A special left hand tap cuts an internal thread that tightens when turned counterclockwise, built to your thread form, size, pitch and material rather than pulled from stock. Taylor Tool, a Canadian tap manufacturer founded in 1918, makes custom taps from your drawing or sample, including left-hand and multi-lead forms on request. This guide covers when you need an LH tap, which thread forms can be made left hand, and how to specify one correctly.
What Are Special Left Hand Taps?
A left hand tap cuts a left-hand thread: the fastener or mating part tightens by turning counterclockwise and loosens clockwise, the reverse of a standard right-hand thread. “Special” means the tap is manufactured to your specific thread form, size, material or tolerance, not selected from a catalogue of stock sizes.
Right-hand taps cover the vast majority of everyday threading. A left hand tap is the exception, used where the thread direction itself is part of the design. Note also that “hand tap” describes a style of tap (typically used by hand or with a wrench) while “left hand” describes thread direction. A tap can be both, or neither: machine taps can be left hand too.
If your requirement extends beyond hand direction to an unusual form or pitch, Taylor Tool’s engineering team can advise on the broader custom range.
When Do You Need a Left Hand Tap?
You need a left hand tap when a fastener or threaded component must tighten against the rotation that would otherwise loosen it. Reversing the thread direction lets the machine’s own motion keep the joint tight.
Typical reasons include:
- Rotating shafts and pulleys: where rotation direction would unscrew a standard right-hand thread over time.
- Counter-rotating assemblies: where mating components turn in opposite directions.
- Mating or safety-driven conventions: where a left-hand thread prevents a part from being fitted to the wrong connection.
- Replacement of existing parts: where the original component was designed with a reverse thread and must be matched.
Taylor Tool builds taps for left-hand threads and multi-lead forms on request. If your application isn’t on this list, send the drawing or sample and the engineering team can advise on feasibility.
Thread Forms Available as Left Hand Special Taps
Most special thread forms can be specified left hand, so the practical step is to ask about your particular form. Taylor Tool manufactures special taps for forms general suppliers don’t stock, alongside standard metric and unified threads.
| Thread form | Typical use |
|---|---|
| Acme | Power transmission and lead screws |
| Trapezoidal | Linear motion and screw drives |
| Buttress | Loads applied in one direction |
| Whitworth | British thread conventions |
| BSPT / BSPP | Pipe threads (tapered and parallel) |
| PG | Conduit and cable-gland fittings |
| Metric and unified | General fastening; see the taps overview |
If your part calls for an unusual pitch, an oversized or large-diameter thread, a left-hand thread, or a multi-lead form, Taylor Tool builds the tap for it. Confirm the exact combination of form and hand when you request a quote.
Choosing the Right Tap Style and Material
Match the flute style and substrate to your hole type and workpiece material; the left-hand direction doesn’t change these fundamentals. The right choice drives chip evacuation, thread quality and tool life.
Flute and style
- Spiral point taps push chips forward, making them ideal for a through hole.
- Spiral flute taps pull chips up and out, ideal for a blind hole and for stainless steel.
- Form taps displace material rather than cutting it, producing stronger threads with no chips in ductile materials.
Substrate
- HSS suits general-purpose threading.
- Carbide taps deliver the wear resistance and rigidity needed for hardened steels, high-silicon aluminum and other abrasive materials, where tool life and consistency drive cost per hole.
- Powdered metal taps use an exceptionally uniform, tough substrate for heavy machining.
For demanding production work, high performance spiral taps are engineered with advanced geometries and premium substrates for higher speeds and longer tool life. Custom tap sets, matched and tuned to your job, are also available.
How to Specify a Special Left Hand Tap
Send a drawing or sample along with the thread form, size, pitch, hand, hole type and workpiece material. Taylor Tool works from either a drawing or a sample, from one-off prototypes to repeat production runs.
