Self-Reversing CNC Tapping

When a machined component needs one tapped hole, cycle time can seem insignificant. When the same component needs twenty, fifty or hundreds across a production run, every spindle reversal becomes part of the equation. Sutton RDT Tapmatic tool holders provide a specialised self-reversing tapping solution for compatible CNC machining centres, allowing tap reversal to occur through the attachment as the machine retracts rather than requiring the spindle to reverse for every hole.

Choosing the right setup involves more than matching a holder to a thread size. Tap capacity, ER collet series, modular shank, machine spindle interface, stop arm, stop block & available centre distance all influence compatibility. Tapmatic's RDT25, for example, is specified for M2–M6 tapping capacity in steel, uses ER11 collets & operates at speeds up to 4000 RPM.

For machinists, production engineers & CNC workshops, the sensible starting point is the complete tapping operation. Establish the thread size, tap type, prepared hole, machine interface & installation geometry before configuring the holder around them.

Working from the thread backwards?  Tap & Die Sets connects directly with threading work, while  Drills supports the holemaking stage that comes before the tap enters the component.

What Does an RDT Tapmatic Tapping Attachment Do?

This isn't simply a device that grips a tap.

An RDT attachment becomes an active part of the tapping cycle.

Tapmatic RDT attachments are designed for high-speed self-reversing tapping on compatible CNC machinery. During the forward tapping stroke, the machine spindle continues rotating in the forward direction. As the machine retracts, the attachment reverses the tap internally.

That changes where the reversing action occurs.

Instead of requiring the spindle to decelerate, stop, reverse & then return to forward rotation around every threaded hole, the tapping attachment handles reversal mechanically.

Across repeated tapping operations, that distinction is exactly why the RDT system exists.

Why Does Self-Reversing Tapping Matter in Production?

Imagine a machined plate with forty identical threaded holes.

The tap isn't changing.

The thread specification isn't changing.

The machine still has to repeat the tapping sequence forty times.

With a self-reversing RDT attachment, the tap reversal occurs within the attachment as the machine retracts rather than through a spindle-reversal command for every hole.

The value becomes easier to understand as repetition increases.

Production tapping isn't about making one impressive thread. It's about producing the required thread repeatedly within a controlled machining process.

RDT25 – Start With the Tap Capacity

The thread requirement establishes the first boundary.

Tapmatic currently specifies the RDT25 around the following key parameters:

Tapmatic also specifies a 25% capacity reduction when roll-form taps are used.

That detail matters.

A thread diameter falling within the nominal cutting-tap range shouldn't automatically be assumed suitable under identical conditions when the tapping method changes.

ER11 Collets – The Tap Still Has to Be Held Correctly

RDT25 uses the ER11 collet series.

That makes the collet part of the tapping system rather than an accessory to think about afterwards.

The attachment, collet & tap need to work as one toolholding assembly. Check the tap shank against the required collet arrangement instead of selecting the tapping attachment from thread diameter alone.

This becomes especially relevant in workshops producing several thread sizes on the same machining centre.

The RDT attachment may remain in the machine while the tap & corresponding holding arrangement change between jobs.

Stop Arm Geometry Can Decide Whether the Setup Fits

The tapping attachment housing needs to remain restrained for the self-reversing mechanism to operate.

Tapmatic achieves this through a stop arm that engages with a suitable stop block on the machine.

RDT25 stop-arm assemblies are available around different centre-distance configurations, including 55mm, 65mm & 80mm options.

That makes installation geometry a buying consideration—not an adjustment to discover after the holder arrives.

Before configuring the setup, check:

► Where is the machine stop block positioned?
► What centre distance is required?
► Which stop-arm arrangement matches the installation?
► Is there sufficient clearance around the attachment?
► Can the stop-block arrangement support the intended tapping operation?

A holder can match the tap perfectly & still be wrong for the machine.

Match the Modular Shank to the Machine

The RDT tapping attachment can form part of a modular toolholding system.

Tapmatic documents RDT arrangements using modular straight shanks with suitable machine interfaces, including CAT, BT & SK steep-taper configurations. HSK arrangements are also documented for RDT25.

The machine spindle therefore belongs near the top of the checklist.

Before ordering, identify the machining centre, spindle interface & complete connection between machine & tapping attachment.

Don't build the setup around the letters “RDT” alone.

Where Does an RDT Tapmatic Setup Make Sense?

Multi-Hole Production Components

A machined plate containing a repeated pattern of M4, M5 or M6 threaded holes is a natural example.

As the number of holes increases, repeated tapping cycles become a larger part of total machining time.

A self-reversing attachment is designed specifically around that repetitive environment.

CNC Brackets & Housings

Machined brackets, housings, covers & equipment components frequently combine drilled features with internal threads.

