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There is a great variety of saw blades on the market. For woodworking there is variety of saw blades obtainable, that are available to both amateur and professional woodworkers, depending upon their particular woodworking needs.
There are blades designed for circular saws, jigsaws, and band saws, as well as hacksaws, coping saws, and other specialized types of saws. The most important factors to consider when choosing a saw blade are the composition, shape, and geometry of its teeth. These three factors will determine what kinds of projects the saw blade is best suited for.
Teeth can blunt and square or pointy, tipped forward or backward, or be the same shape or different shapes. As a general rule, the more teeth a blade has, the smoother it cuts.
However, more teeth always means slower cutting and more force required; fewer teeth means faster cutting speed and a reduction in force required.
In addition to the number of teeth on a blade, their shape and location affect the force that is needed to cut, as well as the speed and quality of the cut. The way the teeth are positioned is called a "grind."
A flat-top tooth is square. While it cuts somewhat like a chisel and is known for plowing nicely with the grain, it also splinters its way roughly across the grain if wood is cut. An alternate top bevel blade has teeth that angle from side to side, and is used to create crisp edges. Because it cuts well both across the grain and against it, it's the most widely used type of tooth grind used on general-purpose blades. While steeper angles cut cleaner, they also aren't as durable.
A third type of major grind is called the triple chip. In the triple chip grind, a chamfered tooth is alternated with a flat-top tooth. This grind is commonly used for sheet goods, as the chamfered teeth score the material, minimizing chipping and tear-out.
Finally, the alternate top bevel plus raker has a combination of teeth, usually a grouping of three alternate top bevels and one raker.
When it comes to blades, there are five basic styles, each designed for different materials and cutting tasks. A rip blade has big, uniform gullets, 24 flat teeth, and 15 degrees to 18 degrees of hook. Different saw blade varieties include fewer or more teeth, as well as different degrees of hook.
A cutoff blade can be recognized by its many teeth. Most have between 60 and 80 teeth and 10 degrees of hook. The high tooth count allows for a smooth cut, and cutoff blades in general are good for slicing cleanly across the grain.
The combination blade is a very popular blade, and is usually made up of 50 or so alternate top bevel plus raker teeth. This versatile blade cuts a variety of materials very quickly, with a minimal amount of splintering.
The all-purpose blade is the most commonly used blade. These blades can do a little of everything, and usually have about 40 teeth.
Saw Blades
by Ran Lancon
Carbide Saw Blades
Thin Kerf Saw Blades
The request is usually the same - "Just give me a blade that will cut everything." The response is just as simple - "there's no such thing!" Carbide tipped saw blades are used to cut almost everything from asbestos to Zirconium, including paper, plastics, rubber, steel, insulation, aluminium, and even food, as well as every kind of wood in the world and all the wood composites. Sure, almost any of the dozens of blade styles will actually cut all of these materials, but when you consider accuracy, finish, tool life and safety, there is no blade that will do everything.
The variety of machines carbide blades run on is just as diverse as the materials they cut. On a table saw, for example, the material is pushed through the blade and the cutting action is downward, whereas the radial arm saw is just the opposite - the blade moves into the material and the cut is upward. It only makes sense that the same style blade will not work equally on both. Because of this wide variety of materials and machines - with new ones being developed all the time - the saw blade industry is constantly updating and modifying blade designs. For our purposes here we will consider blades for cutting wood and wood composites. The first consideration in a carbide saw blade is quite simple - diameter. Use the saw diameter the machine was designed for. Cutting the cost by going to a smaller blade is not saving anything. Even if the material being cut doesn't require the depth of cut you will get from the proper size blade, you want the rim speed attained by a full diameter blade. The reduction in blade life and the likely decrease in cut quality will more than outweigh the initial saving. Next consider tooth count. The basic rule is the more teeth the finer the cut, but you also have to consider the thickness of the cut and the cutting feed rate. The fine tooth saws do tend to leave a smoother finish, because each tooth takes a smaller bite. However, if the material is too thick (remember, it's the overall thickness when it's stacked that's important), or if it is being fed at a high rate, the gullet capacity of fine tooth blades is too small. The gullet is the open space between the teeth and inadequate gullet capacity will cause burning, poor quality cut, and possibly heat damage to the blade. Conversely, not enough teeth will cut aggressively, at lower feed, or on thinner materials and leave a rougher finish.