Use this checklist when you request a quote:
- Thread form: Acme, buttress, Whitworth, BSPT, BSPP, PG, metric, unified or other
- Hand: left hand (state this explicitly)
- Size and pitch: nominal diameter and pitch or threads per inch
- Lead: single or multi-lead
- Tolerance class: the class your mating part requires
- Hole type: through hole or blind hole
- Workpiece material: and hardness if known
- Tap style and substrate: spiral point, spiral flute, form tap; HSS, carbide or powdered metal
- Quantity: prototype, small batch or repeat production
- Drawing or sample: attach or ship whichever you have
Leaving a field open is fine; the engineering team can recommend a style and substrate based on your application.
Tapping Left Hand Threads: Practical Tips
Reverse the machine rotation and confirm your setup before the tap touches the part. Most left-hand tapping problems come from setup oversights, not the tap itself.
- Check spindle direction: confirm the machine is set for the correct rotation for an LH tap before cutting.
- Verify the tap holder: make sure it suits the reversed rotation and holds the tap securely.
- Review the CNC program sequence: confirm the M-codes and feed-out direction match a left-hand cycle.
- Prove out on scrap: test the first part or a sample piece before committing production stock.
- Follow your tap’s guidance: consult speed and feed recommendations for your specific tap and material rather than reusing right-hand settings blindly.
- Mark and store LH taps clearly: label them or keep them in a dedicated location so they aren’t mistaken for right-hand taps. Telling them apart on sight is difficult without a marking, since the flute and thread hand aren’t always obvious at a glance.
Why Order Custom Taps from Taylor Tool
Taylor Tool is a Canadian manufacturer, established in 1918, that makes its own taps rather than reselling them. Controlling production end to end lets the team manage quality and deliver fast, on-time shipments, including 24 HR Jet Tap service for production-critical needs.
Customers range from the smallest job shops to the largest industrial manufacturers in automotive, aerospace and power generation. Explore the full special purpose taps range or browse the main taps page for standard and high performance options.
Frequently Asked Questions
What is a left hand tap used for?
A left hand tap cuts threads that tighten counterclockwise. It’s used where the fastener must tighten against the rotation that would loosen a right-hand thread, such as rotating shafts, pulleys and counter-rotating assemblies, or where a reverse thread is a deliberate mating convention.
What is the difference between a left hand tap and a right hand tap?
A right hand tap cuts a thread that tightens clockwise; a left hand tap cuts one that tightens counterclockwise. The tap geometry is the mirror of the other, so the two are not interchangeable.
Can you get a custom left hand tap in a special thread form?
Yes. Taylor Tool builds taps for left-hand threads and multi-lead forms on request, across special forms such as Acme, buttress, Whitworth and pipe threads. Confirm your specific form and hand when requesting a quote.
How do I specify a special left hand tap?
Provide a drawing or sample plus thread form, size, pitch, hand, hole type and workpiece material. Note the tolerance class and whether the thread is single or multi-lead. See the checklist above.
Are left hand taps available in carbide or HSS?
Taylor Tool manufactures taps in HSS, carbide and powdered metal substrates. Ask about your left-hand requirement when quoting, and the team can recommend the substrate for your material and volume.
Can left hand taps be made for blind holes?
Blind-hole threading is a standard application for spiral flute taps, which pull chips up and out. State your hole type when you specify the tap so the right style is recommended.
Does Taylor Tool make left hand Acme or Whitworth taps?
Taylor Tool manufactures both Acme and Whitworth special taps and builds left-hand and multi-lead forms on request. Send your drawing or sample and confirm the hand when requesting a quote.
Can a left hand tap be made from a sample or drawing?
Yes. Taylor Tool works from your drawing or sample to deliver a tap that performs in your application, from one-off prototypes to repeat production runs.
How do I tell a left hand tap from a right hand tap?
Left-hand taps aren’t always obvious by eye, so rely on markings and clear storage. Label LH taps and keep them separate from right-hand stock to prevent mix-ups.
How do I order special taps from Taylor Tool?
Call 1-800-265-2145 or email sales@taylortool.com, and the sales team will direct you to the right ordering route, including your nearest distributor in Canada. If you are outside Canada, contact sales for ordering information.
Ready to get started? Request a quote or call 1-800-265-2145 with your drawing or sample.