive. The lap is used to cut a harder material—the workpiece; the abrasive embeds within the softer material, which holds it and permits it to score across and cut the harder material. Taken to a finer limit, this will produce a polished surface such as with a polishing cloth on an automobile, or a polishing cloth or polishing pitch upon glass or steel. Taken to the ultimate limit, with the aid of accurate interferometry and specialized polishing machines or skilled hand polishing, lensmakers can produce surfaces that are flat to better than 30 nanometers.
This is one twentieth of the wavelength of light from the used 632.8 nm helium neon laser light source. Surfaces this flat can be molecularly bonded by bringing them together under the right conditions.. This is way of example, a piece of lead may be used as the lap, charged with emery, used to cut a piece of hardened steel; the small plate shown in the first picture is a hand lapping plate. That particular plate is made of cast iron. In use, a slurry of emery powder would be spread on the plate and the workpiece rubbed against the plate in a "figure-eight" pattern; the second picture is of a commercially available lapping machine. The lap or lapping plate in this machine is 30 centimetres in diameter, about the smallest size available commercially. At the other end of the size spectrum, machines with 8-to-10-foot-diameter plates are not uncommon, systems with tables 30 feet in diameter have been constructed. Referring to the second picture again, the lap is the large circular disk on the top of the machine.
On top of the lap are two rings. The workpiece would be placed inside one of these rings. A weight would be placed on top of the workpiece; the weights can be seen in the picture along with two fiber spacer disks that are used to the load. In operation, the rings stay in one location as the lapping plate rotates beneath them. In this machine, a small slurry pump can be seen at the side, this pump feeds abrasive slurry onto the rotating lapping plate; when there is a requirement to lap small specimens, a lapping jig can be used to hold the material while it is lapped. A jig allows precise control of the orientation of the specimen to the lapping plate and fine adjustment of the load applied to the specimen during the material removal process. Due to the dimensions of such small samples, traditional loads and weights are too heavy as they would destroy delicate materials; the jig sits in a cradle on top of the lapping plate and the dial on the front of the jig indicates the amount of material removed from the specimen.
Where the mating of the two surfaces is more important than the flatness, the two pieces can be lapped together. The principle is that the protrusions on one surface will both abrade and be abraded by the protrusions on the other, resulting in two surfaces evolving towards some common shape, separated by a distance determined by the average size of the abrasive particles, with a surface roughness determined by the variation in the abrasive size; this yields closeness-of-fit results comparable to that of two accurately-flat pieces, without quite the same degree of testing required for the latter. One complication in two-piece lapping is the need to ensure that neither piece flexes or is deformed during the process; as the pieces are moved past each other, part of each will be unsupported for some fraction of the rubbing movement. If one piece flexes due to this lack of support, the edges of the opposite piece will tend to dig depressions into it a short distance in from the edge, the edges of the opposite piece are abraded by the same action - the lapping procedure assumes equal pressure distribution across the whole surface at all times, will fail in this manner if the workpiece itself deforms under that pressure.
Lapping can be used to obtain a specific surface roughness. Surface roughness and surface flatness are two quite different concepts. A typical range of surface roughness that can be obtained without resorting to special equipment would fall in the range of 1 to 30 units Ra microinches. Surface accuracy or flatness is measured in Helium Light Bands, one HLB measuring about 0.000011 inches. Again, without resort to special equipment accuracies of 1 to 3 HLB are typical. Though flatness is the most common goal of lapping, the process is used to obtain other configurations such as a concave or convex surface; the easiest method for measuring flatness is with a height gauge positioned on a surface plate. Note that you must set up the part on three stands and find the minimum variation while adjusting them, just placing the part on the surface plate and using a dial indicator to find
Sharpening stones, water stones or whetstones are used to sharpen the edges of steel tools and implements through grinding and honing. Examples of items that can be sharpened with a sharpening stone include scissors, knives and tools such as chisels, hand scrapers, plane blades. Sharpening stones come in a wide range of shapes and material compositions. Stones may be flat, for working flat edges, or shaped for more complex edges, such as those associated with some wood carving or woodturning tools, they may be composed from man-made material. Stones are available in various grades, which refer to the grit size of the abrasive particles in the stone. Grit size is given as a number. A higher number denotes a higher density and therefore smaller particles, which leads to a finer finish of the surface of the polished object. Though "whetstone" is mistaken as a reference to the water sometimes used to lubricate such stones, the term is based on the word "whet", which means to sharpen a blade, not on the word "wet".
