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The Fundamentals of External Threading

The Fundamentals of External Threading


External threading is accomplished by using a variety of cutting tools design for cutting threads on the outside diameter of a workpiece.


Die Types:

Round Adjustable Dies
• Originates a new thread
• Ideal for maintenance jobs
• Will cut the external thread when held in a die stock
• Chamfered on both faces – one side has a 2-3 thread chamfer for threading, and the other side has 1 – 1-1/2 thread chamfer for threading close to the shoulder
• Standard in right-hand Unified and American National Thread Form

Hex Rethreading Dies
• Ideal for maintenance jobs
• Designed to repair a bruised or rusty thread
• Can be used in free machining materials
• Most cost-effective rethreading tool available
• Can be used with a wrench instead of a die holder or die stock

Two Piece Die Blank Systems ( Little Giant® )
• Collet system designed for greater die adjustability for new threading or thread repair
• Consists of a cap and a guide (dies not included)

• Die Stock - Holds round adjustable dies but is specifically designed for holding open-type adjustment dies
• Die Adapter - Converts a round die into a hex die. Good for jobs where die stocks can not be used due to lack of space
• Die Holders - These tools have a straight shank and are used to hold round split adjustable dies

Die Materials
HSS – Used for cutting new threads in mild steels and non-ferrous materials


Thread chasers are used to cut external threads and consist of self-opening die heads and collapsing taps. An advantage of chasing is after cutting the threads,
the die head self-opens and retracts eliminating the need to be backed off the workpiece. All chasers protrude slightly from the face of the die heads to permit close-to-the-shoulder threading.
• For machine threading applications
• Supplied in sets of four
• Ground thread for better surface finish and tighter tolerances
• For use in a variety of ferrous and non-ferrous materials

Chaser Styles:
• Available in standard or projection
• Projection type offers more regrind life therefore more parts can be produced in between regrinds
• Will fit styles D, DD, DS, DSA & DJ die heads

H&G™ Inserts
• Available in 00 Series or 100 Series
• 100 Series Chasers will fit 101, 102 and 103 series die heads
• Used with Carriers that hold the chaser in place. The range of the carrier allows threads of different diameters to be cut

Chasers can be used for:
• Small or large diameter work on excessively abrasive or hard materials
• Fast changes on short-run jobs or minimum set-up changes for long-run jobs
• For single or multiple spindle machine tools

Thread Rolls:
• Reversible, can be used on both sides
• Sold in sets of three
• Designed for rolling threads from the end of the workpiece
• Style N - threads diameters from #6 - 1-1/4”
• For rotating or stationary use
• Available in low or standard helix

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