WASTING OF MATERIALS
A saw is a tool consisting of a tough blade, wire, or chain with a hard toothed edge. It is used to cut through material, most often wood. The cut is made by placing the toothed edge against the material and moving it forcefully forth and less forcefully back or continuously forward. This force may be applied by hand, or powered by steam, water, electricity or other power source. An abrasive saw has a powered circular blade designed to cut through metal.
"Kerf" redirects here. For other meanings, see Kerf (disambiguation).
Diagram showing the teeth of a saw blade when looking front-on. The teeth protrude to the left and right, so that the saw cut (kerf) is wider than the blade width. The term set describes how much the teeth protrude. The kerf may be sometimes be wider than the set, depending on wobble and other factors.
- Heel: The end closest to the handle.
- Toe: The end farthest from the handle.
- Front: The side with the teeth (the "bottom edge").
- Back: The side opposite the front (the "top edge").
- Teeth: Small, sharp protrusions along the cutting side of the saw.
- Gullet: The valley between the points of the teeth.
- Fleam: The angle of the faces of the teeth relative to a line perpendicular to the face of the saw.
- Rake: The angle of the front face of the tooth relative to a line perpendicular to the length of the saw. Teeth designed to cut with the grain (ripping) are generally steeper than teeth designed to cut across the grain (crosscutting)
- Points per inch (25 mm): The most common measurement of the frequency of teeth on a saw blade. It is taken by setting the tip (or point) of one tooth at the zero point on a ruler, and then counting the number of points between the zero mark and the one-inch mark, inclusive (that is, including both the point at the zero mark and any point that lines up precisely with the one-inch mark). There is always one more point per inch than there are teeth per inch (e.g., a saw with 14 points per inch will have 13 teeth per inch, and a saw with 10 points per inch will have 9 teeth per inch). Some saws do not have the same number of teeth per inch throughout their entire length, but the vast majority do. Those with more teeth per inch at the toe are described as having incremental teeth, in order to make starting the saw cut easier.
- Teeth per inch: An alternative measurement of the frequency of teeth on a saw blade. Usually abbreviated TPI, as in, "A blade consisting of 18TPI." [Compare points per inch.]
- Kerf: The width of a saw cut, which depends on several factors: the width of the saw blade; the set of the blade's teeth; the amount of wobble created during cutting; and the amount of material pulled out of the sides of the cut. Although the term "kerf" is often used informally, to refer simply to the thickness of the saw blade, or to the width of the set, this can be misleading, because blades with the same thickness and set may create different kerfs. For example, a too-thin blade can cause excessive wobble, creating a wider-than-expected kerf. The kerf created by a given blade can be changed by adjusting the set of its teeth with a tool called a saw tooth setter.
- Set: The degree to which the teeth are bent out sideways away from the blade, usually in both directions. In most modern serrated saws, the teeth are set, so that the kerf (the width of the cut) will be wider than the blade itself. This allows the blade to move through the cut easily without binding (getting stuck). The set may be different depending on the kind of cut the saw is intended to make. For example, a rip saw has a tooth set that is similar to the angle used on a chisel, so that it rips or tears the material apart. A "flush-cutting saw" has no set on one side, so that the saw can be laid flat on a surface and cut along that surface without scratching it. The set of the blade's teeth can be adjusted with a tool called a saw tooth setter.
- Abrasive saw: A saw that cuts with an abrasive disc or band, rather than a serrated blade.
Manufacture of saws by hand
Until at least the mid-19th century, saws were made laboriously by hand. The teeth were filed out individually, then "set" by striking alternate teeth with a hammer against a "stake" or small anvil. Due to risk of breaking teeth, beginners were given saw set pliers which set even more slowly.
Main articles: Whipsaw, Saw pit and Two-man saw
A pit saw was a two-man rip saw. In parts of early colonial North America, it was one of the principal tools used in shipyards and other industries where water-powered sawmills were not available. It was so-named because it was typically operated over a saw pit, either at ground level or on trestles across which logs that were to be cut into boards by the pit-saw were mounted. The pit saw was "a strong steel cutting-plate, of great breadth, with large teeth, highly polished and thoroughly wrought, some eight or ten feet in length" with either a handle on either end or a frame saw. A pit-saw was also sometimes known as a whipsaw. It took 2-4 people to operate. A "pit-man" stood in the pit, a "top-man" stood outside the pit, and they worked together to make cuts, guide the saw, and raise it. Pit-saw workers were among the most highly paid laborers in early colonial North America.