The verb nowadays used to describe the process of using a sharpening stone is to sharpen, but the older term to whet is still sometimes used. The term to whet is so rare in this sense that it is no longer mentioned in for example the Oxford Living Dictionaries. One of the most common mistaken idioms in English involves the phrase "to whet your appetite", too mistakenly written as "to wet", but to "whet" quite appropriately means "to sharpen" one's appetite, not to douse it with water. The Roman historian Pliny described use of several occurring stones for sharpening in his Natural History, he describes the use of both oil and water stones and gives the locations of several ancient sources for these stones. The use of natural stone for sharpening has diminished with the widespread availability of high-quality, consistent particle size artificial stones; as a result, the legendary Honyama mines in Kyoto, have been closed since 1967. Belgium has only a single mine, still quarrying Coticules and their Belgian Blue Whetstone counterparts.
Modern synthetic stones are of equal quality to natural stones, are considered superior in sharpening performance due to consistency of particle size and control over the properties of the stones. For example, the proportional content of abrasive particles as opposed to base or "binder" materials can be controlled to make the stone cut faster or slower, as desired. Natural stones are prized for their natural beauty as stones and their rarity, adding value as collectors' items. Furthermore, each natural stone is different, there are rare natural stones that contain abrasive particles in grit sizes finer than are available in artificial stones. One of the most well-regarded natural whetstones is the yellow-gray "Belgian Coticule", legendary for the edge it can give to blades since Roman times, has been quarried for centuries from the Ardennes; the coarser and more plentiful "Belgian Blue" whetstone is found with the yellow coticule in adjacent strata. These are prized for their natural elegance and beauty, for providing both a fast-cutting surface for establishing a bevel and a finer surface for refining it.
This stone is considered one of the finest for sharpening straight razors. The hard stone of Charnwood Forest in northwest Leicestershire, has been quarried for centuries, was a source of whetstones and quern-stones. Whetstones may be artificial stones. Artificial stones come in the form of a bonded abrasive composed of a ceramic such as silicon carbide or of aluminium oxide. Bonded abrasives provide a faster cutting action than natural stones, they are available as a double-sided block with a coarse grit on one side and a fine grit on the other enabling one stone to satisfy the basic requirements of sharpening. Some shapes are designed for specific purposes such as sharpening drills or serrations. Natural stones are formed of quartz, such as novaculite; the Ouachita Mountains in Arkansas are noted as a source for these. Novaculite is found in Syria and Lebanon a part of the Ottoman empire, hence the use of the older name in America of Turkey stone; when the block is intended for installation on a bench it is called a bench stone.
Small, portable stones are called pocket stones. Being smaller, they are more portable than bench stones but present difficulty in maintaining a consistent angle and pressure when drawing the stone along larger blades. However, they still can form a good edge. Fine grained pocket stones are used for honing "in the field". Despite being a homophone with wet in most dialects of modern English, whetstones do not need to be lubricated with oil or water, although it is common to do so. Lubrication carries swarf away; the Japanese traditionally used natural sharpening stones lubricated with water They have been doing this for many hundreds of years. The geology of Japan provided a type of stone which consists of fine silicate particles in a clay matrix, somewhat softer than novaculite. Japanese stones are sedimentary; the most famous are mined in the Narutaki District just north of Kyoto. There are three broad grades of Japanese sharpening stones: the ara-to, or "rough stone", the naka-to or "middle/medium stone" and the shiage-to or "finishing stone".
