Ryobi
Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only)
$49.97Cheaper
Best Angle Grinders · head-to-head
Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) vs Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only)
A sourced, side-by-side comparison. Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) is cheaper at $49.97. Every spec and price links to its source.
Which is better: the Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) or Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only)?
The Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only) wins 1 of the 1 specs we compare head to head; the other wins 0. The Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) is the cheaper at $49.97. Get the Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only) for the stronger spec sheet, the Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) to spend less.
Check Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) price See Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only) on Amazon
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Full spec sheet
✓ marks the stronger figure where "more" — or "less", for price and weight — is unambiguously better.
| Spec | Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) |  Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only) |
|---|---|---|
| US price | $49.97 | $99 |
| Brand | Ryobi | Ridgid |
| Released | — | — |
| Disc size (in) | 4.5 in | 4.5 in |
| Power source | cordless | cordless |
| Amps or voltage | 18 V | 18 V |
| Max (rpm) | 6500 | 9000 |
| Brushless | No | No |
| Switch type | trigger | slide |
| No volt release | — | — |
| Weight (lb) | 4.8 | 4.5 |
Sources — Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only): ryobitools.com (verified 2026-06-20). Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only): homedepot.com (verified 2026-06-20).
What's the difference between the Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) and Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only)?
Where the two actually differ on the specs we track (3 of 8). Matching specs are omitted.
- Max (rpm): Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) 6500 vs Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only) 9000
- Switch type: Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) trigger vs Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only) slide
- Weight (lb): Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only) 4.8 vs Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only) 4.5
What reviewers say
Sourced tester consensus for each — the "what people who used it think" layer, not just specs.
Ryobi P421 18V ONE+ 4-1/2 in. Cordless Angle Grinder (Tool Only)
No sourced tester review yet.
Ridgid R86040B 18V X4 4-1/2 in. Cordless Angle Grinder (Tool Only)
Only one whitelisted tester, Pro Tool Reviews, hands-on tested this exact R86040B. PTR scored it 8.2/10, praising cordless mobility and strong cutting torque, but flagged fast battery drain (6-7 cuts per charge) and a single fixed speed with no variable control. (1 sourced review, 1 lab-tested.)
Praised: Cordless mobility and freedom from tangled cords; Strong torque that pushed through steel without backing down; Handy overload-indicator LED and easy tool-less guard adjustment.
Flagged: Fast battery drain; two or three batteries effectively mandatory (6-7 cuts per charge); Single fixed speed with no variable-speed control for precise work; On/off switch tricky with thick welding gloves; spanner wrench not stored on the tool.