Types of saws
Rip sawing circa 1425 with a frame or sash saw on trestles rather than over a saw pit
Hand saws typically have a relatively thick blade to make them stiff enough to cut through material. (The pull stroke also reduces the amount of stiffness required.) Thin-bladed handsaws are made stiff enough either by holding them in tension in a frame, or by backing them with steel or brass (on account of which the latter are called "back saws.") Some examples of hand saws are:
- Bow saw or Buck saw: a crosscut saw with the thin blade held in tension in a frame;
- Coping saw: for cutting wood patterns;
- Crosscut saw: for cutting wood perpendicular to the grain;
- Dovetail Saw: for cutting intricate joints, mainly found in drawers;
- Frame saw or "sash saw": In general any saw with a thin blade held in tension by a frame, this term often specifically means the rip saw also called a whipsaw.
- Fret saw: for cutting intricate wood patterns;
- Hacksaw: a fine-toothed tempered blade under tension, for cutting metal, bone, and other hard materials;
- Japanese saw or pull saw: a thin-bladed saw that cuts on the pull stroke;
- Pad saw or "keyhole saw" or "jab saw": a narrow-bladed saw;
- Plywood saw: a fine-toothed saw (to reduce tearing), for cutting plywood;
- Rip saw: for cutting wood along the grain;
- Turning saw: a frame saw with a narrow blade used for cutting curves, larger than a coping saw.
- Two-man saw :a general term for a large crosscut saw or rip saw for cutting large logs or trees;
- Veneer saw: a two-edged saw with fine teeth for cutting veneer;
- Whipsaw or pit saw: a kind of rip saw for cutting logs into lumber;
- Wire saw: a toothed or coarse cable or wire wrapped around the material and pulled back and forth.
Main articles: Backsaw and Japanese saw
"Back saws," so called because they have a thinner blade backed with steel or brass to maintain rigidity, are a subset of hand saws. Back saws have different names depending on the length of the blade. Some examples are:
Mechanically powered saws
Circular wood-cutting saw at Maine State Museum in the capital city of Augusta, Maine
This particular circular saw, which cut wood into segments to fit a wood-burning kitchen stove, is displayed at the Cole Land Transportation Museum in Bangor, Maine.
- Circular saw: a saw with a circular blade which spins. Circular saws can be large for use in a mill or hand held up to 24" blades and different designs cut almost any kind of material including wood, stone, brick, plastic, etc.
- Table saw: a saw with a circular blade rising through a slot in a table. If it has a direct-drive blade small enough to set on a workbench, it is called a "workbench saw." If set on steel legs, it is called a "contractor's saw." A heavier, more precise and powerful version, driven by several belts, with an enclosed base stand, is called a "cabinet saw." A newer version, combining the lighter-weight mechanism of a contractor's saw with the enclosed base stand of a cabinet saw, is called a "hybrid saw."
- Radial arm saw: a versatile machine, mainly for cross-cutting. The blade is pulled on a guide arm through a piece of wood that is held stationary on the saw's table.
- Rotary saw or "spiral-cut saw" or "RotoZip": for making accurate cuts, without using a pilot hole, in wallboard, plywood, and other thin materials.
- Electric miter saw or "chop saw," or "cut-off saw" or "power miter box": for making accurate cross cuts and miter cuts. The basic version has a circular blade fixed at a 90° angle to the vertical. A "compound miter saw" has a blade that can be adjusted to other angles. A "sliding compound miter saw" has a blade that can be pulled through the work, in an action similar to that of a radial-arm saw, which provides more capacity for cutting wider workpieces.
- Concrete saw: (usually powered by an internal combustion engine and fitted with a Diamond Blade) for cutting concrete or asphalt pavement.