There is a fourth type o
Drill bit shank
The shank is the end of a drill bit grasped by the chuck of a drill. The cutting edges of the drill bit contact the workpiece, are connected via the shaft with the shank, which fits into the chuck. In many cases a general-purpose arrangement is used, such as a bit with cylindrical shaft and shank in a three-jaw chuck which grips a cylindrical shank tightly. Different shank and chuck combination can deliver improved performance, such as allowing higher torque, greater centering accuracy, or moving the bit, but not the chuck, with a hammer action; this shank was common before 1850, is still in production. At first, the tapered shank was just rammed into a square hole in the end of the drill. Over time, various chuck designs have been invented, modern chucks can grasp and drive this shank effectively, it has been difficult to find a reference to the included angle of the taper, but 7 different bits were measured, they all had an included angle of 8 ± 0.25 degrees. Easy to make in a forge Very wide tolerances allowable Moderate torque transmission but without the slipping possible with round shanks Appropriate chuck required The straight shank is the most usual style on modern drill bits, by number manufactured.
The whole of the drill bit and shank, is of the same diameter. It is held in a three-jaw drill chuck. Bits of diameter too small to grip can have straight shanks of larger diameter than the drill, which can be held in a standard size collet or chuck. Large drill bits can have straight shanks narrower than the drill diameter so that they can be fitted in chucks not able to chuck the full diameter; such a drill bit is called blacksmith's drill. For example, this allows a 1⁄2-inch bit to be used in a pistol-grip drill's 3⁄8-inch chuck. One particular type of reduced-shank drill bits are Silver & Deming bits, whose sets run from 9⁄16-inch to 1 1⁄2-inch drill body diameter with a standard 1⁄2-inch reduced shank for all; this allows drill presses with 1⁄2-inch chucks to run the larger drills. S&D bits are 6 inches long with a 3-inch flute length; the name comes from a company in Salem, Ohio that broke up into other companies circa 1890. Easy to centerless grind or turn on a lathe Minimum of turning or grinding needed if the drill bit is made from appropriately sized round bar stock Can be held in a standard drill chuck, which must be tightened—only friction prevents slipping Can be held in a collet chuck for smaller sizes Very accurate centering Torque transmission limited by slipping of cylindrical shank The flats of a hex shank can either be machined on a round shank, as in the photograph, or be the natural flats of hex bar stock.
A hex shank can be grasped by a 3-jaw drill chuck or held in a chuck for hex shanks. Quarter-inch hex shanks are common for machine screwdriver bits and have spread from that application to be used for drill bits that are compatible with screwdriver machinery. Zero manufacturing if the drill bit is made from hex bar stock Can be held in a drill chuck made for cylindrical shanks Can be held in a hex screwdriver bit chuck High torque transmission, limited only by strength No need to tighten, shape does not allow slipping Moderately accurate centering Cannot be held in a regular round colletA special 3c or 5c HEX collet must be used; the diameter of an SDS and SDS Plus shank is 10 millimeters. The SDS shank has the advantage of fitting into a simple spring-loaded chuck, so that bits are pushed into the chuck without tightening; this shank and chucks made for it are suited to hammer drilling with masonry drills in stone and concrete. The drill bit can slide back and forth like a piston; the hammer of the drill acts to accelerate only the drill bit itself, not the large mass of the chuck, which makes hammer drilling with an SDS shank drill bit much more productive than with other types of shank.
Rotational drive uses the sliding keyways that open to the end of the shank, which mate with keys in the chuck. The smaller indentations that do not open to the end are grasped by the chuck to prevent the drill bit falling out; the hammer of the drill hits the flat end of the shank. The shank must be lubricated with grease to allow it to slide in the chuck. There are three standard sizes of SDS: SDS-Top and SDS-max. SDS-plus is the most common by count of tools manufactured, with masonry drills from 4 mm diameter to 30 mm diameter ordinarily available; the shortest SDS-plus masonry drill bits are about 110 mm overall length, the longest 1500 mm. SDS-max is more common for larger rotary hammers and chipping guns, common sizes start at 1⁄2 inch diameter up to 1 3⁄4 inches diameter. Standard lengths are 12 to 21 inches. SDS-Top has been phased out in North America and is not common except for older tools. Hilti's TE-S system is similar to these SDS systems, but is designed for chipping only in tools for applications larger than could be handled by SDS-Max.