If you are cutting material that is finished on two sides, the tooth count may have to be higher and/or the feed rate lower, unless there is a scoring blade. Pre-scoring will allow a coarser tooth count and therefore a higher feed. So. if you make any changes to the material thickness, feed rate, or finish requirements, you may want to adjust tooth count accordingly.
The last consideration is the tooth style. Blade manufacturers usually have specific brand names or numbers for the various tooth styles they offer. Generally, however, they fall into one of three categories: Square Top style - rip saw, for down grain cutting of solid wood; Alternate Top Bevel (ATB) style - cut-off saw, for cross grain cutting; and Triple Chip style - designed primarily for composite board cutting. In addition to these basic designs there are specialty blades for specific applications that represent a small percentage of the saw blade market. These are often overlooked, yet can be very useful for solving specific problems, improving the product, or even eliminating a manufacturing step. The following is a few of the more common specialty blades available at most saw blade suppliers.
Thin Kerf/Thin Rim Saws - These blades come in all tooth styles, depending on the application. Thin rim saws have a thick body core, but the plate is thinner at the outer rim. On thin kerf saws the entire plate is thin. Thin rim blades have a maximum cutting depth limited by the depth of the rim. They can be used with standard saw collars. Thin kerf saws have no preset depth of cut limitations, but usually should be used with larger and very accurate saw collars or stabilizers for strength and accuracy. Neither of these blades is recommended for deep cutting. Thin Kerf/ Thin Rim blades are very popular in the plastic display business, but can also be very useful in fine woodworking, thin material cutting, and even cutting melamine and other laminates. The advantages are low resistance cutting, low waste, and generally an excellent finish. Overheating, running them too dull, pushing them too hard, or running them on poorly maintained equipment and/or collars will take away all the advantages of thin kerf sawing and could cause permanent damage to the blade. Attention must be paid to setting the blade height correctly, and they should never be used on unstable or green material. Sharpening is also critical, as the tooth geometry must be maintained. Thin blades should only be used for finish cutting.
Chip Limiter Rip Saws - These blades are more widely used in Europe than North America. Between each tooth there is a hump-like shape, designed to limit the amount that the tooth following the hump will bite. The primary purpose of this is safety in hand feed ripping applications. The chip limiting hump will resist over-feeding, jamming and possible kick-back by controlling the in-feed rate of the material.
Double End Tenon Saws - The tooth style on these is usually 3 or 4 teeth all top bevelled one way, and one tooth bevelled the opposite way. The purpose is so that 75 to 80% of the teeth are giving a clean finish on one side of the material, because the other side is waste. For obvious reasons, these blades come in left and right hand for each side of the tenoned. This style is also used on edge benders for trimming, and has also been used on other types of machines when one side is always waste.
Negative Hook Saws - These blades are available in Alternate Top Bevel and Triple Chip tooth styles. There are two primary applications for this type of blade - the first being on overhead machines, particularly mitre saws ( they are absolutely necessary on sliding mitre saws) and often on radial arm saws. On these machines the negative angle of the tooth prevents the material from lifting and jamming the blade, plus the surface finish is usually better than the standard positive hook blades. The other application for negative hook blades is on table saws cutting double sided melamine board where there is no pre-scoring. In this application, when the blade is set at the correct height, a satisfactory surface finish can usually be achieved, as well as a reasonable life to the blade's cutting edge.
Hollow Ground or Hollow Face Saws - These are specifically used for cutting double sided composite board, usually melamine. By design, the edges are very sharp and they do an excellent job of leaving a chip-free finish, top and bottom. The downside is that they tend to wear faster than some other styles and are little more expensive to sharpen. When conventional blades designed for this purpose will not work satisfactorily on a particular machine, usually the hollow ground blade will solve the problem.
High ATB (Alternate Top Bevel) and Alternate Face Bevel Blades - These are used in composite board applications where surface chipping is a problem. Each tooth is ground to a very sharp and fragile point for cutting the surface fibres as cleanly as possible. They should never be used for solid wood sawing as the intermittent cutting resistance can cause tooth breakage.
