Tapping Operation | Formula , Types , Tapping Process

Tapping Operation | Formula , Types , Tapping Process

 Tapping Operation : 

Tapping is the operation of cutting internal threads in a hole using a cutting tool called Tap. A tap has cutting edges in the shape of threads. When the tap is screwed into a hole it removes metal and cuts internal threads for tapping the hole
drilled will be smaller than the tap size.

Tap drill size = 0.8 * Outer diameter of the threads

For Example For M8 Size tap ,Drill Size should be = 0.8*8 = 6.8 mm Diameter 

To understand the application and importance of the involvement of semi automation in conventional drilling machine in manufacturing.

Read more : Drilling machine | Interview Question and AnswersOpens in a new tab.

Types Of Tapping Process 

Tapping may be done by:

– hand
– lathe machine
– milling machine
– tapping machine


1 Select drill size from chart.

When choosing a tap size, this chart is the first place to look.

Tapping Drill Size Calculation 

tapping drilling size calculation
tapping drilling size calculation

2. If necessary, add chamfer to the hole before tapping. Chamfers and countersinks are additional features that are sometimes desired for screws. For best results, the speed of the spindle should be between 150 and 250 rpm.

3. Get a tap guide. The hole is now ready to tap. To do this, use the taps and guide blocks near the manual mills. The guide blocks will have several holes for different sized taps. Select the one closest to the size of the tap being used and place it over the drilled hole.

4. Tap the block. Peck tap using the tap wrenches. Apply gentle pressure while turning the wrench a complete turn in, then a half-turn out. Peck tap to the desired depth.

5. Complete the tap. If the tap does not go any further or the desired depth has been reached, release pressure on the tap; it has likely bottomed out. Remove the tap from the hole.

hand tap
Hand tap Tool



1. Mount the workpiece in the chuck.

2. Face and center drill.

3. Select the proper tap drill for the tap to be used.

4. Example: ¼ – 20 unc used # 7 drill.

5. Set the lathe to the proper speed and drill with the tap to the required depth. Use plenty cutting fluid.

6. Note: the workpiece will rotate when tapping using the lathe power. Use a very slow spindle speed. (40 to 60 rpm) and plenty of cutting fluid.

7. Chamfer the edge of the hole.

Read more : Basic and related Drilling machine OperationsOpens in a new tab.

More Resources /articles
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Sachin Thorat

Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.

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