# Expanding mandrels

Internal-bore workholding, expanding sleeve designs, axial location, diameter ranges, runout, and product-specific force and speed limits.

Reviewed: 2026-11-02

Tags: tooling, workholding, mandrels, internal-clamping

Royal's model A sleeve expands **0.020 inch diametrally (0.508 mm)**, equivalent to **0.254 mm** radial movement under ideal concentric expansion. It cannot span a hypothetical **0.60 mm** bore variation. RÖHM separately lists **20–28 mm** clamping coverage and **1.3 mm** diametral expansion for ABSIS 00. To choose a sleeve, check its individual diameter interval, loading clearance and axial seating. [Royal CNC I.D. workholding](https://royalproducts.com/product-line/royal-id-workholding/royal-cnc-i-d-workholding/), [RÖHM mandrels catalog, edition 8.2, printed p. 7036/PDF p. 38](https://www.roehm.biz/fileadmin/user_upload/produkte/PG7_Spanndorne_Spannzangenfutter/2025_04/2503_04_E_Mandrels_and_Collet_chucks_web_En.pdf#page=38).

Use [Choosing workholding](../workholding-and-fixtures.md) to compare location, support and restraint across fixture types.

## Identity and locating surfaces

A mandrel grips the workpiece from inside its bore, leaving its exterior accessible. [RÖHM cartridge mandrels](https://www.roehm.biz/en/products/mandrels-collet-chucks/cartridge-mandrels-force-actuated/).

Drewco distinguishes expanding collet arbors from solid arbors ground to a clearance fit. [Drewco arbors and mandrels](https://drewco.com/custom-products/arbors-and-mandrels/).

## Mechanisms and actuation

| Design | Mechanism in the cited example | Distinction |
| --- | --- | --- |
| Solid arbor | Drewco's ground shaft fits the workpiece bore | Clearance-fit location rather than sleeve expansion |
| Slotted cartridge sleeve | RÖHM expands a double-slotted sleeve through a clamping taper | Mechanical conversion of actuation into radial expansion |
| Segmented bushing | HAINBUCH uses hardened steel segments joined by vulcanization | Separate rigid segments, rather than a continuous spring-steel sleeve |
| Hydrostatic expansion | Mongtec uses internal fluid pressure to deform an expansion element elastically | Fluid-driven deformation of the clamping element |

Check the actuator and expanding element separately. [Drewco](https://drewco.com/custom-products/arbors-and-mandrels/), [RÖHM](https://www.roehm.biz/en/products/mandrels-collet-chucks/cartridge-mandrels-force-actuated/), [HAINBUCH MANDO](https://www.hainbuch.com/en/products/mandrels/mandrel-mando/), [Mongtec](https://www.mongtec-tools.com/en-US/p343-expanding-mandrels).

## Expansion range versus family coverage

A wide diameter range across bodies and interchangeable sleeves is different from the movement of one sleeve. Royal's CNC I.D. system lists 0.032 inch expansion for its general sleeve range and 0.020 inch for model A. Its double-angle design expands the sleeve parallel to the bore for full-length contact; these statements apply to that system. [Royal CNC I.D. workholding](https://royalproducts.com/product-line/royal-id-workholding/royal-cnc-i-d-workholding/).

For an original conversion, `0.020 × 25.4 = 0.508 mm` diametral expansion corresponds to `0.508 / 2 = 0.254 mm` radial movement in an ideal concentric expansion. A hypothetical 0.60 mm bore spread exceeds that 0.508 mm interval by 0.092 mm. This comparison does not locate the usable interval around a nominal sleeve size or establish sufficient loading clearance and gripping force. [Royal model-A range](https://royalproducts.com/product-line/royal-id-workholding/royal-cnc-i-d-workholding/).

RÖHM's ABSIS 00 table separately lists 20–28 mm clamping coverage and 1.3 mm diametral expansion. The 8 mm span is consequently not one sleeve's expansion stroke. [RÖHM mandrels catalog, edition 8.2, printed p. 7036/PDF p. 38](https://www.roehm.biz/fileadmin/user_upload/produkte/PG7_Spanndorne_Spannzangenfutter/2025_04/2503_04_E_Mandrels_and_Collet_chucks_web_En.pdf#page=38).

