There is a wide variety of rotary saw blades being marketed for fire service use. Many of these blades are quite expensive, and I’ve yet to have a “loaner” blade offered. So, not only might you spend money on a blade that doesn’t meet your needs, you may have to make do for a while.
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The purpose of this article is to provide users with information to make a more informed decision when sorting through the specifications. Aside from misspending money, you may void your saw warranty and create a safety problem for your crews.
A historical perspective is always helpful: What have you had to cut on past calls? And, how did the saw and blade combination perform? Are there any new risks moving into the community?
BLADE RPM VS. SPINDLE SPEED RPM VS. PERIPHERAL SFPM
When shopping for a blade, compare the spindle speed (revolutions per minute, or rpm) of your saw to the rpm rating of the blade. Matching the blade specifications to the saw capabilities is important to get the best, safest performance from both.
The peripheral speed of a blade is measured at the outer edge of the blade and will be different for a 12- and 14-inch blade, typically between 16,000 and 18,000 surface feet/minute (sfpm), respectively. What you want is the spindle speed, or the actual rpm of the saw arbor, and this will be different from engine rpm (the rate the spark plug fires, typically a maximum of 9,000 rpm), so read your manual and be sure to correctly match the “right” rpm to your saw and blade. These speeds create a gyroscopic effect on the saw so it resists changes in orientation.
Three major saw manufacturers’ spindle speeds range from 5,100 to 5,400 rpm at no load, full speed. When using a 12-inch blade, the cutting depth will be 3 inches. A 14-inch blade has a cutting depth of 5 inches. Adjust the blade guard to control cutting depth. For comparison, an electric 7¼-inch circular saw has a maximum rpm of 1,500. The rpm is not a good indicator of cutting speed—that will be dictated by blade condition/application, material size/type, and density. Cutting speed/feed rate is also greatly determined by how well your saw is operating. With any blade, cut at 90° to the work piece, if possible. Do not force the saw so much that it slows more than 10% of full unloaded speed. If the blade stops rotating, let off the trigger and remove the blade from the cut to prevent damage to the drive belt. Listening to the saw/blade is key to efficient cutting.
Whenever possible, do not stand directly in line with a blade when cutting. Do not twist the blades while cutting; they can only be loaded in a radial manner (pushing straight down). Use caution if cutting in the upper quadrant of any blade. This may cause an unwanted reaction force and make the saw climb up and away from the operator, possibly causing an injury.
SAW/BLADE ARBOR SIZE
Your saw will most certainly have an arbor (where the saw blade mounts) of 20 mm, 7â„8 inch, or 1 inch. Bushings are available to adapt 20 mm to 17â„8 inch and 7â„8 inch to 1 inch. These bushings can be metal or plastic, worth having in your toolbox. To secure the blade, torque the arbor bolt 22 to 25 foot-pounds.
ABRASIVE COMPOSITE BLADES
Abrasive composite blades have maximum rpm of 5,200 for 12-inch blades and 6,000 for 14-inch blades. These are offered for specific applications and will be labeled as such: wood, plastic, ceramic, stainless steel, steel, aluminum, iron, and so on. These cutting discs are made of highly abrasive materials (for our purposes) such as aluminum oxide and silicon carbide. They are the most affordable rotary saw blade; however, they wear out fast.
These blades lose diameter as they grind, cutting shallower and shallower as they go. This process exposes fresh grit to maintain uniform grinding. Take care not to side load any blades but especially these, as they will crack and shatter. Inspect blades for any cracks or damage. Any damage is reason enough to throw them away. When first starting up a saw with a fiber blade, hold it away from everyone and run it at full speed to see if the centrifugal forces tear it apart. If it stays together, put it to work.
Do not allow these blades to be exposed to gasoline and oils, which can degrade the resin bonding of the fibers and grit. Silicon carbide has a harder grit compared with aluminum oxide, but silicon carbide is less durable because it is brittle and has a narrower shape that wears down at an increased rate.
CARBIDE BLADES
Twelve-inch carbide blades have a maximum rpm of 6,000, while 14-inch blades have a maximum rpm of 5,500. It is usually not recommended by gas rotary saw manufacturers to use a carbide blade (check the manual), but carbide blades are used by many fire departments. The Occupational Safety and Health Administration (OSHA) requires a fully guarded blade on any cutoff blade larger than 4 inches. Fire departments are not exempt from OSHA regulations. The risk OSHA is trying to control is a carbide segment breaking off from the core and flying at high speed, injuring someone. However, if you use this type of blade on your rotary saw, document that you have trained your staff in the risks involved with using this blade plus the dos and don’ts (see sidebar). Sometimes the carbide segments can be resharpened by the factory or have fresh segments reattached. For emergency work, it is better to just buy a new blade that has not been stressed. Look for worn-down, chipped, broken, and missing teeth or chipped carbide tips.
