Q:

I want to see if the tables of my jointer are within the manufacturer’s specifications for flatness, but I’m  confused about how to do it.

Thompson Callahan, Las Vegas, NV

A:

Flatness isn’t the only important thing. To work correctly, the tables must also be parallel to one another.

To check for flatness, use a straightedge and a set of feeler gauges. Place the straightedge lengthwise along each edge and down the middle of both tables. If there is a gap of more than 0.005 in. over a large area, you’ll need to return the table to the manufacturer, or have it reground by a machine shop.

Now set the straightedge on the outfeed table with at least 2 ft. extending over the infeed table. Raise the infeed table until it just touches the straightedge. If the tables are parallel, there won’t be any gaps. If not, you’ll have to shim the ways. See FWW #142, p. 41 (Joiner Tune Up) for more on that.

Check for flatness first. Use a straightedge and feeler gauge to test each table at each edge and in the middle. Tables must be parallel to straighten boards. Hold the straightedge on the outfeed table. Raise the infeed table until it just touches the straightedge and check for gaps along the length of the table.

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