3.3: Jointer

3.3 Jointer

The jointer creates flat and straight reference surfaces.

It is one of the most important machines in the milling process because accurate woodworking depends on having reliable surfaces from which other dimensions can be established.

The jointer is primarily used to:

• flatten one face of a board; and
• straighten and square an edge.

Learning Outcomes

After completing this section, you should be able to:

• Explain the primary functions of the jointer.
• Identify its major parts.
• Explain why the stable side of a board is placed on the table.
• Distinguish between face jointing and edge jointing.
• Describe the basic safety limits for the jointer.

Major Parts

Important jointer components include:

Infeed Table — Supports the board before it reaches the cutterhead.

Outfeed Table — Supports the newly cut surface after it passes the cutterhead.

Cutterhead — Contains the knives or cutters that remove material.

Guard — Covers the cutterhead when it is not occupied by the workpiece.

Fence — Provides a reference surface when jointing an edge.

Depth-of-Cut Adjustment — Controls how much material is removed.

Pushstick or Pushblock — Helps control the board while keeping the operator’s hands away from the cutterhead.

Jointer labeled with infeed table, outfeed table, fence, cutterhead and guard, depth-of-cut adjustment, power switch, pushblocks, and pushstick.

Figure: Jointer

Face Jointing

The first jointer operation in the milling sequence is to create one flat face.

A rough board may rock when placed on a flat surface because of cup, bow, or twist.

Place the board with its most stable side down on the jointer table.

Often, but not always, this means placing the more concave face toward the table.

The purpose is to keep the board from rocking while it passes over the cutterhead.

Do not press a warped board flat against the table before it reaches the cutterhead. If you force the board flat during the cut, it may spring back to its original shape afterward.

The goal is to remove the high points until the machine creates a truly flat reference surface.

Edge Jointing

After one face is flat and the opposite face has been planed parallel, the jointer is used again to straighten one edge.

Place the flat face firmly against the fence.

The newly jointed edge should become:

• straight; and
• square to the reference face.

This gives you two dependable reference surfaces:

one flat face + one straight, square edge

These reference surfaces are essential for later table-saw operations.

Depth of Cut

For most normal jointer operations in the WMT lab:

Typical depth of cut: 1/32 inch

Maximum depth of cut: 1/16 inch

Light cuts are generally easier to control and produce better surfaces.

Important WMT Limits

For normal student use:

• Minimum stock length: 14 inches
• Minimum stock thickness for face jointing: 3/8 inch
• Maintain at least 6 inches between your body parts and the cutterhead.
• Use a pushstick or pushblock when required.
• Never joint end grain.
• Use only clean, dry lumber.
• Special operations require instructor approval.
• The outfeed table is never adjusted by students.

The guard must remain over the cutterhead during operation.

Never Joint End Grain

End grain should not be jointed on the jointer.

The cutterhead can catch the fibers at the end of the board and break away material suddenly. On narrow pieces, this can be especially dangerous.

Use an appropriate crosscutting method to square ends instead.

Severely Warped Lumber

A badly warped board may be difficult or unsafe to flatten while it is still wide or long.

One useful strategy is to first:

• rough crosscut it shorter on the radial arm saw; and/or
• rough rip it narrower on the band saw.

Breaking a badly warped board into smaller blanks often removes much of the distortion and makes the stock easier to joint safely.

What the Jointer Does Not Do

A jointer makes a surface flat.

It does not automatically make the opposite face parallel.

If you joint both faces independently, you may create two flat faces that are not parallel to each other.

That is why the planer follows the jointer in the milling sequence.

The jointer establishes the reference.

The planer works from that reference.

Check Yourself

1. What are the two primary jobs of the jointer?
2. Why is the most stable side placed against the table?
3. What is the typical depth of cut?
4. What is the maximum depth of cut?
5. Why should you not joint both faces of a board independently?
6. Why is end-grain jointing prohibited?