Mortising Table, Microadjust Detail

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Microadjust Detail

A side detail view of the microadjust attachment. The oak parts are simply glued (I've become partial to Titebond III) and screwed.
There's more than meets the eye in the adjustment bolt assembly, which I did not disassemble for pictures. Mounting the protractor dial is discussed below. Here, I'll try to make the right words to describe how the thing went together.
The bolt was overlength and cut off to suit. There are thrust washers let in to the oak's surface (via a Forstner bit from a set in 64ths), and the whole is retained with a nylok-insert nut tightened just enough to eliminate end play. A drop of oil on the washers is all that's needed for lubrication. Because of the nylok, I wanted wrench access on both the bolt head and the nut, so I added a 5/16 jam nut (thinner than a standard nut) under the bolt head to fill the pocket in the knob, thus forcing the bolt head to project from the top of the knob. As well, I felt it necessary to use the knob's underside face as a thrust surface, which required that the protractor be bored out and mounted to the circumference of the knob body (see below) - that is, the protractor couldn't be allowed to touch the oak. Here's an assembly sketch:

Mounting the Dial

A center hole was bored in the protractor with a 7/8 Forstner bit using slow, intermittent feed to avoid tearing or melting of the plastic. The center hole I.D. was measured with a dial caliper.
The block to the left was cut perfectly square on 6 sides, and drilled through to barely pass a 5/16 bolt, at height to allow knob perimeter to clear saw table.
A 5/16 bolt was passed left-to-right through the block, and a knob threaded on to thread bottom, as shown below.
The block was clamped to the miter gauge (omitted for clarity) so that the knob portion over the saw blade was equal to the thickness of the protractor plus a skosh, as seen in the picture. The blade was slowly raised through the wood to contact the knob. A full, light cut around the knob base was made by simply rotating the bolt head. That slightly smaller diameter was measured with the dial caliper, and the blade raised by a little less than 1/2 the amount of the difference between knob ledge diameter and protractor through-hole diameter. Because the saw was fitted with its microdial readout, I was able to raise it in increments of less than 1/2 thousandth, and quickly arrived at a knob base O.D. that equaled the protractor I.D. (a probable interference fit.)
As luck would have it, the protractor slipped onto the knob with only mild pressure, and gripped well enough to call that friction fit successful.
The knob+protractor was assembled with remaining parts as at top of page.

JOHN W. POPP

A side detail view of the microadjust attachment. The oak parts are simply glued (I've become partial to Titebond III) and screwed. There's more than meets the eye in the adjustment bolt assembly, which I did not disassemble for pictures. Mounting the protractor dial is discussed below. Here, I'll try to make the right words to describe how the thing went together. The bolt was overlength and cut off to suit. There are thrust washers let in to the oak's surface (via a Forstner bit from a set in 64ths), and the whole is retained with a nylok-insert nut tightened just enough to eliminate end play. A drop of oil on the washers is all that's needed for lubrication. Because of the nylok, I wanted wrench access on both the bolt head and the nut, so I added a 5/16 jam nut (thinner than a standard nut) under the bolt head to fill the pocket in the knob, thus forcing the bolt head to project from the top of the knob. As well, I felt it necessary to use the knob's underside face as a thrust surface, which required that the protractor be bored out and mounted to the circumference of the knob body (see below) - that is, the protractor couldn't be allowed to touch the oak. Here's an assembly sketch:

Mounting the Dial	A center hole was bored in the protractor with a 7/8 Forstner bit using slow, intermittent feed to avoid tearing or melting of the plastic. The center hole I.D. was measured with a dial caliper. The block to the left was cut perfectly square on 6 sides, and drilled through to barely pass a 5/16 bolt, at height to allow knob perimeter to clear saw table. A 5/16 bolt was passed left-to-right through the block, and a knob threaded on to thread bottom, as shown below. The block was clamped to the miter gauge (omitted for clarity) so that the knob portion over the saw blade was equal to the thickness of the protractor plus a skosh, as seen in the picture. The blade was slowly raised through the wood to contact the knob. A full, light cut around the knob base was made by simply rotating the bolt head. That slightly smaller diameter was measured with the dial caliper, and the blade raised by a little less than 1/2 the amount of the difference between knob ledge diameter and protractor through-hole diameter. Because the saw was fitted with its microdial readout, I was able to raise it in increments of less than 1/2 thousandth, and quickly arrived at a knob base O.D. that equaled the protractor I.D. (a probable interference fit.) As luck would have it, the protractor slipped onto the knob with only mild pressure, and gripped well enough to call that friction fit successful. The knob+protractor was assembled with remaining parts as at top of page.