Left Hand Reverse Thread Hand Taps
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Fractional Left Hand Reverse Thread Taps
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Metric Left Hand Hand Taps
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Special Size Left Hand Reverse Thread Taps
Left Hand Reverse Thread Taps for Specialized Threading
Shop high-speed steel (HSS) left hand reverse thread taps for cutting new internal left-hand threads or repairing existing reverse-threaded holes. Unlike standard right-hand threads, left-hand threads tighten counterclockwise and loosen clockwise.
Left-hand hand taps are used in machinery, rotating equipment, industrial maintenance, fabrication, and specialized repair applications where reverse thread direction is required. Choose from fractional, metric, and special-size left-hand taps to match your thread specifications.
What Are Left Hand Reverse Thread Taps?
Left-hand taps are cutting tools designed to produce internal threads with a left-hand helix. They are used when a component requires a fastener that tightens counterclockwise rather than clockwise.
These taps are manufactured from high-speed steel (HSS), providing durability and wear resistance for general metalworking and threading applications. They can be used to cut new left-hand threads or carefully restore existing threads with minor damage.
Left-Hand vs. Right-Hand Threads
Standard right-hand threads tighten clockwise. Left-hand threads tighten counterclockwise. The correct thread direction must be matched to the intended fastener or component because the two are not interchangeable.
Why Are Reverse Threads Used?
Left-hand threads are sometimes used on rotating equipment, mechanical assemblies, and specialized components where the design calls for reverse rotation or a particular fastening arrangement. Their use depends on the equipment design and operating conditions.
High-Speed Steel Construction
HSS taps offer good toughness, wear resistance, and cutting performance for threading many common metals. They are suitable for both new threading and appropriate repair applications when the correct tap geometry and cutting conditions are used.
Common Applications for Left-Hand Thread Taps
Rotating Machinery and Equipment
Some rotating shafts, spindles, and mechanical assemblies use left-hand threads as part of their fastening design. Reverse-thread taps allow these specialized components to be manufactured or serviced.
Industrial Maintenance and Repair
Left-hand taps can help restore existing reverse-threaded holes affected by minor wear, burrs, or thread damage. Always confirm the original thread diameter, pitch, and direction before attempting a repair.
Custom Fabrication and Specialty Components
Machine shops and fabricators use reverse-thread taps when manufacturing components requiring left-hand fasteners, adjustment mechanisms, or other specialized threaded connections.
Choosing the Correct Left Hand Tap
Fractional Left Hand Reverse Thread Taps
Fractional left-hand taps are used for inch-based thread sizes specified by nominal diameter and threads per inch (TPI). Verify the required UNC, UNF, or other thread specification, along with the left-hand thread direction.
Metric Left Hand Hand Taps
Metric left-hand taps are specified by nominal diameter and pitch, such as M6 x 1.0 LH. The LH designation identifies the reverse thread direction. Confirm both diameter and pitch before ordering.
Special Size Left Hand Reverse Thread Taps
Special-size left-hand taps are used for uncommon inch thread diameters or pitches. They are particularly useful for specialized machinery, replacement components, and equipment requiring less common reverse-thread specifications.
Need help identifying the correct tap drill size? Consult our Tap and Drill Chart, Metric Tap Drill Calculator, or Special Tap and Drill Size Calculator.
Taper, Plug, and Bottoming Left Hand Taps
Taper Taps
Taper taps feature a longer lead chamfer that helps start threads gradually and maintain alignment. They are useful when beginning a new threading operation by hand.
Plug Taps
Plug taps have a moderate chamfer and are commonly used for general-purpose threading, including through holes and applications with sufficient starting clearance.
Bottoming Taps
Bottoming taps have a short chamfer that allows threads to be cut closer to the bottom of a blind hole. They are generally used after the thread has been started with another tap style.
Available tap styles vary by size and product. Confirm the required style before ordering.
Tips for Cutting Left-Hand Threads
1. Confirm the Thread Direction
Verify that the application requires left-hand threads. A left-hand tap cannot be substituted for a standard right-hand tap of the same diameter and pitch.
2. Drill the Correct Size Hole
Choose the tap drill size according to the required diameter and pitch. The basic tap drill sizing principles are the same for left-hand and right-hand threads of equivalent specifications.
3. Rotate Counterclockwise to Cut
Unlike standard right-hand taps, left-hand taps advance into the workpiece when rotated counterclockwise. Maintain proper alignment and use a suitable tap wrench.
4. Use Cutting Fluid and Clear Chips
Apply suitable cutting fluid when appropriate for the material. Advance carefully and periodically reverse the tap clockwise to help break chips during conventional hand tapping.
5. Verify the Finished Thread
Remove chips and inspect the finished hole. Confirm proper engagement with the intended left-hand threaded fastener or an appropriate thread gauge.
Frequently Asked Questions About Left Hand Taps
What is a left-hand reverse thread tap?
A left-hand tap cuts internal threads that advance counterclockwise, opposite the direction of conventional right-hand threads.
Which direction do you turn a left-hand tap?
Turn a left-hand tap counterclockwise to cut and advance into the hole. Turn it clockwise to back it out.
Can left-hand taps repair damaged threads?
Yes. They can be used to restore minor damage in existing left-hand internal threads, provided the correct diameter and pitch are selected. Severely damaged threads may require a different repair method.
Are left-hand taps used to remove broken bolts?
Left-hand taps are intended to cut or restore internal left-hand threads. They are not the same as left-hand drill bits or screw extractors, which are commonly used during broken fastener removal.
Are left-hand tap drill sizes different?
For equivalent thread diameter and pitch, the basic tap drill size is generally the same regardless of thread direction. Always verify the specifications for your particular application.
Can I use a left-hand tap for a standard right-hand bolt?
No. Left-hand and right-hand threads have opposite helix directions and are not interchangeable, even when their nominal diameter and pitch are identical.
Learn More About Taps and Thread Cutting
Watch our Drill America video to learn more about taps and threading tools. For additional threading options, explore our complete Taps selection.