Case Study: Solve Carbide Small Bore Scratches with Resin Diamond Mounted Points

Precision internal grinding of cemented carbide components faces a widespread industry challenge: the identical resin diamond internal grinding wheel delivers perfect surface finish, high yield rate and long service life for large-bore workpieces, yet generates regular inner wall scratches and sharply rises rejection rates once switched to small-bore parts. Most manufacturers immediately suspect defective grinding wheels and replace them repeatedly without resolving production bottlenecks. Combined with real mass-production service cases from Moresuperhard, this article analyzes the root causes of scratches exclusive to small bores, and elaborates on the core advantages and matching selection standards of customized Moresuperhard resin diamond grinding heads and internal grinding wheels, providing implementable process solutions for enterprises engaged in precision internal grinding of cemented carbide and ceramics.

On-site Mass Production Conditions of Client

Basic Machining Parameters

Workpiece material: Cemented carbide tungsten steel inner bore parts
Grinding tool adopted: Moresuperhard D25-T25-H12 600# resin diamond internal grinding wheel; customized integrated resin diamond grinding heads of the same specification are available
No adjustments were made to processing equipment, grinding parameters, workpiece material or coolant formula, only the inner bore dimension of workpieces was changed.

Comparison of Working Conditions

1. 30mm large inner bore workpieces: Stable mass production with qualified mirror surface finish, free of scratches, edge burns and burrs. Moresuperhard resin wheels maintain stable self-sharpening performance and meet mass-production service life standards with zero batch defects.
2. 27mm small inner bore workpieces: Uniform fine scratches emerge on inner walls right after switching product specifications, drastically boosting defective rates. Production lines have to reduce operating speed and shut down frequently for rework, which directly increases production costs and delays delivery schedules.

After comprehensive on-site inspection, Moresuperhard technical engineers confirmed that scratches are not triggered by quality defects of Moresuperhard resin diamond wheels or grinding heads. Instead, they are process matching problems resulting from insufficient chip removal and cooling gaps in the confined grinding space of small bores, a typical drawback of universal wheels applied to both large and small bores.

Two Root Causes of Scratches on Small Bores

Cooling and chip removal in internal grinding fully rely on the gap between the outer surface of the wheel and the workpiece inner bore to circulate cutting fluid. Reducing workpiece bore size will significantly worsen working conditions in two aspects:

1. Narrowed gap drastically weakens chip flushing capacity of coolant

Resin-bonded diamond tools feature inherent self-sharpening performance. Tiny diamond grains fall off naturally during grinding, together with ultra-fine alloy debris generated from cemented carbide processing, which are normal processing phenomena. The ample gap of 30mm bores allows high-pressure cutting fluid to wash away loose particles instantly. In contrast, the narrow flow channel of 27mm bores limits coolant flow and velocity, trapping abrasive grains and metal debris at the grinding contact surface. These particles rotate at high speed with the wheel and scrape the inner bore wall, forming persistent scratch defects.

2. Expanded grinding contact area boosts heat and chip generation

When a fixed-size Moresuperhard resin diamond wheel or grinding head processes smaller inner bores, the contact arc between the wheel and bore wall widens remarkably. Higher material removal per unit time generates far more grinding heat. The narrow cooling and chip removal channel plus accumulated chips and heat create a vicious cycle where scratches and workpiece burns grow worse as processing proceeds.

Two Practical Solutions to Eliminate Small Bore Scratches

Solution 1: Optimize Cooling System (Temporary Relief, No Permanent Fix)

Increase coolant pressure and flow simultaneously, and adjust nozzles to align precisely with grinding contact zones for stronger chip flushing.
On-site test results show scratch defects decrease slightly, yet core contradictions of insufficient gaps remain unresolved due to limitations of original cooling pipelines and pump power. Scratches will recur during mass production, so this method only suits temporary transitional processing.

Solution 2: Custom Special Moresuperhard Resin Diamond Grinding Heads & Wheels Matched to Bore Size (Optimal Long-term Fix)

Based on the 27mm small bore inner diameter, Moresuperhard technical department customizes outer diameter-matched resin diamond internal grinding heads and compact internal grinding wheels. The design moderately widens the cooling and chip removal gap between the grinding tool and workpiece inner wall, optimizes the length of grinding contact arc, and balances heat generation and chip evacuation space.

Implementation effect: Smooth circulation of cutting fluid instantly washes away shed diamond particles and alloy debris, completely eliminating inner wall scratches. Workpiece dimensional accuracy and surface finish recover to stable standards, and the service life of Moresuperhard wheels returns to normal levels, enabling full-speed mass production without defects.

Core Product Advantages of Moresuperhard Resin Diamond Grinding Heads & Internal Grinding Wheels

For precision internal finishing of cemented carbide, ceramics and magnetic materials, Moresuperhard full-series resin diamond tools include integrated shank grinding heads and standard internal grinding wheels. Developed exclusively for small bores, deep holes and mirror precision grinding, they solve common industry pain points of universal wheels: poor adaptability for mixed bore sizes, easy scratching, workpiece burning and short service life.

