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CSM Problems and Answers

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CSM Problems and Answers

All saws have one common enemy. This is the person who installs and uses them.

To install a saw by using a piece of wood or other object against the teeth to hold it from turning when the nut is tightened is inexcusable. The more the nut is tightened, the more the teeth are bent.

When a new saw or a serviced saw is returned because it cuts rough, look first for a bent tooth, especially if it cuts rough on only one side.

There are several things that can create poor saw performance. Don't put all the blame on the saw blade. Check the machine. Check the bearings. Check the arbor. Check alignment and power or other factors as well as the saw.

RIP SAWS

The top of a rip saw tooth cuts across the grain of the wood and the tooth cuts with the grain on the sides. This makes the tooth act like a chisel cutting cross grain. This is also why hook is so necessary in a rip saw. The more hook you have the easier you cut through the cross grain.

Because carbide is hard and brittle, the hook should be limited to a maximum of 30° on green woods and 25° on dry wood. The included angle on the carbide should never exceed 45°.

Tough grades of carbide are sometimes necessary to keep from having too much tip breakage especially on hard knots.

As the tip is forming a chip, it is compressing the wood fiber and creating friction and heat. This action forces the resins and pitch out of the chip in a hot liquid form.  This liquid deposits itself on the saw plate behind the teeth and on the sides of the plate. When it builds up too much, it rubs on the sides of the board and will get so hot it will swell a spot on the plate and burn up, causing a blue spot on the plate.

To help prevent this, the saw needs more side clearance. Rip saws should have a minimum of .020 side clearance.

CROSS CUT SAWS

The top of a cross cut tooth cuts with the grain and the sides cut or shear across the grain. Top beveled teeth cut the grain diagonally, but still cut mostly with the grain.

The sharper and more needle-like the tips are, the easier they penetrate and shear the grain fiber on the sides of the cut. Here again carbide angles are limited because of its hardness. The advantage carbide saws have is the accuracy to which they are ground. Each tooth has uniform loading that cannot be obtained on a steel saw by grinding or filing.

You must do a good job to maintain and build the reputation carbide has gained.

ALUMINUM RIP SAWS

The two major problems are galling or sticking of the aluminum to the blade, and sawing pieces of aluminum with improper clamping.

If a saw is galling with aluminum, there is only one reason, inadequate and improper lubrication. Do not use water soluble oils mixed 50 parts water to 1 part oil.  This mixture may prevent rust and work as a coolant, but it does not lubricate.  Mix not more than 5 parts water to 1 part oil.  If galling still occurs, mix 2 or 3 to 1.  There are a lot of applications that require better lubrication than water soluble products provide.  A good grade cutting oil or sulphur base oil may be needed.  The method of applying the lubricant is also very important. Don't try to lubricate into the rim of the saw.  The fan action of the teeth blow it away. Put the lubricant on both sides of the saw.  This will allow it to oil the side of the saw and feed out to the teeth by centrifugal force.

The cutting problem can be dangerous if not handled properly. The biggest problem is holding the material being cut. Some people will fix a solid stop on the machine, particularly radial arm and chop saws, and then proceed to cut the piece that is against the stop without clamping it.  The saw will cut through the part o.k., but when it is returned through the cut is where the danger lies.  The part is wedged between the stop and the saw.  If it moves slightly, the teeth will grab it and turn it until it either breaks the saw or it flies through the air like a bullet.  If you see someone cutting like this, clear the area and run like mad.

SAW NOISE

This is a very elusive subject and the cure has baffled many people for a long, long time.

The first thing that should be recognized is where the sound comes from. There are three main sources of sound.  Number 1 is Air Noise created by the fan action of the teeth. Number 2 is Plate Noise created by plate vibration induced into the body of the plate by both the air turbulence and the material being cut. Number 3 is Cutting Noise.

Air noise can be down to a soft purr or up to a high ear piercing siren type sound. The air noise generally is progressive with the rim speed of the saw. At low R.P.M. the saw noise may be bearable, but as the R.P.M. is increased so is the noise.  If saws could a11 be run at a fixed rim speed, it would be a lot easier to design teeth in such a way that you could predict the air noise level.  Of course, saws run at all different rim speeds so we have to compromise and attempt to design saw tooth geometry so the saw will do a satisfactory job and disturb the air as little as possible.

Plate noise is started by the action of the teeth fan in the air and creating a vibration in the plate. Each plate seems to have its own sound. The plates that vibrate at an annoying frequency are the trouble makers.  Plates that are manufactured to the very same specifications will not necessarily produce the same sound.  Plate noise can be altered by numerous methods.  The most common is to install expansion slots in the rim of the saw. The next effort would be to plug the expansion slot holes with a soft metal or plastic plug. Going further with plate sound, it is possible to cement sound deadening material to the sides of the plate.  Plates are also laminated with different metals. These approaches only tend to make hammering and servicing more difficult.

Cutting noise is a tough problem and it occurs from the teeth producing chips and then throwing them at a high velocity, thus creating a noise by the chips accelerating through the air and also contacting each other.  The problem here is the size of the chips. Large chips have greater velocity than small ones and make more noise on impact with other chips or other objects.  In considering cutting noise it is necessary to reduce the chip size and shape. This can be done in many ways.  One way is to put more teeth in the saw. Decreasing the feed speed will also reduce chip size. Altering tooth geometry can be effective. In any event a change in chip shape and size must be accomplished.

In summarizing saw noise, it should be noted that a lot of things can be done to generally improve noise. There are, however, a lot of noise problems that must be dealt with individually and in some cases the actual noise must be stopped by deadening the object being cut. We also must recognize that there are so many different operating conditions and materials to saw that it is impossible to curb saw noise by approaching the problem from just one aspect. About the time you feel you have solved the problem; you'll find that another one exists. Time, study, and patience are what it is going to take.

 

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