Anatomy of Shoulder Planes

Stanley No.93 and Lie-Nielsen No.73, disassembled, explained, and reassembled, ready to make shavings

Let me demystify the anatomy of the metal bodied shoulder plane. This time I use my Stanley No.93 and Lie-Nielsen No.73.

The video shows all the main points:



Commonly used to fit tenons, and clean out housings, the shoulder plane, with it's iron extending right through to the sides of the body, is also useful for any number of planing tasks which require planing along an inside corner. They come in a variety of sizes, but unless there is restricted width access, the larger planes, with their inherently greater mass, are easier to use.
Both fixed and adjustable mouth planes are available. Some, like the No.93, can be used as chisel planes, with the entire front demounted.

Main considerations for good performance:

• A 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.

• Squared sides
  Prepared in the same way as the sole, but using an engineer's try square and uneven pressure to correct inaccuracies.
  
• If the plane has an adjustable mouth, then it is essential that the contact tracks are parallel to the sole. Otherwise adjusting the mouth will throw the sole out of flat.

• Well prepared blade
  Since the blade is installed bevel up, the bevel angle will directly affect the angle of attack during a cut, and therefore you can tailor the angle to suit the work in hand. In practice, you would have two or three blades ground at different angles, and install the appropriate one for each task.

• All sharp edges eased (not the blade edge!) - to prevent injury to either work or user

In Use:
The shoulder plane is designed to be used against two reference surfaces at the same time, and doing so will produce the most consistent results.
The over-wide blade should be set in line with whichever side of the plane body is being used, so that the cut reaches, but does not exceed the corner.
Since the blade is wider than the mouth, take care not cut yourself.