Skil Dado Insert

Why I picked up this dado insert

I rely on the SPT99T portable worm drive table saw for jobsites and small-shop projects because it packs a lot of power in a compact footprint. The one thing it can’t do out of the box is safely run a stacked dado set. This dado insert is the missing piece. After a few weeks of cabinet work and on-site shelving with it, I can say it turns the SPT99T into a much more versatile joinery machine—within clear limits you should understand before you buy.

Design and compatibility

This is a dedicated throat plate designed specifically for the SPT99T. It accepts stacked dado cutters up to 1/2 inch wide and comes with a washer meant to secure the stack correctly on the arbor. The geometry of the plate matches the saw’s table opening precisely, including the front finger access and rear catch. On my saw, the insert seated flush without fuss, with no rocking or rattling.

The opening is wide enough to accommodate common chipper/groover combinations and the gullets of standard dado sets. It’s not a zero-clearance plate out of the box—you’ll kerf it during setup so the cut line matches your exact stack width. That’s a good thing: kerfing creates zero-clearance support, which helps reduce tear-out along dado shoulders.

One important note: this is not a universal insert. It’s made for the SPT99T. If you’re running another model (including other saws from the same brand), check for a dedicated part.

Setup and installation

Getting up and running was straightforward:

• With the saw unplugged, I removed the standard blade and guard/riving knife assembly. Like most compact jobsite saws, the SPT99T doesn’t support a riving knife for dado cuts, so plan your workholding accordingly.
• I built a stack not exceeding 1/2 inch using my preferred dado set and shims. The included washer mattered here—it helped position the stack on the arbor so the nut engaged fully without bottoming out. On portable saws, arbor thread engagement can be tight with wider stacks; this washer solves that.
• I installed the dado insert, set the blade height fully down, placed a sacrificial board across the opening, and slowly raised the running stack through to kerf the plate. That created a clean, zero-clearance slot custom to the stack width.

The insert locks in securely and stayed put during height and bevel adjustments. I didn’t need to tweak fit or level, and it removed and reinstalled cleanly between operations.

Performance: cut quality and support

Once kerfed, the insert did exactly what it should: support the work close to the cutters. On plywood, MDF, and solid wood, shoulder tear-out was minimal—noticeably better than running a dado stack with a wide factory throat opening. The zero-clearance edge also collected some of the smaller chips that otherwise spray out, improving visibility of the cut line.

I didn’t detect flex in the insert around the cut opening, even during wider 1/2-inch passes. Cuts felt stable, and the workpiece tracked smoothly across the plate. On narrow work, I’m always cautious of edges dipping into the insert opening; here, the support stayed consistent, and my push blocks glided over cleanly.

As expected with a compact saw, you’ll give up maximum depth compared to a full-size cabinet saw—more a function of blade diameter than the insert. For typical groove and housing depths, it wasn’t a limitation. If you’re attempting deep, wide dados in dense hardwood, you’ll need to pace the feed and let the saw clear chips. The insert’s close-in support makes that easier.

Capacity limits and workarounds

The headline limit is width: the insert supports stacked dado cutters up to 1/2 inch. For many cabinet and furniture tasks—1/4-inch drawer bottoms, 3/8-inch shelf grooves, 1/2-inch rabbets—that’s plenty. Where it falls short is full “3/4-inch” shelf dados. Modern plywood often measures about 23/32 inch, which exceeds this insert’s max capacity.

Two workarounds worked well for me:
- Make two passes with a 1/2-inch stack, nudging the fence for the remainder. The zero-clearance kerf keeps the shoulder clean on both sides.
- Use a router for ultra-precise shelf dado widths and leave the saw for smaller grooves, rabbits, and lap joints.

If you frequently cut wide dados in one pass, a larger saw and 13/16-inch-capable insert would be the better fit.

Safety and ergonomics

With the riving knife removed for dado work, I rely on push blocks, featherboards, and a stop fence to manage kickback risks. The insert’s snug fit and zero-clearance kerf help keep offcuts from dropping into the blade cavity, which keeps the cut calmer and reduces surprises. I recommend:
- Always kerf the insert for each dado width you run.
- Use featherboards on the infeed side to maintain consistent pressure.
- Support long workpieces with outfeed rollers or a helper.

The included washer deserves another mention. Ensuring proper nut engagement and stack alignment isn’t optional—it’s safety-critical. I appreciated having the correct hardware in the box instead of hunting through a bin of washers and hoping for the best.

Dust collection and cleanup

Dado cuts throw a lot of chips, and compact saws aren’t known for stellar dust collection. The kerfed insert helps by closing down the opening, but you should still expect more shavings topside than with a standard blade. With a vac attached to the saw’s port, the mess was manageable. A blast of compressed air cleared the zero-clearance slot when I changed widths.

Durability and build quality

The insert feels rigid and well-machined (or well-molded), with clean edges and a consistent surface finish that’s easy to slide stock over. After multiple kerfs and a few accidental brush-ups with a carbide tooth when raising through, the slot edge held up without chipping. I wouldn’t expect infinite life—any zero-clearance plate is a consumable item if you frequently change widths—but there’s no sign of premature wear.

The fit remained tight over the course of the review, with no developing play. I keep a light coat of paste wax on the insert and the table to keep things slick and corrosion-free.

Tips for best results

• Kerf slow, raise slow: When cutting the initial slot, take your time and let the stack do the work.
• Mark your widths: A piece of tape under the plate noting common shim stacks (1/4, 3/8, 1/2) saves time.
• Max out at 1/2 inch: Don’t try to push beyond the stated capacity; use two passes if you need wider.
• Store the washer with the plate: I keep them together so I’m never tempted to “make do” with the wrong hardware.

Who it’s for

• SPT99T owners who need to add grooves, rabbets, and narrow-to-medium dados to their workflow without hauling a second machine.
• Jobsite carpenters doing built-ins, shelving, and face-frame joinery where 1/4–1/2 inch cuts are common.
• Small-shop woodworkers who prefer the table saw for repeatable grooves and use a router for the widest dados.

Who it’s not for: anyone needing one-pass 23/32-inch shelf dados or those looking for cross-compatibility across different saw models.

The bottom line

The dado insert does what it promises: it enables safe, clean, repeatable dado work on the SPT99T up to 1/2-inch wide. The included washer simplifies setup and keeps the stack secure, the fit is precise, and the zero-clearance kerf improves cut quality and chip control. It doesn’t transform a compact jobsite saw into a cabinet saw—but within its capacity, it’s a genuinely useful, confidence-building upgrade.

Recommendation: I recommend this insert to any SPT99T owner who wants reliable dado capability for grooves, rabbets, and medium-width housings. It’s purpose-built, installs easily, and delivers better support and cleanliness than running a stack over a wide-open throat. If your work demands one-pass 3/4-inch dados, look to a larger saw and insert; otherwise, this is the right accessory to unlock the joinery your compact saw was missing.