Autocenter for a drill

To make holes in the center of the workpiece using a drill, you must first, using a ruler and a pencil, mark the center line and drill along it already.
But you can forget about marking forever if you make a simple device that allows you to drill holes with a drill along the symmetry line of the workpieces, which is very convenient, especially if you have to deal with such a thing regularly.

Will need

We will prepare some materials for work:

• two steel rods;
• four compression springs;
• two wooden bars;
• a small piece of steel wire;
• a wooden rectangular blank of small thickness;
• round head bolt, washer and nut;
• glue on wood.

To make the elements of the centering device and assemble them, you can not do without the following tools and devices: clamp and clamp; a drilling device with ring and twist drills; vice of metalwork; hacksaws for metal; pliers and pliers; measuring square, ruler and pencil; hammer and wrench.

The procedure for working on the device

In wooden blocks we drill from one end to the middle of the hole for steel rods, on the other hand - holes of a larger diameter for the rods with springs put on them.
We clamp the rods alternately in a vice and precisely in the center with a hacksaw for metal, we perform a circular groove.
We wind the wire in one revolution onto the groove in the ring and cut off the resulting wire ring with pliers.
Using pliers, we recess the rings of wire in the grooves. The ends of the double springs will abut against them.
We insert rods with springs into the holes of larger diameter in the wooden blocks and for now put them aside.
We mark a rectangular wooden blank for a large central circular cut, two lateral grooves horizontally and symmetrical with respect to the center of the large cut, as well as its external contour.
We fix the marked workpiece with a clip and clamps vertically and with the help of an annular drill we make a central cut.
Using a spiral drill, we make two recesses on the sides and with a drill in the center of the recesses we drill through holes for the rods to exit.
In the lower part of the workpiece, we draw two vertical lines from the central hole to the edge of the workpiece at some distance from each other and symmetrical to the center of the circle.
According to the markings, we form the external contour of the workpiece and make a slot. Perpendicular to the slot we drill a through hole under the coupling bolt closer to the edge of the workpiece.
We give a cylindrical shape matching the diameter of each end of the wooden blocks to the depth of the blind holes in the flat blank.
We put glue on the cylindrical part of the bars, insert the rods with springs into place and install them in blind holes in a flat workpiece. We remove excess glue with a napkin.
We press the rods with our fingers and make sure that they are reliably spring-loaded and move freely in the holes.
We insert the drill all the way into the central hole in the device so that the cartridge is between the rods, and tighten the coupling bolt. As a result, the centering device is firmly and rigidly fixed to the cylindrical part of the drill body.
The presence of such a device allows you to drill holes in workpieces of any width (within the distance between the rods) exactly in the center without marking. The main thing is that the rods are in contact with the sides of the workpieces.