Threading: Tap & die



Threading: Tap & die

Internal threads:

• Taps are used to cut internal threads. (Major diameter)

• You have to drill the correct diameter hole for the thread that you want. To find out the correct diameter hole you can work out the following formula:

o Drill bit size = (1.08253 x %) size

No. threads per inch

65%-75% thread depth is suitable.

………. OR YOU CAN USE A TAP DRILL SIZE CHART (

External threads:

• Dies are used to cut external threads. (Minor diameter)

CAUTIONS FOR TAPPING:

• Make sure that you hold the tap straight (perpendicular) to the material or your threads will be off. Use a square to double check!

• Use a cutting fluid.

• Taps are very hard and brittle, and can break when forced.

• Always use light pressure, don’t force it. Removing a broken tap can be difficult or impossible.

• Remember to turn tap wrench a half a turn forward and then a quarter turn back to break the metal chips and prevent jamming the tap in the material.

• The smaller the tap, the easier it breaks. Be careful you don’t want to start over again!

CAUTIONS FOR DIE:

• Diameter of rod must be the same size as the major diameter of thread. For example a 3/8-16 UNC die would require a 3/8” or 0.375” diameter rod.

• The serial numbers must match on a split die or you will wreck the die teeth and your threads.

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• Taper tap: 4( for starting taps in hard metals.

• Plug tap: 8( for general use.

• Bottoming tap: 23( for finishing blind holes.

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