Carbide blades do not have a set; the alternating bending of teeth to the right and left creates a kerf (space) wider than the blade to reduce the blade getting jammed. This is compensated for on carbide blades because the carbide teeth are wider than the saw core. These blades cut, making chips, not dust.
Thin sheet metal (bendable by hand) can be easily cut with a carbide blade. It will also cut polycarbonate plastic quite well. It cuts thin high strength steel alloy (HSSA) with ease. This blade works well for shingles and roof sheathing. It can handle nails easily enough, but do not try to cut heavy metal or concrete with this blade. You will see “carbide” blades for cutting steel and concrete. These are a different type of carbide called “cermet,” and cermet needs to run at a speed too slow for gas-powered rotary saws to cut these materials.
1 With a fiber wheel, point in a safe direction and run the saw up to full speed to test blade integrity/security before cutting. (Photos by author unless otherwise noted.)
2 Do not side load or expose a fiber wheel to gas or oil.
3 Inspect a carbide blade for any missing tips.
4 A carbide chunk, also marketed as a stump grinder.
For more information, please visit XMF.
WARTHOG BLADE© (12-INCH CARBIDE TIPPED)
This blade is constructed with carbide tips and designed for fire departments cutting through floors, walls, and roofs. A thicker blade design provides greater strength and durability. Always follow the manufacturer’s operating guidelines. Fewer teeth than a typical carbide blade results in a more aggressive cut. The large gullets between the teeth are necessary to provide space for the material being removed so it doesn’t jam up the blade. This is a heavy/wide saw blade—be prepared for the large pieces of debris it throws. This blade does not like being taken on and off, as it tends to put excessive wear on the bolt.
CHUNK CARBIDE BLADES
These blades have a maximum rpm of 5,350 for both 12- and 14-inch blades. Just as the name implies, chunks of carbide are attached to a steel core wheel rather than uniform tips. The core is thicker than other saw blades, and it cuts a wider kerf than a typical carbide blade. The chunks can cut the same materials as the carbide-tipped blades. They are typically more expensive than a traditional carbide-toothed blade. They can be used wet or dry.
CERMET BLADES
Cermet blades have rpm ratings of 1,800 to 3,500. Often called the new carbide, cermet has been around since the s and is also marketed as Carbide II. It is a blade tipped with a composite material of carbide, ceramic tungsten, titanium, and other elements, depending on the application. We use it to cut carbon steel, nonferrous metals, stainless steel, wood, and composite materials. It is a very efficient, durable blade that will outperform carbide or diamond.
Cermet blades cost up to 30% more but can last 50% longer. Some of the larger blades can be sent back to the manufacturer for resharpening, but the smaller blades are disposable. If you have missing and/or chipped teeth, replace the blade. These blades are rated to run slow—1,800 to 3,500 rpm—when compared with a two-cycle rotary saw, which can turn at more than 5,300 rpm.
DIAMOND BLADES ( MAX RPM 12-INCH: MAX RPM, 14-INCH)
Diamond blades have 6,400 maximum rpm for 12-inch blades and 5,400 for 14-inch. One of the most common questions related to this type of blade is, “Are diamond cutting wheels made of diamond?” The short answer is no. Diamond blades are very durable, abrasive wheels coated with diamond crystals on their cutting edge. The diamond crystals used are synthetic diamonds, not natural diamonds. Synthetic diamond crystals are some of the hardest materials available. These blades grind, creating dust. There are three types of shapes for the diamond cutting wheels:
- Segmented rim: Features narrow, U-shaped slots that improve air flow and dissipate heat when cutting. Suitable for dry cutting. Use for concrete, reinforced concrete, masonry, natural stone, and cement. Good for rescue.
- Continuous rim: Features solid J-slots that are suitable for wet application as the J-slots around the edge help to dissipate heat and increase cutting speeds. This type of wheel is ideal for very fine separating cuts. Use for porcelain, tiles, granite, marble, and ceramics—not for rescue work.
- Turbo rim: Features a continuous rim with an edge that is serrated for easy, fast, and smooth cutting. Suitable for both wet and dry cutting. Use for concrete, reinforced concrete, masonry, natural stone, and cement. It has the best heat resistance and is best for rescue.
