CNC Machined Trunnion Blocks, Reviewed Before Production

Fixed Pivot Blocks

Fixed blocks locate a shaft or pin at one defined centerline for fixtures, hinges, and indexed tooling. Provide bore size, datum scheme, mounting-hole pattern, and allowable positional error.

Adjustable Pivot Blocks

Adjustable blocks use slots, shims, or eccentric features to set alignment during assembly. Specify adjustment travel, locking method, preload condition, and the final inspection position.

Single And Dual Pivots

Single-pivot forms suit one-sided supports; dual-pivot layouts control a rotating member at two interfaces. Define center-to-center distance, coaxiality requirement, shaft retention, and applied load direction.

Clevis And Bearing Blocks

Clevis blocks capture a mating lug between two ears, while bearing-supported blocks add a controlled rotating interface. Show pin fit, ear spacing, bearing designation, lubrication provisions, and assembly access.

Tooling And Mold Blocks

Tooling or mold blocks often combine pivots with locating faces, guide features, or clearance pockets. Supply the assembly model, critical datums, hardened-component interfaces, and revision-controlled mating dimensions.

Load And Bearing Interfaces

4140-type alloy steel supports higher-load shafts when hardness and final-grinding allowance are specified. Confirm heat-treatment distortion before holding bearing-bore geometry.

6061-T6 reduces weight and machining cost for lighter structures. Repeated bearing loads may require a sleeve or insert to limit fretting.

Environment And Wear

304/316 stainless addresses corrosive exposure, although galling against a mating shaft needs review. Finish and lubricant selection matter at sliding interfaces.

Tool steel suits wear-critical features after controlled hardening and grinding. Engineering plastics fit light-duty or chemical-service duties, not highly loaded bearing seats.

Critical Machined Features

Critical bores, dowel holes, keyways, slots, threads, and reliefs need datums and individual tolerances. Define whether hole size, true position, thread engagement, or burr condition governs the mating assembly.

• Mark critical bores and dowel holes
• State thread class and engagement depth
• Define relief geometry and tool access

Finish Is A Dimensional Change

Coatings, anodizing, black oxide, plating, and passivation serve different functional purposes. Finish thickness can reduce bore clearance, alter thread fit, or change a locating face, so mask or machine critical interfaces afterward when required.

• State finish type and applicable surfaces
• Identify masked bores, threads, and datum faces
• Specify edge-break condition before treatment

Marking And Final Verification

Part marking and engraving support identification but should not substitute for revision control. Request post-treatment inspection for affected dimensions and confirm that cosmetic acceptance criteria do not conflict with assembly-fit requirements.

• Define marking location and content
• Inspect treated critical dimensions
• Record revision on order documentation

Datum And Geometric Control

Datum A should be the mounting face; datums B and C should locate the primary bore and side face.

0.01 mm may be meaningful only when perpendicularity, parallelism, flatness, and bore position are tied to stated datums.

Bores, Threads, And Edges

100% of functional bores should specify size, position, and concentricity where rotating or mating shafts depend on them.

2D drawings should state thread standard, class, engagement depth, entry chamfer, burr limits, and surface-roughness requirements.

Inspection And Mating Fit

First-article reports should identify the drawing revision, measured datums, instruments, and actual critical-dimension results.

CMMs verify positional relationships; pin gauges, bore gauges, and height gauges support feature-specific checks. Heat-treatment distortion and mating-part fit require agreed inspection timing and representative mating evidence.

Review DFM Evidence

A written DFM response should identify datums, critical features, tool access, workholding, and proposed setup count. Ask how tolerances, burr control, and distortion risk will be managed.

A marked-up drawing should distinguish questions from approved changes. Require revision-controlled closure before machining begins.

Verify Process And Inspection

A process route should name CNC milling or turning plus needed grinding, EDM, heat treatment, or finishing. Request confirmation that each operation suits the specified material and geometry.

A first-article plan should link every critical dimension to an inspection method. Ask for sample reports, material certificates, gauge status, and traceability format.

Assess Program Control

A prototype quantity should be quoted with the same revision discipline expected for low-volume repeats. Confirm the contact owner, response path, milestone updates, and escalation route.

A packing plan should protect datum surfaces and identify each part, revision, and quantity. Request documentation retention, deviation approval, and formal change-control records.

Define Functional Datums

Three datum references should establish the locating faces, pivot axis, and mounting relationship. Ambiguous datums permit a technically conforming part that misaligns in assembly; identify primary, secondary, and tertiary datums on the drawing.

Complete Material And Finish

One material callout must state grade, supply condition, heat treatment, and hardness when applicable. Missing condition can change machinability and stability; state whether coating, anodize, or plating dimensions apply before or after finish buildup.

Prioritize Critical Bores

Two bores with different mating functions should not receive identical controls by default. Classify each bore by fit, positional requirement, and inspection method, then provide mating-pin or bearing information where function depends on it.

Specify Evidence And Value

One inspection plan should name critical dimensions, sampling expectations, report format, and revision identifier. Selecting solely on piece price can omit setup control and records; compare quotations against the same drawing revision, process route, and deliverables.

Release The Technical Package

Step 1: issue the revision-controlled 2D drawing, native or neutral 3D model, material specification, quantity, and application context. Identify datums, CTQ dimensions, threads, mating interfaces, surface requirements, and heat-treatment sequence.

Close The DFM Review

Step 2: review tool access, workholding, machining allowance, EDM or grinding needs, and inspection method before quotation. Design, manufacturing, and quality stakeholders should sign off deviations, assumptions, and the proposed process route.

Approve First Article Evidence

Step 3: compare quotations by scope, exclusions, lead time, inspection deliverables, and revision basis—not unit price alone. Approve a prototype or first article against the drawing, material evidence, and agreed dimensional report before production release.

Control Production Changes

Step 4: approve packaging protection for finished faces, bores, and identified sets before shipment. Maintain a change log; any drawing, process, material, or acceptance-criteria revision requires customer and supplier confirmation before the next lot.