Leveling the Drill Press Table
Posted: Mon Feb 16, 2009 12:07 am
For years I have used a try-square or machinist's square to check that the drill bit and the drill press table were perpendicular. That has worked pretty well.
A couple nights ago, I stumbled upon an alternative method that cuts the error in half and led to a quick adjustment of my drill press table. At the same time, it proves (or disproves) the orientation quality of the drilled holes. Here are the steps:
1. set the fence across the drill press table (approx perpendicular to the table's axis of rotation.)
2. Drill left-side holes in two separate "car bodies", carefully assuring that the opposite side was firmly against the drill press table and the bottom of the car body was firmly against the fence.
3. Insert spare #44 bits in the drilled holes, leaving 2/3 to 3/4 of the drill bits' lengths exposed.
4. Slide the car bodies against each other with the right side against a good plane surface (e.g. drill press table) so that the exposed drill bits appear side-by-side as viewed from the top of the car bodies.
5. Observe whether the space between the drill bits disappears "all at once" or "gradually moving up or down." Holes from quality drilling technique will exhibit the "disappear all at once" behavior. If not, Stop the Test NOW.
6. Turn one of the car bodies end-for-end (car bodies top-to-top or bottom-to-bottom) and again slide them until the exposed drill bits appear nearly side-by-side.
7. Observe whether the space between the drill bits disappears "all at once" or "gradually moving up or down." Holes from quality drilling technique when the table is perpendicular to the drill bit will exhibit the "disappears all at once" behavior.
Why? Because the drill bits' deviation from perpendicular happens on both sides of perpendicular, and the angle between the two drill bits is twice the deviation from perpendicular.
A couple nights ago, I stumbled upon an alternative method that cuts the error in half and led to a quick adjustment of my drill press table. At the same time, it proves (or disproves) the orientation quality of the drilled holes. Here are the steps:
1. set the fence across the drill press table (approx perpendicular to the table's axis of rotation.)
2. Drill left-side holes in two separate "car bodies", carefully assuring that the opposite side was firmly against the drill press table and the bottom of the car body was firmly against the fence.
3. Insert spare #44 bits in the drilled holes, leaving 2/3 to 3/4 of the drill bits' lengths exposed.
4. Slide the car bodies against each other with the right side against a good plane surface (e.g. drill press table) so that the exposed drill bits appear side-by-side as viewed from the top of the car bodies.
5. Observe whether the space between the drill bits disappears "all at once" or "gradually moving up or down." Holes from quality drilling technique will exhibit the "disappear all at once" behavior. If not, Stop the Test NOW.
6. Turn one of the car bodies end-for-end (car bodies top-to-top or bottom-to-bottom) and again slide them until the exposed drill bits appear nearly side-by-side.
7. Observe whether the space between the drill bits disappears "all at once" or "gradually moving up or down." Holes from quality drilling technique when the table is perpendicular to the drill bit will exhibit the "disappears all at once" behavior.
Why? Because the drill bits' deviation from perpendicular happens on both sides of perpendicular, and the angle between the two drill bits is twice the deviation from perpendicular.