These are just a few of the many designs of carbide saw blades. Combinations of these tooth styles and others, along with variations in hook, kerf, clearance angles, carbide grades, and tooth pitch, make it possible to solve most sawing problems in wood and other machinable materials.
Thin
Kerf Saw Blades
Thin Kerf Sawing is the principle of reducing the thickness of the saw
tooth., which reduces the width of the cut. This reduction in kerf can
have a significant effect on waste reduction. For example, a standard 12
inch diameter Rip Saw has a kerf of approximately 0.155". A Thin Kerf
Saw at 0.095" would reduce waste by almost 40%. This would also
create an increase in either finished size or, quantity of pieces
produced.
Thin Kerf Sawing is primarily used in Multi-Rip applications, because the
gains are more predominant. Ripping 6 inch wide material to a finish of
3/4's of an inch would produce one full extra piece, if using the example
above. At 50 ft. / min. this translates to 3000 lineal ft. per hour that
you are getting paid for, with no increase in material or labour cost.
Unless your goal is to increase finished size there may be little to gain
in single or even double line ripping, or for that matter in
cross-cutting, or trimming applications.
The upside to thin kerf sawing is quite simple and obvious, so why isn't
it an accepted normal practice? This is where it can get complex and why
in some applications it just won't work. Every application for thin kerf
sawing is unique, in that there is such a large number of questions and
specifics to be considered, there is always some variations.
The kerf you are trying to achieve is probably the first thing to
consider. The finish size and the raw board size will determine the ideal
kerf. In the example above, reducing the kerf further would not improve
yield, and since the kerf required is inversely proportional to the degree
of difficulty, there is little benefit to asking for 0.070" kerf, and
a whole lot more to be addressed. The biggest obstacle to overcome is
dealing with the body weakness of extra thin saw blades. The tooth is not
the problem. It's the saw plate supporting the tooth that fails if the
correct conditions for cutting are not maintained. Whatever the kerf is,
the saw body has to be even thinner, to provide adequate side clearance
(how much thinner depends on the material being cut) . Without side
clearance, friction would occur between the saw plate and the wood,
causing heat generation. Heat is your worst enemy. If heat is created in
the body, expansion and warpage will follow, creating even more heat, by
friction and cutting resistance. In heavy kerf saws a limited amount of
heat can be absorbed and dissipated by the heavy body, but with thin
bodies the heat builds faster, has no place to dissipate, and will do more
damage because the blade is more fragile.
It is well known that different materials have different machining
properties. Also, different materials have differing affects on the on the
cutting tool. Harder woods have more cutting resistance and require a
stronger blade. All other conditions being equal, you could reduce kerf a
little more when ripping softwood. Factor in moisture content here. A dry
wood machine better (unless, of course, it is too dry) and is a lot easier
on the blades than wet wood. The higher the moisture content the more side
clearance is required (therefore higher kerf) to keep the material from
rubbing on the plate. Wetter wood also greatly increases the wear on the
teeth, again increasing the cutting resistance. Dressing is critical
before thin ripping. Rough material will not go smoothly through the feed
system and the material needs to be fed into the blade(s) firmly and
securely, without any movement or vibration, therefore it must be D4S
before ripping. How thick is the cut? This can affect how the blade is
designed and how it is mounted. If, for example, the depth is 3/4",
the blade could be designed to be thin only on the outer 1 to 1 1/4 inch
of the rim, giving it greater strength and a bit better at heat
dissipation. In lieu of this stepped body, or in conjunction with it, the
spacers or saw collars could be made larger, strengthening the saw and
absorbing some heat.
Feed and Speed. The feed rate is dependant on several factors. Higher
blade speeds allow higher feed rates, but, particularly with thin kerf
sawing, material dimensions have a significant affect on the rate of
cutting. Over-loading the blades will damage them - often irreparably -
and under-feeding can cause substantial increased wear on the teeth.
The last thing we need to know is the type of machine and blade diameter.
Thin kerf ripping can be done on a Multi-Rip or a Moulder. Moulders have
certain advantages over Rip Saws in that they usually run at higher RPM.
This allows for either increases in feed and/or using smaller diameter
saws. The smaller the diameter, the more stable the blade is.