- Pendulum saw or "swing saw": a saw hung on a swinging arm, for the rough cross cutting of wood in a sawmill and for cutting ice out of a frozen river.
- Abrasive saw: a circular or reciprocating saw-like tool with an abrasive disc rather than a toothed blade, commonly used for cutting very hard materials. As it does not have regularly shaped edges the abrasive saw is not a saw in technical terms.
- Hole saw: ring-shaped saw to attach to a power drill, used for cutting a circular hole in material.
Reciprocating blade saws
- Jigsaw or "saber saw" (US): narrow-bladed saw, for cutting irregular shapes. (Also an old term for what is now more commonly called a "scroll saw.")
- Reciprocating saw or "sabre saw" (UK and Australia): a saw with an "in-and-out" or "up-and-down" action similar to a jigsaw, but larger and more powerful, and using a longer stroke with the blade parallel to the barrel. Hand-held versions, sometimes powered by compressed air, are for demolition work or for cutting pipe.
- Scroll saw: for making intricate curved cuts ("scrolls").
- Dragsaw: for bucking logs (used before the invention of the chainsaw).
- Frame saw or sash saw: A thin bladed rip-saw held in tension by a frame used both manually and in sawmills. Some whipsaws are frame saws and some have a heavy blade which does not need a frame called a mulay or muley saw.
- Sternal saw: for cutting through a patient's sternum during surgery.
- Ice saw: for ice cutting. Looks like a mulay saw but sharpened as a cross-cut saw.
Types of blades and blade cuts
Most blade teeth are made either of tool steel or carbide. Carbide is harder and holds a sharp edge much longer.
Band saw blade
A long band welded into a circle, with teeth on one side. Compared to a circular-saw blade, it produces less waste because it is thinner, dissipates heat better because it is longer (so there is more blade to do the cutting, and is usually run at a slower speed.
In woodworking, a cut made at (or close to) a right angle to the direction of the wood grain of the workpiece. A crosscut saw is used to make this type of cut.
In woodworking, a cut made parallel to the direction of the grain of the workpiece. A rip saw is used to make this type of cut.
A circular saw blade with many small teeth, designed for cutting plywood with minimal splintering.
A special type of circular saw blade used for making wide-grooved cuts in wood so that the edge of another piece of wood will fit into the groove to make a joint. Some dado blades can be adjusted to make different-width grooves. A "stacked" dado blade, consisting of chipper blades between two dado blades, can make different-width grooves by adding or removing chipper blades. An "adjustable" dado blade has a movable locking cam mechanism to adjust the degree to which the blade wobbles sideways, allowing continuously variable groove widths from the lower to upper design limits of the dado.
Strobe saw blade
A circular saw blade with special rakers/cutters to easily saw through green or uncured wood that tends to jam other kinds of saw blades. Plane (tool)
From Wikipedia, the free encyclopedia
A Japanese plane in use
A hand plane is a tool for shaping wood. When powered by electricity, the tool may be called a planer. Planes are used to flatten, reduce the thickness of, and impart a smooth surface to a rough piece of lumber or timber. Planing is used to produce horizontal, vertical, or inclined flat surfaces on workpieces usually too large for shaping. Special types of planes are designed to cut joints or decorative mouldings.
Hand planes are generally the combination of a cutting edge, such as a sharpened metal plate, attached to a firm body, that when moved over a wood surface, take up relatively uniform shavings, by nature of the body riding on the 'high spots' in the wood, and also by providing a relatively constant angle to the cutting edge, render the planed surface very smooth. A cutter which extends below the bottom surface, or sole, of the plane slices off shavings of wood. A large, flat sole on a plane guides the cutter to remove only the highest parts of an imperfect surface, until, after several passes, the surface is flat and smooth. When used for flattening, bench planes with longer soles are preferred for boards with longer longitudinal dimensions. A longer sole registers against a greater portion of the board's face or edge surface which leads to a more consistently flat surface or straighter edge. Conversely, using a smaller plane allows for more localized low or high spots to remain.
Though most planes are pushed across a piece of wood, holding it with one or both hands, Japanese planes are pulled toward the body, not pushed away.
