All-Metal Lock Nuts
Manufacturer
India · Mumbai
Anatomy of an All-Metal Lock Nut — Distortion as the Locking Mechanism
An all-metal lock nut is, in almost every visible respect, an ordinary hex nut — no conical spring face, no serrated rim, no separate feature added to the base the way our K-Lock nuts combine spring tension with mechanical bite. The entire locking mechanism instead lives inside the thread form itself: a short section of the nut’s upper threads — typically the top two or three turns — is deliberately deformed slightly out-of-round (elliptical) or, in a related design, the top of the nut is slotted and the slot pinched fractionally inward, distorting the thread pitch at that specific point.
Because that distorted section is genuinely narrower than the bolt’s thread crest at that point, the bolt cannot simply spin through it — it must forcibly displace the distorted metal as it advances, generating continuous interference friction along the full engagement of the deformed section. This friction is what resists back-rotation from vibration once the nut is torqued down; there is no separate locking feature working alongside the thread the way a spring washer or nylon ring would — the distorted thread section is the entire locking mechanism, machined directly into the nut body during manufacture rather than assembled as an additional part.
DIN 980 covers two primary variants: Type M, where the distortion is formed directly into a solid thread section without any slot, and Type V, where a slot is cut into the top of the nut and the two sides of the slot are pinched slightly together to create the same interference effect through a different forming method. Both are fully metallic, both develop prevailing torque purely from thread interference, and both share the same fundamental reuse limitation covered in detail below.
Why All-Metal Lock Nuts — No Polymer, No Temperature Ceiling
No Polymer Component at Any Point
With the locking function built entirely into the metal thread form, there is nothing in the nut that can soften, melt, swell, or chemically degrade — the same core benefit shared with our K-Lock range, but achieved here through thread geometry alone rather than a combination of spring tension and serration.
Simplest Possible Locking Geometry
Because the lock is a modification to the thread itself rather than an added spring or serrated feature, an all-metal lock nut has no additional moving or flexing part to fatigue or fail independently of the thread engagement — the locking mechanism and the load-bearing thread are, in a real sense, the same feature.
Standard, Widely Recognised DIN 980 Reference
Type M and Type V distorted-thread nuts are manufactured to a long-established, internationally recognised standard, giving procurement teams a straightforward, unambiguous specification reference rather than a proprietary or drawing-specific locking geometry.
Compact — No Added Height or Diameter
Because the distortion is formed within the standard nut body height rather than adding a spring cone or separate collar, all-metal lock nuts occupy essentially the same overall dimensional envelope as a standard hex nut of the same grade — useful where clearance for an added locking feature’s extra height is genuinely limited.
Reuse Degradation — Each Reinstallation Straightens the Distortion Slightly
Every time an all-metal lock nut is threaded onto and off a bolt, the bolt’s own thread crest forces the distorted section back toward round, however slightly — a small, cumulative, largely irreversible straightening with every cycle. The prevailing torque this nut can generate is a direct function of how far out-of-round that section remains; as it straightens, prevailing torque falls, cycle after cycle, until the distortion is no longer sufficient to reliably resist vibration-induced back-rotation.
This reuse degradation is more pronounced for a purely thread-based locking mechanism than for a design combining thread interference with a separate feature — a K-Lock nut’s conical spring section is engineered specifically to return toward its original shape after removal, giving it materially better reuse consistency across multiple installation cycles. An all-metal lock nut’s distorted thread, by contrast, has no separate spring element working to restore its shape; each reuse cycle represents a genuine, largely one-way reduction in remaining locking capacity.
ISO 2320 defines the test methodology for minimum and maximum prevailing torque, including reuse testing across a specified number of installation cycles for a given nut style and property class. Manufacturers typically rate distorted-thread all-metal lock nuts for somewhere in the region of 5 to 15 reuse cycles depending on size and style, after which the nut should be replaced rather than reinstalled — a genuinely different practical guidance point from either a nylon insert nut (single-use is common practice) or a K-Lock nut (typically rated for more consistent multi-cycle reuse due to its spring-return design).
All-Metal Lock Nut vs K-Lock vs Nylon Insert — Family Comparison
Three distinct locking philosophies, each with a specific best-fit operating envelope.
All-Metal Lock Nut (DIN 980)
Thread interference alone, no separate feature. Standard hex nut envelope. Simplest all-metal design, moderate rated reuse count (5–15 cycles typical), well-established DIN reference.
