Diamond Burnishing Tools

Diamond burnishing is a single-point cold-working surface-finishing process in which a synthetic diamond tip is pressed against a rotating workpiece on a lathe, plastically deforming the surface peaks into the valleys of the machined finish to produce a smooth, dense, mirror-like surface.

Unlike grinding or honing which remove material, burnishing does not cut it displaces and consolidates the surface layer, closing machining marks and producing a work-hardened, compressively-stressed surface with improved wear resistance and fatigue strength.

Because the diamond tip is a single contact point rather than a roller line, it can follow curved, tapered and spherical profiles that a roller burnishing tool cannot, making it ideal for contoured and precision components.

Diamond burnishing produces surface finishes in the sub-micron Ra range (often well below 0.1 µm Ra) giving a true mirror finish without the time, cost and mess of grinding or lapping.

It also work-hardens the surface layer, producing a compressive residual stress that improves fatigue strength and wear resistance which is why it is used on hydraulic shafts, valve spindles and sealing surfaces.

The process is fast (a single pass after machining), clean (no chips, no coolant contamination) and economical (one tool finishes many parts).

It also improves dimensional control, since the burnishing pass can size and finish a feature in one operation and the single-point diamond can reach into profiles and features that a roller cannot.

Integi diamond burnishing tools can be used on workpieces made of a wide range of materials with hardness up to 63 HRC.

This covers most steels (including hardened steels up to around 63 HRC), stainless steels, cast irons, non-ferrous metals and many alloys.

The diamond tip is extremely hard and wear-resistant, so it can burnish materials that would rapidly wear a conventional carbide or steel roller.

The process works on both ferrous and non-ferrous materials although the degree of surface improvement depends on the material's ductility and hardness: softer, more ductile materials burnish more readily and produce the finest finishes, while harder materials require higher pressure and may benefit from a coarser starting finish.

If you are unsure whether your material is suitable, our engineers can advise.

The Integi diamond burnishing tool holders are designed for use on CNC lathes and turning centres.

They mount in the lathe turret or toolpost in the same way as a turning tool and the burnishing pass is programmed as a standard finishing feed move (the diamond tip is fed along the profile of the rotating workpiece under spring pressure).

The HBED series is specifically designed for sliding head (Swiss-type) lathes with a compact, straight body suited to the limited tool space on these machines.

The other holders (HBMD, HBCD, HBUD, HBSD) are suited to conventional CNC lathes and turning centres.

Burnishing can be incorporated into the same setup as the machining operation, so the part is finished complete without being moved between machines.

The straight holders (HBCD, HBMD & HBED) present the diamond tip in line with the shank, making them suited to burnishing external diameters and straight or gently-curved profiles where the tool can approach along the workpiece axis.

The HBCD has the tip aligned with the centre of the shank, the HBMD has the tip aligned with the top face of the shank and the HBED is a Swiss-type version with adjustable pressure.

The angled holders (HBSD30, HBSD45, HBSD60) have the head set at 30, 45 or 60 degrees allowing the tool to reach under shoulders, into recesses and onto angled faces where a straight holder would foul the workpiece or holder.

The choice depends on the geometry of the feature being burnished (straight holders for open profiles, angled holders for features with restricted access).

These three straight holders differ in the position of the diamond tip relative to the shank and in the pressure-adjustment system:

• The HBCD has the diamond tip aligned with the centre of the shank, which gives a balanced approach for general work

• The HBMD has the tip aligned with the top face of the shank, which can be advantageous when burning profiles where the tip needs to sit at the top of the workpiece

• The HBED is specifically designed for sliding head (Swiss) lathes, with the tip aligned with the top face and an externally adjustable pressure head, allowing the operator to set the burnishing pressure to suit the material and required finish.

All three use an internal spring system to regulate tip pressure and can be used on materials up to 63 HRC.

The HBUD-P & HBUD-G holders feature a rotating head that allows the diamond tip to be presented to the workpiece at a range of angles, making them the most versatile holders in the range.

The rotating head allows a single tool to burnish straight diameters, tapers, radii and complex contoured profiles by simply re-orienting the head (the tip can be set to follow the profile rather than being constrained to a fixed angle).

The HBUD-P uses a plain rotating head, while the HBUD-G has a graduated scale on the head, allowing the angle to be set precisely and repeatably, which is valuable for production work where the same setting must be reproduced across batches.

