Adjusting Guide Blocks And Thrust Bearings

Set guide blocks llu In. to Vjj behind blade tooth gullet.

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Set guide blocks .003 in. to .005 in. from side of blade.

blades. (Wider blades run at higher tension.) Trouble is, the tension indicators arc notoriously inaccurate, especially on older saws because the tension spring fatigues in use. Still, the indicator is a good place to start, so adjust the tension according to the indicator scale on your saw.

There are a lot of differing opinions on bandsaw tension adjustments. Some woodworkers advocate tensioning the blade much higher than the tension indicator shows. I prefer to use the least amount of tension that yields satisfactory results for the type of cutting I'm doing.

If your saw doesn't have a tension indicator, test the tension by plucking

The guide blocks and thrust bearings are mounti'd in a guide assembly (upper guide assembly shown). Knobs adjust the clearance between the guide Mocks and the blade, ami the thrust l>cariiig and the blade. Thumb screws lock the adjustments.

the blade like a guitar string, and notice how the tone changes as the tension increases. You want a clear, musical tone rather than a dull thud. The tension required will vary with the width of the blade. Experiment to find the tension that makes you and your saw comfortable. Avoid cranking the tension way up as a panacea for all cutting problems. Excessive tension can shorten blade and bearing life and stress the frame of the saw.

Adjust the blade tracking—Track the blade by turning the adjustment screw that tilts the top wheel as you spin the wheels by hand. Aim to get the blade tracking in the center third of the tire. If the wheels are round,

The guide blocks and thrust bearings are mounti'd in a guide assembly (upper guide assembly shown). Knobs adjust the clearance between the guide Mocks and the blade, ami the thrust l>cariiig and the blade. Thumb screws lock the adjustments.

balanced, and coplanar, you shouldn't have to tilt the top wheel much to track the blade properly. In fact, some woodworkers claim you should leave the wheels coplanar (by not tilting the top wheel at all after wheel alignment) and allow the blade to find its own equilibrium tracking position near the center of the tire's crown.

Align the drive belt and pulleys—

Inspcct for worn, lumpy, and cracked belts. Check the pulleys on the motor and the saw to see if they're running true. A wobbling pulley can cause vibration. Lesser-quality die-cast pulleys sometimes have off-center shaft holes or lumps and bumps in the drive surface. In this case, buy higher-quality machined pulleys as replacements. The pulleys on the motor and saw should line up, making the belt run straight. Align them as necessary by moving the pulleys in or out on their shafts or by shifting the motor position a bit.

Reassemble the saw—Put the wheel covers, guards, and table in place. Install the blade guides (above and below the table). Loosen the blade guide adjustments and back the guide blocks and thrust bearings away from the blade.

Adjusting the Guides

Bandsaws have two guide assemblies—one above and one below the table. The guides keep the blade aligned during the cut, as shown in the photo at left.

To keep the blade from twisting in the cut, most guides have two metal guide blocks that hug the sides of the blade. Instead of guide blocks, some more expensive saws have ball bearings that guide the blade.

A thrust bearing behind the blade prevents the blade from being pushed off the wheels while cutting.

To adjust the guides, position the upper guide assembly about 2 in. above the table. If the guide blocks are worn, grind or sand them square and smooth on the ends, and install them loosely in the guide assemblies. Adjust the upper and lower guide assemblies forward until the front edges of the guide blocks are about '/<* to V\i in. behind the gullets of the teeth on the blade. (See Fig. 2.) Spin the blade through a couple of revolutions to make sure the whole length of the blade has proper clearance.

Adjust the clearance between the guide blocks and the side of the blade. Generally, metal guide blocks should be set with about .003 in. to .005 in. clearance between the block and the blade. You can use a dollar bill as a gauge to set the blocks—a dollar is about .004 in. thick. If your bandsaw

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