How to Replace Table Saw Trunnion Bearings and Inspect the Arbor
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Contents
Diagnose the Noise Before Ordering Parts
On most table saws, the trunnions are the cast or machined supports that let the blade tilt and raise. The arbor—the shaft that carries the blade—runs in bearings mounted in or near the saw’s arbor assembly. Owners sometimes call these “trunnion bearings,” but the bearings usually support the arbor, not the trunnions themselves. Check your saw’s parts diagram before buying anything: bearing locations and replacement procedures vary by model.
A dry bearing may growl, rumble, or feel rough as the arbor turns. First unplug the saw and remove the blade, throat plate, and blade guard or riving knife as needed for access. Rotate the arbor by hand. A smooth, quiet turn is normal; a repeating gritty feel, scraping, or noticeable looseness deserves further inspection. Noise alone is not proof of a bad bearing. A loose blade, dirty pulley, worn belt, or motor bearing can sound similar.
To separate the motor from the arbor, remove the drive belt and turn each shaft by hand. If the motor is rough, diagnose its bearings separately. If the arbor is rough, check for play by gently moving the arbor up and down and side to side. A small amount of measurable movement can be normal depending on the design, so compare it with the manufacturer’s service limits rather than assuming any movement means failure. Do not run the saw with the belt off as a substitute for a proper diagnosis.
Choose the Right Replacement
Look up the saw’s exact model and serial number, then confirm the bearing part numbers in its parts list. Match the bearing type, internal clearance, seals or shields, and dimensions. A bearing with the same outside diameter may still be wrong if its bore or width differs. Avoid choosing by appearance or by a generic “table saw bearing” listing.
| Option | Best fit | Trade-off |
|---|---|---|
| Original-equipment bearing | Saws with a model-specific bearing or unusual fit | Usually the least guesswork, but may cost more or be harder to find |
| Quality equivalent bearing | When the manufacturer’s part number and bearing specifications are confirmed | Can save money; the buyer must verify dimensions, clearance, and sealing |
| Generic bearing of matching dimensions | Only when the full specification is known and the application is suitable | Low price, but a dimensional match alone does not guarantee a proper fit or service life |
For an older saw with an uncommon arbor, buying the correct assembly may be more sensible than pressing in bearings individually. Compare the cost of the replacement arbor assembly with the price of bearings, shop labor, and the risk of damaging a shaft during disassembly. If you cannot confirm the bearing specification, ask the manufacturer or a repair shop before ordering.
Prepare the Saw and Work Area
Unplug the saw; do not rely on its switch. Remove the blade and disconnect the dust hose. Take clear photos of the belt path, washers, spacers, and wiring before removing parts. Support heavy components, especially on cabinet saws. A tilting arbor assembly can be awkward and may drop when its supports are loosened.
Gather the service manual, correctly sized wrenches and sockets, snap-ring pliers if required, a soft-faced mallet, and a way to press bearings squarely. A bearing separator and puller set can help remove a bearing without levering against a thin pulley or casting. If a bearing is interference-fit, a press is safer and more controlled than hammering. Wear eye protection, and keep fingers clear of pinch points.
Remove and Replace the Bearings
Follow the saw’s service instructions to expose the arbor assembly. Some saws allow bearing replacement with the assembly in place; others require removing the motor, belt, pulleys, or trunnion-supported arbor. Mark the original positions of shims and spacers, and keep parts in order. Their placement can affect blade alignment and smooth tilt or elevation.
Before pulling a bearing, note how it is retained. Remove circlips, locknuts, or retainers with the correct tool. Pull only on the bearing race that is fitted to the shaft; when pressing a bearing into a housing, apply force to the outer race. Force through the balls or rollers can brinell the bearing and leave it noisy before the saw is even used. Do not heat a bearing with a torch or strike the arbor directly. If the shaft is mushroomed, scored, or seized in the inner race, stop and get professional help rather than damaging the arbor.
Install the new bearing in the same orientation, using a clean, square press fit. Replace damaged seals, retainers, or locking hardware, and use lubricant only where the manual specifies it. Many sealed bearings arrive lubricated and should not be packed with extra grease. Turn the arbor by hand before reinstalling the belt; it should rotate smoothly without binding.
Inspect the Arbor and Reassemble
With the bearings removed—or with the assembly accessible—inspect the shaft journals for scoring, corrosion, discoloration from heat, and wear where the bearing seats. Check the blade flange and arbor threads for damage. A nick on the flange can keep a blade from seating flat; damaged threads can prevent the nut from clamping securely. Replace a bent, cracked, or badly worn arbor rather than treating new bearings as a cure.
To check for runout, mount a dial indicator on a stable part of the saw and place its tip against a clean arbor surface or the blade flange. Rotate the arbor slowly by hand and note the total indicator reading. Use the service manual’s tolerance: acceptable runout depends on the saw and on where it is measured. If the reading is high, first clean the contact surface and check that the indicator is mounted firmly. A blade can also be warped, so do not diagnose a bent arbor from blade-edge runout alone.
Reassemble in the original order, tension the belt to the manufacturer’s specification, and confirm that the blade rises, lowers, and tilts through its full range without rubbing. Check blade-to-miter-slot alignment and bevel stops if the arbor assembly was removed; moving the trunnions can change alignment. With guards restored and the work area clear, reconnect power and make a brief no-load test from a safe position. Stop immediately if there is vibration, smoke, unusual heat, or renewed grinding. A successful repair should run quietly, track the blade correctly, and hold its adjustments—not merely spin without noise.