Gas-Powered (2-Cycle) Rotary Saw Equipped with a Carbide-Tooth Blade SOP
The intent of this procedure is to provide guidance on safe and proper operation, including maintenance and inspection of a rotary saw carbide blade. All staff are to read this and comply.
- Any personnel operating (or nearby) the above name powered tool will be in full bunker gear, including eye protection. As possible, other support staff engaged in the operation will stay clear and not be in front of the saw while cutting.
- The gas rotary saw will be fueled and maintained per the manufacturer’s recommendations.
- The blade shall be made secure to the proper sized arbor.
- Carbide blades are suitable to cut roof coverings, sheet metal, car hoods, metal/wood doors, floor, and wall coverings. They are not to be used to cut concrete, block or bricks, or heavy gauge steel in rod or sheet form. If the suitability of the material is unknown, seek supervision.
- Personnel shall train until they are deemed proficient with handling and cutting (saw and blade) of various approved materials under supervision.
- Saw blades will be kept clean and free of corrosion. Any missing carbide teeth or other deformities shall be reported.
- Personnel are to be advised that there are multiple hazards when operating this saw, including but not limited to, laceration, the saw kicking back if the blade becomes pinched by the work piece, and carbide segments getting knocked off and becoming projectiles.
These blades are composed of a steel core or wheel with alloy segments on the tips containing bits of industrial diamond. Diamonds are embedded in the alloy, and as the blade grinds through the work piece, the alloy scrapes away, exposing fresh diamonds. When cutting some materials such as asphalt or steel, you may “glaze” your diamond blade, giving it a shiny appearance. Diamond segments should appear slightly rough and visible as small bumps in the alloy. If your cutting slows down, inspect the segments for glazing. To sharpen, or dress, a diamond blade, simply cut into some clean concrete, as this will reexpose fresh diamonds and increase cutting speed. Continued cutting with a glazed blade will cause the diamond segment/alloys to overheat and come loose from the steel core. As your diamond blade wears out, it will cut slower and slower and eventually won’t cut at all because the cutting segments have completely worn down.
The loose segments can fly off at extreme speed and cause injury to the operator or others. The alloy, or powdered metal, holding the diamonds is what gives the blade its application rating. Harder powdered metal will be rated for a softer application such as asphalt or green concrete. Softer powdered metal will be rated for harder material like older, more cured concrete.
You can cut steel with a diamond blade, especially concrete encased steel such as rebar. The blade will not become glazed because as the diamonds grind through the steel, it immediately passes against the concrete, which instantly resharpens. The problem with cutting steel with a diamond blade is the alloy matrix in which the diamonds are suspended. Nickel, almost always present in the matrix, becomes sticky when hot, and the steel adheres to it, clogging the diamonds and preventing grinding. Any missing, damaged, or cracked segments are cause for taking the blade out of service and replacing it. Diamond blades cannot be put on backward. You can determine the proper direction by looking for the comet trails, which is a tapering path left as the diamond grit wears away. Some blades will have a directional arrow on the core.
5 The Warthog is an aggressive, durable blade designed for fire departments. [Photo courtesy of the Miami Valley (OH) Fire District.]
6 When inspecting a diamond saw blade, rotate it and look for straightness, no missing/cracked segments, a thin coating of oil, and that it is properly secured.
Diamond blades can be rated for wet cutting (spraying water on the blade) or dry cutting (where the use of water is not required but can be used). The diamond blades used in the fire service are usually dry cut blades so, if you are without water, you can still cut. Using water will not damage a dry cut diamond blade, greatly reduces the amount of harmful dust created by cutting, creates a slurry for faster concrete cutting, and extends the life of the blade.
A common mistake when applying water to a diamond blade operation is to use too much water. The slurry (mixture of water and concrete dust) should form a peak when pinched. This abrasive mixture will speed your cutting. We often apply far too much water, overflushing the needed grit. Considerations for applying water include the following:
- Water placement: Ensure that adequate water flow is evenly distributed on each side of the blade during cutting.
- Water volume: Water volume should be roughly 4 gallons per minute and not a high-pressure flow to the blade. The proper water volume will increase as the depth of grind increases.
- Let the blade do the cutting: Excessive pressure on the blade while in the cut may cause the diamonds to glaze over, also creating stress cracks in the core, causing the blade to become out of round. When dry cutting, the blade should be allowed to cool off by allowing it to spin freely out of the cut every minute or so. Avoid dry cutting plastic pipe with this blade, as the heat will melt the plastic, sticking to the blade and almost certainly causing a kickback.
When water cannot be used, take measures to ensure that the operator does not inhale the dust/silica created by sawing. Concrete dust can cause silicosis, a serious lung disease. OSHA has regulations regarding silica dust and requires a (minimum) P100 NIOSH-approved respirator where silica dust is present.