1. Self-developed controllable self-sharpening formula, burn-free and crack-free finishingMoresuperhard adopts high-retention modified resin bond paired with high-shape diamond micropowder. Abrasive grains shed evenly and minimally without massive peeling. Low heat output and buffering grinding performance make them ideal for low thermal conductivity brittle hard materials such as tungsten steel and cemented carbide, eliminating inner bore microcracks and oxidation burn marks. Stable surface roughness reaches Ra0.02~Ra0.2 mirror standards.
2. One-to-one non-standard customization of full sizes, exclusive matching for large and small boresMoresuperhard accepts custom orders based on drawings, samples and raw materials for resin diamond grinding heads of arbitrary outer diameter, shank diameter, grain size and concentration, covering full processing scenarios of workpieces with 2mm~100mm inner bores. Heavy-duty models for large bores feature reinforced wear-resistant substrates, while dedicated small bore versions optimize outer wall gaps and widen chip removal channels. Custom solutions tailored to single-specification workpieces completely solve the process defect of “one wheel for all bore sizes”.
3. Extra-long service life reduces comprehensive processing costs for enterprisesMoresuperhard selects high-grade diamond abrasives with far higher utilization efficiency than ordinary domestic consumables. Its service life is dozens of times that of regular corundum wheels under equal grinding volume. It effectively cuts losses caused by frequent tool changes, machine dressing and workpiece rejection. Mass processing significantly lowers consumable procurement and manual rework costs, compatible with CNC internal grinders, jig grinders and all types of compact precision grinders.
4. Easy dressing and wide equipment compatibilityMoresuperhard resin substrates are precisely calibrated for hardness. Conventional dressers can quickly flatten surface fatigue abrasive grains, and simple dressing before batch production stabilizes processing conditions. No equipment modification is required; compatible with ordinary water-based cutting fluids on the market. Low grinding dust creates an eco-friendlier production environment.
5. Integrated sintered grinding heads with high concentricity for tiny deep holesMoresuperhard integrated sintered resin diamond grinding heads feature tight bonding between steel shanks and abrasive layers without delamination, delivering zero runout under high-speed rotation. They outperform split wheels in precision finishing of tiny deep holes, stepped holes and special-shaped inner bores. Uniform dimensions across batches minimize dimensional fluctuation during long-term processing.

Extended Process Suggestions for Long-term Mass Production

1. Regular wheel dressing to reduce chip trapping scratches at source

Even with customized Moresuperhard resin diamond grinding heads, fatigue and partially shed abrasive grains will accumulate on the surface after long continuous processing. A simple dressing cycle every 2–4 hours removes unstable grains in advance, preventing mass abrasive shedding that clogs gaps and stabilizing workpiece surface finish.

2. Differentiated Selection Standards by Bore Size

• Workpiece bore ≥30mm large bores: Choose Moresuperhard standard universal resin diamond internal grinding wheels to balance processing efficiency and consumable costs.
• Workpiece bore ＜30mm small/deep bores: Prioritize custom small outer diameter dedicated Moresuperhard resin diamond grinding heads to reserve sufficient cooling and chip removal gaps.
• Mirror precision finishing: Select Moresuperhard 600#~1500# fine-grain diamond tools matched with special cutting fluid for cemented carbide.

3. Optimize Supporting Coolant

Adopt high-settling tungsten steel dedicated cutting fluid for small bore grinding to rapidly precipitate suspended diamond debris and alloy powder, avoiding secondary scratches caused by circulating impurities. Paired with custom Moresuperhard resin grinding heads, the yield improvement effect is doubled.

Full Case Summary & Universal Industry Reference Logic

1. Universal Moresuperhard resin diamond wheels and grinding heads cannot fit all bore sizes. Applying large-bore optimized tools to small bore processing easily triggers batch inner wall scratches.
2. Three core control indicators for small bore internal grinding: gap between grinding tool and workpiece inner bore, cooling & chip removal channel, grinding contact area. When scratches occur, inspect these three factors first instead of blindly suspecting quality issues of Moresuperhard grinding tools and replacing wheels frequently.
3. Optimal permanent solution: Contact Moresuperhard technical team to customize resin diamond grinding heads and internal grinding wheels exclusive to workpiece inner diameter, together with optimized cooling processes, to fully resolve scratches, rejection and production slowdown issues in one go.
4. Moresuperhard resin diamond tools are the preferred consumable for precision internal grinding of cemented carbide. Supported by three core strengths – controllable self-sharpening, low-heat grinding and on-demand customization, they adapt to mass production of multi-specification precision parts. Long-term procurement greatly boosts yield rates and cuts enterprises’ comprehensive production costs.