Tom LaRussa
01-13-2005, 12:53 PM
Here is a thingie I made to align the blades in my $12.50 Davis & Wells jointer.
It's just a piece of acrylic, some rare earth magnets, some cups for the rare earth magnets, and some #4 machine screws with nuts.
The key to the whole thing is really the cups, which come from Lee Valley, because they are counter-sunk for the heads of #4 screws.
So long as the plastic is flat, then the screws hold the cups coplanar.
So long as the cup-bases are of equal thicknesses, the cups, in turn, hold the magnets coplanar.
So long as the magnets are of equal thicknesses, then the whole dealy-bobber is coplanar.
So long as the outfeed table of the jointer is flat and parallel to the infeed table, which is also flat, then the blades will be held at the perfect position, provided the cutter head is stopped precisely at top dead center.
I was pretty sure about all of the above, but just to be certain I had everything checked out according to standards set by the National Institutes for Standards and Technology, (NIST), standards for Optical Reference Planes, (ORFs).
As you probably know, ORFs are tested interferometrically, with the test surface horizontally supported on three equally spaced pads located at 0.7 of the radius from the center. The measurement is, of course, performed along two marked orthogonal diameters.
The whole assembly, (not counting the testing), cost about $12, bringing the total cost of my jointer up to nearly $60, including a set of brand new, M2 High Speed Tool Steel blades.
Anyway, here is a pick of the thingamjig.
It's just a piece of acrylic, some rare earth magnets, some cups for the rare earth magnets, and some #4 machine screws with nuts.
The key to the whole thing is really the cups, which come from Lee Valley, because they are counter-sunk for the heads of #4 screws.
So long as the plastic is flat, then the screws hold the cups coplanar.
So long as the cup-bases are of equal thicknesses, the cups, in turn, hold the magnets coplanar.
So long as the magnets are of equal thicknesses, then the whole dealy-bobber is coplanar.
So long as the outfeed table of the jointer is flat and parallel to the infeed table, which is also flat, then the blades will be held at the perfect position, provided the cutter head is stopped precisely at top dead center.
I was pretty sure about all of the above, but just to be certain I had everything checked out according to standards set by the National Institutes for Standards and Technology, (NIST), standards for Optical Reference Planes, (ORFs).
As you probably know, ORFs are tested interferometrically, with the test surface horizontally supported on three equally spaced pads located at 0.7 of the radius from the center. The measurement is, of course, performed along two marked orthogonal diameters.
The whole assembly, (not counting the testing), cost about $12, bringing the total cost of my jointer up to nearly $60, including a set of brand new, M2 High Speed Tool Steel blades.
Anyway, here is a pick of the thingamjig.