The RDT attachment enters after the correct tapping hole has already been produced.

For that upstream operation,  Drill Accessories provides a relevant connection to supporting drilling tooling.

Repeated Small-Thread Tapping

RDT25's M2–M6 capacity in steel places it in a defined small-thread range.

That makes it relevant for repeated smaller threaded features on compatible CNC equipment rather than positioning it as a universal tapping head for every diameter.

Mixed Production Runs

A workshop might run M4 threads on one component followed by M6 threads on another.

Thread diameter is only one change.

Tap style, collet compatibility, workpiece material, tapping method & machine program still need to match the next operation.

Flexibility comes from understanding the system—not assuming one configuration covers everything.

RDT Tapmatic or Rigid Tapping Holder?

The two systems shouldn't be treated as interchangeable names.

An RDT self-reversing attachment performs tap reversal internally as the machine retracts.

A rigid tapping holder works with a machine capable of rigid tapping & relies on the machine's tapping cycle, including spindle reversal. Sutton's Z100 rigid tapping holders, for example, require machine reversal.

The useful question isn't which system sounds more advanced.

It's which system matches the machine & tapping process being used.

Build the RDT Setup From the Machine Outwards

Identify the Machining Centre

Record the machine model & spindle interface before selecting the complete toolholding arrangement.

Define the Thread Range

Establish the tap sizes the attachment will actually need to run.

Check the Tapping Method

Cutting tap or roll-form tap?

Tapmatic specifies reduced RDT capacity when roll-form taps are used, so tapping method belongs in the selection process.

Match the ER Collet

Confirm the tap shank can be held correctly within the required ER11 arrangement.

Establish Stop-Arm Position

Measure the installation rather than estimating where the machine stop block sits.

Check the Complete Assembly

Machine interface, shank, tapping attachment, stop arm, collet & tap all need to belong to the same setup.

Review the Tapping Cycle

Mechanical compatibility gets the tool into the machine.

The program, tap, prepared hole, workpiece material & cutting conditions still determine how the operation runs.

Every Thread Starts With the Hole Before It

The tapping head can't rescue an incorrectly prepared hole.

Before the RDT attachment enters the component, the tapping hole needs to suit the thread & tap being used.

That means hole diameter matters.

Depth matters.

Blind or through-hole geometry matters.

The tap style matters.

For repeated CNC work, consistency in the pre-drilled feature is part of consistency in the finished thread.

Blind Hole or Through Hole? Plan the Available Depth

A through hole allows the tap to travel beyond the required threaded section where the component geometry permits.

A blind hole doesn't.

That makes depth planning more important.

Before running a blind-hole tapping cycle, account for the drilled depth, required full thread depth, tap geometry & available clearance before the tool reaches the bottom.

Thread depth & drilled-hole depth are not the same measurement.

That difference deserves attention before the cycle starts rather than after the tap reaches the bottom.

Cutting Tap or Roll-Form Tap?

The thread can be produced in fundamentally different ways.

A cutting tap removes material to generate the thread profile.

A roll-form tap displaces material to form it.

For the RDT system, that difference directly affects selection because Tapmatic specifies that attachment capacity must be reduced by 25% when roll-form taps are used.

So if forming taps are part of the production process, don't choose the tapping attachment from nominal thread diameter alone.

Tap type changes the calculation.

Measure the Result, Not Just the Setup

A production tapping process eventually has to produce a component that meets the job requirement.

Dimensions around machined features, hole positions & component geometry may need checking before, during or after machining depending on the work.

For general dimensional checking around workshop machining,  Calipers provide a useful supporting category.

The tapping holder controls one part of the process.

The finished component remains the thing that matters.

Practical RDT Tapmatic Setup Tips

Start with the machine. The attachment needs to integrate with the machining centre before anything else matters.

Confirm the spindle interface. Every connection in a modular toolholding arrangement needs to match.

Check the actual tap range. RDT25 is specified for M2–M6 tapping capacity in steel under its stated operating conditions.

Treat forming taps separately. Tapmatic specifies a 25% reduction in capacity when roll-form taps are used.

Match the ER11 collet correctly. Tap diameter alone doesn't confirm the complete holding arrangement.

Measure the stop-arm requirement. Centre distance is an installation dimension worth checking before ordering.

Prepare the tapping hole correctly. The attachment can't compensate for the wrong pre-drill diameter.

Allow for blind-hole depth. Required thread depth doesn't tell you how deep the complete drilled hole needs to be.

Check machine clearance. Attachment body, stop arm & surrounding machine components need room to operate.

Keep RDT & rigid tapping terminology separate. They achieve tap reversal through different machine/toolholder relationships.