The SDS bit was developed by Hilti and Bosch in 1975. The name comes from the German "Stecken – Drehen – Sichern". In German-speaking countries the back-formation "Spannen durch System" is used, though Bosch uses "Special Direct System" for international purposes. Complex to manufacture Better hammer drilling performance than rigidly gripped bits
A lathe dog known as a lathe carrier, is a device that clamps around the workpiece and allows the rotary motion of the machine's spindle to be transmitted to the workpiece. A carrier is most used when turning between centers on a lathe, but it may be used on dividing heads or any similar situation, it is used in conjunction with a drive plate and drive pins: the plate is mounted directly on the machine spindle and the drive pin is attached to the plate. In use the carrier and workpiece are inserted between centers and the leg of the carrier rests against the drive pin. Carriers may be of the straight bent leg type; the straight leg requires the drive pin, the bent leg fits into a slot machined into the drive plate. The bent leg type is considered safer. Spindle speeds are reduced. Care must be taken by the operator when using carriers, as it is easy to get snagged on one. Lathe faceplate Mandrel
A latch or catch is a type of mechanical fastener that joins two objects or surfaces while allowing for their regular separation. A latch engages another piece of hardware on the other mounting surface. Depending upon the type and design of the latch, this engaged bit of hardware may be known as a keeper or strike. A latch is not the same as the locking mechanism of a door or window, although they are found together in the same product. Latches range in complexity from flexible one-piece flat springs of metal or plastic, such as are used to keep blow molded plastic power tool cases closed, to multi-point cammed latches used to keep large doors closed. A single-throw bolt; the bolt can be engaged in its strike plate. The locking mechanism prevents the bolt from being retracted by force. Latchbolt or Latch bolt An common latch type part of a lockset, it is a spring-loaded bolt with an angled edge; when the door is pushed closed, the angled edge of the latchbolt engages with the lip of the strike plate.
Once the door is closed, the bolt automatically extends into the strike plate, holding the door closed. The latchbolt is disengaged when the user turns the door handle, which via the lockset's mechanism, manually retracts the latchbolt, allowing the door to open. Deadlocking latchbolt is an elaboration on the latchbolt which includes a guardbolt to prevent “shimming” or “jimmying” of the latch bolt; when the door is closed, the latchbolt and guardbolt are retracted together, the door closes with the latchbolt entering the strike plate. The strike plate, holds the guardbolt in its depressed position: a mechanism within the lockset holds the latchbolt in the projected position; this arrangement prevents the latchbolt from being depressed through the use of a credit card or some other tool, which would lead to unauthorized entry. Draw Latch is a two part latch where one side has an arm that can clasp to the other half, as it closes the clasp pulls the two parts together. Used on tool boxes, chests and windows.
Doesn't need to be closed to secure both halves. Spring bolt lock: A locking mechanism used with a latchbolt A slam latch uses a spring and is activated by the shutting or slamming of a door. Like all latches, a slam latch; the slam latch derives its name from its ability to slam doors and drawers shut without damaging the latch. A slam latch is rugged and ideal for industrial and construction applications. A cam lock is a type of latch consisting of a cam; the base is where the key or tool is used to rotate the cam, what does the latching. Cams can offset. Found on garage cabinets, file cabinets, tool chests, other locations where privacy and security is needed. A Norfolk latch is a type of latch incorporating a simple thumb-actuated lever and used to hold wooden gates and doors closed. In a Norfolk latch, the handle is fitted to a backplate independently of the thumb piece. Introduced around 1800–1820, Norfolk latches, originating in the English county of the same name, differ from the older Suffolk latch, which lacked a back plate to which the thumbpiece is attached.
A Suffolk latch is a type of latch incorporating a simple thumb-actuated lever and used to hold wooden gates and doors closed. The Suffolk latch originated in the English county of Suffolk in the 16th century and stayed in common use until the 19th century, they have come back into favour on garden gates and sheds. They were common from the 17th century to around 1825, their lack of a back plate made them different from the and neighbouring Norfolk latch. Both the Suffolk latch and Norfolk latch are thought to have been named by architectural draughtsman William Twopenny. Many of these plates found their way into other parts of the world. A crossbar, sometimes called a bolt, is a primitive fastener consisting of a post barring a door. Crossbars were common, simple fasteners consisting of a plank or beam mounted to one side of a door by a set of cleats; the board could be slid past the frame to block the door. Alternatively, the bar can be a separate piece, placed into open cleats or hooks, extending across the frame on both sides.
