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26 September 2014

Anatomy of Bailey Pattern Bench Planes

Components of a Stanley Bailey Bench Plane, disassembled, explained, and reassembled, ready to make shavings

Let my demystify the anatomy of these popular hand planes. I'll use images of my Stanley Bailey No.4 and No.5 bench planes, but this applicable to many other manufacturer's 'copies'.

The video shows all the main points:

Patented in the mid-1860's by Leonard Bailey, and then developed further by Stanley, the Bailey Pattern Plane is the basis for most metal bodied bench planes produced today.

These planes, classified from No.1 to No.8, are designed primarily to be used at a workbench, for tasks from truing up, flattening, and jointing, through to finish smoothing, of internal carpentry, fittings, and furniture. Of course they are used in a much wider range of woodworking; which speaks greatly of the design.

The Anatomy:

A flat metal sole, with flat perpendicular sides, makes up the main body of the plane. Originally cast iron, modern alternatives are now more common, such as ductile iron and bronze. A thin slot traverses the sole between the sides. This mouth is where the blade emerges.

A cast block, with machined pads and an inclined face, called a frog, attaches to the main body with two machine screws which allow it to be fixed within a small range along the body. This movement is controlled by a third machine screw, set in the body, with a collared neck that rides in a pressed steel collar attached to the frog. Moving the frog forward positions the blade closer to the front of the mouth ('closing up the mouth'), allowing greater support ahead of the cut (leading to less tearout) whilst reducing the maximum depth of cut. 'Opening up the mouth' has the opposite effect.

The frog also has an iron advancement wheel, tab, and yoke, and a lateral adjustment lever. The iron advancement tab engages in the chip breaker (see below), whilst the lateral adjustment lever engages in the plane iron's slot.

The plane iron has a single sided bevel blade, which rests bevel side down on the frog's inclined face. It has a long slot, through which is attached a chip breaker. The chip breaker both supports the iron close to the blade edge, and breaks (by bending) thicker shavings which might otherwise choke the plane.

The plane iron, with attached chip breaker, is held in position by the lever cap, which pivots on a screw into the frog.

The user holds the plane by means of the rear handle ('tote' in USA), and optionally the front knob (greater control is often achieved by simply exerting pressure on or near the front knob, rather than grasping it).

Main considerations for good performance:

  • Flat sole
    Prepared, with an iron installed and set at working tension, by lapping on a surface plate, hand scraping, or sanding on top of a flat reference surface.
  •  Flat frog face
    The face of the frog should be flat to provide good support of the blade. Prepare as per the sole.
  • Well prepared iron
    Since the blade is installed bevel down, the bevel angle does not affect the angle of attack during a cut. It does determine the clearance angle, and if set too high will hinder the blade from cutting. However, the lower it is set, the weaker the edge becomes. So, a compromise must be struck. For softer woods, an angle of about 25°, and for harder woods about 33°, is a rough guide.
    It is also possible to introduce a back bevel, to increase the angle of attack. Something I shall cover another time.
  • Chip breaker and iron well fit(ted)
    There should be no gap between chip breaker and iron along the leading edge of the chip breaker, and that leading edge should flow from the contact point, so as to present as little friction as possible to shavings.
  • Frog and plane body well fit(ted)
    Pads should have as much contact surface area as possible, and all contact at the same position, so that the frog and body move as one, with minimal relative motion in use.
  • Mouth well prepared
    Straight and perpendicular to sides, and level with rest of sole across it's front.
  • Squared sides
    Prepared in the same way as the sole, but using an engineer's try square and uneven pressure to correct inaccuracies.
    Strictly only an advantage if you plan to shoot with the plane, or use the side as a reference during use in some other way.
  • Handles fixed firmly - so the plane is as one with the user
  • All sharp corners eased - to prevent injury to either work or user
In Use:
Best results are usually achieved by using a light touch.
Don't try to take deeper cuts than you can comfortably manage to push.
In many instances, skewing the plane will yeild a smoother cut, as this lowers the effective angle of attack and reduces the width of cut.
Pressing down in front of the forward knob is more stable than on the knob itself.
Start a cut with downward pressure near the toe and forward pressure from the rear handle. Progressively change to lower downward pressure near the toe, and more downward pressure at the rear handle, as the shaving is taken.