Skil Brush Cap & Assembly

A tired worm drive can feel like a different saw after a simple brush swap. I was reminded of that after installing this Skil brush kit on a well-used SPT99 that had started to arc, hesitate under load, and leave that telltale burnt smell. Ten minutes later—new brushes and caps in—my saw spun up cleaner, held torque through rips, and generally behaved like it had shed a few hard years on the job.

What’s in the kit and why it matters

This kit is as straightforward as it gets: two carbon brushes and two caps, sized for Skil’s worm drive motors and explicitly compatible with the SPT99. Brushes are consumables; they wear down as they ride the commutator, and as they shorten you’ll see more sparking, erratic power, and a motor that feels “scratchy” at startup. Swapping brushes restores proper contact, reduces arcing, and protects the armature from unnecessary heat and wear. It’s routine maintenance, but it makes a very real difference in performance and longevity.

The caps matter, too. Worn or damaged caps can bind or lose tension on the brush spring. Fresh caps with clean threads and healthy springs maintain even pressure, which helps the new brushes seat quickly and evenly.

Installation: simple, with a few watch-outs

On the SPT99, access covers make this a straightforward job:

• Unplug the saw and blow out the motor housing with dry compressed air. A soft brush helps loosen caked dust.
• Back out the old caps; catch the brushes as they spring forward.
• Inspect the old brushes. If they’re chipped, tapered, or nearly down to the pigtail, the timing is right.
• Drop in the new brushes, making sure the lead and spring sit naturally without binding.
• Thread in the new caps finger-tight, then snug with a screwdriver—do not over-torque.

The caps in this kit threaded in cleanly without cross-threading, and the spring tension felt consistent. Seating took about five minutes of no-load running; I let the saw run free for a few minutes, then made a couple of light cuts on scrap before leaning into heavier rips.

A couple of tips:

• Don’t crank the caps. Over-tightening can fracture the plastic or deform the seat.
• If you see heavy arcing on initial start-up, stop and confirm the brushes are aligned and the springs aren’t hung up.
• Clean is king. Carbon dust is conductive; get it out before you button up.

Fit and compatibility

On the SPT99, fit was spot on. The brush length and cross-section matched what came out, and the caps seated flush. This kit is positioned for Skil’s worm drive lineup, but I’d caution anyone planning to drop it into a sidewinder or an older non-SPT model: verify the part number and brush dimensions. Brush pockets and cap threads can vary. I’ve seen cases (especially on older sidewinders) where a brush is a hair oversized and needs a light kiss with a file to slide freely. That’s not ideal, and you shouldn’t have to modify a new brush, but it’s better than forcing a tight fit that could bind as the brush wears.

If you’re not working on an SPT99, take thirty seconds and measure the old brush: width, thickness, and length. Compare that to the new brush before you install. Free, smooth movement in the holder is non-negotiable.

Performance after the swap

The improvement was immediate on my saw:

• Startup felt smoother, with less scratchy chatter from the motor.
• Under load, the blade held speed better in 2x stock and sheet goods. The bogging I’d been compensating for mostly disappeared.
• Sparking at the brush windows reduced to a faint, normal glow once the brushes seated; the brief initial fireworks you sometimes see calmed down within a minute.

None of this is magic—fresh carbon against a clean commutator is simply what the motor wants—but it’s gratifying to feel a saw you know well return to its baseline. If you’re chasing inconsistent power, don’t skip this maintenance step before assuming the armature or switch is failing.

Build quality and materials

The carbon compound on this kit appears to be the typical moderate-hardness mix Skil uses for worm drives: firm enough to resist chipping, not so hard that it chews the commutator. The pigtail leads are well-crimped, and the springs deliver even pressure throughout travel. Caps thread cleanly, the slots are cut deep enough to take a proper screwdriver blade, and the sealing faces sit square. Nothing fancy here—just competent, OEM-grade parts that behave predictably.

After a few hours of cutting post-install, brush wear looked even, with a clean contact patch forming across the commutator radius. That’s what I want to see: no troughing, no edge chipping, and no uneven polish on the commutator bars.

Value and what you’re actually buying

For the price of a decent blade, you extend the life of a motor that costs an order of magnitude more to repair or replace. That trade is a no-brainer. I also like that the kit includes both caps. Some sets ship brushes only, and while you can reuse old caps in a pinch, fresh caps eliminate one more variable.

At roughly a couple of ounces, the kit disappears in a pouch. Keeping a spare set on the truck is painless, and it can bail you out on a job when a saw starts acting up after lunch.

Common pitfalls and how to avoid them

• Misdiagnosis: Brushes aren’t a cure-all. If your saw trips breakers instantly, smells like burnt varnish at idle, or screams with a high-pitched whine, you might be looking at an armature or bearing issue instead.
• Dirty commutator: If the copper is black and streaky, consider a light clean with a commutator stone or a gentle rub with 600-grit paper while rotating by hand. Never use aggressive abrasives.
• Uneven seating: Give the saw a few minutes of no-load run time. Jumping straight into a heavy rip can chip fresh edges.
• Cross-threading: Start caps by hand and back them off a quarter-turn to feel the thread engagement before driving them home.

Who this kit is for

• SPT99 owners who’ve noticed increased sparking, reduced torque, or intermittent power.
• Shops that want to keep maintenance parts on hand for worm drive saws without stocking a dozen SKUs.
• Users comfortable with basic tool maintenance who prefer to extend service life rather than replace tools at the first hiccup.

If you’re working on a different Skil model, or especially a sidewinder from another series, do your homework. Brush dimensions and cap threads are not universal. A quick check of the model’s parts diagram or the old brush’s dimensions will save you hassle.

The bottom line

This brush kit does exactly what it should: it fits the SPT99, installs easily, and restores motor performance without drama. The materials are up to snuff, the caps are cleanly made, and the springs apply consistent pressure. After installation and a brief break-in, my saw settled into smooth, predictable operation with reduced sparking and better load handling. There’s nothing exotic here, and that’s the point—reliable, boring maintenance that pays off every time you pull the trigger.

Recommendation: I recommend this kit for SPT99 owners and other compatible Skil worm drive saws. It’s an inexpensive, effective way to revive performance and stave off bigger repairs. My only caveat is compatibility: don’t assume it will drop into every Skil sidewinder or older model without checking the part number and brush dimensions. If your saw matches the intended application, this simple kit earns its keep.