What Is a Zero-Clearance Insert?

Zero-Clearance Inserts at a Glance

A zero-clearance insert replaces the stock throat plate on your table saw with one that has a slot exactly matching your blade width. That tight fit supports the wood fibers right at the cut line, eliminating the torn edges you get on the underside of cuts. You can make one from 1/2" MDF in 15 minutes, or buy a phenolic Leecraft insert for $30-40 that will outlast a dozen shop-made ones.

| Stock throat plate gap | 3/8" to 1/2" | | Zero-clearance insert gap | Blade width only | | DIY blank material | 1/2" MDF or Baltic birch plywood | | DIY cost | ~$2-5 | | Leecraft phenolic insert | ~$25-41 | | Time to make | 15-30 minutes | | Inserts needed | One per blade type and bevel angle |

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In this guide:

• Why the stock throat plate causes tearout
• How to make a zero-clearance insert
• Pre-made inserts worth buying
• What goes wrong and how to fix it

Part 1: Why Your Stock Throat Plate Causes Tearout

The stock throat plate on most table saws has a gap of 3/8" to 1/2" around the blade. That gap is intentional. It gives clearance for different blade angles and for the riving knife (the thin metal plate that rides directly behind the blade to prevent the kerf from closing and pinching). But it's also why you get blown-out fibers on the underside of cuts.

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Table saw teeth exit through the bottom of your workpiece on the upstroke. As each tooth breaks through, it momentarily lifts the wood fibers before shearing them. With nothing supporting those fibers at the cut line, they peel away instead of being cleanly cut. The result: the splintered, furry bottom face you get when ripping hardwood or crosscutting plywood.

A zero-clearance insert closes that gap to blade width only. As Rockler describes in their ZCI guide, "the tight-fitting slot fully supports the wood fibers right at the point of the cut." There's nowhere for the fibers to go. They get sheared, not lifted.

The same gap that causes tearout also swallows small offcuts. A strip ripped narrower than the throat opening falls into the blade well mid-cut and gets caught by the blade. The result is a piece launched back at you. A zero-clearance insert prevents anything narrower than the blade slot from falling through.

RELATED: What Is Table Saw Kickback? The same throat plate gap that allows tearout also lets small offcuts fall into the blade — one of three kickback failure modes explained in detail.

Part 2: How to Make a Zero-Clearance Insert

What you need:

• 1/2" MDF or Baltic birch plywood (MDF is cheaper; birch is more durable)
• Jigsaw or bandsaw
• 4 small set screws (1/4"-20, about 1/2" long) for leveling
• Polyurethane finish
• Your stock throat plate as a template

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The steps:

1. Trace the blank. Remove the stock throat plate. Set it on your 1/2" MDF and trace the profile with a pencil. Mark where the leveling screws sit at the four corners.

2. Cut it slightly oversized. Cut about 1/8" outside your traced line with a jigsaw.

3. Sand or file to fit. Work slowly toward the line, checking the fit frequently. You want a snug drop-in with no side-to-side wiggle.

4. Drill a finger hole. A 3/4" diameter hole at the front edge makes it easy to remove. Place it where the stock plate has its hole.

5. Add leveling screws. Drill four small holes at the corners and tap in set screws. These let you adjust the blank until it sits flush with the table surface. Check with a straightedge. The insert must be flush or just a hair below the table. Never above it.

6. Seal all surfaces. Apply two or three coats of polyurethane to every face, including the underside and edges. This keeps moisture out. Skip this step and the MDF will warp within a few uses.

7. Cut the kerf (safety-critical). Lower the blade completely below the table. Install the blank. Clamp a board across the front and back edges of the insert to hold it down firmly. The upward blade force will push the blank out of the opening as the teeth exit. Start the saw. Raise the spinning blade slowly all the way to full height through the blank. Shut off the saw. Wait for the blade to stop completely before touching anything.

Woodsmith's guide to making ZCI plates covers the leveling screw setup in more detail, including how to cut the blank flush using the stock plate as a router template if you want a cleaner fit.

The tape shortcut. If you need a ZCI for one cut and don't want to make a blank, Jonathan Katz-Moses' quick-tip method works: lower the blade, lay blue painter's tape over the stock plate gap, slit the tape at the riving knife slot, then slowly raise the blade through the tape. It takes two minutes. It won't hold up for repeated use, but for a single crosscut in figured maple, it does the job.

