What Factors Affect Saw Cut Quality? - TigerStop

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What Factors Affect Saw Cut Quality?


The quality of your saw cut can vary from superb to poor depending on many factors. If your TigerSaw is not cutting as it should, there are many places to look for the cause of this problem. Sometimes the cause of inferior saw cut quality is quite simple, but at other times, it can be caused by a combination of several conditions. In other words, more than one condition can be responsible for badly cut parts.

Every component part in the energy transmission lineup will affect saw cut quality.

We will attempt to go through all the possible factors affecting cut quality and leave it to you to check those you suspect are responsible if you’re experiencing problems.

Operation Considerations

Cutting speed and feed rate

Various materials will require minor adjustments in both cutting speed and feed rate to achieve optimal cut quality. Not only the rotation speed of the saw blade but also the speed of activation and retraction (return) of the saw lift mechanism will affect cut quality.

When cutting metals, titanium tube stock, for example, a variation in blade speed as little a 1 rpm can make a significant difference in quality. When the blade cuts through a piece of tubing, the teeth generate heat as they remove the material. Slowing the blade speed reduces the heat, but the cutting rate is too slow to be economical in a production application. If the blade speed is too fast, the heat generated leads to premature dulling of the tool. The chips produced during the cutting process must be extracted at the correct rate or they might stick in the gullets of the teeth. This results in a loss of cutting efficiency, which in turn increases heat buildup, causing galling as well as shortened blade life. While cutting fluids and the correct tooth pitch are important factors, finding the correct blade speed is essential for cutting metals.

Material straightness and internal tension

Some materials, particularly wood, but also metals, can be subject to straightness problems and internal tension, making cutting difficult. Stock with these characteristics can close around the saw blade during a cut, resulting in poor cuts. There is not much that can be done about this, as it’s a material defect or characteristic.

Saw Blade Considerations

Saw blade condition and type

The condition and type of saw blade used will definitely affect the quality of the cut. Being out of balance, out of round, dull on one side, or improperly tensioned—all these conditions will cause inferior cut quality.

Using the wrong type of saw blade for the job will also cause problems.

Saw teeth and gullets

Sawtooth profile and the straightness of the tooth grind will affect cut quality. Also, take into consideration the size and shape of the gullets. They determine the amount of waste material that passes through the saw. Consider also the correct tooth shape for your materials. The angle and design of a tooth factors into blade speed, cut quality, and the type of material it can cut.

Hook angle

The greater the hook angle, the more the blade wants to climb into the wood and the rougher the cuts, that is, the more tear-out. The smaller the hook angle, the more force it takes to push the blade into the wood. For crosscutting saw blades, 10° to 15° is a common hook angle.

what-factors-affect-saw-cut-quality-tigerstopDiagram of Saw Hook Angle

Plate thickness

The plate of a saw blade is often 1/8- to 1/4-inch thick. The thinner plate means that there is less sawdust and potentially less waste. However, thin blades (often called thin-kerf blades) are very sensitive to heating and wobbling, which in turn means non-straight (wavy or snaky) cuts. As a result of this one factor, most people opt for a thicker and therefore stiffer plate.

Tensioning

Saw blades are pre-tensioned during manufacture to take on a true, flat shape when spinning. Check the blade for trueness by thumping it with your finger while suspending it through the hole. A true saw blade will have very little ring. The more ring, the more standing wave it has. Standing wave is a saw blade deformation that causes an hourglass-shaped throat plate cut.

Saw blade wobbling caused by standing wave can seriously affect cut quality. Hammering is a process of making sure the blade is true and flat. Plate tension (the stiffness of the plate) is more important than the flatness of the plate. Even a perfectly flat plate can wobble if proper tension is not met. Make sure wherever you send your blades for service is capable of tensioning as well as sharpening your blades.

Flatness

Once the blade is mounted on the arbor, it should be flat. When turned by hand, it should not have any sizeable wobble or drift. Use a dial indicator to check this.

Drift can be a problem with the blade or with the arbor bearings or collar flatness.

what-factors-affect-saw-cut-quality-tigerstop
Both sides of the saw blade should be checked with a dial indicator for rise drift in both high and low positions, and from the left and the right sides of the blade.

Factory testing yielded an acceptable reading of 0.003-inch TIR for rise drift on both sides of the blade.

Checking blade flatness with rise drift

Blade condition

Waste material in the gullets as well as pitch buildup on the sides of the blade can cause it to overheat. Avoid overheating the blade, because heat can ruin the blade quickly. Another cause of overheating can be a dull blade. Keep the saw clean and sharp.

Saw blade specification

Recommended blade: Kanefusa 17.717 inches x 0.126 inch x 132 x C – BC, 15-5-15-5

Setup Considerations

Saw bed and throat plate

The throat plate must be perfectly flush and level with the saw bed. The TigerSaw throat plate is very slightly thinner than the depth of the recess for it. To adjust it to be perfectly flush with the saw bed, a layer of masking tape of the appropriate thickness is added to the underside of the plate.

