Bandsaw Alignment and Maintenance

by Robert Feeser

This article first appeared in a thread on theWoodNet woodworking forum. It was compiled and reproduced here for easier public consumption. All Text are the property of Robert Feeser.

INSPECTION

• Electrical cord, for fraying, cracking
• Switch, secure on frame, easy-off attachment works well
• Motor. for dirt, bearings smooth and tight, mounting bolts tight, rubber mount condition
• Pulleys, tight, look for wear on inside surfaces
• Drive belt, wear, stretching, bends permanently set in
• Wheels, tight on shafts, bearings smooth and tight
• Tires, crowned, no grooves or flat spots, round, clean
• Frame joint, tight
• Blade tensioning rod and nut threads for wear, lubrication
• Shop made tension crank handle, secure
• Instant tensioning attachment, securely attached, lubricated, working
• Sliding bracket (that holds the upper wheel axle and is pushed up by the tensioning spring), wear, lubrication
• Table, flat, tight, tilts smoothly, locks, rust, condition of miter slot, alignment pin in place
• Table insert, wear, excessive opening around blade, flush with table
• Blade guard, secure, proper motion, effectiveness
• Left blade guard, wear, warping, rubbing against blade
• Upper guide post, smooth motion, locks securely.
• Guide blocks, flat, square ends, fit in Y-bracket, clamped securely
• Thrust bearing, wear, smooth motion, tight
• Dust collection ports, obstructions

DRIVE SYSTEM ALIGNMENT

• Align motor and drive pulleys.
  • The shafts have to be parallel, which may mean moving the motor. Then adjust the pulleys in or out until they are coplanar.
• Stretch tires evenly to make them round.
  • Use a dial indicator, measuring against the side of the ½ in. blade, not the surface of the tire itself. (The blade is a better surface to measure-hard and smooth-and it's the roundness with a tensioned blade that counts.). Bird's book says 0.025 in. runout is enough to cause vibration. Alternatively, just measure how much the blade moves sideways near the table when the wheels are rotated.
• Balance upper wheel.
  • After seating the tire properly so they are truly round, balance the wheels by drilling into the outer web just inside the rim, like the factory did. Remove old balancing marks with naphtha. Spin the wheel several times and when it stops, mark the rim at the bottom. If the marks accumulate in one area, lighten the wheel there. This works for the upper wheel, but the lower wheel does not turn freely enough on its bearings.

VIBRATION TROUBLESHOOTING

To find out where any vibration is coming from, isolate the sources by checking the motor alone, then gradually adding more moving parts and rechecking, in the following order.

• Remove the drive belt, motor pulley (after marking its position on the shaft), blade, and lower wheel.
  • Turn the motor on and check vibration. Any vibration is in the motor itself. Nothing can be done about that except for replacing or repairing the motor.
• Replace the motor pulley, using the mark on the shaft to locate it.
  • Turn the motor on and check vibration. Any new vibration is from an imbalanced motor pulley.
• Replace and tension the drive belt.
  • Turn the motor on and check vibration.
  • New vibration has to be from: eccentricity, wear, or balance of motor pulley or drive pulley, eccentric or imbalanced drive pulley, belt with a set in it, or misalignment of the two pulleys.
• Replace the lower wheel.
  • Turn the motor on and check vibration. Additional vibration has to be from imbalanced lower wheel.
• Mount and tension a ½ in. blade.
  • Withdraw guide blocks and thrust bearings. Turn the motor on and check vibration. Additional vibration has to be from eccentric upper or lower wheel or tire, imbalanced upper wheel, or kink or bend in blade.

FRAME AND WHEEL ALIGNMENT

All of these alignments are made by adjusting the frame at the joint in the middle of the left hand column. They are all closely coupled; changing any of them affects the others. The frame column joint bolt has to be loosened slightly and then the upper frame moved sideways, forward-and-back, twisted, and/or shimmed. This is a very iterative process since all the alignments are interrelated. With an organized approach, though, this is really not too difficult, just tedious. There are enough degrees of freedom to accomplish all the alignments at once. My Jet 14 in. saw cannot be aligned with the riser block unless the alignment pins at one end of the block are removed.

These alignments have to be made with a properly tensioned blade. So you have to tension the blade, check the alignment, remove tension, loosen the big bolt at the frame joint, shift, twist, or shim the joint, tighten the big bolt, retension the blade, and recheck the alignments. You have to do this over and over and over again. That will either make you install a quick tension release or a tension crank or else give you forearms like Popeye's.