Part 3: Pre-Made Inserts Worth Buying

If Leecraft makes an insert for your saw model, buy it instead of making one. The phenolic laminate material is flat, hard, and dimensionally stable in a way that shop-made MDF blanks aren't. At $25-40, it costs less than the time you'd spend making your own.

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Leecraft inserts are the benchmark in this category. Made from high-density phenolic laminate (a resin-impregnated composite that is extremely flat, hard, and moisture-resistant) with a bonded melamine surface, they're 1/2" thick and fit most major saw brands: DeWalt, Delta, Craftsman, Jet, Powermatic, SawStop, Grizzly. Available at Woodcraft, Amazon, and Grizzly for $25-41 depending on the model.

When to skip the commercial option: if Leecraft doesn't list your saw model, make one. Also, for dado stacks and bevel cuts, you'll be making custom inserts regardless. There are no commercial options sized to every dado width combination.

One material to avoid: HDPE and UHMW plastic blanks. Multiple woodworkers on Fine Woodworking's forums and LumberJocks threads have reported these warp and cup at table-saw insert dimensions. Stick to phenolic for purchased inserts, and MDF or Baltic birch for shop-made ones.

Part 4: What Goes Wrong

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1. Insert warps or cups. You didn't seal the MDF. Moisture enters through the unfinished faces and causes the blank to bow. Fix: make a new blank and coat every surface (top, bottom, edges) with polyurethane before the first use.

2. Insert sits high. The blank is too thick, or the leveling screws are extended too far. A workpiece catching the insert edge is a kickback scenario. Fix: check the insert height with a straightedge, adjust leveling screws down, or sand the underside of the blank until it sits flush.

3. Insert sits low. Not a safety risk, but it reduces support right at the cut. Fix: raise the leveling screws. If the blank has no leveling screws, build up the underside with strips of tape until the insert sits flush.

4. Kerf is wider than the blade. You swapped blades after cutting the kerf, or the blade wobbled when you cut it. Fix: make a new insert calibrated to the current blade. ZCI blanks cost $2 in material. Replace them freely.

5. Small pieces still catch at the back of the insert. The back edge of the kerf slot is rough, or the insert sits slightly above the table at the back. Fix: file or sand the back edge of the slot smooth. Re-check leveling at all four corners.

Part 5: One Insert Per Setup

A zero-clearance insert is calibrated to one blade and one blade angle. That's it.

You need a separate insert for each dado stack width you use, for each bevel angle you care about, and for thin-kerf blades versus standard-kerf blades. Most woodworkers keep a stack of labeled ZCIs: one for the standard blade at 90°, a few calibrated to dado widths, and bevel inserts made as the cuts demand.

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Making a bevel insert: Set the blade to the desired angle first. Then lower the blade (still at that angle) and install the blank. Raise the blade through the blank at the bevel angle. Sawmill Creek's forum thread on bevel inserts documents the critical safety rule: never tilt the arbor while the blade is inside the insert. Set the angle before installing the blank, not after.

RELATED: Best Table Saw Blade Each blade you use (different kerf width, different thickness) needs its own ZCI. When you upgrade blades, make a new insert.

Sources

Sources informing this guide range from Fine Woodworking and Woodsmith project guides to practitioner forums and manufacturer product data.

• Rockler: How To Make Zero Clearance Throat Plate Inserts — mechanism explanation and step-by-step DIY guide
• Woodsmith: How To Make a Zero-Clearance Insert Plate — construction steps and leveling details
• Katz-Moses Tools: Easiest Zero Clearance Insert — tape shortcut method
• Woodcraft: Leecraft Zero Clearance Insert Product Guide — Leecraft phenolic specs and brand overview
• Sawmill Creek: Angled blade and zero clearance inserts — bevel insert safety procedure
• Popular Woodworking: Zero-Clearance Inserts — construction project with leveling screw details
• Fine Woodworking: Shopmade Tablesaw Inserts — material selection and construction
• Fine Woodworking Forum: Homemade Zero-Clearance Throat Inserts — HDPE/UHMW warping reports
• LumberJocks: Table Saw Zero Clearance Insert Warp — plastic insert failure modes