Although thinner blades offer less cutting resistance a gang of them can
require a lot of power to drive them. Inadequate horse power will result
in too much load on the blade. The blade will bog down, and heat up.
Heavier blades, again, may be able to absorb a certain amount of increased
cutting pressure, but not extra thin blades, and depending on the job, a
standard machine may not have enough power to achieve the desired
productivity from thin kerf saws.
Glossary of Saw Blade Terms
Anti-Kick Saw Blades: Saw Blades with anti-kickback shoulders that limit the amount of material that can safely be cut by each tooth. This virtually eliminates the kickback caused by overfeeding. Also called safety saw blades.
Anti-Stick Coatings: As used on saw blades, these coatings decrease friction and heat buildup and help provide cleaner, smoother and quieter cutting action. Anti-stick coatings also resist resin and pitch buildup and improve safety conditions.
Arbor: The shaft, driven by the saw's motor, which turns the saw blade. Also called a mandrel.
Chipper: In dado sets, small cutting tools with varying widths. Chippers are places between the cutters, or the outside blades, of the dado set to adjust the width of the cut.
Chipping: The condition caused when the saw blade lifts and tears the wood fibers as it exits the material. This causes the edge of the cut to be ragged.
Clearance Angle: The angle between the lower face of a saw blade and the material being cut.
Combination Saw Blade: Saw blades used for both ripping (cutting with the grain of the wood) and crosscutting (cutting across the grain).
Crosscut: A cut made across the grain of the wood.
Cutoff: Refers to the smooth cutting of wood, plywood, chipboard, paneling, pressboard, etc.
Cutter: In dado sets, the two larger, outside blades.
Cutting Angle: The angle between the upper face of the saw blade and the material being cut. Also known as a rake angle.
Dado: (1) A flat-bottomed recessed cut made across the grain of a board. (2) A set of blades used to produce precision grooves.
Dampener: Used to improve saw blade performance by stiffening the saw blade plate and dampening sound and vibration caused by the saw's belt, motor, and bearings. Dampeners are mounted on the saw's arbor directly next to the blade. Also called a saw blade stabilizer.
Ferrous: Of or containing iron.
Finishing Saw Blade: A saw blade with higher tooth counts to provide smoother cuts. Typically refers to 7 1/4 inch blades with more than 40 teeth and 10 inch blades with more than 60 teeth.
Framing Saw Blades: Carbide tipped saw blades used to make fast sizing cuts in all types of wood. (the fastest cutting is achieved with thin kerf saw blades.)
General Purpose Saw Blades: Saw blades with low tooth counts used for fast crosscutting and ripping in most woods and wood-related materials. This designation is commonly used with opening price point carbide blades.
Groove: A recessed cut made across the grain of the wood. A groove has two straight sides that are at a 90 degree angle with a flat bottom. See also Plough.
Hollow Ground: A concave bevel edge on a tool.
Miter: The process of cutting material for an equal angle joint.
Nonferrous: Materials and metals not of or containing iron, such as aluminum, copper, brass and lead.
Plane: In woodworking, to make a surface smooth or even.
Plough: A recessed cut made with the grain of the wood. A plough cut has two straight sides that are at a 90 degree angle to a flat bottom. See also Groove.
Precision Finishing Saw Blade: Precision sharpened saw blades with a high tooth count and thicker kerf. These blades provide very smooth cuts in hardwood, softwood, plywood, chipboard, panelling, and Marlite.
Rabbet: An open-ended cut made along the edge of a work piece that receives or interlocks with another piece to form a joint
Ripping: The process of sawing a board in the direction of the grain of the board.
Runout: The amount of wobble in a saw blade, or how much the blade moves from left to right during use. Also called wobble or warp. Oldham saw blades have very little or no runout.
Shim: (1) A thin, often tapered piece of material such as metal or wood used to fill in space between things. (2) A round, usually magnetic disc used with a dado blade to provide a wider cut.
Stopped Groove: A cut made along the grain that stops short of one or both ends of the work piece.
Tear-out: A condition in which the saw blades tears out the grain of a work piece.
Thin Kerf Saw Blades: A saw blade with a kerf, or cut width, between .065 and .070 inches.
Worm Drive Saw: A saw that has a diamond-shaped arbor instead of a round arbor.