Cold saw
Encyclopedia
Cold
Cold describes the condition of low temperature.Cold may also refer to:*Common cold, a contagious viral infectious disease of the upper respiratory system*Chronic obstructive pulmonary disease...
, unlike an abrasive saw
Abrasive saw
An abrasive saw, also known as a cut-off saw or metal chop saw, is a power tool which is typically used to cut hard materials, such as metals. The cutting action is performed by an abrasive disc, similar to a thin grinding wheel...
, which abrades the metal and creates a great deal of heat in the metal and cutting blade. Cold saws use either a solid high speed steel
High speed steel
High speed steelMost copyeditors today would tend to choose to style the unit adjective high-speed with a hyphen, rendering the full term as high-speed steel, and this styling is not uncommon . However, it is true that in the metalworking industries the styling high speed steel is long-established...
(HSS) or tungsten carbide
Tungsten carbide
Tungsten carbide is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery,...
-tipped, resharpenable circular saw blade. They are equipped with an electric motor and a gear reduction unit to reduce the saw blade's rotational speed while maintaining constant torque. This allows the HSS saw blade to feed at a constant rate with a very high chip load per tooth. A cold saw cut produces minimal burr, no sparks, no discoloration and no dust. The material being cut must be mechanically clamped to prevent movement during the cutting process. Extra care should be taken to choose the appropriate number of teeth, saw blade type, cutting speed and feed rate. All of these variables are based on the type and size of material being cut. Cold saws are capable of machining most ferrous and non-ferrous alloys. Cold saws are intended to be used with a flood coolant system to keep the saw blade teeth cooled and lubricated.
Portable saws
These saws were primarily designed for sheet metal roofers in the building industry. Cold saws, as opposed to abrasive sawAbrasive saw
An abrasive saw, also known as a cut-off saw or metal chop saw, is a power tool which is typically used to cut hard materials, such as metals. The cutting action is performed by an abrasive disc, similar to a thin grinding wheel...
s, are used so that protective coating is not damaged. They also have a heavy duty aluminium catcher which is useful for capturing the swarf
Swarf
Swarf, also known as turnings, chips, or filings, are shavings and chippings of metal — the debris or waste resulting from metalworking operations including milling and grinding. It can usually be recycled, and this is the preferred method of disposal due to the environmental concerns regarding...
.
They can cut up to 6 mm (0.236220472440945 in) thick mild steel. They use cermet
Cermet
A cermet is a composite material composed of ceramic and metallic materials. A cermet is ideally designed to have the optimal properties of both a ceramic, such as high temperature resistance and hardness, and those of a metal, such as the ability to undergo plastic deformation. The metal is used...
tipped blades.
Blades
Cold saw blades are circular metal cutting saw blades categorized into two types: solid HSS or tungsten carbide-tipped (TCT). Both types of blades are resharpenable and may be used many times before being discarded. Cold saw blades are used to cut metal using a relatively slow rotational speed, usually less than 5000 surface feet per minute (SFM) (25m/s), and a high chip load per tooth, usually between .001" - .003" (0.025 - 0.08mm) per tooth. These blades are driven by a high power motor and high-torque gear reduction unit or an AC vector drive. During the cutting process, the metal is released in a shearing action by the teeth as the blade turns and the feed mechanism moves the blade forward. They are called "cold saw blades" because they transfer all the energy and heat created during the cutting process to the chip. This enables the blade and the work material to remain cold.Classification
The first type of cold saw blade, solid HSS, may be made from either M2 tool steelTool steel
Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures...
or M35 tool steel, alloyed with additional cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
. Solid HSS saw blades are heat treated and hardened to 64/65 HRC
Rockwell scale
The Rockwell scale is a hardness scale based on the indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. There are different scales, denoted by a single...
for ferrous cutting applications and 58/60 HRC for non-ferrous cutting applications. This high hardness gives the cutting edges of the teeth a high resistance to heat and wear
Wear
In materials science, wear is erosion or sideways displacement of material from its "derivative" and original position on a solid surface performed by the action of another surface....
. However, this increased hardness also makes the blades brittle
Brittle
A material is brittle if, when subjected to stress, it breaks without significant deformation . Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a snapping sound. Brittle materials include most ceramics and glasses ...
and not very resistant to shock
Electric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
. In order to produce a high quality HSS cold saw blade, you must start with very flat and properly tensioned raw material. The blades must be press quench
Quench
In materials science, quenching is the rapid cooling of a workpiece to obtain certain material properties. It prevents low-temperature processes, such as phase transformations, from occurring by only providing a narrow window of time in which the reaction is both thermodynamically favorable and...
ed after hardening to prevent them from being warped. The term HSS doesn't necessarily mean what it implies. These blades are usually never run at surface speeds higher than 350 SFM. Solid HSS cold saw blades may be used for cutting many different shapes and types of metal including: tubes, extrusion
Extrusion
Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section...
s, structural sections, billets, bars, ingot
Ingot
An ingot is a material, usually metal, that is cast into a shape suitable for further processing. Non-metallic and semiconductor materials prepared in bulk form may also be referred to as ingots, particularly when cast by mold based methods.-Uses:...
s, casting
Casting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...
s, forging
Forging
Forging is a manufacturing process involving the shaping of metal using localized compressive forces. Forging is often classified according to the temperature at which it is performed: '"cold," "warm," or "hot" forging. Forged parts can range in weight from less than a kilogram to 580 metric tons...
s etc. These blades may also be coated with special wear resistant coatings such as titanium nitride
Titanium nitride
Titanium nitride is an extremely hard ceramic material, often used as a coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface properties....
(TiN) or titanium aluminum nitride (TiAlN).
The second type of cold saw blade, tungsten carbide-tipped (TCT), are made with an alloy steel body and tungsten carbide inserts brazed to the tips of the teeth. These tips are ground on all surfaces to create tangential and radial clearance and provide the proper cutting and clearance angles on the teeth. The alloy body is generally made from a wear resistant material such as a chrome vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
, heat treated to 38/42 HRC. The tungsten carbide tips are capable of operating at much higher temperatures than solid HSS, therefore, TCT saw blades are usually run at much higher surface speeds. This allows carbide-tipped blades to cut at faster rates and still maintain an acceptable chip load per tooth. These blades are commonly used for cutting non-ferrous alloys, but have gained significant popularity for ferrous metal cutting applications in the last 10 years. The tungsten carbide inserts are extremely hard (98 HRC) and capable of very long wear life. However, they are less resistant to shock than solid HSS cold saw blades. Any vibration during the cutting process may severely damage the teeth. These cold saw blades need to be driven by a backlash free gear box and a constant feed mechanism like a ball-screw
Ball screw
A ball screw is a mechanical linear actuator that translates rotational motion to linear motion with little friction. A threaded shaft provides a helical raceway for ball bearings which act as a precision screw. As well as being able to apply or withstand high thrust loads, they can do so with...
feed.
Future
The popularity of cold saw blades is increasing due to the technological advancements in cold saw machines. They are the sawing method of choice when high production requirements are needed. They consistently produce the lowest cost per cut among all sawing methods: hot sawing, friction sawing, bandsawing and hacksawHacksaw
A hacksaw is a fine-tooth saw with a blade under tension in a frame, used for cutting materials such as metal or plastics. Hand-held hacksaws consist of a metal arch with a handle, usually a pistol grip, with pins for attaching a narrow disposable blade. A screw or other mechanism is used to put...
ing.