Wood jointer and planer blade sharpening holder

A device for low-cost and convenient sharpening of wood jointer and planer blades or knives. The device comprises a rectangular block of sufficient thickness to embody an angled kerf for holding the blade or knife and thumbscrews to turn up against the blade or knife to hold it in place, the block with the blade or knife inserted to lay flat against the bed of a conventional workshop table saw in an inverted position, a stone grinding wheel to be installed on the saw arbor, the grinding stone to engage the surface of the blade or knife to be sharpened, an elongated guide to be installed on the underside of the block to engage the miter slot in the bed of the table saw to guide the blade or knife to be sharpened along its entire length while in contact with the stone griding wheel, operator to employ repeated reciprocal movements of the block and blade or knife to be sharpened, gradual raising of the stone grinding wheel arbor until visual inspection of object to be sharpened has been ground uniformly over its entire length.

BACKGROUND OF THE INVENTION 
This invention relates to an improvement in sharpening planer and wood 
jointer blades involving a blade holding device used together with a 
conventional table saw mechanism but equipped with a grinding wheel 
instead of a saw in the saw arbor. 
Present day methods of sharpening planer blades are based on 
long-established patents and generally involve either the use of a milling 
machine or a sharpening device attached to the planer itself. For the home 
workshop, these methods of sharpening blades are costly and inconvenient. 
The present invention teaches the use of an inexpensive blade holding block 
equipped with a tracking guide which moves the blade to be sharpened along 
the face of the grinding wheel while maintaining the correct angle of 
sharpening and doing this along the entire length of the blade to be 
sharpened. 
Present day automatic grinders generally employ a grinding wheel which 
travels the length of the blade to be sharpened and at a right angle to 
the blade. These are variations of the M. W. Palmer planter knife grinder, 
U. S. Pat. No. 267,579, Nov. 14, 1882, and H. Leverentz's planing machine 
attachment, U. S. Pat. No. 316,156, Apr. 21, 1885. 
SUMMARY OF THE INvENTION 
The present invention discloses a rectangular block of sufficient length to 
hold common planer blades in position for sharpening on a grinding wheel 
installed in a common woodworking table saw. The block is of sufficient 
width for a long narrow guide extending down from its underside to engage 
the longitudinal miter slot in the bed of the table saw. The block may be 
made of plastic, wood or metal. On the operational underside and well to 
the right there is an angled kerf which is the receptacle for the planer 
blade, the angle to be 40 degrees to the block, more or less. 
To hold the planer blade firmly while sharpening is being done, a number of 
thumbscrews installed in the right edge of the block are turned in and are 
tightened against the blade to hold it when it is in position for 
sharpening. 
A relief slot of undetermined depth but 3/32' deep, more or less, and 1 
inch, more or less, wide is built into the block to extend to either side 
of the kerf. 
To sharpen a planer blade, the blade is first placed into the holder with 
the edge to be sharpened on a plane with the underside. Thumbscrews 
tighten it securely in place. Next, the holder block is placed on the bed 
of the table saw with the blade to be sharpened on the underside where it 
will engage with the grinding wheel, and with the guide of the holder 
riding in the miter slot of the saw. 
To operate, first make sure that the grinding wheel is adjusted at 90 
degrees to the bed of the saw. 
Then the saw motor is turned on and raised carefully until it slightly 
engages the blade to be sharpened. The operator grips the block and pushes 
it the full length of the planer blade being sharpened. The operator then 
gradually raises the grinder wheel as he repeats pushing the block back 
and forth the entire length of the planer blade. He repeats this until 
visual inspection indicates the entire length of the planer blade has been 
ground to uniform sharpness. During this procedure, care is taken not to 
overheat the planer blade to the point it turns bluish in color as this 
will take the temper out of the blade. For added convenience of the 
operator, though not required, hand gripping blocks are installed on the 
operational upper side of the block.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring now to FIG. 1, there is at 1 a rectangular block resting on its 
left edge on the bed of table saw 2. There is at 3 a relief slot running 
the full length of block 1. At 4 there is a kerf running the full length 
of the block and cut into the block at the preferred depth and angle to 
properly hold the planar blade for engagement with grinding wheel. 
There is a full length guide 6 extending below the planar blade sharpening 
holder to track inside of miter slot 7 in the bed of table saw 2. 
Planar blade 9 is inserted into kerf 4 and tightened into place by 
thumbscrews 8. 
FIG. 2 represents a cross-sectional view of the rectangular block planar 
blade sharpening holder 1 laying on top of bed of table saw 2. Rectangular 
block 1 contains a full length relief slot 3. Kerf 4, which runs the full 
length of block 1 is perfectly machined to retain planar blade 9 at chosen 
angle. Blade 9 is held firmly in place by thumbscrews 8. Block guide 6 
engages miter slot 7. Grinding wheel 10 mounts on saw arbor 11. 
Sharpening of blade 9 is accomplished by moving block 1 over table 2 to 
make lengthwise contact with grinding wheel at point 12. 
Gripping block 13 provides raised surface and edge for hands of operator in 
order to move block 1 forward and back as grinder does its work. 
In FIG. 3 the action of the planar blade sharpening holder 1 is shown being 
moved in sliding directions 14. Operators hands rest gently on gripping 
blocks 13 as grinder under the block makes continuous contact with planar 
blade being sharpened.