MULTIPURPOSE DIAMOND BLADES
Great advances have been made in diamond saw blades. Several of the “multipurpose” diamond blades offer good performance over a wide range of materials. These blades are manufactured using a process called vacuum brazing. This process bonds the diamond segment to the steel core without using flux, giving it a stronger connection. This brazing process gives the blade better resistance to heat. But, as with most multipurpose things, it loses some performance by trying to meet all material applications. These blades make for good RIT blades where you may need to cut through multiple types of materials.
CLEANING AND MAINTENANCE
Often these rotary blades get built up with pitch, rust, tar, or gum, creating friction and slowing down the cut. Get a shallow pan large enough to immerse the blade. Soak it in a degreaser solution for 10 to 15 minutes. For other built up “gunk,” use a citrus-based cleaner. After soaking, use steel wool, a wire brush to remove, and polish. Apply a film of oil to prevent corrosion. This works for tarred-up chainsaw chains too.
Just because you may have not done any tough saw work in a while doesn’t mean your blade has not sustained damage. Regularly inspect your blade for any damage, cracks, missing segments, or bent cores. If you are feeling increased resistance to the saw/blade making progress, the blade may be dull, need to be dressed (exposing fresh grit), or cleaned. Keep fresh fuel in your well-tuned saw. Train your crews on what they can and can’t cut.
As an operational suggestion, have two rotary saws. Equip one with a carbide-tooth blade for vertical ventilation, floor, and wall cuts in ordinary construction. Outfit the second saw with a multipurpose diamond blade to cut commercial doors, heavy metal, car hoods (engine compartment fires), brick, and block. And, keep a supply of abrasive blades handy as a backup.
Contact us to discuss your requirements of Saw Blade Manufacturers. Our experienced sales team can help you identify the options that best suit your needs.
A common question that seems to appear very often on forums is "What sawblade should I get for my radial arm saw?" or "What's the best blade for my table saw?" and the answers never really change, so I thought I would compile this guide to help those asking the question.
I think for the hobbyist it can be quite daunting to select the correct blade for your machine and uses since there is such a massive variety of blades to be had and even more varying price differences. I hope I can break down all the jargon that all the manufacturers use and lay it out in simple terms to help you understand the differences between blades and what would be the best choice for you. If you're a newcomer to using a table saw I strongly recommend purchasing Steve Maskery's Workshop Essentials on the Table Saw which goes over all the health and safety aspects and how to use your machine properly, and above all else, make sure you do not annoy the push stick crusader.
Selecting a Size
Blades come in a massive variety of sizes, but there are a few standard diameters that most machines are made to accommodate which are namely 200mm, 216mm, 250mm, and 300mm. You should already know what diameter of blade your machine takes but what is often overlooked is what the diameter of the shaft of the saw is so that you can select the correct bore blade for the saw. There are a few different sizes of bore but the main three are 5/8", 1", and 30mm, 30mm bore is the new standard on pretty much all machines of the last couple of decades and there is a far greater variety of blades available with this bore size.
If your machine has a smaller diameter shaft than 30mm, you can still use 30mm blades but you will need what is called a "Bore Bushing" or "Reducing Ring" or "Blade Washer" which will reduce the bore of your blade from 30mm down to the size needed for your saw. Something to keep in mind though is if your saw has "cupped flanges" the bore spacer can work loose out of the blade into the hollow spaces left between the flanges which will allow the blade to become unbalanced and an accident can occur. The best course of action is to superglue the reducer into the bore instead of peining or centre punching it into place as that can upset the tension of the saw plate and potentially warp the plate, It would also be good practice to use 30mm bore fibre washers either side of the blade that fit in the space in the flanges so that the reducer cannot work free. It is worth seeking out a lathe-turned bushing rather than one that's been punched out of a sheet like a washer, the turned bushing will be more accurate and concentric which will eliminate any wobble or vibration that you may get with a more inaccurate, stamped bushing.
There are also different sized "Kerfs" (The width of material removed in a cut) ranging from just under 2mm up to 3mm, the narrower blades tend to require a new, narrower riving knife to be fitted so that the timber does not bind on it, it's best to stick to the kerf of blade your machine is designed for until you need a more specialized width of kerf.
