Stanley Black & Decker MB656 Tool Failure Covered Under Warranty, Internal Material Flaw

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PROPER USE & CARE OF TOOL BITS

TOOL FAILURE COVERED UNDER WARRANTY

INTERNAL MATERIAL FLAW

This failure occurs when a foreign material is rolled into the steel during the manufacturing process, causing an imperfection in the internal material flaw grain. The re- sult is an inherent weakness in the tool shank and even- tual breakage.

The fatigue failure is started by the defects within the tool bit. The broken surface exhibits a shell pattern around the starting point of failure, like that in the fatigue failure. The other parts of the broken surface are brittle.

This is the only kind of tool bit failure that is always covered under warranty.

Figure 25. Internal Material Flaw

As a rule, working steel failures can be diagnosed by looking at the break itself, and at the place on the steel where the break occurred. Discoloration, like “rainbow” effects or blue bands, is the result of extreme heat.

Look for surface cracks, galling, or gouge marks. Breaks that start as surface damage have a “sea shell” pattern, with the damaged spot at the center. A large “sea shell” indicates a slow growing break; a small one indicates one compounded by side stress.

Stress failures start small, and spread into the center of the steel. In a stress failure, the coarser the grain, the greater the stress was, and the more rapid was the failure.

•Failures in this area are usually the result of blank firing, worn bushing(s), worn re- tainer pin(s) or the lack of lubrication.

•Failures in this area are usually the result of worn retainer pin(s) or blank firing.

•Failures in this area are usually the result of prying, metal-to-metal contact or corro- sion. Prying failures often exhibit a shell- like formation near the edge of the steel diameter where the break began, and a “tail” opposite that where the remaining steel bent and tore.

•Failures in this area are usually the result of heat build-up, mushrooming, or improp- er contact with the work.

Figure 26. Diagram of Tool Bit Failures

22 ► MB656 User Manual

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Contents MB656 Declaration of Conformity Weisbeck, AndyTable of Contents Safety Symbols Local Safety RegulationsSafety Precautions Be Thoroughly Trained Before Operating the Unit Alone Obey Safety RulesKnow the Work Conditions Parking Brake 66219 Guaranteed Sound Power Level Sticker Tool Stickers & TagsPRE-OPERATION Procedures PRE-INSTALLATION InstructionsOperation Preparation for USE Operating a BreakerLong Term Storage Positioning the CarrierPositioning the Breaker Tool on the Work Material BackhoesMaintain Down Pressure BreakingBlank Firing Underwater Usage Grease the BITTroubleshooting Problem Cause SolutionDaily Maintenance Checks MaintenanceTool Stop and Lower Bushing Charging the Accumulator NormalFlow Control KIT Instructions Hose RoutingsTool Stop Item Wear TolerancesLower Bushing Item Retainer PIN ItemProper USE & Care of Tool Bits Tool Failure not Covered Under WarrantyWORN-OUT Front Bushings or Retainer Pins Blank Firing or Free RunningPrying CorrosionTool Failure Covered Under Warranty Internal Material FlawChisel MoilBlunt Flow Test Procedures Test ProcedureTroubleshooting Heat Load TestDefinitions ToolSpecifications Dimensions and WeightsAccessories MiscellaneousMB656 Power Cell Illustration Housing Parts Illustration MB656 Parts List Charge Valve Assy InclMB656 Mounting Brackets Page Stanley Hydraulic Tools SE Naef Road Milwaukie, Oregon
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