K-Lock Nut
Conical spring face plus serrated rim as a dedicated added feature, working alongside standard thread engagement. Spring geometry gives materially better multi-cycle reuse consistency than pure thread distortion.
Nylon Insert (Nyloc) Nut
A nylon ring insert provides friction-based prevailing torque — simple and low-cost at ambient temperature, but limited by the nylon’s own thermal (~120°C) and chemical compatibility ceiling, unlike either all-metal option on this page.
All-Metal Lock Nut Material & Strength Options
Standard property class convention applies — the distorted-thread locking mechanism performs identically across all grades.
All-Metal Lock Nut Configurations
Both DIN 980 variants across the full grade range, plus matching washers. M5–M36.
Type M All-Metal Lock Nut
Elliptical thread distortion formed directly into a solid thread section, no slot. M5–M36. The most common all-metal lock nut configuration across general high-temperature and vibration-resistant applications.
Type V All-Metal Lock Nut
Slotted top section, pinched slightly inward to create thread interference. M8–M30. An alternative forming method achieving the same distorted-thread locking principle as Type M.
Matching Flat Washers
Plain flat washers matched to all-metal lock nut thread size and grade for applications requiring additional bearing area distribution beyond the nut’s own contact face.
Custom All-Metal Lock Nuts
Non-standard sizes, inch UNC/UNF thread, and drawing-specific configurations in any available material grade. Contact sales@akbarfasteners.in with thread size, grade, and quantity.
All-Metal vs K-Lock vs Nyloc — Side by Side
A direct feature comparison across the three most common vibration-resistant nut categories in our range.
| Criterion | All-Metal (DIN 980) This Page | K-Lock Nut | Nylon Insert |
|---|---|---|---|
| Locking mechanism | Thread distortion only | Spring + serration | Friction (nylon) |
| Max continuous temp. | Limited by base metal | Limited by base metal | ~120°C (nylon limit) |
| Added dimensional height | None — standard envelope | Slight (cone feature) | Slight (insert) |
| Typical rated reuse cycles | 5–15 | Higher — spring returns | Low — single-use common |
| Chemical/solvent resistance | No polymer to attack | No polymer to attack | Nylon may soften/swell |
| Mechanism complexity | Simplest — thread only | Moderate — dual feature | Simple — single insert |
All-Metal Lock Nuts Application Areas
High-temperature machinery, chemical-exposed environments, and standard-envelope vibration-resistant applications across general industry.
Automotive Engine & Exhaust
hot-zone connections
Vibrating Machinery
agricultural equipment
Chemical Processing
process equipment nuts
Power Generation
boiler and furnace nuts
Industrial Ovens & Furnaces
furnace casing hardware
Rail & Heavy Transport
high-vibration chassis hardware
Oil & Gas Equipment
fuel-exposed connections
Marine Engine Rooms
engine mount hardware
All-Metal Lock Nut Standards Coverage
Same ISO 9001:2015 quality system as our complete fastener range. Thread distortion depth and reuse prevailing torque verified against DIN 980 on every production lot.
Complete Documentation Package
Grade / Standard Stated
Proof Load · Hardness
ISO 2320 (on request)
Conformance
Distortion Depth
Related Nut Types & Materials
All-metal lock nuts for straightforward, standard-envelope high-temperature locking. K-Lock nuts for more consistent multi-cycle reuse. Full nut range for the complete fastening schedule.
K-Lock Nuts
The dual-mechanism all-metal alternative — spring tension and serrated bite working together, offering more consistent locking performance across many reuse cycles than pure thread distortion.
View K-Lock Nuts →Full Nut Range
Complete nut manufacturing capability at Akbar Fasteners — hex, heavy hex, square, K-Lock, all-metal lock, T-slot, weld, wing, and all specialty forms across carbon steel through exotic alloy.
View Nut Range →SS 316L Fasteners
For all-metal lock nut applications in marine, coastal, or chemical process environments where carbon steel’s corrosion resistance is insufficient — SS 316L distorted-thread lock nuts with full chloride resistance.
View SS 316L →Carbon & Alloy Steel Fasteners
For the complete strength ladder and surface finish options used in all-metal lock nut manufacture across general industrial and high-temperature applications.
View Carbon Steel →Need All-Metal
Lock Nuts?
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