Something else to also keep in mind is whether your saw needs a blade with pinholes or not, some modern saws have pinned flanges to keep the blade, outer flange and nut/screw locked to the shaft without coming undone under braking. Good-quality saw blades usually come with pinholes pre-drilled into the saw plate so it's best to select a blade with them already put in if your saw requires it but it is possible to drill holes in an existing saw plate to make it work, a saw plate is fairly hard so you will want to use at least a cobalt drill bit or ideally a solid carbide drill bit a little larger than the pinhole diameter, clamp the saw plate solidly to a piece of timber and slowly drill the holes at the required spacing with plenty of oil/coolant, you really do not want to introduce heat or stresses into the saw plate which can mess with the tension of the blade and warp it .
Cutting Tooth Materials
At the moment there are three different types of cutting teeth you will find on circular saw blades, one of them being obsolete and should be avoided. There is the very common and abundant Tungsten Carbide Tipped Blades (TCT), The eye-wateringly expensive Polycrystalline Diamond Tipped Blades (PCD) and the dangerous Plain Steel Blades.
TCT Blades have been the standard tooth tipping for a blade for decades now, almost every blade you can buy off the shelf these days is TCT tipped but not all blades are made equal. When looking for a TCT blade you should compare between blades how large the carbide pieces are, this will indicate how many sharpens you will be able to get out of a blade before it will need to be re-tipped or thrown out. TCT is an excellent material that lasts for a very long time, so the average hobbyist who is only working at weekends may not need to send blades off for re-sharpening often so long as clean, nail and debris free wood is used.
Image courtesy of Scott and Sargeant
PCD blades are a fairly new innovation which claim up to 20x longer cutting life than their TCT counterparts. As with all new innovations they are exceedingly expensive and way out of the reach of most hobbists pocket-money I would think. Their main use is long periods of cutting in very abrasive materials such as MDF I do think in the next 20 years or so they will become the new standard when costs come down.
Image courtesy of Scott and Sargeant
Plain steel blades are what gave the circular saw blade it's fearsome reputation, they were a primitive piece of equipment that could easily warp, bend teeth in the cut, crack down a gullet and all sorts of other nasty situations that could cause many problems from kickback to amputation depending on circumstances. I am a firm believer that leaps and bounds in the manufacturing of modern, stiffer saw plates and tipped blades have drastically reduced the number of accidents involving a saw blade compared to the bad old days. These are very outdated and should be avoided at all costs, although some do say that a very high-quality surface finish can be obtained from a well set up and very sharp steel blade and they are still quite commonly used on saws with diameters exceeding 16".
Cutting Tooth Geometry
Having the correct cutting geometry on your teeth is what will make all the difference when you're selecting a blade for your particular machine. Known as rake or hook angle the teeth on a blade can be positioned so that they cleave material out very aggressively and quickly with a positive rake or they're positioned that they scrape the material and are more gentle for crosscutting applications with negative rake.
Positive rake blades are best suited to ripping tasks on a table saw and they tend to have a 20-degree positive angle to the teeth relative to the centre of rotation, they are aggressive in the cut and cut very efficiently when ripping because the teeth clear the material away rather than clog up.
Neutral and Negative rake blades are best suited to crosscutting machines such as a mitre saw or radial arm saw because they won't have a tendency to "snatch" when you're cutting into the material as a positive rake blade will, they're not suited to ripping as they don't clear stringy material from the gullets very efficiently and cut very slowly.
Types of cutting teeth pattern
The two main types of teeth you're likely to encounter when you're looking to buy a blade off the shelf are Alternating Top Bevel (ATB) or Triple Chip Grind (TCG), there are also a few different types of teeth but those two are the main ones you will find on most blades.
ATB Blades are the most common type and are used in most machines with good effect, they work in a way that scores each side of the cut which results in a very clean top surface cut. They work well in both crosscutting and ripping applications hence why they are the most common type.
TCG Blades are second most common, they're designed to deal with more abrasive materials such as MDF and laminates as the tooth design is more durable and will hold up much longer in these materials.
Hi-ATB blades are quite rare in the UK, They're designed for very fine crosscutting and panel cutting with very smooth cut surfaces. The sharpness of their points makes them very fragile though and prone to chipping.
Flat Top Grind (FTG) blades are quite rare in the UK as well, as far as I'm aware you can't buy them off the shelf in sizes larger than around 6" in diameter and you'll have to ask a saw doctoring company to grind one to an FTG grind if you want one for doing joinery with the saw. Bear in mind, these blades are really only good for rip cuts as trying to crosscut with them is very similar to trying to cut down a tree with the flat face of a spade.
Hollow Ground (HDF) blades are similar to a triple chip grind with the exception that the faces of the teeth are ground with a hollow rather than a flat cutting face, there are almost exclusively for cutting sheet material with veneers or coatings, due to the hollow grind on the face of the tooth it can produce exceptional cuts without chipping of the veneer or coating.