## Axial seating and runout

HAINBUCH distinguishes MANDO T211 and T212 pull-back designs from T812 deadlength clamping. The former stabilize the workpiece by drawing it against an end stop; T812 clamps radially without pulling back against that stop. T212 and T812 omit the draw bolt, supporting blind-bore applications. These differences matter when a part face must seat axially or remain at an existing axial position. [HAINBUCH MANDO comparison](https://www.hainbuch.com/fileadmin/Mediendatenbank/English/Other/Comparison_page/MANDO_segmented_mandrels_at_a_glance.pdf).

Royal guarantees system runout of 0.0005 inch TIR or better, equivalent to 12.7 µm. That is a manufacturer's system statement, not a finished-part concentricity tolerance or a guarantee for an arbitrary bore, mounting, or cutting load. TIR is total indicated runout. [Royal](https://royalproducts.com/product-line/royal-id-workholding/royal-cnc-i-d-workholding/).

As an engineering implication, locating on a bore makes that bore's geometry and relation to the intended machining datum consequential. Bore roundness, contact length, stop-face condition, and the mounted assembly can affect the result. A mandrel's catalog accuracy does not establish the relationship between an existing bore and an unrelated design datum.

## Contact, thin walls, and torque

RÖHM identifies KFS cartridge mandrels for thin-walled and long workpieces, while distinguishing KFR designs without axial tightening. This is a product/application distinction, not proof that internal expansion cannot distort a thin wall. [RÖHM cartridge mandrels](https://www.roehm.biz/en/products/mandrels-collet-chucks/cartridge-mandrels-force-actuated/).

HAINBUCH's forming-mandrel troubleshooting identifies a workpiece-form error caused by elastic deformation of imperfect stock: after machining, the released part returns toward its original form. The example concerns that clamping product, but explains why accuracy while clamped and accuracy after release are separate questions. It supplies no universal permissible pressure for thin walls. [HAINBUCH forming-mandrel manual, printed p. 36](https://www.hainbuch.com/fileadmin/Mediendatenbank/English/Service/Downloads/Installation-manuals/Mandrels/HAINBUCH-Forming-mandrel-Installation-manual.pdf#page=36).

A simple friction model illustrates the torque distinction. Assume total normal contact force `N = 4,000 N`, coefficient of friction `μ = 0.10`, and contact radius `r = 0.020 m`. The ideal friction torque is `T = μNr = 8 N·m`. This original model assumes uniform effective radius, stable contact, and no competing axial load. It is not a mandrel rating: lubrication, bore form, sleeve contact, axial cutting force, and dynamic loading can change the available margin.

## Product-specific force and speed

RÖHM's catalog lists these ABSIS limits. Actuation force is the input to the mechanism; total clamping force is its stated output, not a torque rating. [RÖHM, printed p. 7036](https://www.roehm.biz/fileadmin/user_upload/produkte/PG7_Spanndorne_Spannzangenfutter/2025_04/2503_04_E_Mandrels_and_Collet_chucks_web_En.pdf#page=38).

| ABSIS size | Maximum actuation force | Maximum total clamping force | Maximum speed |
| --- | --- | --- | --- |
| 00 | 7 kN | 32 kN | 5,000 rpm |
| 04 | 30 kN | 138 kN | 3,500 rpm |

These are limits for named mandrels, not a universal safe operating point or proof that every combination of maximum force, speed, workpiece mass, and overhang is permitted. A family name or sleeve bore alone does not specify the complete rotating assembly.

## Source dates and coverage

The RÖHM catalog identifies edition 8.2 and back-cover ID 1178267 / 2025. The July 2024 date elsewhere in that document labels its terms and conditions, not the technical tables. The other cited product pages, HAINBUCH comparison, and forming-mandrel manual do not establish technical issue dates in the inspected material. The article's reviewed date records research review.

This reference does not establish a universal expansion percentage, bore tolerance, contact pressure, torque capacity, speed, or workpiece deformation limit. Those remain specific to the mandrel, sleeve, bore geometry, axial restraint, machine interface, and machining load. A family catalog range does not establish a shop's installed components or approved process settings.

For broader context, see [Workholding and fixture references](index.md).