TAIKI 8″ JAW BORING RING (3900-4654)

Taiki 8″ Soft Jaw Boring Ring for CNC Power Chucks

The Taiki 8-inch soft jaw boring ring provides a controlled way to preload the jaws of a compatible 3-jaw CNC power chuck while machining a workpiece-specific gripping diameter.

Its adjustable front-contact system engages the soft-jaw counterbores, applies balanced pressure across all three jaws and helps compensate for jaw lift. Because the center remains open, the boring tool can pass completely through the jaw profile without interference from an internal disc or plug.

This model is intended for shops using an 8-inch chuck and looking for a faster, more repeatable alternative to searching for a suitable setup piece every time a new set of soft jaws must be prepared.

How Do You Bore Soft Jaws Without Blocking the Center?

A conventional jaw-boring setup may use a disc, plug or scrap component clamped inside the jaws. That method can preload the chuck, but the setup piece occupies the same space the boring bar may need to enter.

The Taiki ring works from the front of the jaws. Its open-center design leaves the internal machining area accessible, allowing the operator to bore through the complete jaw profile when the operation requires it.

This is especially useful for:

• Deep gripping diameters
• Through-bored soft jaws
• Second-operation jaw profiles
• Jaws with an axial locating step and rear clearance
• Workpieces that require greater boring-bar reach

Preload the Jaws in Their Working Position

Chuck jaws move slightly as clamping force is applied. If soft jaws are machined in an unloaded position, their final gripping profile may not represent the position they occupy while holding the actual workpiece.

The boring ring simulates a loaded chuck condition while the jaws are being machined. This helps the operator create the gripping diameter relative to the jaw position used during production.

The preload direction and chuck pressure should match the intended workholding operation as closely as practical. A setup prepared for external clamping may not reproduce the loading condition of an internal expansion-gripping operation.

Compensates for Normal Jaw Lift

Jaw lift occurs when clearance and clamping forces cause the front portion of a jaw to rise or tilt. This movement can affect workpiece seating, bored diameter and concentricity.

By engaging the jaws at their front counterbores, the Taiki ring is designed to account for normal jaw lift during soft-jaw machining.

The ring cannot correct excessive chuck wear, damaged master jaws, contaminated serrations or mechanical problems inside the chuck. Those conditions should be inspected before a precision jaw set is machined.

Equal Loading Across Three Jaws

The ring’s adjustable contacts engage the counterbores of the three soft jaws. When correctly positioned, the system distributes preload across the jaw set instead of depending on an improvised plug with uncertain contact.

Balanced preload can help reduce variation caused by:

• Unequal contact with a makeshift setup piece
• Off-center preload components
• Different loading conditions between jaws
• Repeatedly searching for a suitable disc diameter
• Changes in jaw position after removing the setup piece

Tool-Free Installation for Faster CNC Setups

The ring attaches to the front of the soft jaws without separate installation tools. Once the ring contacts are correctly located in the jaw counterbores, the operator adjusts the ring until snug and actuates the chuck to apply preload.

This tool-free mounting approach is valuable in CNC job shops where soft-jaw preparation is part of the non-cutting setup time assigned to every new order.

Installation Overview

1. Install the soft jaws in their correct numbered positions.
2. Clean the chuck, jaw serrations and counterbores.
3. Place the boring ring over the front of the chuck.
4. Locate each ring contact in the corresponding soft-jaw counterbore.
5. Adjust the ring until all contacts are secure and evenly positioned.
6. Actuate the chuck to apply the required preload.
7. Verify boring-bar, ring, jaw and machine-enclosure clearance.
8. Machine the jaws to the required gripping diameter.
9. Stop the spindle completely before releasing the chuck or touching the ring.
10. Remove the ring, clean the jaws and test the workpiece setup.

Always follow the chuck and machine manufacturers’ safety procedures. A maximum operating RPM is not included in the supplied specifications; use only a safe jaw-machining speed approved for the complete setup.

Why an 8″ Chuck Shop Benefits from a Dedicated Ring

An 8-inch power chuck is common on CNC turning centers used for medium-size components, general job-shop work and second operations. A dedicated ring avoids adapting a tool intended for a larger chuck or repeatedly manufacturing disposable preload plugs.

