09Power tool parts · millimetres
Carbon brushes are sold by three numbers in millimetres, not by the drill on the box.
Carbon brushes for power tools measured as width, depth and length, plus keyed and keyless drill chucks matched to the spindle thread. Brushes run $8 to $26 a pair, chucks $16 to $48, both indicative until the counter has the old part on the caliper.
Worn pair left · replacement right
PT-01 · Carbon brushes
Carbon brushes for power tools, measured face and length
A universal motor in a corded drill, grinder or circular saw sends current to the commutator through two blocks of graphite pressed on by springs. They wear. When they get down to about 6 mm long the tool sparks, loses power and then stops. Replace both together, always.
We size a brush as width × depth × length, like 6×10×13 or 5×8×11. Then the lead: a braided shunt with a spade, a ring, or a plain end soldered to the holder. Then the spring: separate coil, captive spring on the brush, or a spring in the holder. Two brushes with the same block size and a different lead will not fit the same holder, and that is the mistake we see weekly.
Some brushes carry an auto-stop pin that cuts the motor before the shunt touches the commutator. If yours had one, the replacement needs one. Cordless brushless tools have no brushes at all, so if the drill says brushless, the fault is elsewhere and we will tell you so.
| Size, mm | Lead | Typical tools |
|---|---|---|
| 5×8×11 | Spade | Small drills, rotary tools |
| 6×10×13 | Spade or ring | Corded drills, jigsaws |
| 6.3×10×16 | Ring, captive spring | Angle grinders |
| 7×17×17 | Ring, auto-stop | Circular saws, large grinders |
$8–$26 per pair · indicative, confirmed on reply
PT-02 · Drill chuck
Keyed and keyless drill chucks, matched to the spindle thread
The chuck screws on to the drill spindle, and most are held by a left-hand screw inside the jaws as well. The size people quote, 3/8 or 1/2 inch, is the largest bit it grips. The mount thread is a separate number and it decides the fit: 3/8-24 UNF on most light drills, 1/2-20 UNF on most 1/2 inch drills. Some metric drills use M12×1.25.
Keyed chucks of hardened steel hold a bit tighter under hammer action and outlast keyless ones on masonry work. Keyless all-metal chucks are quicker and fine for wood and driving. Plastic-sleeve keyless chucks are what wears out first; that is usually why you are here.
We need the drill model or the old chuck. Removing it takes a hex key in the jaws and a sharp tap, and we explain the order before you start. Clockwise to loosen the retaining screw. That surprises everyone.
| Mount | Capacity | Type |
|---|---|---|
| 3/8-24 UNF | 0.8–10 mm | Keyed or keyless |
| 1/2-20 UNF | 1.5–13 mm | Keyed or keyless |
| M12×1.25 | 1.5–13 mm | Keyless, metric drills |
| Taper B16 | 3–16 mm | Drill presses, on request |
$16–$48 per chuck · indicative, confirmed on reply
Switches are matched by the tool model, not by appearance. The same body can come with or without a variable-speed board, and with a forward/reverse lever on one side or the other. Send the model plate photo and a photo of the switch with its wires still attached. We do not sell switches for tools rated over 15 amps over the counter without the old part, because the contact rating on a look-alike is often lower.
→Bench to counter
How a tool part gets matched
- Read the plate
Model and type number from the label on the motor housing. The type number is the one that splits revisions.
You · photo is enough - Pull the brushes or the chuck
Brush caps unscrew on most corded tools. Some need the housing opened; we tell you which.
You · if you can - Caliper and thread gauge
Block size to a tenth of a millimetre, lead type, spindle thread pitch.
Counter · a few minutes - Confirmed number, then the part
On the shelf, it leaves with you. Ordered parts get a confirmed price first.
Counter · on reply
?Before you open the housing
Straight answers on tool parts
My drill sparks a lot. Is it the brushes?
Often. Heavy sparking plus loss of power is the usual sign. If new brushes still spark hard, the commutator is scored or a winding has failed, and a brush will not fix that. We will say so rather than sell you a second pair.
Can a brush be filed down to fit?
A few tenths, yes. A full millimetre, no. A loose brush rocks in the holder and burns the commutator. Buy the right size.
Who is this not for?
Anyone looking for battery packs, chargers or electronics boards. We do not sell or rebuild lithium packs. It is also not for tools still under the maker's warranty; take those back where they came from first.
Ask about this part
- Model and type number from the motor label
- Both old brushes, even if one looks fine
- The chuck, or the drill with it still on