Tool Reconditioning and Diamond Recovery

A worn tool is not always a finished tool

When a diamond tool stops cutting well, the instinct is to discard it. In many cases that wastes value. A tool body, a diamond layer or the diamond itself may still be usable. Reconditioning is the set of practices for restoring a tool to service, and recovery is the set of practices for reclaiming material from tools that cannot be restored.

Which route applies depends on the construction of the tool, how it wore, and whether the work of restoring it costs less than a new one. The figures vary by tool and supplier, so this article describes the options and the questions to ask.

Route 1: Regrinding and resharpening

Many tools with a solid diamond edge, such as polycrystalline diamond inserts and brazed tips, can be reground when the edge dulls. A shop removes a small amount of material to produce a fresh, sharp edge. Each regrind makes the tool a bit smaller or shorter, so the number of possible cycles is limited by how much usable material remains.

Points worth knowing:

• The edge geometry has to be maintained; a poorly reground edge can perform worse than a worn original.
• Regrinding hard compacts is itself done with diamond tools or specialized processes such as electrical discharge machining, which adds cost.
• The diamond layer must be thick enough to sacrifice some material. Thin layers may have only one regrind in them.
• Tools that are chipped deeply may need substantial removal, which may not be worth it.

Route 2: Stripping and recoating

Diamond-coated tools, such as solid carbide end mills with a thin film, are usually not reground in the same way, since the coating is part of the surface. A common route is to strip the worn coating, inspect and clean the substrate, and apply a new coating by chemical vapor deposition.

Considerations include:

• Substrate condition. The base must still be within tolerance. Each stripping step can remove a little material, change the edge radius or leave surface damage.
• Surface preparation. Good bonding depends on cleaning and treating the surface, a topic covered under coating adhesion.
• Edge geometry. The edge may need re-honing before recoating so that performance matches that of a new tool.
• Dimensions. Because coatings add thickness, the recoated tool needs to meet the dimensions the process expects.

Not every supplier offers recoating, and not every tool design suits it. Some tools are made so that stripping and recoating is practical, while others are treated as disposable.

Route 3: Re-tipping and refurbishing assemblies

For tools with a replaceable or brazed diamond element, such as some saw segments or drill bodies, the steel body can be reused and new diamond-bearing elements attached. This can be an economical choice when the body is costly to make and has not worn.

Grinding wheels have a related practice. Rather than reconditioning the diamond layer itself, operators use wheel dressing to expose fresh diamond and restore the wheel’s cutting action, which extends life without sending it to a shop. The design of the bond types affects how a wheel behaves during this.

Route 4: Diamond recovery and recycling

When a tool cannot be restored, the diamond or the carrier material may still have value. Recovery may include:

1. Reclaiming the carbide or steel body for scrap or reprocessing. Cemented carbide scrap is commonly recycled because tungsten is a valuable raw material.
2. Recovering diamond grit from spent segments or wheels by dissolving or breaking down the bond.
3. Reusing recovered grit in lower-demand applications, such as polishing or lapping, if it is still intact enough.
4. Reprocessing worn grit and compacts into feedstock for other products or crushing for use as fine abrasive powder.

Recovered diamond is usually worth less than new material, because grit that has been used often has fractured or been contaminated by bond material, and sorting it takes effort, as the process described under grit grading shows. Recovery rates and recycling arrangements vary between suppliers and regions.

Inspecting before deciding

Before sending a tool for reconditioning, a basic inspection helps avoid wasted spend:

• Look for cracks in the body, a worn-through coating, or broken diamond layers.
• Check whether the substrate is bent or has changed dimensions.
• Review why the tool was retired. Gradual wear is a good candidate. Overheating, impact damage or chemical attack may mean the substrate is compromised.
• Consider a more formal failure analysis if the tool failed earlier than expected, since restoring a tool that failed for a process reason may only repeat the problem.

Weighing the economics

A simple comparison helps. Add the reconditioning price, shipping and downtime while the tool is away, and divide by the expected remaining life. Compare that with the same calculation for a new tool. Reconditioning wins when:

• the tool body is expensive relative to the cutting layer,
• reconditioned performance is close to new,
• the number of possible cycles is high,
• turnaround is short enough that a spare set can cover the gap.

It is less attractive when the tool is cheap, when quality demands are very tight, or when the process cannot tolerate small variation between regrinds. These considerations feed into the broader lifetime view in the article on total cost of ownership.

Practical habits

Facilities that reuse tools well tend to track each tool by serial number, record its history of regrinds and recoats, and set a maximum number of cycles. They also keep the retired-tool data to see which uses wear tools badly. Such records turn reconditioning from an afterthought into a controlled part of tooling management.

Reconditioning does not remove the need to buy new tools, and not every tool is a candidate. But used carefully it spreads the initial cost of diamond tooling across more parts and reduces waste of both materials and manufacturing effort.