Woodworking machinery that perform the same function as hand planes include the jointer and the thickness planer, also called a thicknesser. When rough lumber is reduced to dimensional lumber, a large electric motor or internal combustion engine will drive a thickness planer that removes excess wood to create a uniform, smooth surface on all four sides of the lumber and may also plane the edges.
A pair of wooden planes found on board the 16th century carrack Mary Rose.
Hand planes are ancient, originating thousands of years ago. Early planes were made from wood with a rectangular slot or mortise cut across the center of the body. The cutting blade or iron was held in place with a wooden wedge. The wedge was tapped into the mortise and adjusted with a small mallet, a piece of scrap wood or with the heel of the user's hand. Planes of this type have been found in excavations of old sites as well as drawings of woodworking from medieval Europe and Asia. The earliest known examples of the woodworking plane have been found in Pompeii although other Roman examples have been unearthed in Britain and Germany. The Roman planes resemble modern planes in essential function, most having iron wrapping a wooden core top, bottom, front and rear and an iron blade secured with a wedge. One example found in Cologne has a body made entirely of bronze without a wooden core. A Roman plane iron used for cutting moldings was found in Newstead, England. Histories prior to these examples are not clear although furniture pieces and other woodwork found in Egyptian tombs show surfaces carefully smoothed with some manner of cutting edge or scraping tool. There are suggestions that the earliest planes were simply wooden blocks fastened to the soles of adzes to effect greater control of the cutting action.
In the mid-1860s, Leonard Bailey began producing a line of cast iron-bodied hand planes, the patents for which were later purchased by Stanley Rule & Level, now Stanley Works. The original Bailey designs were further evolved and added to by Justus Traut and others at Stanley Rule & Level. The Bailey and Bedrock designs became the basis for most modern metal hand plane designs manufactured today. The Bailey design is still manufactured by Stanley Works.
In 1918 an air-powered handheld planing tool was developed to reduce shipbuilding labor during World War I. The air-driven cutter spun at 8000 to 15000 rpm and allowed one man to do the planing work of fifteen men who used manual tools.
Modern hand planes are made from wood, ductile iron or bronze which produces a tool that is heavier and will not rust.
Parts of a plane
Two styles of plane are shown with some parts labeled. The top of the image is a bench plane; the bottom is a block plane.
A bench plane iron with chipbreaker.
- A: The mouth is an opening in the bottom of the plane down through which the blade extends, and up through which wood shavings pass.
- B: The iron is a plate of steel with a sharpened edge which cuts the wood. Some people refer to it as the blade.
- C: The lever cap holds the blade down firmly to the body of the plane.
- D: The depth adjustment knob controls how far the blade extends through the mouth.
- E: The knob is a handle on the front of the plane.
- F: The chipbreaker or Cap iron serves to make the blade more rigid and to curl and break apart wood shavings as they pass through the mouth.
- G: The lateral adjustment lever is used to adjust the iron by skewing it so that the depth of cut is uniform across the mouth.
- H: The tote is a handle on the rear of the plane.(Some aficionados object to the use of the word tote preferring handle).
- I: The finger rest knob Block planes are held in the palm of the hand while the tip of the user's index finger rests in the indentation on top of the knob. On some planes the knob is used to adjust the size of the mouth by allowing a sliding portion of the sole to be moved back or forward to accomplish this.
- J: The frog is a sliding iron wedge that holds the plane iron at the proper angle. It slides to adjust the gap between the cutting edge and the front of the mouth. The frog is screwed down to the inside of the sole through two parallel slots and on many planes is only adjustable with a screwdriver when the plane iron is removed. Some planes, such as the Stanley Bedrock line and the bench planes made by Lie-Nielsen and WoodRiver/WoodCraft have a screw mechanism that allows the frog to be adjusted without removing the blade.
Modern wooden plane
A smoothing plane
Stanley No. 32 transitional jointer plane (26 inches long)
Stanley No. 55 Combination Plane
Finger planes, seen in Copenhagen. Note the size.
