Repair 7

How to Build a Center Drill Jig for Tubing

A jig ensures that when parts are made, drilled, welded or bent, they are made exactly the same way as the jig and will fit the application they were designed for. A center drill jig for tubing would be designed to ensure that when using the jig, the holes you drill will be in the center of the tubing. Two methods for accomplishing this are the drill press method and the external drill jig.

Instructions

Drill Press Jig Method

1

Place a machined V-block onto a level drill press table.

2

Insert a large bit into the drill chuck. Bring the quill handle down so the bit centers perfectly into the V-block. You might need to reposition the V-block to match the drill-bit point perfectly. Release the quill and raise the drill bit.

3

Clamp the V-block to the level drill press table. Pull the quill handle down again to visually center the drill bit into the machined V-block again. This ensures that the V-block did not move during the clamping process. Recheck to be sure the drill bit is perfectly centered in the V-block.

4

Clamp a metal stop to the end of the V-block to adjust the depth of the hole you are drilling.

5

Remove the large drill bit and replace it with the correct size bit needed to center drill the tubing.

6

Place the tubing into the V-block and against the depth stop, turn on the drill and bring the quill down to drill the hole.

External Drill Jig Method

7

Cut a piece of triple wall tubing that fits snugly over the tubing you are drilling. Cut the triple wall tubing longer than the distance between the hole and the end of the tubing to be center drilled. For example, if the hole in the tubing is to be center drilled eight inches from the end of the tubing, cut the triple wall tubing to 10 inches.

8

Place the triple wall tubing into the V-block of the drill press jig and drill a 5/16-inch hole all the way through the triple wall tubing a half-inch from one end. You might need to remove the triple wall tubing from the V-block once the drill bit begins to exit the bottom of the tubing, so that the drill does not damage the V-block.

9

Insert the 5/16-inch drill bit into the portable drill and finish drilling the 5/16-inch hole through the triple wall tubing. Place a long 5/16-inch bolt through the hole and tighten a nut onto it. This bolt will be the jig stop.

10

Measure the precise distance from the bolt stop to where the center drill hole is desired. For example, if the center hole is to be drilled eight inches from the end of the tubing, then measure precisely eight inches from the 5/16-inch drilled hole edge and mark that point with a prick punch.

11

Insert a 1/8-inch drill bit into the chuck on the drill press. Place the triple wall tubing into the drill press jig V-block so that the prick-punch mark aligns precisely with the drill bit point when the quill brings the drill down to meet the punch mark.

12

Clamp the triple wall tubing into the V-block. Drill the 1/8-inch hole into the triple wall tubing. If the center hole is to go all the way through the tubing when it is drilled, then drill all the way through the triple wall tubing and stop drilling before the bit touches the V-block. Drill the remaining part of the hole with the 1/8-inch bit in the portable drill.

13

Re-clamp the triple wall tubing into the V-block. Bring the quill down so the 1/8-inch drill bit goes through both drilled holes in the triple wall tubing. Raise the quill on the drill press and change the drill bit in the chuck to the intended drill size and enlarge the hole.

14

Clamp the triple wall tubing jig into a vise. Place the undrilled tubing into the jig until it bottoms out on the 5/16-inch bolt. Insert the proper size drill bit into the portable drill, stick the drill bit into the jig and drill the tubing. If the hole needs to go all the way through the tubing, drill into the jig from both holes in the jig. For example, drill the fist hole, stop and place the drill in the other hole, 180 degrees from the first hole.