The Anatomy of a Hand Plane

The Body Structure

The Sole

The sole is the plane's bottom surface that rides on the workpiece. It must be absolutely flat—any twist, bow, or hollows will transfer directly to your work. The sole contains the mouth opening and provides the reference surface for all cutting.

Most plane soles are cast iron, precisely ground at the factory. Over decades of use and storage, soles can develop rust, pitting, or wear that compromises flatness. Learn how to flatten a plane sole.

Toe and Heel

The toe is the front portion of the sole, forward of the mouth. The heel is the rear portion, behind the iron. In proper planing technique, you apply downward pressure on the toe at the start of the stroke, balanced pressure in the middle, and pressure on the heel at the stroke's end.

The Mouth

The mouth is the throat opening where shavings emerge. Mouth width critically affects performance. A narrow mouth (about 0.020") supports wood fibers close to the cutting edge, preventing tearout in figured grain. A wider mouth (0.060"+) allows thick shavings for rapid stock removal but offers less support.

Cheeks

The cheeks are the plane's sides. They must be square to the sole for accurate edge jointing. Some woodworkers use the plane on its side to shoot miters and end grain on a shooting board.

Bed

The bed is the angled surface inside the body where the frog sits. The bed angle determines the basic cutting geometry. Most bench planes have a 45-degree bed angle.

The Cutting Assembly

The Plane Iron (Blade/Cutter)

The plane iron, also called the blade or cutter, is the sharpened steel component that cuts wood. Modern irons are typically 2-3mm thick, made from high-carbon steel (Stanley) or A2 tool steel (modern premium brands).

The iron has a flat back and a beveled cutting edge, usually ground to 25 degrees and honed to 30 degrees. Width varies by plane size: a No. 4 has a 2-inch iron, a No. 7 has a 2-3/8-inch iron.

Quality irons hold an edge longer. Vintage Stanley irons from the pre-WWII era are excellent. Modern thick irons from Hock, Veritas, or Lie-Nielsen resist chatter and hold edges even longer.

The Chipbreaker (Cap Iron)

The chipbreaker or cap iron is a curved piece of steel that bolts to the plane iron's back. Its functions are critical:

• Breaks and curls shavings so they eject cleanly through the mouth
• Stiffens the iron, reducing chatter and vibration
• Prevents tearout by forcing shavings to break before they follow the grain

The chipbreaker's distance from the cutting edge determines cutting behavior. For smoothing difficult grain, set it 0.5mm or less from the edge. For general work, 1-2mm is appropriate. For thick shavings in straight grain, 3-5mm works fine.

The Lever Cap

The lever cap clamps the iron and chipbreaker assembly firmly to the frog. It's held by a cam lever mechanism that provides tremendous pressure. The lever should require firm hand pressure to engage—not too loose (iron moves) or too tight (you can't lock it).

The lever cap screw adjusts tension. Turn it clockwise to increase clamping force. Most planes work best with the cam lever requiring moderate pressure to close—you should be able to lock it with your thumb without needing a second hand.

The Frog and Adjustment System

The Frog

The frog is the angled casting that holds and positions the cutting assembly. It's the plane's heart, containing all adjustment mechanisms. The frog bolts to the bed and can slide forward or backward to adjust mouth opening.

A well-machined frog has a flat bearing surface for the iron, perpendicular sidewalls for the lateral adjustment lever, and precise threads for the depth adjustment mechanism. Quality here separates excellent planes from poor ones.

Depth Adjustment Wheel

The depth adjustment wheel (also called the adjusting nut) controls how far the iron protrudes below the sole. Turning it clockwise (looking from behind) extends the iron for a heavier cut. Counterclockwise retracts it for a lighter cut.

The wheel engages a Y-shaped yoke that grips the chipbreaker's tab. When properly set, the wheel should turn smoothly with no play or binding. Start with the iron fully retracted, then slowly extend it until you see a hairline of iron below the sole.

Lateral Adjustment Lever

The lateral adjustment lever tilts the iron left or right to ensure the cutting edge is parallel to the sole. Look down the sole from the toe: both corners of the iron should protrude equally. Tap the lateral lever left or right until perfect.

Frog Adjustment Screws

Most Stanley planes from Type 11 (1910) onward have frog adjustment screws accessible from the top of the plane. These allow you to move the frog without disassembly:

1. Loosen the two frog mounting screws slightly (one or two turns)
2. Turn the frog adjustment screw—clockwise moves the frog forward (narrower mouth), counterclockwise moves it back (wider mouth)
3. Retighten the frog mounting screws firmly

Older planes (Types 1-10) require complete disassembly to adjust the frog.

Handles and Grip

The Tote (Rear Handle)

The tote is the rear pistol-grip handle. It provides control, steering, and downward pressure during planing. Quality totes are shaped ergonomically from rosewood, beech, or walnut.

The tote attaches with a single bolt through the sole and often a small screw at the top. Vintage totes sometimes crack from overtightening or drying out.

The Knob (Front Handle)

The knob is the rounded front handle. It guides the plane's direction and applies forward thrust. Like totes, knobs are typically hardwood, attached with a bolt through the sole.

Proper grip: wrap your palm over the knob with fingers curled underneath. This provides control without death-gripping the tool. Your tote hand does most of the work; your knob hand guides.

How All Parts Work Together

Understanding anatomy is one thing; understanding interaction is another. Here's the sequence of how these components function during a cut:

1. The sole rides on the workpiece, providing a flat reference
2. The iron's cutting edge, protruding slightly through the mouth, encounters wood fibers
3. The sharp edge slices fibers cleanly at the programmed depth
4. The shaving curves upward and contacts the chipbreaker
5. The chipbreaker forces the shaving to curl tightly and break off
6. The mouth opening, properly sized, supports fibers right up to the cut
7. The broken shaving ejects through the mouth
8. The frog, firmly clamped by the lever cap, prevents any iron movement or chatter

When all components are properly tuned and adjusted, this sequence produces effortless, whisper-thin shavings. When any component is out of spec—dull iron, poorly fitted chipbreaker, unlevel frog, unflat sole—performance suffers dramatically.

Materials and Manufacturing

Cast Iron Bodies

Most plane bodies are cast from grey iron, a material chosen for its excellent vibration damping, dimensional stability, and ease of machining. Quality castings are stress-relieved before machining to prevent warping over time.

Premium planes like Stanley's Bedrock series and modern Lie-Nielsen planes use higher-grade iron with more precise casting and machining. You can feel the difference in weight distribution and surface finish.

Steel Components

Irons, chipbreakers, lever caps, and screws are steel. Vintage Stanleys used high-carbon steel for cutters. Modern premium brands use A2 tool steel (air-hardened, holds edge longer but slightly harder to sharpen) or O1 steel (oil-hardened, easy to sharpen, excellent for beginners).

Wood Handles

Totes and knobs are traditionally rosewood (imported species, now restricted) or stained beech. Modern manufacturers use bubinga, cocobolo, cherry, or walnut. The wood species matters less than proper shaping and comfortable ergonomics.