Cutting Depth Optimization
Proper cutting depth prevents router bit damage, ensures safety, and produces quality results. 78% of router bit failures result from excessive cutting depth in single passes.
Last updated: 2026-02-27
Router Bit Depth Calculator
Professional router bit depth calculator for precision woodworking. Calculate optimal cutting depths, feed rates, router speeds, and safety parameters for various router bits and materials.
Depth Analysis Speed Control Feed Rates Safety Guide
Router Specifications
Router Bit Type
Bit Specifications
Material & Cut Parameters
Router Settings
HP
RPM
Routing Analysis
Enter router bit specifications and cutting parameters to calculate optimal depths, speeds, and safety guidelines for your routing operation.
Always use proper safety equipment when operating routers. Follow manufacturer guidelines for bit speeds and depths. Never exceed recommended cutting depths or feed rates. Secure workpiece properly before routing.
78% of router bit failures result from excessive cutting depth. Use the Rule of Half: never cut deeper than half the bit diameter in one pass.
How to Use This Calculator
- 1 Select Bit Type Choose from 6 types: Straight, Roundover, Chamfer, Cove, Ogee, or Flush Trim.
- 2 Enter Bit Specs Input bit diameter, cutting length, flute count, and bit material (HSS/carbide/diamond).
- 3 Set Material & Cut Choose material type (8 options), thickness, desired depth, and cut type (6 options).
- 4 Configure Router Enter router power (HP), speed (RPM), feed rate (IPM), and number of passes.
- 5 Review Analysis Get optimal depth per pass, recommended speed, feed rate analysis, and safety assessment.
Pro Tip: Rule of Half: never cut deeper than 50% of bit diameter in one pass. This reduces vibration by 65% and extends bit life significantly. For hardwoods, reduce depth an additional 30-40% compared to softwood settings.
| Bit Diameter | Softwood (Pine) | Hardwood (Oak) | Plywood/MDF | Recommended Passes |
|---|---|---|---|---|
| 1/4" (6mm) | 1/8" max | 1/16" max | 3/32" max | Multiple shallow |
| 3/8" (10mm) | 3/16" max | 1/8" max | 5/32" max | 2-3 passes |
| 1/2" (12mm) | 1/4" max | 3/16" max | 3/16" max | 2 passes typical |
| 3/4" (19mm) | 3/8" max | 1/4" max | 5/16" max | 1-2 passes |
| 1" (25mm)+ | 1/2" max | 3/8" max | 7/16" max | Single pass OK |
These are maximum safe depths per pass. Reduce by 30-40% for very hard exotic woods.
Pro Tips: Safe Routing Depths
- Rule of Half: Never cut deeper than half the bit diameter in one pass — reduces vibration by 65%
- Material Matters: Hardwoods require 30-40% shallower cuts than softwoods at same speed
- Listen to Router: Laboring sound indicates too deep/fast — reduce depth or feed rate immediately
- Final Pass Light: Leave 1/32" for final cleanup pass — improves surface finish significantly
- Climb Cut Caution: Reduce depth 50% when climb cutting — increased kickback risk
Router Speed & RPM Guidelines
Bit diameter determines optimal router speed. Larger bits must run slower to prevent overheating and dangerous rim speeds.
| Bit Diameter | Optimal RPM | Maximum RPM | Rim Speed (FPM) | Common Applications |
|---|---|---|---|---|
| Up to 1" | 20,000-24,000 | 24,000 | 6,280 | Small trim, edging |
| 1" to 2" | 16,000-18,000 | 20,000 | 9,420 | Profile bits, dados |
| 2" to 2.5" | 12,000-16,000 | 16,000 | 10,470 | Panel raising, large profiles |
| 2.5" to 3.5" | 8,000-12,000 | 12,000 | 11,000 | Raised panels, door making |
| Over 3.5" | 6,000-8,000 | 8,000 | 9,420 | Large panel bits (table only) |
Rim speed should not exceed 12,000 FPM. A 3.5 inch bit at 24,000 RPM creates dangerous 21,200 FPM — always reduce speed for large bits!
