How to Check Table Saw Arbor Runout Before Installing a Blade
What's inside
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Arbor runout is the amount an arbor’s mounting surface moves off-center as it rotates. On a table saw, excessive runout can make a blade wobble, leave washboard marks, produce a wider-than-expected kerf, and make a cut wander. It can also be mistaken for a bad blade, a dirty flange, or a bent washer.
Check the arbor before installing a new blade. The test takes only a few minutes and tells you whether the problem is in the saw or the blade assembly.
Contents
What you need
Disconnect the saw from power and remove the throat plate, blade guard, riving knife, and blade. You need clear access to the arbor flange or the exposed arbor shaft. Lock the arbor if your saw has a built-in spindle lock; otherwise, use the supplied wrench carefully. Do not rely on the switch being off.
The best tool is a dial indicator with a magnetic base. A basic 0.001-inch reading indicator is suitable for this job. A 0.0005-inch indicator gives more resolution but is not necessary for diagnosing an ordinary contractor or cabinet saw.
You can also use a fixed pointer made from stiff wire and a piece of paper, but that only shows relative movement. It will not give you a reliable measurement. A feeler gauge can help locate a gap between a flange and a straightedge, but it is not a substitute for an indicator.
Prepare and inspect the arbor
Brush or vacuum away sawdust around the arbor. Wipe the threaded shaft, inner flange, outer flange, and the shoulder behind the flange with a clean rag. Pitch, rust, and a single packed chip can hold a blade at an angle and look exactly like arbor runout.
Inspect the threads for crushed areas and check that the arbor nut spins on smoothly by hand. Look at the flange faces under a bright light. They should be flat, clean, and free of raised burrs. Do not file away material unless you have identified a genuine burr; removing metal unevenly can make the problem worse.
Before measuring, rotate the arbor by hand and verify that it turns freely. If it feels rough, tight, or notchy, the bearings may be damaged. Runout testing will not repair a failing bearing, and forcing the arbor through a rough spot can produce misleading readings.
Measure the arbor runout
Mount the indicator base to the table or another rigid part of the saw. Keep the base away from the motor, belt guard, or any part that can move during the test. Position the indicator tip against the smooth cylindrical portion of the arbor, as close to the front bearing as practical. The tip should contact the shaft at 90 degrees to its surface.
Preload the indicator by roughly 0.020 to 0.050 inch. Zero the dial, then rotate the arbor slowly by hand through a complete revolution. Record the total indicated runout: the difference between the highest and lowest readings. Repeat the measurement two or three times, stopping at the same reference point each time.
| Measured total runout | What it usually means | Next step |
|---|---|---|
| 0.001–0.002 inch | Very good for most woodworking saws | Look elsewhere if the blade still wobbles |
| 0.002–0.005 inch | Generally usable, depending on blade quality and cut requirements | Check the flanges and test with a known-good blade |
| 0.005–0.010 inch | Borderline; vibration or visible blade movement is possible | Inspect for damage, dirt, or a bent arbor |
| Over 0.010 inch | Excessive for accurate table-saw work | Stop and diagnose the arbor, bearings, or shaft alignment |
These are practical woodworking guidelines, not a universal manufacturer specification. A low-cost saw may operate acceptably with more movement than a precision cabinet saw, while a thin-kerf blade can make a small error more noticeable.
Check the arbor flange separately
Move the indicator tip to the flat face of the inner flange. Keep the tip pointing axially toward the flange, then rotate the arbor one full turn. This measures face runout, which is different from the shaft measurement. A shaft can run nearly true while a flange face wobbles.
Next, check the outer flange if it can be installed without a blade. Record the high and low readings. If the inner flange has a high spot, remove it and clean both mating surfaces before testing again. If the reading follows the flange when you rotate or reinstall it, the flange is bent or damaged.
Do not run the saw with only an indicator or pointer touching a powered arbor. All of these tests are performed by turning the shaft by hand with the saw unplugged.
Separate arbor problems from blade problems
If the arbor and flanges measure acceptably, install a clean, known-good blade. Tighten the arbor nut firmly, but do not use excessive force or an impact tool. Measure runout at the blade plate near the teeth, avoiding the carbide tips. Then rotate the blade 180 degrees on the arbor and test again.
A reading that changes substantially after flipping the blade points toward the blade or its mounting hole. A bent blade plate, inaccurate bore, resin on the flange, or a damaged tooth can create visible wobble. A blade can also have normal plate tension variations that make the rim move even when the arbor is straight.
For checking blade plate movement, a blade alignment gauge or dial indicator setup is more useful than judging by eye. A visible wobble does not automatically mean the blade is unsafe, but a blade with a crack, bent plate, or damaged teeth should not be used.
When repair is justified
First correct simple causes: dirty flanges, a burr, a loose arbor nut, a bent washer, or a blade with a damaged bore. If shaft runout remains above about 0.005 inch after cleaning, inspect the arbor for a bend and check the bearings for play. Push and pull the shaft axially and radially with the power disconnected. Noticeable clunking is not normal.
Replacing a flange or arbor is often worthwhile on a quality cabinet saw. On an inexpensive saw, compare the part cost and labor with the price of a replacement machine. Do not attempt to straighten an arbor with a hammer. It can damage the bearings and leave the mounting threads unsafe.
A precision straightedge can help confirm a visibly bent flange, but the dial indicator is the better buying choice if you expect to service other stationary machines. The same indicator can check band-saw wheels, planer cutterhead components, jointer tables, and drill-press quills.
