The pitch-circle diameter (PCD) can be calculated using:

$PCD = OD - 2 \times module$

Substituting the values:

$PCD = 112 - 2 \times 4 = 104 \ mm$

Therefore, the pitch-circle diameter is 104 mm.

The cutting depth can be calculated with the following relation:

$Cutting\ Depth = 2.157 \times module$

Substituting the values:

$Cutting\ Depth = 2.157 \times 4 = 8.628 \ mm$

Thus, the cutting depth is 8.63 mm.

The addendum can be derived from the module as:

$Addendum = module \approx 4 \ mm$

Thus, the addendum is 4 mm.

The dedendum is calculated using:

$Dedendum = 1.25 \times module \approx 1.25 \times 4 = 5 \ mm$

Therefore, the dedendum is 5 mm.

Clearance can be calculated as:

$Clearance = 0.25 \times module \approx 0.25 \times 4 = 1 \ mm$

Thus, the clearance is 1 mm.

The number of teeth can be found using:

$Number\ of\ Teeth = \frac{PCD}{module} \approx \frac{104}{4} = 26$

Therefore, the number of teeth is 26.

To calculate the indexing, we use the formula:

$Indexing = \frac{40}{n}$

where n is the number of teeth. Here, n = 26:

$Indexing = \frac{40}{26} \approx 1.538$

Approximate to the nearest turn, indexing is 1 full turn and 21 holes on the 39-hole circle.

Procedure for Cutting External Metric V-Screw Thread

Step 1: Set Up

• Set up the workpiece in the lathe and turn the part to be threaded to the major diameter of the thread.

Step 2: Angle Adjustment

• Set the compound slide to the correct angle (30° to the right) and set the tool accurately in the tool post.

Step 3: Consult Index Plate

• Consult the index plate of the quick-change gearbox for 2 mm pitch and move the levers accordingly.

Step 4: Select Tool

• Start the lathe and set the cutting tool so that it just touches the workpiece.
• Set graduated dials to zero (cross feed and compound slide).

Step 5: Initial Movement

• Move the tool a short distance off the workpiece and feed the compound slide say 0.06 mm inwards.

Step 6: Cutting

• With the turning, engage half nuts at the correct line on the chasing dial, putting the cut in progress.

Step 7: Disengage

• Without cutting, try to quickly disengage the half-nut lever.

Step 8: Check Position

• Return the carriage to the starting point and repeat the process if necessary.

Step 9: Check Thread

• Check with thread gauge to see if thread pitch is correct.

Step 10: Final Adjustments

• Ensure screw with successive cuts until finish is complete. (Remember to bring cross slide collar back to zero for each cut.)
• Each successive cut is set by means of the compound slide. Check thread with ring gauge for correct fit.