Case Study: Panel Raising Bit Setup (3.5 inch bit, Oak)
- Bit: 3.5" vertical panel raising bit, 1/2" shank
- Material: Oak hardwood, 3/4" thick
- Speed: 10,000 RPM (reduced from 18,000) → Rim speed: 9,160 FPM ✅
- Feed Rate: 15-20 IPM (slow, controlled)
- Depth/Pass: 1/8" maximum → 6 passes @ 1/8" each
- Result: No burning, smooth surface, quiet operation, 3 min/panel
- ⚠️ Warning: This bit at 24,000 RPM = 21,200 FPM rim speed — dangerously above 12,000 FPM limit!
Glossary of Terms
Safety guideline: never cut deeper than 50% of the bit diameter in a single pass. Reduces vibration by 65% and prevents 78% of common bit failures.
The cutting edge/groove on a router bit. More flutes produce smoother cuts but require slower feed rates. 2 flutes is standard for most woodworking.
Basic router bit material. Lower cost, stays sharp in softwoods. Dulls faster in hardwoods and abrasive materials. Good for occasional use.
Harder, longer-lasting bit material. Stays sharp 10-20x longer than HSS. Standard for professional use. Required for abrasive materials like MDF and particle board.
Inches Per Minute — the speed at which the router moves along the workpiece. Hardwoods: 40-80 IPM. Softwoods: 60-120 IPM. MDF: 80-150 IPM.
The velocity of the outermost cutting edge, measured in Feet Per Minute (FPM). Safe range: 8,000-12,000 FPM. Exceeding 12,000 FPM is dangerous.
The amount of material each flute removes per revolution. Calculated as: Feed Rate / (RPM * Number of Flutes). Optimal chip load prevents burning and extends bit life.
Routing in the same direction as bit rotation. Produces smoother finish but increases kickback risk. Reduce depth 50% and use only with router table or CNC. Not recommended for handheld routers.
Frequently Asked Questions
What's the maximum safe cutting depth for router bits?
Rule of Half: Never exceed 50% of bit diameter in one pass — 78% of bit failures result from excessive depth.
- 1/4" bit: 1/8" max in softwood, 1/16" in hardwood
- 1/2" bit: 1/4" max in softwood, 3/16" in hardwood
- 3/4" bit: 3/8" max in softwood, 1/4" in hardwood
- 1" bit: 1/2" max (multiple passes for deeper cuts)
Hardwoods require 30-40% shallower cuts than softwoods.
How do I determine the correct router speed?
Bit diameter determines safe speed. Guidelines:
- Up to 1": 20,000-24,000 RPM
- 1-2": 16,000-18,000 RPM
- 2-2.5": 12,000-16,000 RPM
- 2.5-3.5": 8,000-12,000 RPM
- Over 3.5": 6,000-8,000 RPM (table-mounted only)
Rim speed should not exceed 12,000 FPM.
What feed rate should I use for different materials?
Feed Rates by Material:
- Hardwoods (Oak, Maple): 40-80 IPM
- Softwoods (Pine, Cedar): 60-120 IPM
- Plywood: 50-100 IPM
- MDF: 80-150 IPM
Reduce 30-50% for climb cutting, 25% for deep cuts (>1/4"). Increase 20-30% for final light passes. Sound test: smooth = correct, laboring = too fast, high-pitched = too slow (burning).
How many passes should I make for deep cuts?
For cuts deeper than 1/4", use multiple passes. Divide total depth by maximum safe depth per pass. Example: 3/4" deep cut with 1/2" bit = 3-4 passes of about 1/4" each. Leave 1/32" for a final cleanup pass for best surface finish.
What causes router bit burning and how to prevent it?
Burning is caused by excessive heat from slow feed rates, dull bits, or wrong speeds. Prevent by using sharp bits, proper speeds, adequate feed rates, and taking lighter cuts. Keep bits clean and properly maintained.
When should I use climb cutting vs conventional cutting?
Conventional cutting (against bit rotation) is safer and standard for handheld routers. Climb cutting (with bit rotation) can provide better finish but requires more control and is typically used with router tables or CNC machines. Reduce depth 50% when climb cutting.