Quick & Easy Jigs and Fixtures by Kerry Pierce

Author:Kerry Pierce
Language: eng
Format: epub
Tags: epub, ebook
Publisher: F+W Media
Published: 2005-03-14T16:00:00+00:00

STEP 4 This table can also be used to drill the front rung mortises on any stools on which the side and front rungs are 90° apart. Once the jig is clamped to the drill press table, so that the fence is a distance from the lead point of my Forstner bit that is half the diameter of the post I'm mortising (see step 2 for fence placement) you can slide the ladder along the fence, stopping to bore mortises at the appropriate locations.

Front Rung Mortise Jig (FRMJ)

INCHES (MILLIMETERS)REFERENCEQUANTITYPARTSTOCKTHICKNESS(mm)WIDTH(mm)LENGTH(mm)

A 1 sliding carriage ½ (13) 2 7/8 (73) 39½ (1004)

B 1 jig bed 7/8 (22) 5 (127) 36 (914)

C 1 fence 7/8 (22) 3½ (89) 39½ (1004)

D 2 lower cleats (14) 1¼ (32) 16 (406)

E 1 top cleat (14) 1 (25) 29 (737)

F 1 tail piece (8) 2 7/8 (73) 3 (76)

It's possible to drill the front rung mortises by pressing the post against a fence (see step 1), and for many years, I used a jig much like that for performing this operation. But eventually I realized that the tiniest of discrepancies in post rotation, as I slid the post under the bit from one rung location to the next, could result in fairly sizable errors in rung angle. To remedy this, I built a front-rung-mortise jig that prevents the post from rotating as it's passed underneath the drill bit. This guarantees that the centerlines of all the rungs on one side of a chair ladder will lie in the same plane.

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