Bolt Holes: Tolerance H7/g6 for precision fit

Component Specifications

Definition

Bolt holes are precisely machined openings in chemical reactor sealing glands designed to accommodate bolts that secure the gland assembly to the reactor flange. These holes ensure uniform clamping force distribution, critical for maintaining hermetic seals under high-pressure and corrosive chemical environments. They are engineered with specific tolerances, thread specifications, and surface finishes to prevent leakage, corrosion, and mechanical failure.

Working Principle

Bolt holes function by providing anchor points for bolts that apply compressive force to the sealing gland, creating a tight seal between reactor components. The holes distribute stress evenly across the gland surface, preventing localized deformation and ensuring the gasket or sealant maintains continuous contact under operational pressures and thermal cycling.

Materials

Typically made from corrosion-resistant alloys such as 316L stainless steel, Hastelloy, or titanium, with hardness ratings of HRC 30-40. Surface treatments may include passivation, plating, or coatings like PTFE for enhanced chemical resistance.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Count	4 to 24 holes per gland (depending on reactor size)
Depth	1.5D to 2.5D (where D is bolt diameter)
Pattern	Circular or rectangular bolt circle (PCD)
Tolerance	H7/g6 for precision fit
Thread Pitch	1.75 mm to 4 mm (metric coarse/fine)
Hole Diameter	M12 to M36 (metric) or 1/2" to 1-1/2" (imperial)
Surface Finish	Ra 1.6 μm max

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 898-1, DIN 931, ASME B16.5, ISO 3506

Engineering Analysis

Risks & Mitigation

Stress corrosion cracking
Thread galling
Improper torque application
Misalignment during assembly
Chemical leakage

FMEA Triads

Trigger: Incorrect torque during bolt installation
Failure: Uneven clamping force leading to seal failure and leakage
Mitigation: Use calibrated torque wrenches and follow manufacturer's torque sequence; implement torque audits.

Trigger: Exposure to chlorides or acids
Failure: Pitting or crevice corrosion in bolt holes
Mitigation: Specify corrosion-resistant alloys (e.g., super austenitic steels) and apply protective coatings; regular inspection and cleaning.

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

±0.05 mm for hole diameter, ±0.1° for angular alignment

Test Method

Dye penetrant testing (PT) for crack detection, ultrasonic testing (UT) for wall thickness, and go/no-go gauges for thread verification.

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Bolt Holes

1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

HLC Metal Parts Ltd

Dongguan, Guangdong, CN

IATF16949 ISO13485

Also makes: CNC Machined Part, Plastic Injection Molded Part, Finishing Assembly and 4 more

Listed on the company's own website · profile compiled by CNFX from public sources

Listed there as: “Metal Flange With Bolt Holes”
View source page ↗ hlc-metalparts.com · checked 2026-08-26

View profile Send enquiry

Manufacturer listings support early research and capability understanding. They are not certification, ranking, or transaction guarantees.

Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

What are the common causes of bolt hole failure in chemical reactors?

Common failures include stress corrosion cracking from chemical exposure, thread stripping due to over-torquing, galvanic corrosion from dissimilar metals, and fatigue from thermal cycling or vibration.

How do you select the right material for bolt holes in corrosive environments?

Material selection depends on the chemical media, temperature, and pressure. For highly corrosive environments, alloys like Hastelloy C-276 or duplex stainless steels are preferred, often with protective coatings or non-metallic inserts.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Bolt Holes