The effect of this device is the opposite of the crash bar in that its operation is to permit the door to be opened inward rather than outward. On a set of double doors, the same principle needn't extend past the frame; the bar extends into another set of cleats on the other door such as to interfere with the door opening. A cabin hook is a hooked bar; the bar is attached permanently to a ring or staple, fixed with screws or nails to woodwork or a wall at the same level as the eye screw. The eye screw is screwed into the adjacent wall or onto the door itself. Used to hold a cupboard, door or gate open or shut. A cabin hook is used in many situations to hold a door open, like on ships to prevent doors from swinging and banging against other woodwork as the ship moves due to wave action; this usage spread to other domains, where a door was required to be held open or a self-closing device is used to close the door. Many buildings are built with fire-resistant doors to separate different parts of buildings and to allow people to be protected from fire and smoke.
When using a cabin hook in such a situation, one should keep in mind that a fire-resistant door is an expensive and h
A grinding dresser or wheel dresser is a tool to dress the surface of a grinding wheel. Grinding dressers are used to return a wheel to its original round shape, to expose fresh grains for renewed cutting action, or to make a different profile on the wheel's edge; the objective of dressing the wheel is to: True the wheel by knocking abrasive particles from the wheel's surface and making the wheel concentric. This minimizes vibration and improves surface finish, eliminating the vibration of the out-of-balance wheel across the workpiece's surface, it is not unusual for grinding wheels to become out of round with use. This is from loaded areas of the wheel wearing at different rates from less loaded areas, it can be exacerbated by grinding when the wheel is not under power, such as using the work to apply braking action to the wheel to stop it from coasting. Dressing restores the roundness; when bench grinders vibrate excessively, it is because the wheels have worn out of round and are thus out of balance.
Truing them by dressing resolves this problem. Dislodge these abrasive particles to expose fresh abrasive from the wheel's surface; each abrasive grain is a small cutting tool. Exposing the fresh grains is thus a sharpening process. Glazing of the wheel is evidence of rounded grains and is noticeable by a reflective surface on the spinning wheel. Clean the wheel. If a workpiece is softer than the grade for which the wheel is designed, the abrasive particles will not be dislodged in time to present fresh, sharp grains; the wheel therefore appears to lose its edge as the pores between grains fill with fragments of the workpiece. The wheel is said to be loaded; this is one reason why the selection of wheel is important. Star dressers — A long handled tool with a row of free running and serrated, wavy discs or star-shaped cutters running at right angles to the handle; these slows down. Force is applied to the face of the slowing wheel with the result that the hardened discs match speed with the face of the wheel allowing the fingers or undulating surface of the dresser, to knock the abrasive grains out.
Diamond dressers — Shorter handled diamond tools that either have a matrix of small diamonds bonded to a broad surface on the end of the dresser or a single diamond mounted in their face. As the diamond is introduced to the wheel's face, the harder diamond remains attached and the looser grains fall away. Dressing sticks — A stick of hard material made from the same materials but with a stronger bonding agent. NorBide is one brand of dressing stick made by Norton Abrasives from boron nitride. An abrasive wheel type that has a small "grinding wheel" in a holder, held against the spinning grinding wheel to dress and clean the face of the grinding wheel. Four types of dressers are used to dress the wheels of CNC grinders used for grinding complex shapes; this type of dresser is in use on CNC grinding machine tools to automatically dress the grinding wheel via computer control in specialist areas requiring complex shapes such as grinding bearing raceways. Stationary dressers — a stationary dresser is a metal blade with a single diamond brazed into the tip.
A CNC dressing program moves it across the face of the wheel, moving in and out to create the desired profile. The grinding wheel's profile is controlled by the CNC program used to dress the wheel, rather than by the profile of the dresser itself. Crush rolls — a crush roll is a high-speed steel or tungsten carbide wheel, its profile is the mirror image of the desired profile of the grinding wheel. It is forced against the grinding wheel, while spinning at the same surface speed as the grinding wheel. Doing so breaks the bond between the abrasive particles on the surface of the wheel, exposing a new surface as particles fall away. One disadvantage is that the wheel profile cannot be adjusted except by replacing the roll with one having a different profile. Diamond crush rolls — a diamond crush roll is a crush roll coated with diamond particles, it wears more and less wear mean they can be used to achieve tighter tolerances than plain crush rolls. Rotary dressers — a rotary dresser is a disc with a hard material - diamond - attached to the edge.