Most planes are broadly categorized as either bench planes, block planes, or specialty planes. In modern-day carpentry, electrically powered hand planers (also called hand or handheld power planers or simply power planes) have joined the family.
Bench planes are characterized by the cutting iron bedded with the bevel facing down and attached to a chipbreaker. Most metal bench planes, and some larger wooden ones, are designed with a rear handle known as a tote. Block planes are characterized by the absence of a chipbreaker and the cutting iron bedded with the bevel up. The block plane is usually a smaller tool that can be held with one hand and is used for general purpose work such as taking down a knot in the wood, smoothing small pieces, chamfering edges, and making the end of a sawed board square and smooth.
Different types of bench planes are designed to perform different tasks, with the name and size of the plane being defined by the use. Bailey iron bench planes were designated by number respective to the length of the plane. This has carried over through the type, regardless of manufacturer. A No. 1 plane is but little more than five inches long. A typical smoothing plane (approx. nine inches) is usually a No. 4, jack planes at about fourteen inches are No. 5, an eighteen inch foreplane will be a No. 6, and the jointer planes at twenty-two to twenty-four inches in length are No. 7 or 8 respectively. A designation, such as No. 4½ indicates a plane of No. 4 length but slightly wider. A designation, such as 5-1/2 indicates the length of a No. 5 but slightly wider (actually, the width of a No. 6 or a No. 7), while a designation, such as 5-1/4 indicates the length of a No. 5 but slightly narrower (actually, the width of a No. 3). "Bedrock" versions of the above are simply 600 added to the base number (although no "601" was ever produced, such plane is indeed available from specialist dealers; 602 through 608, including all the fractionals, were made).
A typical order of use in flattening, truing, and smoothing a rough sawn board might be:
- A scrub plane, which removes large amounts of wood quickly, is typically around 9 inches (230 mm) long, but narrower than a smoothing plane, has an iron with a curved cutting edge, and has a wider mouth opening to accommodate the ejection of thicker shavings/chips.
- A jack plane is around 14 inches (360 mm) long, continues the job of roughing out, but with more accuracy and flattening capability than the scrub.
- A jointer plane (including the smaller fore plane) is between 18 to 24 inches (460 to 610 mm) long, and is used for jointing and final flattening out of boards.
- A smoothing plane, up to 10 inches (250 mm) long, is used to begin preparing the surface for finishing.
- A polishing plane is a traditional Japanese woodworking tool which takes an even smaller shaving than a western smoothing plane to create an extremely smooth surface. Polishing planes are the same length as western smoothing planes.
Planes may also be classified by the material of which they are constructed:
- A wooden plane is entirely wood except for the blade. The iron is held into the plane with a wooden wedge, and is adjusted by striking the plane with a hammer.
- A transitional plane has a wooden body with a metal casting set in it to hold and adjust the blade.
- A metal plane is largely constructed of metal, except, perhaps, for the handles.
- An infill plane has a body of metal filled with very dense and hard wood on which the blade rests and the handles are formed. They are typically of English or Scottish manufacture. They are prized for their ability to smooth difficult grained woods when set very finely.
- A ""side-escapement plane"" has a tall, narrow, wooden body with an iron held in place by a wedge. They are characterized by the method of shaving ejection. Instead of being expelled from the center of the plane and exiting from the top, these planes have a slit in the side by which the shaving is ejected. On some variations, the slit is accompanied by a circular bevel, cut in the side of the plane which causes the shaving to eject to the side through the open body of the plane.
Some special types of planes include:
- The spokeshave, is held horizontally by two symmetrical handles in line with the cutting edge of the iron. It has a very short sole, either flat, concave, or convex and is used for smoothing curved surfaces such as wagon spokes or tool handles.
- The shoulder plane, is characterized by a cutter that is flush with the edges of the plane, allowing trimming right up to the edge of a workpiece. It is commonly used to clean up dadoes (housings) and tenons for joinery.
- The moulding plane, which is used to cut mouldings along the edge of a board.
- The grooving plane which is used to cut grooves along the edge of a board for joining. Grooves are the same as dadoes/housings, but are being distinguished by running with the grain.
