Safety— Stop before you diagnose
Switch off and unplug the saw before looking at the blade, and take it off to inspect it. A cracked blade or one with missing teeth is not a cutting problem to work around: OSHA requires cracked saws to be taken out of service, and SawStop warns that damaged teeth can make an injury worse on its saw.
Symptoms and causes
Symptoms
- Burn marks, or the blade labouring, on cuts the saw used to make cleanly
- Chipped or rough edges after a blade change, or on veneered panels
- A blade that visibly wobbles, or vibration that changes with the blade
- A riving knife that drags or binds in the cut
- A brake-equipped saw that trips without contact
Likely causes
| Cause | How to check |
|---|---|
| Pitch or resin on the teeth and plate | Look for brown build-up on the plate and the faces of the teeth. |
| A dull or badly set blade | Edges rounded at the tips; the saw needs more feed force than it did. |
| A chipped, cracked or missing tooth | Turn the blade slowly under a light, tooth by tooth, with the saw unplugged. |
| A warped plate | A straightedge across the plate, both faces. |
| A blade the knife is not marked for | The blade's kerf and body against the marking on the riving knife. |
| A bore or washers that do not match | Arbor hole shape and size; washers and flanges clean and undamaged. |
| The wrong blade for the material | The blade's stated use and depth against the cut. |
Fixes
| Problem | Fix |
|---|---|
| Pitch | Clean the blade with a cleaner made for saw blades, as its maker directs. |
| Dull or badly set | Replace, or have it sharpened by a specialist. |
| Cracked plate or damaged teeth | Take the blade out of service. |
| Warped plate | Replace the blade. |
| Knife or bore mismatch | Fit a blade within the knife's marking and the saw's arbor specification. |
| Wrong blade for the job | Change to a blade made for the material and cut. |
The blade, or the saw?
Many symptoms — burning, rough edges, binding — can come from either. SawStop's troubleshooting table lists blade causes (dull, pitch-coated, wrong for the material, damaged) beside saw causes (fence out of line, worn bearings, an uneven floor). A practical way to split them is to fit a blade you know is sound and suited to the cut: if the fault goes, it was the blade; if it stays, work through saw problems — fence, alignment, stock and support.
| Fault | Shows up as | Check | Action |
|---|---|---|---|
| Cracked plate | A line running in from the rim or a gullet | The plate under a light, saw unplugged | Remove from service (OSHA) |
| Chipped, loose or missing teeth | Rough cuts; on SawStop saws, a possible false brake trip | Each tooth in turn (Freud: before each use) | Do not use the blade |
| Warped plate | Wobble, a wide kerf, vibration | A straightedge across both faces | Replace (DEWALT: never use a warped blade) |
| Pitch build-up | Burning, a blade that needs more push | Brown deposit on teeth and plate | Clean it off (OSHA: at once) |
| Dull or badly set | Burning or rough edges on a clean blade | Rounded tooth tips; more feed force needed | Replace, or sharpen by a specialist |
| Blade the knife is not marked for | The riving knife drags or binds | Kerf and body against the knife's marking | Fit a blade within the marking |
| Mismatched bore or hardware | Wobble; the blade runs off-centre | Arbor hole, washers and flanges | Use the saw's own clean, undamaged hardware |
From OSHA 1910.213(s), DEWALT's and SawStop's manuals and Freud's dado instructions. Your saw's manual takes precedence.
Damage you can see
- Cracks in the plate, often starting at the rim or a gullet: OSHA requires the blade to be removed from service.
- Chipped, loose or missing teeth: Freud's check before each use is for exactly these, and for dullness; do not use a cutter with any of them. On SawStop saws, damaged or missing teeth can also cause a false activation of the brake.
- A warped plate: DEWALT tells owners never to use a warped blade. A straightedge across the plate, on both faces, shows a warp a glance can miss.
Pitch and dullness
Pitch and resin build up on the teeth and plate, especially from sap-coated wood and plastics; DEWALT warns that the build-up raises the risk of the blade overheating and binding, and OSHA requires gum on a blade's sides to be cleaned off at once. The first sign is often burning or a blade that seems to need more push. Clean it as described in cleaning and adjusting a blade. If a clean blade still burns or leaves rough edges, it is probably dull: OSHA's standard calls for dull or badly set saws to be taken out of service before they cause sticking, jamming or kickback, and restricts sharpening to people of demonstrated skill.
