3.4: Planer

3.4 Planer

The planer makes one face of a board parallel to another and brings the board to a controlled thickness.

It depends on the flat reference face created on the jointer.

This relationship is critical:

The jointer creates flatness.
The planer creates parallel thickness.

Learning Outcomes

After completing this section, you should be able to:

• Explain the primary function of the planer.
• Explain why a board must have a flat reference face before planing.
• Identify the major parts of the machine.
• Describe how thickness is reduced accurately.
• Explain the major safety limits for planer use.

How the Planer Works

A board is placed on the planer table with the jointed face down.

Feed rollers pull the board through the machine.

A cutterhead above the board removes material from the upper face.

Because the flat reference face rides on the table, the newly cut upper face becomes parallel to it.

Repeated passes reduce the board to the required thickness.

Major Parts

Important components include:

Table or Bed — Supports the board and provides the reference surface.

Cutterhead — Removes material from the upper face.

Infeed Rollers — Pull the board into the machine.

Outfeed Rollers — Help move the board out after cutting.

Table-Height Adjustment Wheel — Changes the distance between the table and cutterhead.

Thickness Gauge — Indicates the approximate thickness setting.

Power Controls — Start and stop the machine.

Thickness planer labeled with table or bed, thickness gauge, table-height adjustment wheel, and on/off controls.

Figure: Planer

Flat First, Then Parallel

A planer does not flatten a warped board by itself.

If a bowed or twisted board is fed into the planer, the rollers may temporarily press the board against the table while it is being cut.

When the board exits, the pressure is released and the board may spring back into its warped shape.

The result may be:

a warped board of even thickness.

This is why the first face must be flattened on the jointer before the board is planed.

Setting the First Cut

Before feeding the board, find the thickest part of the stock.

Set the planer so that the first cut removes only a small amount of material from that thickest area.

Do not make a heavy first cut.

Depth of Cut

For normal use in the WMT lab:

Maximum material removal per pass: 1/16 inch

Several light passes are better than one heavy pass.

As the board approaches its desired thickness, lighter cuts can help improve surface quality.

Plane With the Grain

Whenever possible, feed the board so the cutter works with favorable grain direction.

Planing against difficult grain can produce significant tearout.

Use the grain-reading method introduced earlier in this chapter as a starting point.

Never feed a board through the planer across the grain.

Important WMT Limits

For normal student use:

• Remove no more than 1/16 inch per pass.
• Set the initial cut from the thickest part of the board.
• Stock must be longer than the distance between the infeed and outfeed rollers.
• Minimum stock length is marked on each planer.
• Do not normally plane stock thinner than 1/4 inch.
• Never place your hands inside the planer.
• Never change the depth after the stock has begun feeding through.
• Do not plane boards with large cracks or loose knots.
• Stand upright and to one side rather than looking directly into the machine while it runs.
• Only the instructor adjusts the feed-roller speed.

Surfacing stock thinner than the normal minimum may require another machine or an instructor-approved special setup.

Plane Similar Stock from Thickest to Thinnest

If several pieces are different thicknesses, begin with the thickest.

Gradually lower the planer setting as you work toward the thinner pieces.

This reduces unnecessary adjustments and helps maintain a logical workflow.

Final Thickness

Do not rush to the final dimension.

Measure the board during the process.

As you approach the required thickness:

1. reduce the amount removed per pass;
2. check the actual thickness;
3. inspect the surface; and
4. stop when the required dimension and surface quality have been achieved.

Removing wood is easy.

Putting it back is considerably more difficult.

Check Yourself

1. What is the primary purpose of the planer?
2. Which face goes down on the planer table?
3. Why must that face already be flat?
4. What is the maximum normal material removal per pass?
5. What can happen if a warped board is planed without first being jointed flat?
6. Why should you plane with the grain?