Conical blades are exclusively for scoring blades in panel saws, you shouldn't need to worry about it unless you've got a panel saw with a scoring unit before the main blade.
Some ripping blades will be what's called "Anti-Kickback", these kinds of blades have prodruding pieces of the plates before the cutting action of the tooth, the idea of this is that it limits how much material the tooth can remove in a single pass therefore lowering the risk of a kickback caused by overly-heavy feeding or a heavy bite which can throw a workpiece up and backwards towards the operator.
The Amount of Teeth
The amount of teeth (as well as how sharp they are) also dictates how aggressive or smooth surfaced your cut is going to be along with the accompanying rake angle. Generalising, For ripping timber the average blade should have between 20-32 postive teeth for effective use, for both ripping and crosscutting in combination on a table saw and cutting panels to size a blade between 36-48 positive teeth should be used for effective used, for crosscutting exclusively in a mitre saw a blade should have between 56-96 either slightly positive (+5 Degrees) or negative rake teeth, for crosscutting exclusively in a radial arm saw a blade should have between 56-96 negative rake teeth to prevent the saw head from snatching the material and pulling itself through. There are exceptions but if you follow those guidelines you should be able to make a good choice.
The amount of teeth is also dictated by the size of workpieces you will be often working with, taking the mitre saw for example, if I were to be cutting mostly 4x4" tanalised posts where clean finish isn't really a problem I would look at selecting a blade with possibly fewer teeth than I mentioned above, but if I was working with smaller workpieces at around 1x1" in size I would definitely be looking at the higher tooth-count blades for smoothness of cut.
Too many teeth can pose a problem though, especially when ripping thicker pieces as with the amount of teeth in contact with the timber a lot of friction is generated which will at best burn the timber and at worst wreck the blade by warping it if excessive heat is generated, I've actually seen saw plates go blue in colour from the heat created by friction before.
Expansion Slots
I would say that expansion slots were one of the biggest safety improvements in circular saw technology, back in the bad old days this would've been a difficult process to achieve when manufacturing blades but as most companies laser-cut their plates out of a sheet it can be done the same time the plate is being cut out with no effort. The idea of the expansion slot is quite simple, when the blade is cutting a lot of heat is generated through friction and this is transferred into the saw plate which will expand with the heat build-up, on blades without the expansion slots if a lot a heat was generated the saw would warp drastically or in the worst case, crack down a tooth gullet from the heat expansion. The expansion slots are in essence "cracks" already put into the blade, so the blade can expand radially in their segments (typically four segments of the blade) without causing any issue to the blade. The slots also reduce the effect of warping on the blade when it does get very hot, it can still warp during cutting as I've experienced (I've seen the blade whipping from left to right by about 5mm before) but generally, once the blade cools down it will come back to perfect or only ever so slightly warped condition and may still be used for rougher work if slightly warped, whereas the older blades would either need to be thrown or serious saw-doctoring to bring back to life.
A typical expansion slot, shaped like a question mark:
Noise-Reduction Slots
Noise reduction slots are cut into the plate of the saw about centrally between the teeth and the bore to reduce the harmonic resonance of the blade during cutting, this is less of an issue on machines with brushed motors such a mitre saw or site-style table saw as they tend to be louder than the blade spinning anyway but on machines with an induction motor such as a decent quality table saw or radial arm saw in can be a benefit to have a blade with noise reduction slots as this will cut down on the noise while the machine is running idly with nothing being cut. Some also claim that the slots cut down on vibration, resulting in a finer cut.
Some noise reduction blades may have the grooves filled with resin, this drastically cuts down on the harmonics of a blade to the point if you tap the side of the blade with a metallic object you almost get a dull thud rather than a "gong" sound that you would normally get.
Here's a video I made just to show the resonance difference between blades, the Freud has no noise reduction slots so it sounds like a classic gong, the standard CMT blade has noise reduction slots which help with the resonance, and the CMT Chrome has resin filled slots which as I said above, makes it sound more like a dull thud in comparison:
[youtubessl]xc4wrxgV-Jg[/youtubessl]
Trenching/Dado Cutting
Another question that frequently pops up is "Where can I buy a dado set", this is clear evidence that someone has been watching too many American youtube videos! :lol:
To get this out of the way early, it is NOT illegal to use a dado stack or adjustable groover in a table saw in the UK, this is false information that has circulated for many years. Due to changes in Woodworking regulations over the years, it has made it harder to use such equipment on saws in a commercial environment as saws now need to come to a 10-second stop time and be adequately guarded for the task. So long as your saw comes to a stop within 10-seconds with the cutter in place (and that it doesn't work loose from the inertia of stopping) and is sufficiently guarded with something like a SUVA guard a groover is perfectly legal to use in a commercial environment. However, this need not apply to the humble shed woodworker as the HSE isn't going to suddenly come banging on the door when you load the cutter into the machine, it's your home workshop and you can put yourself at any risk you want to, just don't moan about it in the A&E.
