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Step 9The base, step six - board jack holes
A board jack is mechanism to provide support to long boards that are being held in the vise. These can be quite sophisticated, involving parts that can be moved both horizontally and vertically. The simplest mechanism is simply to stick a dowel into a hole drilled into the front of your bench.
The "Getting Started in Woodworking" video showed only one hole, drilled in the right front leg, level with the vise. This is useful only for a narrow range of boards. I decided to drill holes at four different heights in each of the front legs, six inches apart.
So that they would accept the same hold downs as the bench dog holes on the top, I decided they should be 3/4" in diameter, and should be drilled through where possible.
The Jig
Drilling a precisely positioned, deep, wide hole isn't easy, without a drill press. So I bought a WolfCraft drill guide. After experimenting with it, and drilling some test holes, I build a jig around it. I screwed it to a scrap of MDF, and then drilled a carefully-centered 3/4" hole. The MDF can be clamped more easily than the base itself, and the 3/4" hole will keep a 3/4" Forstner bit drilling precisely where it is supposed to.
Marking the holes
I wanted my first hole 1-1/4" from the top, and three others at six inch intervals, all of them on the centerline.
To mark the centerline, set a compass to span something more than half the width of the leg. Draw an arc from corner of the leg. The point where the arcs intersect will be on the centerline. With a centerline point on each end of the leg, place a scribe on the point, slide a straightedge up to touch the scribe. Do the same on the other end. When you have the straightedge positioned so that you can touch both points with the scribe, and in each case it is touching the straightedge - without moving the straightedge - scribe the line. Use scribes, rather than pencils or pens, because they make more precise marks.
Use the compass, again, to mark the center of the top hole, 1-1/4" from the top, on the centerline. Then mark the second hole on the centerline, six inches below the first. Repeat for the other two holes. To precisely set the span of the compass, use a rule with etched markings, and set the points of the compass into the etched grooves.
Place a centerpunch on each of your four points in turn, and press down to make an indentation. This will mark the center of the hole.
Drilling the holes
Because of the depth of the holes, drilling each hole became a four step process:
1. With the jig positioned and clamped, start the hole with a 3/4" Forstner bit, to give a clean entry. Drill perhaps 1/2" deep.
2. Extend the hole with a 3/4" spade bit, to as deep as the jig will allow.
3. Remove the jig and extend the hole further with the 3/4" spade bit, until the point of the bit is just starting to protrude from the other side.
4. Flip the leg, position the jig, and finish the hole off with the Forstner bit. This gives a clean exit.
The top hole on each does not extend through, and only steps 1 and 2 are necessary.
The "Getting Started in Woodworking" video showed only one hole, drilled in the right front leg, level with the vise. This is useful only for a narrow range of boards. I decided to drill holes at four different heights in each of the front legs, six inches apart.
So that they would accept the same hold downs as the bench dog holes on the top, I decided they should be 3/4" in diameter, and should be drilled through where possible.
The Jig
Drilling a precisely positioned, deep, wide hole isn't easy, without a drill press. So I bought a WolfCraft drill guide. After experimenting with it, and drilling some test holes, I build a jig around it. I screwed it to a scrap of MDF, and then drilled a carefully-centered 3/4" hole. The MDF can be clamped more easily than the base itself, and the 3/4" hole will keep a 3/4" Forstner bit drilling precisely where it is supposed to.
Marking the holes
I wanted my first hole 1-1/4" from the top, and three others at six inch intervals, all of them on the centerline.
To mark the centerline, set a compass to span something more than half the width of the leg. Draw an arc from corner of the leg. The point where the arcs intersect will be on the centerline. With a centerline point on each end of the leg, place a scribe on the point, slide a straightedge up to touch the scribe. Do the same on the other end. When you have the straightedge positioned so that you can touch both points with the scribe, and in each case it is touching the straightedge - without moving the straightedge - scribe the line. Use scribes, rather than pencils or pens, because they make more precise marks.
Use the compass, again, to mark the center of the top hole, 1-1/4" from the top, on the centerline. Then mark the second hole on the centerline, six inches below the first. Repeat for the other two holes. To precisely set the span of the compass, use a rule with etched markings, and set the points of the compass into the etched grooves.
Place a centerpunch on each of your four points in turn, and press down to make an indentation. This will mark the center of the hole.
Drilling the holes
Because of the depth of the holes, drilling each hole became a four step process:
1. With the jig positioned and clamped, start the hole with a 3/4" Forstner bit, to give a clean entry. Drill perhaps 1/2" deep.
2. Extend the hole with a 3/4" spade bit, to as deep as the jig will allow.
3. Remove the jig and extend the hole further with the 3/4" spade bit, until the point of the bit is just starting to protrude from the other side.
4. Flip the leg, position the jig, and finish the hole off with the Forstner bit. This gives a clean exit.
The top hole on each does not extend through, and only steps 1 and 2 are necessary.
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