Wobble
A blade that runs out of true leaves a wide or ragged kerf and shakes the saw. The causes are mostly at the blade and its mounting:
- A warped plate — replace the blade.
- A mismatched bore or damaged washers and flanges. DEWALT warns that a blade whose arbor hole does not match the saw's mounting hardware runs off-centre; use the saw's own washers, clean and undamaged.
- Play in the arbor or worn bearings. OSHA requires arbors free from play; SawStop lists worn bearings among the causes of vibration. With the saw unplugged, check for movement in the arbor by hand; bearing work is a service job.
- Wobble dado sets are a different thing: an adjustable dado that is meant to wobble. Bosch's 4100 manual forbids wobble and adjustable dado sets on that saw, and OSHA prohibits the improvised wobble saw made by wedging a blade between its collars. If your saw takes a dado set at all, use the kind its manual allows — see dado blades.
A blade that does not suit the saw
- The riving knife drags or binds. The blade's body must be thinner than the knife and its kerf wider, DEWALT states, and its knives are marked with the range they suit. Where a blade's figures are not given, DEWALT's test is a shallow cut in scrap and sliding the knife through it: it should not bind or drag. See table saw blades.
- A brake-equipped saw trips without contact. SawStop lists damaged teeth among the causes, and rules out coated teeth and blades outside its kerf range for its brake.
- Rough cuts in panels or across the grain. A rip blade with few teeth is made for a different job; SawStop lists "not the correct blade for the material or cut" among the causes of rough cuts.
Blade inspection
- The saw is unplugged and the blade is off
- No cracks in the plate or at the gullets
- Every tooth present, unchipped and tight
- The plate is flat against a straightedge, both faces
- No pitch on the plate or teeth
- The bore, washers and flanges match the saw and are undamaged
- The kerf and body suit the riving knife's marking
Sources
This page covers faults that start with the blade. Faults in the fence, alignment, stock and set-up are covered in the companion saw-problems guide. Procedures are the named makers' and OSHA's; check your own saw's manual.
- 1.
29 CFR 1910.213, Woodworking machinery requirements. U.S. Department of Labor, Occupational Safety and Health Administration.
Used for: Dull, badly set, improperly filed or tensioned saws removed before they cause sticking, jamming or kickback, and gum on the sides cleaned immediately ((s)(1)); cracked saws removed ((s)(7)); arbors free from play ((s)(4)); machines free from sensible vibration with the largest tool idle at full speed ((a)(1)); improvised wobble saws prohibited ((s)(8)); sharpening by people of demonstrated skill ((s)(5)).
- 2.
DWE7485 8-1/4" (210 mm) Compact Job Site Table Saw, Instruction Manual. DEWALT.
Used for: Material building up on the blade raising the risk of overheating and binding; blades kept clean, sharp and with sufficient set; never warped or cracked blades or ones with broken teeth; mismatched arbor holes or mounting hardware running a blade off-centre; the knife's marking and the rule that body is thinner, and kerf wider, than the knife.
- 3.
DWE7491 10" (254 mm) Job Site Table Saw, Instruction Manual. DEWALT.
Used for: Checking a blade against the riving knife by a shallow test cut when its kerf and body are not given; the knife should not bind or drag.
- 4.
Owner's Manual, 10" Professional Cabinet Saw, Model PCS31230. SawStop.
Used for: Damaged or missing teeth causing a more serious injury or a false activation of the brake; no coated teeth; kerf limits for the brake; the troubleshooting causes for rough cuts and vibration (dull, pitch-coated, wrong or damaged blade).
- 5.
Creating a Dado Sled — safety instructions. Freud Tools.
Used for: Inspecting carbide before each use for dullness, cracks and loose, missing or broken teeth, and not using a damaged cutter.
- 6.
Formula 2050: Blade & Bit Cleaner. CMT Orange Tools.
Used for: A cleaner made to remove pitch and resin from saw blades, applied as its maker directs.
- 7.
4100XC-10 Operating/Safety Instructions. Bosch Power Tools, 2019.
Used for: Bosch's instruction not to use wobble or adjustable dado sets on its 4100 saw.
About this troubleshooting
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