Table Saw Trunions and Friction Polish Techniques

A table saw's trunnions are the cast iron or aluminum brackets that hold the arbor assembly and let the blade tilt from 0 to 45 degrees. When a saw starts cutting slightly out of square, or the blade angle drifts after a bevel cut, the trunnions are usually the first place to check, not the fence.

What the Trunnions Actually Do

Most cabinet and contractor saws use two trunnions, a front trunnion and a rear trunnion, bolted to the underside of the table. The arbor, motor mount, and tilt mechanism hang from these two castings. A worm gear or rack and pinion assembly moves the trunnions together when you turn the bevel handwheel, and a separate handwheel raises or lowers the arbor for depth of cut.

Common Trunnion Problems

• Blade not parallel to the miter slot, causes burning on rip cuts and can lead to dangerous kickback
• Bevel angle drifting under load, usually a loose bevel lock or worn worm gear
• Excess play in the arbor, felt as vibration or a rough cut edge
• Binding when tilting, often caused by dried grease or built up sawdust in the trunnion ways

Aligning the Trunnions

Alignment starts with the blade to miter slot relationship, sometimes called the blade parallelism check. Mark a tooth with a pencil, rotate it to the front of the blade, and measure the distance from that tooth to the miter slot with a combination square or a dial indicator. Rotate the same tooth to the back of the blade and measure again. On most saws a difference of more than 0.005 inch between the two readings is enough to cause burning and should be corrected.

To correct the alignment, loosen the four bolts that hold the trunnions to the underside of the table just enough to let the table shift, then use a dead blow mallet to tap the table into position while watching the dial indicator readings. Retighten the bolts in a crossing pattern, checking the readings again after each bolt, since tightening one corner can shift the others. Most saws need two or three rounds of loosen, tap, and retighten before the readings hold steady across a full rotation of the blade.

Bevel Stop and Detent Adjustment

Most cabinet saws have set screws that control the 0 and 45 degree stops. After realigning the trunnions, check both stops with a machinist's square against the blade, not the table, since the table surface can be slightly out of flat. Adjust the stop screws until the blade reads a true 90 and 45 degrees, then verify the bevel scale pointer still matches by loosening its screw and resetting it to zero. Many saws also have an intermediate stop around 22.5 degrees for compound miters, which is worth checking at the same time since it is often ignored during routine maintenance.

Lubrication and Maintenance Schedule

Dry or gummed up trunnion ways are the most common cause of a bevel adjustment that binds or jumps. A light coat of dry lubricant, such as a paste wax or a PTFE based spray, on the curved trunnion ways lets the table tilt smoothly without attracting sawdust the way oil or grease does. Wipe the ways clean with a stiff brush before reapplying, since old grease mixed with sawdust turns into an abrasive paste that accelerates wear.

Friction Polishing for Shop-Made Parts

Friction polish is a metalworking finishing technique that produces a bright, even shine on turned or machined metal parts using nothing more than fine abrasive and friction generated heat. It is useful in a woodworking shop whenever you make or refurbish small brass, steel, or aluminum hardware, such as shop built jig components, knobs, or drawer pulls on a metal lathe or drill press.

How Friction Polishing Works

The part spins at moderate speed, typically 1000 to 1800 RPM on a lathe or drill press, while you hold a fine abrasive such as 400 to 600 grit wet or dry paper against the surface with light, even pressure. The friction between the spinning metal and the abrasive generates localized heat, which helps burnish the surface rather than simply scratching it. Progressing through finer grits, then following with a metal polishing compound on a cloth, produces a mirror finish without buffing wheels.

1. Start at 320 or 400 grit to remove tool marks from turning or machining
2. Progress to 600 grit, changing direction slightly to cross hatch the scratch pattern
3. Switch to a folded cloth charged with polishing compound, held with the same light pressure
4. Wipe the part clean between stages to avoid dragging coarse grit into the finer passes

Where This Applies in a Wood Shop

Friction polishing shows up most often when woodworkers make their own hardware, turned brass ferrules for shop made screwdrivers or chisels, steel pins for jigs, or small fittings for boxes. It is also a practical skill for restoring old tool parts, such as the depth stop on a vintage marking gauge or the brass fittings on a hand plane, without needing a full metal shop setup. A drill press with a variable speed head and a set of wet or dry sandpaper is enough equipment to get a usable result on small parts.

Both trunnion alignment and friction polishing reward patience over speed. A saw that cuts true saves time and material on every project that follows, and a well finished shop made part looks as intentional as anything bought off a shelf. Neither task takes long once you have gone through it once, and both become quick checks you can run in fifteen minutes during routine shop maintenance.

Buying Guidance if the Trunnions Are Beyond Repair

If a trunnion casting is cracked, or the worm gear teeth are stripped, replacement parts are often available directly from the saw manufacturer using the model number stamped on the motor plate or the trunnion casting itself. On older or discontinued cabinet saws, a used trunnion assembly pulled from a parts machine is frequently the fastest fix, since aftermarket reproductions are rare for anything beyond the most common contractor saw models. Before replacing a full assembly, confirm the problem is not simply a stripped set screw or a bent tilt rod, both of which are inexpensive fixes compared to a full trunnion casting.