Since those regulations came into force, the sale of dado stacks in particular dwindled and there are only a couple of options available for a new set. However, while dado stacks are very versatile in the width of groove they can produce from 6mm all the way up to 30mm in some cases, they are considered quite outdated and clumsy to use compared to modern adjustable groovers.
An adjustable groover is simply two pieces of overlapping steel with replaceable carbide inserts as the knickers and cutters. Some are adjusted by placing shims between the two plates and some can be adjusted with a screw dial. Generally, they don't have the range of size that a dado stack can do with the most common size starting at 8mm to 15mm although you can purchase ones that go from 4mm to 15mm which are made from three plates, then there are larger sizes such at 15mm to 28mm and so on. These adjustable groovers create a far cleaner cut than a dado stack and are cheaper to maintain in the long term as you get multiple turnings out of an insert which are relatively inexpensive whilst having a whole dado stack sharpened professionally isn't particularly cheap.
Another thing perhaps worth considering is the "wobble saw" or "drunken saw" which is a saw blade held captive in an adjustable holder that will hold the blade at an angle to the rotation which will create a groove once passed over with a piece of wood. They're fairly inexpensive as well as being easily adjustable without shimming. A negligible downside to these saws is since they're cutting by oscillating side to side it does create an ever so slightly curved bottom groove.
Before looking too far at grooving tooling though, you need to ensure your saw can run the tooling with no issue as many saws made for the European market have short arbours that are only capable of running the single blade as intended although a few newer saws are being made now with long arbours. Some people get around this by having longer arbours made for their saws but you still need to ensure that your saw is powerful enough to run such tooling, I would say you need 3HP to comfortably use the tooling at their maximum settings.
American Blade Nonsense
With the sheer amount of American writings online, please do not fall for any American salesman nonsense you may see online such as "glue line rip" blades, these are only expensive versions of the TCG blades and offer no more "smooth" cut than a regular TCG blade. Another one which I think are a bit dubious are the "combination" blades that have four ATB teeth followed by a FTG tooth with a larger gullet, back in the bad old days of solid steel blades with set teeth I think this would've made sense as the tooth with the larger gullet would be left unset to remove the material from the centre of the cut whilst the four alternating teeth would leave a clean surface either side. I think it's a bit pointless with an unset carbide toothed blade where all the teeth are cutting in unison and looks to me to be more of a marketing gimmick than an actual reasonable feature. Stick to information from the United Kingdom and Europe and you should be OK.
Manufacturers
As I said earlier, not all blades are made equal and there are some manufacturers that stand head and shoulders above the rest, so I'll make a little list in descending order of the best you can buy in my opinion.
Atkinson Walker, I've recently learned that Atkinson Walker have started up again under "Sheffield Industrial Saws" and still make blades as excellent as ever. If you can stretch the budget you can't go wrong with one of their blades.
Swedex, A very expensive industrial blade manufacturer that are possibly making the best blades on the continent at the moment.
Leitz, a well-regarded German firm who makes top-notch tooling including saw blades.
Felder, Very good quality but very pricey for their SilentPower blades.
OMAS, An excellent Italian manufacturer.
CMT, another Italian blade manufacturer that produces very high-quality blades with large carbides without breaking the bank, they have a massive variety of blades too.
Freud, yet another Italian manufacturer, These are very good blades for the money and are recommended by most as they're so easy to find everywhere.
When looking at different blades as a novice, it's difficult to tell what makes a good quality blade and one that's not such good quality. As I mentioned previously, the size of the carbide dictates how much life you will get from your saw blade as a larger carbide will grant many resharpens of the teeth, in my photo below I have three of my 250mm blades, at the top I have a Metabo blade that was supplied with my mitre saw, in the middle I have a Freud crosscutting blade and at the bottom is a CMT fine crosscutting blade. From the photo, it's pretty obvious that the Metabo blade's carbides are much smaller than the other two blades and the CMT has marginally larger carbides than the Freud.
There are probably some other brands worth looking at but these are the ones I can recommend myself, there are a lot of sub-par blades out there like the Trend blades which are expensive but no better than really cheap blades from elsewhere.