At 6 lbs, this model remains manageable during setup while providing the working diameter required for compatible 8-inch chuck jaws.

Applications in CNC Production

The Taiki ring can support soft-jaw preparation for:

• Recurring CNC production jobs
• First- and second-operation workholding
• Finish turning pre-machined components
• Dedicated jaw sets for repeat orders
• Thin-wall rings and sleeves
• Flanges, collars and bushings
• Workpieces requiring an axial locating step

Reduce Setup Time in CNC Job Shops

For a short production run, the time spent preparing jaws may represent a significant portion of the total job. A dedicated ring gives the setup machinist a known tool for loading the jaws instead of looking for a suitable plug or machining a temporary disc.

This can be especially useful when:

• The shop changes jobs frequently
• Several operators prepare jaws on the same machine
• The same part returns periodically
• Jaw setups must be documented and reproduced
• Through-boring is required

Second-Operation Workholding

Soft jaws are frequently used when a part must be reversed after the first machining operation. The jaws can be bored close to a finished diameter and machined with a locating step to control axial position.

Correctly preloaded jaws can provide a larger gripping area than standard hard jaws, helping support finished or thin-wall surfaces with less localized pressure.

The workpiece should always be checked for runout and deformation before production begins.

Automotive and Mechanical Repair Applications

For suitably sized components, the ring can help prepare soft jaws for:

• Hubs and pulley components
• Bearing retainers
• Pump and motor parts
• Adapter flanges
• Bushings and repair sleeves
• Previously machined parts requiring rework

The boring ring is a setup tool. It does not determine whether a safety-critical component is suitable for machining or return to service.

Maintenance and Toolroom Use

Maintenance departments frequently handle unique repair parts rather than standardized production runs. A jaw boring ring allows the toolroom to prepare workpiece-specific soft jaws without relying on a correctly sized scrap part.

Potential applications include:

• Machine repair components
• Custom fixture parts
• Hydraulic and pneumatic components
• Replacement collars and spacers
• Obsolete parts that must be reproduced

Reference Dimensions

Use these dimensions together with the manufacturer’s diagram. The letters identify locations on the product drawing and should not be interpreted without that visual reference.

Technical Specifications

What Should You Check Before Buying?

Confirm all of the following:

• The chuck is nominally 8″ in diameter.
• It uses three compatible soft jaws.
• The jaw counterbores can accept the ring contacts.
• The required jaw position falls within the ring’s adjustment range.
• The 8.60″ overall ring dimension fits inside the machine enclosure.
• The boring bar can pass through the required profile.
• The ring does not interfere with tooling, guards or the chuck body.

Frequently Asked Questions

What boring ring fits an 8″ CNC lathe chuck?

The Taiki JB-08 is designed for compatible 8-inch, 3-jaw CNC power chucks. Actual fit depends on jaw-counterbore geometry, jaw position, adjustment range and machine clearance.

Can I bore completely through the soft jaws?

Yes, when the jaw geometry and boring tool permit it. The ring loads the jaws from the front and leaves the central machining area open.

Does it require a disc or plug?

No. The ring’s front-contact design eliminates the need to clamp a disc or bung inside the soft-jaw opening.

Does it eliminate jaw lift?

It is designed to compensate for normal jaw lift during boring. It cannot correct excessive movement caused by chuck wear, damaged master jaws or contamination.

Can it be used for internal-gripping jaws?

The loading direction used while machining the jaws must represent the final workholding direction. Confirm the required preload method before preparing jaws for internal expansion gripping.

Is the chuck included?

No. This product includes the jaw boring ring only. The chuck, soft jaws, boring bar and workpiece are not included.

What is the difference between 3900-4654 and 3900-4668?

The 3900-4654 is a JB-type ring dedicated to an 8-inch chuck. The 3900-4668 is a different adjustable fixture designed for several chuck sizes.

Ready to Stop Making Temporary Jaw-Boring Plugs?

The Taiki JB-08 gives CNC shops a dedicated, reusable method for loading soft jaws while preserving full access through the gripping profile.

Buy with confidence: send SHOP TOOL USA your chuck manufacturer, model, jaw photographs and counterbore measurements. We can help compare the setup before you place the order.

Taiki 5″ jaw boring ring for compact CNC chucks