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Step 20The top, step five - benchdog holes, part one
You'll want to get as much done on each of the two layers of the top separately, before we join them, because handling the top after the two layers are joined is going to be a major hassle.
So drill the benchdog holes through the MDF layer. Begin by laying out their positions. You'll want these to be precise, so that the distances between the holes are consistent. The vises you are using will constrain your benchdog spacing. My front vise worked most naturally with two rows of holes four inches apart, my end vise with two pairs of rows, with four inches between the rows and eight inches between the pairs. Because of this, I decided on a 4" by 4" pattern.
I made a template by scribing two adjoining squares on a piece of MDF, using compass and straightedge, then marking each corner with a centerpunch, then drilling the points with a 1/16" bit. I find I'm always breaking small bits, so I picked up a couple of each size some months ago, and on looking I found I had three 1/16" bits, which worked fine for what I intended.
I marked out the one hole location, drilled a shallow 1/16" hole into the top. I then put a 1/16" bit through the hole in my template and into the hole I had just drilled. I lined up the template, and drilled a second hole, then put another bit through that. From then on, I worked entirely from the template. With two bits through the holes pinning the template in place, the other holes in the template would be precisely located (or so the theory goes) on a 4x4" grid.
Having done all this, I'm not sure I'd do it this way again. It might well be faster to layout the positions with compass and straightedge directly onto the top. Either way, you'll want to use a scribe rather than a pencil. Scribe lines are hard to see, and impossible to photograph, but the scribe and compass points click into them, allowing a precision that pencils simply cannot match.
Once you have all the positions marked, drill them through. I pulled out my drill guide and a 3/4" Forstnet bit. With this I drilled in 1/2", to give the hole a clean start. Then I went back and drilled the depth the each hole with a 3/4" spade bit, to a depth where the spike of the spade bit just extended from the other side.
Next, I flipped the top, and from the other side and drilled out the exit with a 3/4" Forstner bit.
Drilling this many holes in MDF burns up bits. You're going to need to either buy several bits or learn to sharpen them. Forstner bits produce holes with cleaner edges than spade bits, but they cost more and they're more difficult to sharpen.
So drill the benchdog holes through the MDF layer. Begin by laying out their positions. You'll want these to be precise, so that the distances between the holes are consistent. The vises you are using will constrain your benchdog spacing. My front vise worked most naturally with two rows of holes four inches apart, my end vise with two pairs of rows, with four inches between the rows and eight inches between the pairs. Because of this, I decided on a 4" by 4" pattern.
I made a template by scribing two adjoining squares on a piece of MDF, using compass and straightedge, then marking each corner with a centerpunch, then drilling the points with a 1/16" bit. I find I'm always breaking small bits, so I picked up a couple of each size some months ago, and on looking I found I had three 1/16" bits, which worked fine for what I intended.
I marked out the one hole location, drilled a shallow 1/16" hole into the top. I then put a 1/16" bit through the hole in my template and into the hole I had just drilled. I lined up the template, and drilled a second hole, then put another bit through that. From then on, I worked entirely from the template. With two bits through the holes pinning the template in place, the other holes in the template would be precisely located (or so the theory goes) on a 4x4" grid.
Having done all this, I'm not sure I'd do it this way again. It might well be faster to layout the positions with compass and straightedge directly onto the top. Either way, you'll want to use a scribe rather than a pencil. Scribe lines are hard to see, and impossible to photograph, but the scribe and compass points click into them, allowing a precision that pencils simply cannot match.
Once you have all the positions marked, drill them through. I pulled out my drill guide and a 3/4" Forstnet bit. With this I drilled in 1/2", to give the hole a clean start. Then I went back and drilled the depth the each hole with a 3/4" spade bit, to a depth where the spike of the spade bit just extended from the other side.
Next, I flipped the top, and from the other side and drilled out the exit with a 3/4" Forstner bit.
Drilling this many holes in MDF burns up bits. You're going to need to either buy several bits or learn to sharpen them. Forstner bits produce holes with cleaner edges than spade bits, but they cost more and they're more difficult to sharpen.
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