How do you select the correct pre-drill size for tapping?

Question

Accepted Answer

The pre drill for tap should be selected based on the material being drilled and the size of the tap.

Consider the material being drilled: Different materials require different pre drill sizes. So, it is important to know the material before selecting the pre drill.
Refer to tap drill charts: Tap drill charts provide recommended pre drill sizes for different tap sizes and materials. These charts can be found in machining handbooks or online.
Calculate the pre drill size: In some cases, the pre drill size can be calculated using formulas or equations based on the tap size and material properties.
Consider the tap type: Different types of taps, such as spiral point taps or spiral flute taps, may require different pre drill sizes.
Test and adjust: It is always a good practice to test the pre drill size on a scrap piece of material before drilling the actual workpiece. Adjustments can be made based on the results.
Example: For a 1/4-20 UNC tap in aluminum, a recommended pre drill size would be #7 (0.2010 inches).

Accepted Answer

Pri drill for drawing pich calculation tap16X1.5 mm size and pri drill size dia14.5 mm

Accepted Answer

Dipende upon tap diameter and pitch( if M16 x 1.5) drill diameter is dia 14.5

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