Reg Ellis, a student from the Woodworking Centre of Ontario, rightly took me to task for being a bit sloppy when I talked about saw tooth configrations in a recent Deck article. Then it occured to us at Home Builder that it might be a good idea to elaborate on saw teeth, given that most site workers generally have two saw blades, rough and fine, and few stores carry a fraction of what is available.
First you need the Eakes defination of a combination blade. A blade that cuts equally poorly in both directions. When you need to do a lot of ripping -- use a true rip blade. When you need to get a real finish cross cut -- use a true finishing blade.
The major defination of saw blade teeth are their shape, their set and their angle of attack; and of course how many teeth on the blade.
The more the tooth leans into the cut, the more aggressive a cut it will be. As the tooth straightens up its bite is less agressive. A table saw usually uses more agressive angles, while Radial Arm Saws and Miter saws reduce the bite to avoid grabbing of the wood. A good blade capable of cutting nails in flooring or demolition will have a zero angle. Some manufacturers make negative angles on the teeth for a scraping action on some plastics and metals while others believe that anything beyond zero simply uses up power and creates heat.
The simplist tooth is an ST or Straight Top Grind. This is the basis of most rip saws as it tends to pull out shavings ? but gives a very rough cut across the grain. 24 teeth in an 8 inch saw is effective, although I use an old 8 tooth 10 inch blade in my Radial and it rips Oak like butter, yes in a Radial.
ATB or Alternate Top Bevel leans alternatively to the right and the left to score the fibres in a cross cut. The steeper the bevel, the better at scoring but the worse at ripping. In an 8 in. blade 40 teeth will give a general purpose cut while 60 teeth will work better on fine cuts and plywood pannels. The AR or Alternate Top Bevel with Raker combines the cross cut and the rip and is probably the standard for miter saw use. On an 8 in. blade 40 tooth is general purpose and usually has a large gully in front of the rip tooth, 60 teeth is a fine cutting blade. Some manufacturers sell this one with a negative tooth angle for double sided veneer.
TCG or Triple Chip Grind is generally used for abrasive materials. It reduces the friction and impact on the material by alternatively cutting the centre, then the sides of the kerf. Different configurations of the Triple Chip will be used to cut thin plastics, thick plastics, metals, extrusions; each with its own best blade.
The variety of specialized blades available is mind boggling, as is the differences in carbide thickness, blade construction techniques and even how many faces of the tooth are polished.
**Originally published as an article by Jon Eakes in Home Builder Magazine, the magazine of the Canadian Home Builder's Association.