Laying Out Centre Holes

While the work-piece is to be machined among the centers on a lathe, it is essential to layout and drills the centre holes before turning the work on a lathe. It is usually more accurate and convenient to drill the lathe centre holes in small round stocks on a lathe. This eliminates the requirement of laying out the holes.

To Locate the Centers of Round Stock

By Using Hermaphrodite Calipers

(1) Place the work in a vise and eliminate the burrs or sharp edges.

(2) Apply layout dye to both of the ends.

(3) Set the hermaphrodite caliper to the approximate radius of the work.

(4) Hold the bent leg along with thumb below the edge of the work and scribe the arc.

(5) Move the bent leg a quarter of a turn and scribe an arc. Repeat the process until four arcs are acquired at each end of the work.

(6) Mark the centre of the arc by using center punch and test the accuracy of the center.

(7) Repeat the step no. 3 to 6 on another end of the work-piece.

By Using Center Head

(1) Place the work in a vise and remove the burrs or sharp edges.

(2) Apply layout dye to both of the ends.

(3) Hold the centre head firmly against the work along with the rule remaining flat on the end of the work.

(4) Hold the sharp scriber at an angle so that its point touches the edge of the rule.

(5) Scribe a line along with the edge of the rule.

(6) Rotate the centre head with one quarter of turn and scribe the second line.

(7) Mark the point where two lines cross each other.

(8) Repeat step 3 to 8 on another end of the work.

(9) Test the correctness of the centre layout.

Using Surface Gauge

(1) Locate the work in a V-block placed on surface plate and remove the burrs or sharp edges along with the help of file.

(2) Apply layout dye to both of the ends.

(3) Set the scriber point of the surface gauge to the approximate centre of the work.

(4) Scribe four lines across the end of the work through rotating it by 90° for each line.

(5) Mark the intersection of four lines by centre punch.

(6) Test the center for accuracy with the divider or lathe centre method.