- The rabbet plane, also known as a rebate or openside plane, which cuts rabbets (rebates) i.e. shoulders, or steps.
- The fillister plane, similar to a rabbet plane, with a fence that registers on the board's edge to cut rabbets with an accurate width.
- The plow/plough plane, which cuts grooves and dadoes (housings) not in direct contact with the edge of the board.
- The router plane, which cleans up the bottom of recesses such as shallow mortises, grooves, and dadoes (housings). Router planes come in several sizes and can also be pressed into service to thickness the cheeks of tenons so that they are parallel to the face of the board.
- The chisel plane, which removes wood up to a perpendicular surface such as from the bottom inside of a box.
- The finger plane, which is used for smoothing very small pieces such as toy parts, very thin strips of wood, etc. The very small curved bottom varieties are known as violin makers planes and are used in making stringed instruments.
- The bullnose plane has a very short leading edge to its body, and so can be used in tight spaces; most commonly of the shoulder and rabbet variety. some bullnose planes have a removable toe so that they can pull double duty as a chisel plane.
- The combination plane, which combines the function of moulding and rabbet planes, which has different cutters and adjustments.
- The circular or compass plane, which utilizes an adjustment system to control the flex on a steel sheet sole and create a uniform curve. A concave setting permits great control for planing large curves, like table sides or chair arms, and the convex works well for chair arms, legs and backs, and other applications.
- The toothed plane, which is used for smoothing wood with irregular grain. and for preparing stock for traditional hammer veneering applications.
- The spar plane, which is used for smoothing round shapes, like boat masts and chair legs.
- The match plane, which is used for making tongue and groove boards.
- Hollows and Rounds, which are similar to moulding planes, but lack a specific moulding profile. Instead, they cut either a simple concave or convex shape on the face or edge of a board to create a single element of a complex-profile moulding. They are used in pairs or sets of various sizes to create moulding profile elements such as fillets, coves, bullnoses, thumbnails ovolos, ogees, etc. When making mouldings, hollows and rounds must be used together to create the several shapes of the profile. However, they may be used as a single plane to create a simple decorative cove or round-over on the edge of a board. Many of these holes and rounds can be classified in the category of side-escampement planes.
Planing with the grain.
Planing against the grain.
Planing wood along its side grain should result in thin shavings rising above the surface of the wood as the edge of the plane iron is pushed forward, leaving a smooth surface, but sometimes splintering occurs. This is largely a matter of cutting with the grain or against the grain respectively, referring to the side grain of the piece of wood being worked.
The grain direction can be determined by looking at the edge or side of the work piece. Wood fibers can be seen running out to the surface that is being planed. When the fibers meet the work surface it looks like the point of an arrow that indicates the direction. With some very figured and difficult woods, the grain runs in many directions and therefore working against the grain is inevitable. In this case, a very sharp and finely-set blade is required.
When planing against the grain, the wood fibers are lifted by the plane iron, resulting in a jagged finish, called tearout. Planing against the grain in this manner is sometimes called "traverse" or "transverse" planing.
Planing the end grain of the board involves different techniques, and frequently different planes designed for working end grain. Block planes and other bevel-up planes are often effective in planing the difficult nature of end grain. These planes are usually designed to use an iron bedded at a "low angle," typically about 12 degrees. Hacksaw
From Wikipedia, the free encyclopedia
Typical full-size hacksaw frame, with 12" blade
This article is about the tool. For other uses, see Hacksaw (disambiguation).
A hacksaw is a fine-toothed saw, originally and principally for cutting metal. They can also cut various other materials, such as plastic and wood; for example, plumbers and electricians often cut plastic pipe and plastic conduit with them. There are hand saw versions and powered versions (power hacksaws). Most hacksaws are hand saws with a C-shaped frame that holds a blade under tension. Such hacksaws have a handle, usually a pistol grip, with pins for attaching a narrow disposable blade. The frames may also be adjustable to accommodate blades of different sizes. A screw or other mechanism is used to put the thin blade under tension. Panel hacksaws forgo the frame and instead have a sheet metal body; they can cut into a sheet metal panel further than a frame would allow. These saws are no longer commonly available, but hacksaw blade holders enable standard hacksaw blades to be used similarly to a keyhole saw or pad saw. Power tools including nibblers, jigsaws, and angle grinders fitted with metal-cutting blades and discs are now used for longer cuts in sheet metals.