  • If the throat plate is too high, it will snag materials passing over it.
  • If it’s too low, the material will deflect into the shallow during saw activation, and the resulting cut can be slightly angled.
  • Make sure the throat plate is perfectly flush.

Throat plate bevel

There is a bevel in the throat plate slot on the outfeed side of the saw. This prevents the leading edge of bowed or warped material from catching on the slot.

However, for some materials, this bevel can be too great and work against precise cut quality due to waste getting caught in it. In this case, the throat plate should be reversed, face down, and installed that way. The screw holes must be beveled with an 82° countersink so the fasteners can be flush.

It may still be desirable to have a slight bevel on the throat plate slot on the outfeed side, and this can be added.

Saw back fence and vertical throat plate

The vertical throat plate must be perfectly flush with the saw back fence. It is important for cut quality to keep the vertical throat plate clear of wood chips or other waste. It is exactly like the throat plate in the saw bed, only shorter; has the same characteristics; and must be installed or modified in the same manner. Improperly seated throat plates can cause cut quality issues.

what-factors-affect-saw-cut-quality-tigerstop
Throat plate

NOT the same scale as back throat plate images.

Uncut back throat plate

cut back throat plate
Cut back throat plate
The bevel on throat plates is ALWAYS on the outbound side of the saw cut.

Mechanical Considerations

Saw lift mechanism

The speed of activation and retraction (return) of the saw blade must be adjusted to achieve the best cut quality.

The pneumatic cylinder has a taper valve that permits the gradual tapering of movement on the downstroke.

  • Valve “A” adjusts the speed of the UP stroke of the saw.
  • Valve “B” adjusts the speed of the DOWN stroke of the saw.

 

what-factors-affect-saw-cut-quality-tigerstop

Side clamps

If side clamps are used, they must be installed perfectly parallel to avoid uneven clamping of the material as it’s cut.

Saw blade perpendicularity and squareness

The first consideration affecting overall saw cut quality is the perpendicularity and squareness of the saw blade in both horizontal and vertical planes. The blade must be absolutely perpendicular and square to achieve good cut quality.

Check squareness and perpendicularity with a precision square.

Measure any deviation by inserting a feeler gauge between the square and saw blade in several places.

Factory testing revealed a gap at any point along the saw blade of less than 0.003 inch in both directions.

Saw collar

The saw collar has a specific orientation and must be mounted on the flange in that orientation. If it is mounted backward, saw cut quality will suffer as a result.

Periodically, the saw collar should be cleaned of dirt, pitch, and other waste.

The collar should be checked with a dial indicator for axial runout.

Factory testing yielded an acceptable reading of 0.0015-inch TIR.

Saw arbor

Arbor bounce will affect overall saw cut quality. Bounce can be caused by improperly adjusted pneumatics, such as the speed of activation and retraction (return) of the saw lift mechanism. Arbor bounce can cause unwanted re-cut of the pieces.

The arbor should be checked with a dial indicator for axial and radial runout.

Factory testing yielded an acceptable reading of 0.0005-inch TIR for axial runout.

Factory testing yielded an acceptable reading of 0.0015-inch TIR for radial runout.

what-factors-affect-saw-cut-quality-tigerstop4 Saw Arbor Bounce Indicator

Saw pivot

Deflection of the saw pivot will affect overall saw cut quality. Deflection can be caused by improper assembly of the components. Saw pivot deflection can cause irregular cut quality.

If the saw blade is subjected to a sudden impact, this can also cause pivot deflection.

Pivot tension should be checked with a dial indicator for axial and radial runout.

Factory testing yielded an acceptable reading of 0.001-inch TIR with the arm slack.

Factory testing yielded an acceptable reading of 0.002-inch + 0.001-inch slack TIR with a 20-pound load.

TigerStop™ Saw Pivot

Saw arbor and pivot bearings

TigerSaw has ball bearings in 2 places: (1) Saw arbor (2) Saw pivot

Ball bearings consist of four components: inner race, outer race, cage, and balls.

When replacing bearings, be sure to replace them with bearings obtained from TigerStop. Replacement with bearings of a different make or standard can cause poor saw performance and mechanical failure.

The tightness of the inner and outer races will affect saw cut quality. The arbor shaft thickness determines the tightness of the inner race; the inner diameter of the housing the tightness of the outer race. Tightness must conform to the following classifications:

  • Arbor bearings: inner race (shaft) – H6, outer race (housing) – J6
  • Pivot bearings: inner race (shaft) – G6, outer race (housing) – J6

what-factors-affect-saw-cut-quality-tigerstop
Anatomy of a ball bearing

This is not an issue within the saw owner’s control, other than to replace worn bearings with new ones obtained from TigerStop.

Belt condition

The condition of the drive belt, if it is damaged or worn, will have a definite effect on saw cut quality. Even a new drive belt, if kept “on the shelf” too long, may become unsuitable for use and cause saw wobble, resulting in bad cut quality.

Saw arm pivot point

The pivot point must be exactly parallel to the arbor.

Saw motor arrangement

The saw motor must be balanced to achieve the best cut quality.

Motor frequency (60 hz)

The motor frequency in combination with other factors can adversely affect saw cut quality.