1 Why Compare These Two Diameters?
A wider cutter promises fewer passes, but every extra half‑inch of diameter multiplies rim speed and torque demands. At 20,000 rpm, a 2‑in bit is already travelling 119 mph at its edge; a 3‑in bit jumps to nearly 180 mph, forcing most users to slow the spindle for safety. (protoolreviews.com) The sweet spot for router sled work sits between 1.5 and 2.5 inches—big enough to save time, small enough to run on a handheld router.
2 Test Bench & Method
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Sled: SpeTool Cratos S01001, 48 in width. (spetools.com)
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Routers: 2 hp fixed‑base (mid‑class) and 3‑¼ hp soft‑start (pro‑class).
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Cutters:
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SpeTool W05001 – 1.5 in, brazed carbide, ¼‑in shank.(spetools.com)
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SpeTool W05003 – 2.5 in, four‑insert, ½‑in shank. (spetools.com)
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Whiteside 6220 – 2 in brazed‑carbide baseline. (amazon.com)
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Amana RC‑2255 – 2.5 in insert pro benchmark. (amazon.com)
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Material: 48 × 30 × 2 in red‑oak slab.
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Pass depth: 1⁄16 in for all tests.
Each cutter made a full face pass on the 2 hp router (if the collet allowed) and again on the 3 ¼ hp router. We logged: pass count, amp draw spikes, spindle temperature, chip evacuation, and after‑sanding time to 120 grit.
3 Results at a Glance
| Metric | 1.5 in (W05001) | 2 in (Whiteside 6220) | 2.5 in (W05003) | 2.5 in (Amana RC‑2255) |
|---|---|---|---|---|
| Passes (48 in width, 20 % overlap) | 26 | 19 | 15 | 15 |
| Avg. amps (2 hp router) | 10 A | 11 A | Stalled | Stalled |
| Avg.. amps (3 ¼ hp router) | 8 A | 10 A | 12 A | 12 A |
| Face time per side | 38 min | 27 min | 19 min | 19 min |
| After sanding to P120 | 9 min | 8 min | 6 min | 5 min |
| Cutter cost (street) | US$ 49.99 | US$80 | US$ 59.99 | US $173 |
Key takeaway: Diameter alone doesn’t save the day; router horsepower and collet size must match. The SpeTool W05003 delivered the fastest cycle, but only on a 3 hp motor with a ½‑in collet.
4 Cost‑Tiered Solutions
4.1 Budget Path—Stick to 1.5 in
Spend: ≈ US$ $150 (bit + misc).
Runs on the 2 hp router most hobbyists already own, no collet swap needed. Expect ~40 min per face on a 4 × 8 slab and more shoulder fatigue, but no motor overload risk.
4.2 Production Path—2.0–2.5 in on 3 hp
Spend: ≈ US$ $450 (bit, 3 hp router upgrade, dust shroud).
A 2.5 in insert cutter plus soft‑start 3 ¼ hp router cuts face time by ~35 %. Inserts flip 4 ways, bringing edge cost down to pennies per square foot.
4.3 Pro Shop Path—2.5 in Premium + Cyclone
Spend: US $800+. Pair a high‑end insert head (Amana or RIP “Slab Slayer”) with a 3 hp router and a 650 CFM dust collector. The setup removes ¹⁄₈ in per pass without chatter and pays back on throughput if you flatten > 30 slabs per year. (ripprecisiontools.com)
5 Compatibility Cheat Sheet
| Trigger Question | Recommendation |
|---|---|
| Router < 2 hp? | Stay at 1.5 in diameter. |
| Only ¼‑in collet? | 1.5 in W05001 is safe; larger bits require ½‑in. |
| Need < 20 min per face? | Move to 2.5 in W05003 + 3 hp motor. |
| Flattening epoxy? | Use a smaller cutter at a higher rpm to limit heat. |
| Tool budget < US$ $200? | 1.5 in brazed‑carbide path. |
6 SpeTool vs Leading Competitors (Neutral Snapshot)
6.1 Router‑Sled Kits
| Feature | SpeTool Cratos S01001 | Rockler Full‑Size Jig | Woodpeckers Slab Mill PRO |
|---|---|---|---|
| Street price | US $245(spetools.com) | US $499.99(rockler.com) | US $1 199+(amazon.com) |
| Max width | 48 in | 28.5 in | 49 in |
| Stock length | User Rails—unlimited | 78.5 in (ext. kits) | 58 in (ext. kits) |
| Rails | 6061‑T6 aluminum | Steel tubes | Steel carriage + Al rails |
| Dust option | 4‑in shroud bundle | none | Curtain + 4‑in port |
| Warranty | 365‑day global | 1 yr | Lifetime (US) |
6.2 Surfacing Bits
| SpeTool W05001 | Whiteside 6220 | SpeTool W05003 | Amana RC‑2255 | |
|---|---|---|---|---|
| Ø (in) | 1.5 | 2.0 | 2.5 | 2.5 |
| Shank | ¼ in | ½ in | ½ in | ½ in |
| Edge style | Brazed | Brazed | 4‑insert | 4‑insert |
| Street price | $49.99(spetools.com) | $80(amazon.com) | $59.99(spetools.com) | $173(amazon.com) |
| Recommended HP | 1.75+ | 2+ | 3+ | 3+ |
Interpretation: SpeTool’s cutters book‑end the market—an affordable 1.5 in option for small routers and a competitively priced 2.5 in insert head that undercuts premium brands by ~25 %.
7 Best Practices That Apply to Any Bit
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Verify run‑out; ≤ 0.003 in keeps wide bits from striping.
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Mind rim speed; cap 2.5 in cutters at 12,000 rpm for ~99 mph edge speed—well within safety tables. (protoolreviews.com)
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Clap the slab, not the sled; vibration rises with diameter.
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Keep chips moving; larger bits throw bigger chips—pair the Cratos shroud with a 4‑in hose.
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Listen for bogging; if pitch changes, raise ⅛ in and slow feed—smoke means armature heat.(forum.onefinitycnc.com)
8 Conclusion—Match the Triangle: Motor ▸ Bit ▸ Budget
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Weekend makers flattening the occasional cookie: a 1.5‑in brazed‑carbide bit on a 2 hp router gets the job done—slow but safe.
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Growth‑phase side hustles: upgrade to a 2.5 in insert cutter and a 3 hp soft‑start router; on the Cratos sled, you’ll halve surfacing time for well under US $500.
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High‑volume shops: pair a pro‑grade 2.5 in insert head with cyclone dust and full‑length rails—cycle time drops below 15 min per face, and insert cost is pennies.
Choose diameter by horsepower, not hope, and your Cratos sled will turn rough slabs into dead‑flat blanks without burning bits—or budgets.