On hacksaws, as with most frame saws, the blade can be mounted with the teeth facing toward or away from the handle, resulting in cutting action on either the push or pull stroke. In normal use, cutting vertically downwards with work held in a bench vice, hacksaw blades should be set to be facing forwards. Some frame saws, including Fret Saws and Piercing Saws, have their blades set to be facing the handle because they are used to cut by being pulled down against a horizontal surface.
While saws for cutting metal had been in use for many years, significant improvements in longevity and efficiency were made in the 1880s by George N. Clemson, a founder of Clemson Bros., Inc of Middletown, New York, USA,. Clemson conducted tests which involved changing the dimensions, shapes of teeth, styles of set, and variable heat treatments of blades. Clemson claimed enormous improvements to the cutting ability of blades and built a major industrial operation manufacturing hacksaw blades sold under the trade name Star Hack Saw. In 1898, Clemson was granted US Patent 601947, which details various improvements in the hacksaw.
Blades are available in standardized lengths, usually 10 or 12 inches for a standard hand hacksaw. "Junior" hacksaws are typically 150mm long. Powered hacksaws may use large blades in a range of sizes, or small machines may use the same hand blades.
The pitch of the teeth can be anywhere from fourteen to thirty-two teeth per inch (tpi) for a hand blade, with as few as three tpi for a large power hacksaw blade. The blade chosen is based on the thickness of the material being cut, with a minimum of three teeth in the material. As hacksaw teeth are so small, they are set in a "wave" set. As for other saws they are set from side to side to provide a kerf or clearance when sawing, but the set of a hacksaw changes gradually from tooth to tooth in a smooth curve, rather than alternate teeth set left and right.
Hacksaw blades are normally quite brittle, so care needs to be taken to prevent brittle fracture of the blade. Early blades were of carbon steel, now termed 'low alloy' blades, and were relatively soft and flexible. They avoided breakage, but also wore out rapidly. Except where cost is a particular concern, this type is now obsolete. 'Low alloy' blades are still the only type available for the Junior hacksaw, which limits the usefulness of this otherwise popular saw.
For several decades now, hacksaw blades have used high speed steel for their teeth, giving greatly improved cutting and tooth life. These blades were first available in the 'All-hard' form which cut accurately but were extremely brittle. This limited their practical use to benchwork on a workpiece that was firmly clamped in a vice. A softer form of high speed steel blade was also available, which wore well and resisted breakage, but was less stiff and so less accurate for precise sawing. Since the 1980s, bi-metal blades have been used to give the advantages of both forms, without risk of breakage. A strip of high speed steel along the tooth edge is electron beam welded to a softer spine. As the price of these has dropped to be comparable with the older blades, their use is now almost universal.
Hacksaw blade specifications: The most common blade is the 12 inch or 300 mm length. Hacksaw blades have two holes near the ends for mounting them in the saw frame and the 12 inch / 300 mm dimension refers to the center to center distance between these mounting holes.
12 Inch Blade
Hole to hole: 11 7/8 inches / 300. mm
Overall blade length: 12 3/8 inches / 315 mm (not tightly controlled)
Mounting Hole diameter: 9/64 to 5/32 inch / 3.6 to 4 mm (not tightly controlled)
Blade Width: 7/16 to 33/64 inch / 11 to 13 mm (not tightly controlled)
Blade Thickness: 0.020 to 0.027 inches / 0.5 to 0.70 mm (varies with tooth pitch and other factors)
The kerf produced by the blades is somewhat wider than the blade thickness due to the set of the teeth. It commonly varies between 0.030 and 0.063 inches / 0.75 and 1.6 mm depending on the pitch and set of the teeth.
The 10 inch blade is also fairly common and all the above dimensions apply except for the following:
Hole to Hole: 9 7/8 inches / 250 mm
Overall blade length: 10 3/8 inches / 265 mm (not tightly controlled)