• Remove table.
  • This makes it easier to put a long straight edge across both wheels. It also makes the lower guides more visible and accessible so it's easier to be sure they are out of the way at all times. (Depending on what you are doing, you might be able to just tilt the table out of the way.)
• Set wheels coplanar.
  • Have a properly tensioned 1/2 in. blade mounted, assuming a 1/2 in. blade is the widest used on the saw. Measure with long straightedge in center and at both sides as well as diagonally across the wheels. Either insert shims or washers, or else displace upper frame forward or backward at the joint.
• Make upper guide post parallel to the back of the blade.
• Check with a tensioned 3/8 in. blade mounted, assuming 1 1/2 in. blade is the widest used on the saw. Check for equal clearance between thrust bearing and back of blade with the upper guides near the highest and lowest positions. Do not raise or lower the guides quite all the way, though, to prevent anything funny at the extremes from affecting the alignment, just like you don't raise a TS blade quite all the way up when aligning it. This requires inserting shims in the front or rear of the frame joint. This adjustment and the previous one affect each other directly; iterate until both are right on.
• Make the blade vertical.
  • Use a small level held against the side of the blade. Insert shims into the left or right side of the frame joint. This adjustment and the previous one affect each other directly; iterate until both adjustments are right on.
• Make upper guide post parallel to the side of the blade.
  • Check with a tensioned ¼ in. blade mounted. Check for equal clearance between guide block and side of blade with the upper guides near the highest and lowest positions. Do not raise or lower the guides all the way, though. This is accomplished either by shifting the upper frame sideways at the joint.
• Really, really tighten the frame joint bolt.
  • When everything is properly aligned, tighten the bolt that holds the frame joint together really, really tight. It is absolutely the only thing holding the saw in alignment against blade tension and other punishment since there are no locating pins in one of the joints to keep things from slipping.
• Clean and lubricate the trunnions.
• Replace the table.
  • Be careful to keep the trunions aligned. Tighten the trunion bolts holding the rear trunion to the table, but only snug up the bolts on the front trunnion. Hold the table in place, with the trunnions mated against the trunnion brackets. Tighten the rear table lock knob all the way. Tighten the front table lock knob down slowly, while pushing the table around to help seat the front trunion. Finally, fully tighten the front trunion bolts.

TABLE

• Check table flatness with alignment pin in place.
• Set the table perpendicular to the side of the blade. Lock the table in place.
• Set the 90 degree stop.
  • Remember to tighten the lock nut. Unlock the table, tilt it, and return it to 90 degrees using the stop. Verify that it is still perpendicular to the blade by verifying some cuts.
• Set table tilt protractor indicator to 00 degrees.
• Set table perpendicular to the back of the blade.
  • Do this by shimming between one of the trunions and the table. The tracking of the blade affects this. For critical joinery, etc., cuts, the upper wheel tracking angle can be changed to tilt the blade slightly forward or back.
• Set the face of the rip fence perpendicular to the table.
  • Use a square sitting on the table. Shim the fence if possible, or make and shim a wood auxiliary fence if necessary.
• Make table insert flush with the table top.
  • If it is low, shim with tape. If it is high, replace or trim.
• Fit miter gauge runner to the slot in the table.
  • To tighten the fit, use a center punch or cold chisel to dent one side of the rod, raising slight bumps on either side.

GUIDE & THRUST BEARING ALIGNMENT

• Set the Y-brackets that hold the guides centered around the blade.
  • Verify that the Y bracket that holds the guide blocks is centered around the blade. This may not be possible, but be sure the blocks can be set correctly.
• Set thrust bearing perpendicular, and guide block faces parallel, to the side of the blade.
  • Loosen the guide mounts and twist the assemblies if necessary.
• Set side-to-side position of thrust bearing.
  • The outer edge of the bearing should extend about 1/8 in. past the blade. Twist the hexagonal mounting rod to move the bearing sideways. The bearing is mounted off center on the rod, so turning the rod moves the bearing sideways.

LUBRICATE AND PROTECT FROM RUST

• Wax the table
• Use dry lubricants on the following:
  • Side guide bracket and thrust bearing posts and locking screws
  • Upper guide post (needs an especially clean lubricant)
  • Upper guide post locking handle threads
  • Trunions
  • Trunion locking knob threads
  • Sliding bracket dovetail (which holds the upper wheel axel, and is pushed upward by the tensioning spring)
  • Blade tensioning rod threads
  • Upper wheel tilt knob threads
  • Upper wheel support pin joint that lets the wheel be tilted by the tracking knob
  • Quick tension release mechanism

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