Buying Guide - Circular and Mitre Saw Blades
Posted by Mark Hunter - September 09, 2013
Buying the correct blade for circular and/or mitre saw is essential for safety; yours and that of the product your're cutting!
In this buying guide we'll show you how to choose the correct circular saw blade for your power tool and for the job you're undertaking.
First off, check the size of the bore on your machine. This is probably going to matter more if you're hiring the saw. Making sure the blade you're about to fit is the right one for the saw you're using starts with the bore. You'll find out this information in the user manual.
A saw with a bore of 30mm will need a blade with a bore of 30mm. It's that simple.
The diameter of the blade also matters. Too large a diameter of blade may affect any guard fitted to your saw. Once again, this is a safety issue.
Again, the user manual for the saw will outline the maximum and minimum blade diameters you can safely use.
The thickness of the blade will determine the width of cut. Finer, more precise cutting applications will need a thinner diameter blade.
All measurements will be etched into the blade itself (see the image above) and will be clearly marked on the packaging.
It's worth pointing out that good quality blades will have notches cut out of the disk itself. This allows the disk to expand as it heats up while cutting and, therefore, prevents warping. A warped blade will mess up your cut and is potentially hazardous to your health!
Buying, and fitting, only the correct size of blade to your saw is essential for your safety.
Blade manufacturers likes Bosch produce a variety of different blade types based around the core application for which they will be used.
The blades are designed within each range to give you the best type of cut depending on what material you're cutting and the quality of finish you wish to achieve.
So, for example, in the Bosch range you can expect to find:
- Optilinewood: designed for precise quality cuts in all standard woodworking applications
- Speedlinewood: perfect for fast rip and cross cuts in all types of wood
- Multi Material: ideal for powerful cuts with clean cut edges in all different kinds of materials
- Construct wood: blades designed for coarse cuts through construction site timber
- Construct metal: suitable for clean, precise cuts in metal
From this list, then, if your application was cutting a hard wood and you want a nice clean face to the cut, then try Multi Material blades. Because of their high tooth count, they'll cut quickly and easily through the material and leave you with a nice, crisp edge on the cut.
The same would apply if you were cutting aluminium or perspex. The shape of the teeth, the number of the teeth and the quality of the tungsten carbide means your cut will be quick but you'll only be left with a lovely, clean straight edge.
However, it's worth pointing out that blades with more teeth usually require your cutting machine, ie. your saw, to work a bit slower and a bit harder. But it's the teeth on the blade that are doing the cutting and it's them that will determine the quality of the final cut.
On the right is a diagram of "triple chip" teeth, demonstrating the various different ways the teeth can be shaped on the blade. Please see below for more info.
The blade you buy and fit to your saw will produce a cut specific to the manufacturer's design. The type of cuts achievable are normally:
very coarse cut
- fast rip cuts and cross cuts in softwood, hardwood, raw chipboards and formwork boards
- rip and cross cuts in softwood, hardwood, raw chipboards, formwork, boards and plywood
cross cuts in softwood, plywood, wood core plywood, chipboards laminated on one side, and parquet
very fine cut
- cross cuts in softwood, hardwood, plywood, wood core plywood, parquet, fibre materials and MDF
Therefore, the type of teeth on the blade you choose will have the biggest impact on the material. Choosing the correct tooth-type is essential, both in terms of cut quality and personal safety.
First of all, the greater number of teeth on the blade denotes a finer, more accurate cut.
For example, the blade on the left is the Bosch Multi Material Circular Saw Blade. It features 80 tungsten carbide metal teeth and has a cutting width of 2.5mm.
The high number of teeth, coupled with the thinness of the blade, means that it's ideal for fine, accurate cuts in parquet and laminates.
And because the teeth (or blades) are made of tungsten carbide, they're extremely hard wearing and they can be re-ground, allowing you squeeze plenty of working life out of them.
Another factor to consider is the shape of the blade's teeth. The shape of the teeth cut into the tungsten blade affect the quality of the cut you'll achieve.
Some examples of shaped teeth is alternate top bevel. This is where one bladed tooth slopes one direction, the one behind it slopes in another direction. Teeth like these are ideal for fast cuts, perhaps through rough wood, particularly along or across the grain.
Teeth like these can be found on Bosch's Optiline wood range of blades and are ideal for cutting soft, hard, pressed and laminated wood, along with chipboard, wood core plywood and MDF boards.
The Multi Material blades have teeth that are "triple chip". This means they're designed to trim and cross cut while giving you a fine finish.
Perhaps the most obvious, but also the most overlooked, is to make sure you buy and use the circular saw blades at the right height.
When buying, and using, circular saw blades, it isn't just a case of making sure you've purchased the correct size of blade with the correct shape and number of teeth for the application, but that you're using the blade at the correct height in your machine.
Bear in mind that it's the teeth that actually do the cutting.
The blade, or disk part, is only their to - literally - support the teeth. The teeth are sharpened, ground and designed to do the cutting.
Therefore, setting your machine to the correct height (or depth) of cut will determine whether you're getting the most out of the blade and not putting your machine under too much stress.
When cutting, the teeth of the blade should only just be protruding from the cut, no more than a couple of millimetres or so.
This means the teeth will be making contact with your cutting material at the correct angle, your machine will be able to operate at the best speed for the cut and you'll experience less resistance and vibration.
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