Both are suited to complex or mixed-profile work on CNC lathes.

A key feature of all the Integi diamond burnishing holders is the ability to place the diamond tip in different positions on the head. Because the diamond tip wears gradually with use, re-positioning it allows a fresh area of the diamond to be presented to the workpiece, extending the usable life of the tip many times over (a single diamond tip can be rotated or re-positioned to expose a fresh cutting contact, dramatically reducing the cost per part compared with a fixed-position tip).

On the rotating-head holders (HBUD-P & HBUD-G) the head itself rotates and on the indexable holders (HBSD) the tip is indexable.

This re-positioning, combined with the extreme hardness and wear resistance of the diamond gives the tools a long and economical service life.

All the Integi diamond burnishing holders use an internal spring system to regulate the pressure of the diamond tip against the workpiece. The spring maintains a constant, controlled force on the tip as it follows the profile, which is essential for producing a uniform finish because without spring compensation, any variation in the workpiece profile or setup would translate directly into pressure variation and an inconsistent finish.

The spring makes the pressure homogeneous across all parts of the profile, so tapers, radii and curved features are burnished with the same force as straight diameters.

On the HBED series (for Swiss lathes) the pressure is externally adjustable, allowing the operator to set the force to suit the material and required finish.

On the HBSD angled holders the head is supported by a preload spring system for constant pressure.

On the angled HBSD30, HBSD45 & HBSD60 holders the diamond tip is not included and must be ordered separately because this allows the user to select the tip grade and radius to suit the application, and to replace the tip independently of the holder when it wears.

On the straight holders (HBCD, HBMD, HBED) and the rotating-head holders (HBUD-P, HBUD-G), the tip arrangement should be confirmed on the product page or with our team at the point of ordering.

Because the tips are re-positionable and indexable they have a long working life and replacement tips are available as a wearing consumable.

Our team can advise on the correct tip grade, radius and replacement schedule for your application.

Diamond burnishing produces surface finishes well below 0.1 µm Ra which is typically in the 0.02–0.08 µm Ra range and is a true mirror finish readable as a reflective surface.

The exact finish achieved depends on the starting finish of the machined surface (burnishing improves the finish but cannot recover a heavily torn or built-up surface), the material, the burnishing pressure, the feed rate and the diamond tip radius.

A good general rule is that burnishing will reduce the Ra by a factor of around 3-5 from the starting machined finish, so a part turned to 0.4 µm Ra can be burnished to around 0.08-0.12 µm Ra. Finer starting finishes, higher pressure and finer feeds produce the best results.

Our engineers can advise on the realistic finish for your material and process.

All the Integi diamond burnishing holders on this page are rated for use on workpieces with hardness up to 63 HRC. This is a high hardness (equivalent to a hardened steel such as bearing steel or a hardened tool steel) and reflects the ability of the diamond tip to deform hard materials that would wear a conventional roller or tip.

Above 63 HRC, the material becomes less ductile and the burnishing process is less effective, as the surface cannot be plastically deformed without cracking.

For materials harder than 63 HRC, grinding or superfinishing is generally the preferred route.

If your material is at or near this hardness limit, our engineers can advise on whether burnishing is suitable and what results to expect.

Selecting the correct holder requires knowing the:

• Machine (Swiss/sliding-head or conventional CNC lathe)

• Workpiece profile (straight, angled, complex or contoured), the access available (open or restricted by shoulders and recesses)

• Material and its hardness (must be within 63 HRC)

• Required surface finish and the production volume.

For straight open profiles on a conventional lathe the HBCD or HBMD is the starting point; for Swiss lathes, the HBED; for restricted access at an angle, the HBSD30/45/60; for mixed and contoured profiles, the HBUD-P or the HBUD-G with graduated scale.

The diamond tip grade and radius are then chosen to suit the material and finish.

Our engineers can guide you through this selection.

Yes. Our team includes time-served engineers who can help you select the correct Integi diamond burnishing holder and tip for your application. Whether that's choosing between straight, angled and rotating-head holders, selecting the right tip radius and grade for your material and target finish, specifying the correct pressure setting or integrating burnishing into an existing CNC turning process.

We can advise on achievable surface finish, the suitability of your material (up to 63 HRC) and the best holder for Swiss versus conventional lathes.

You can reach us by phone, online chat or email and we will be happy to help you specify the correct diamond burnishing tooling for your job.