Care for Saw Blades
Whilst a fairly straightforward piece of equipment, a saw blade needs care and maintenance just the same as any other to keep it working in top form.
When a lower cut quality and burn marks appear, sometimes it is not the blade going dull but rather the build-up of resin on the teeth and body of the saw blade. Periodically, blades should be cleaned to remove this build-up, this can be done with special "blade cleaners" which some companies such as Trend offer, I have no experience of using them but I use methylated spirits as it is what I have on hand. I like to put the blade on a couple of paper towels and put it on an impermeable surface, which is usually my planer table and douse the blade both sides with the meths and leave it to sit for five minutes or so, I then come back with an old toothbrush and scrub off the resin. Sometimes it takes a couple applications of the meths to get rid of the resin completely but once it's removed you can remount the blade in the machine. I suggest running the blade into a non-critical piece of wood before doing any proper cutting first as the first cut will shed any meths and soft resin still on the blade onto the workpiece, if this was the problem with the blade the difference between the cut quality before and after cleaning will be night and day.
When the blade is genuinely dull, on an ATB blade it can be spotted by cutting into the timber and inspecting the cut, on a sharp blade the two points of the teeth that form a W will be a very sharp point shown on the timber, on a dull blade these will be rounded over, and obviously, with rounded points it isn't going to cut as efficiently or cleanly. Hopefully, in the photos below, you will see on some rubbish timber (I think it shows up better in lower quality timber) the cut quality with two identical 80 tooth cross-cutting blades, but one being very dull and one being brand new.
A rough finish with the softer earlywood being torn out of the end grain, this would be an acceptable finish from a coarser blade with fewer teeth, but on an 80 tooth blade, this really struggled to cut through.
A very smooth cut that feels glassy to the touch with almost no flaws to the surface excepting some cut marks which is to be expected, absolutely flew through the timber with no struggling from the machine whatsoever. Rough cut on the right for comparison.
Blades should be kept sharp and I suggest this isn't a task for at home, there are plenty of "DIY saw blade sharpening" videos on youtube (Mainly from America) going over many different methods of sharpening a saw blade such as mounting a diamond tile cutting blade in your table saw and touching the carbides to it to sharpen them up, or using a diamond hone of some kind. Whilst you could use these methods if you so wish, I much prefer to send off blades to have them professionally ground so that all the carbides are cutting in the exact same cut-circle and are actually ground sharp rather than sort-of sharp from a diamond file or similar. There are many companies in Britain that will do this for you and the going rate at the moment is around £5-10 a blade depending on the blade, any damage such as missing teeth, and the rates the company themselves charge, I will put a small list of companies that sharpen blades below, the only one I have experience with is Beverstock Saws, and it is always a good experience, the others I have heard good things about and have a good reputation.
Beverstock saws (Cwmbran) http://beverstocksaws.com/
NLS Tools (London) https://www.nlstools.co.uk/
12 Point Tools (Portsmouth) https://www.12pointtools.co.uk/
Tewkesbury Saw (Tewkesbury, obviously) http://www.tewkesburysaw.co.uk/
Bennet Saw (Sheffield) https://www.ebsaws.com/
In a Nutshell
For effective dedicated ripping on a table saw you need a positive rake, low tooth count (20-32) blade ideally with anti-kickback nodules.
For effective combination ripping and crosscutting on a table saw you need a positive rake, medium tooth count (36-48) blade.
For effective dedicated crosscutting on a table saw, you need a very slightly positive (+5 degrees) or a negative rake, high tooth count (56-96) blade
For effective crosscutting on a mitre saw you need a you need a very slightly positive (+5 degrees) or a negative rake, high tooth count (56-96) blade.
For effective crosscutting on a radial arm saw you need a negative rake, medium to high tooth count (48-96) blade.
Trusted Suppliers
Here's a list of trusted suppliers of quality saw blades, if you've got any recommendations feel free to post them down below.
Scott and Sargeant: https://www.scosarg.com/
Cutting Solutions: http://www.cutting-solutions.co.uk/
Sheffield Industrial Saws / Atkinson Walker: https://www.sheffsaws.com/
Bennet Saw: https://www.ebsaws.com/
Swedex Saws UK: https://www.swedex.co.uk/
Leitz Tooling: https://www.leitz.org/en-gb/
Appleby Woodturnings: https://www.applebywoodturnings.co.uk/
If there's anything you think I've missed out please tell me and I can amend the post to add it
This thread used to reside elsewhere on the internet, it is now a Woodhaven2 exclusive which has now been expanded upon with updated images and knowledge.
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