The grinding wheel's profile is controlled by the CNC program used to dress the wheel, rather than by the profile of the dresser itself
Tool and cutter grinder
A tool and cutter grinder is used to sharpen milling cutters and tool bits along with a host of other cutting tools. It is an versatile machine used to perform a variety of grinding operations: surface, cylindrical, or complex shapes; the image shows a manually operated setup, however automated Computer Numerical Control machines are becoming common due to the complexities involved in the process. The operation of this machine requires a high level of skill; the two main skills needed are understanding of the relationship between the grinding wheel and the metal being cut and knowledge of tool geometry. The illustrated set-up is only one of many combinations available; the huge variety in shapes and types of machining cutters requires flexibility in usage. A variety of dedicated fixtures are included that allow cylindrical grinding operations or complex angles to be ground; the vise shown can swivel in three planes. The table moves longitudinally and laterally, the head can swivel as well as being adjustable in the horizontal plane, as visible in the first image.
This flexibility in the head allows the critical clearance angles required by the various cutters to be achieved. Today's tool and cutter grinder is a CNC machine tool 5 axes, which produces endmills, step tools, etc. which are used in the metal cutting and woodworking industries. Modern CNC tool and cutter grinders enhance productivity by offering features such as automatic tool loading as well as the ability to support multiple grinding wheels. High levels of automation, as well as automatic in-machine tool measurement and compensation, allow extended periods of unmanned production. With careful process configuration and appropriate tool support, tolerances less than 5 micrometres can be achieved on the most complex parts. Apart from manufacturing, in-machine tool measurement using touch-probe or laser technology allows cutting tools to be reconditioned. During normal use, cutting edges either wear and/or chip; the geometric features of cutting tools can be automatically measured within the CNC tool grinder and the tool ground to return cutting surfaces to optimal condition.
Significant software advancements have allowed CNC tool and cutter grinders to be utilized in a wide range of industries. Advanced CNC grinders feature sophisticated software that allows geometrically complex parts to be designed either parametrically or by using third party CAD/CAM software. 3D simulation of the entire grinding process and the finished part is possible as well as detection of any potential mechanical collisions and calculation of production time. Such features allow parts to be designed and verified, as well as the production process optimized within the software environment. Tool and cutter grinders can be adapted to manufacturing precision machine components; the machine, when used for these purposes more would be called a CNC Grinding System. CNC Grinding Systems are used to produce parts for aerospace, medical and other industries. Hard and exotic materials are no problem for today's grinding systems and the multi-axis machines are capable of generating quite complex geometries.
A radius grinder is a special grinder used for grinding the most complex tool forms, is the historical predecessor to the CNC tool and cutter grinder. Like the CNC grinder, it may be used for other tasks; the tool itself consists of three parts: The grinder head, work table, holding fixture. The grinder head has three degrees of freedom. Vertical movement, movement into the workpeice, tilt; these are set statically, left fixed throughout operations. The work table is a T-slotted X-axis table mounted on top of a radial fixture. Mounting the X axis on top of the radius table, as opposed to the other way around, allows for complex and accurate radius grinds; the holding fixtures can be anything one can mount on a slotted table, but most used is a collet or chuck fixture that indexes and has a separate Y movement to allow accurate depth setting and endmill sharpening. The dressers used on these grinders are quite expensive, can dress the grinding wheel itself with a particular radius; the D-bit grinder is a tool bit grinder designed to produce single-lip cutters for pantograph milling machines.
Pantographs are a variety of milling machine used to create cavities for the dies used in the molding process. With the addition of accessory holders, the single-lip grinding capability may be applied to grinding lathe cutting bits, simple faceted profiles on tips of drill bits or end mills; the machine is sometimes advertised as a "universal cutter-grinder", but the "universal" term refers only to the range of compound angles available, not that the machine is capable of sharpening the universe of tools. The machine is not capable of sharpening drill bits in the standard profiles, or generating any convex or spiral profiles. Angle grinder Bench grinder Centerless grinding Flick grinder Surface grinder