Changing a saw blade

saw tooth directionCarbide is so dependable, one can almost be lulled into forgetting the habit of changing saw blades. Gradually, feed rate gets slower until the saw can't cut at all. You might not notice burning until a puff of smoke wafts into view. If a new saw burns and resists feeding, check which way it was put on. Naturally, it should always be put on facing the rotation direction. It is possible for a blade to run faced backward, but you wouldn't want to risk running it in reverse intentionally. It is destructive to carbide. A tip is flat in front where it cuts. This one faces and rotates right. Mark an arrow to leave no doubt about the direction of the teeth.

To change a blade, first immobilize it. Don't put a screwdriver in an expansion slot even temporarily, because it might twist or distort the plate. To facilitate changing a blade, you can very gently wedge a softwood scrap straight on into the tips to keep it still. How to take off the blade is by loosening the nut the same way the teeth face; forward, not in reverse.

Printing that is scratched off in the center gives evidence of slipping. A burr or trapped dirt interferes with clamping. It is not uncommon for a big, cumbersome table saw clamped by a little collar to be shifting or slipping slightly. After installation, the collar should clamp firmly. The nut tightens backward from the spin. It may tighten during use. Brushing off the threads before mounting the arbor nut is helpful for avoiding sticking.

Saw feed rate

A board can travel past the blade at either fast or slow speeds, called saw feed rate. Manual feed is partly controlled by the amount of pressure or effort you apply in pushing. Cutting while you push slowly can improve neatness, but it also causes burning. A closely spaced, fine saw passing through dense wood without feeding fast enough causes binding and burn marks. Feeding at a quicker pace is one way to prevent this.

The strategy for ripping is to install a circular saw that is as coarse as possible while still producing an acceptable cut. A rip saw needs to be open for preventing heat retention, and agressive for quick feeding speeds to avoid burns. If sawdust is rubbing, raise or extend it so less rim is in the wood. Dust should spill out freely when you rip, but if humidity is high it may cling. If clogging becomes obstructive, the saw can't cut efficiently. When the pace is too slow, the saw may bind. Improvements to dust collection help prevent burning.

A steel tooth is spread to the side to broaden the rim so it won't cause binding. Carbide doesn't need this because each tip already has enough breadth to pass through without rubbing. A design with almost flat sides is made for burnishing and glazing the cut, but of necessity it runs hot. Overly flattened or rounded sides further slow down the rate. Binding and burning are often noticed when a saw blade needs sharpening.

Density and burning

The hardness of the material is a condition that limits the cutting rate. Stock with hard density is likely to get a burn mark. The harder it is, the sooner the burning becomes noticeable. Examples are MDF, a hardwood like maple or oak, or plywood. Trying to take too deep of a cut in thick oak or dense maple stock is a common reason why a blade gets hot. A scraper can usually take off burn marks more effectively than abrasives, but marks on end grain can be more stubborn. Materials of greater density, such as plastic laminate, solid surface and soft metal merit concern. If the feed rate is too slow, they may begin to melt. Smears can transfer onto the plate, compounding the issue.

As you handle work just completed, monitor its temperature. Accommodate rising heat by taking occasional short cooling pauses and avoiding lengthy sessions of sawing non-stop. Handheld portable circular saws can do a lot, but their downside is that they quickly get hot and worn out. They don't have as much mass as bigger saws to dissipate heat. Work is more frequently delayed by the recurring necessity to change saw blades. If you can't spare this brief interruption in order to avoid burns, you may end up wasting more time erasing burnt spots afterward. Heat is commonly assumed to be an inevitable result of saw rotation speed, but on further exploration, one might conclude otherwise.

Warp

Burns can shorten the life of a circular saw. Prolonged use causes the rim to overheat and expand. If it gets intolerably hot, that can eventually cause it to be warped or dished permanently. Dishing puts burns on one side. Cutting bevels is one sort of stress that causes distortion. Warping eventually develops a floppy, wobbly rim that cuts rough. Warp leaves scorches on both sides where there are high spots. Getting rid of the discoloration doesn't stop it from returning as soon as it begins to rub and it gets hot again.

Your table saw blade could be getting warped if its space is cramped. Fence alignment should be parallel to the blade so that wood won't get wedged in. For preventing burning, you could change alignment slightly by nudging it just barely farther apart toward the rear. The stock must be kept square and not pivot either way. While ripping, lumber may close up as it exits. Behind the heel, place a spreader just narrower than the tips.