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DIN 2510 · Types L, K, KU, Z, ZU · ASME reduced body

Reduced Shank Studs Manufacturer in India

A shank thinner than the thread, so the stud stretches like a spring and holds its preload. We make reduced shank studs to DIN 2510 (types L, K, KU, Z and ZU) and ASME reduced body studs for turbines, valves and hot flanged joints. Below: the five types, full dimensions, the DIN length rule, why the waist works and a length and stretch finder.

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  • ISO 9001:2015 certified manufacturer
  • Waist turned and polished
  • M12 to M180
  • EN 10204 3.1 / 3.2
Reduced shank stud with waisted shank and slotted end
DIN 2510 M12 – M180 Waist ≈ 0.9 × root Types L, K, KU, Z, ZU
Overview

DIN 2510 Waisted Studs (Reduced Shank Studs): Manufacturer & Distributor

A reduced shank stud has a plain shank thinner than its thread. Tightened, the long slim waist stretches like a spring, and the joint keeps its clamping force when it settles, heats up or is loaded and unloaded.

Exotic Alloy manufactures waisted and reduced body studs in Mumbai, India, for turbine, valve, compressor and pressure-vessel builders and for power and process plants. We supply across India and export to Iraq, the Middle East, Central Asia and Africa.

Waisted or reduced body?

DIN 2510 waisted studs have a turned waist of about 0.9 times the thread root diameter. ASME B18.31.2 reduced body studs are only slightly thinner than the thread, about the pitch diameter. For a shank equal to the thread see double end studs; for flange sets see flange bolting.

DIN 2510-3 Types L, K, Z KU, ZU (cap nuts) ASME reduced body High temperature
Reduced shank stud at a glance
Standard
DIN 2510-3 types L, K, KU, Z, ZU
Sizes
M12–M180 (type L to M52)
Waist
≈ 0.86–0.92 × thread root
Ends
Spigot with two flats; KU, ZU second spigot
Length
Clamping length + 2c (DIN 2510-1)
Inch
ASME B18.31.2 reduced body
Related
Double end, flange bolting, nuts
DIN 2510-3 type L waisted stud M24 drawn to scale, length 154 mm for a 100 mm clamping length: thread b of 32 mm at both ends, waisted shank ds of 18 mm, about 0.89 of the thread root diameter, smooth transitions, and on one end a spigot of 14 mm with two flats 11 mm apart and 6 mm long; end view of the spigot b 32 b 32 ds 18 (waist) l1 = 154 = clamping length 100 + 2 × c1 27 z2 6 d flats s 11 on spigot d1 14 spigot end (enlarged) DIN 2510-3 type L waisted stud M24, for a 100 mm clamping length, to scale Transition shape schematic; DIN 2510 gives the waist and thread dimensions. EXOTIC ALLOY
A DIN 2510-3 type L waisted stud M24, to scale. The waist ds of 18 mm runs between two 32 mm threads; the spigot with flats lets the stud be held while the nuts are turned.
Specification

Reduced Shank Stud Specification

The range we manufacture and supply.

Metric standardDIN 2510-3 waisted studs, types L, K, KU, Z, ZU
Inch standardASME B18.31.2 reduced body studs (also metric B18.31.1M)
SizesM12–M180 (L to M52, Z and U types to M120); 1/4–4 in
LengthsClamping length + constants, 1 mm (L, K) or 5 mm (Z) steps
ThreadMetric coarse to M64, 6 mm pitch M72–M120, 8 mm above; large-clearance thread to DIN 2510-2
FeaturesSpigot with flats, centre holes, axial bore from M64
Materials21CrMoV5-7, 42CrMo4 (EN 10269); A193 B16, B7; stainless; nickel alloys
WithNuts, cap nuts and expansion sleeves to order
CertificationEN 10204 3.1; 3.2 on request
SupplySets or single studs, individually protected
Types

DIN 2510 Types L, K, KU, Z & ZU

Same waist, different threads and ends.

The five DIN 2510-3 waisted stud types in size M24 at the same scale, each at its DIN 2510-1 length for a 100 mm clamping length: type L with 32 mm threads, 154 mm; type K with 24 mm threads, 154 mm; type KU with a 16 by 17 mm second spigot for cap nuts, 175 mm; type Z with 42 mm threads, 160 mm; type ZU with a 16 by 8 mm spigot, 180 mm l1 154 Type L DIN 2510-3 thread 32 l1 154 Type K DIN 2510-3 thread 24 ≈ 1 d l1 175 Type KU DIN 2510-3 as K + spigot dp 16 × 17 l1 160 Type Z DIN 2510-3 thread 42 l1 180 Type ZU DIN 2510-3 as Z + spigot dp 16 × 8 M24, same scale; lengths l1 from DIN 2510-1 for a 100 mm clamping length; transitions schematic EXOTIC ALLOY
All five types in M24 for the same 100 mm clamping length. The thread length and the end spigots change the stud length the joint needs.
TypeThread, M24EndsNuts (DIN 2510-1 examples)Sizes
L32 mmSpigot with flatsNF hexagon nutsM12–M52
K24 mm (≈ 1 d)Spigot with flatsNF; TF with sleeves DM12–M180
KU24 mmFlats + round spigot dpAF cap nuts; BF with sleeves DM12–M120
Z42 mmSpigot with flatsNF hexagon nutsM12–M120
ZU42 mmFlats + round spigot dpAF cap nutsM12–M120

In DIN 2510-3 type K runs to M180, types KU, Z and ZU to M120 and type L to M52. From M64 the studs have an axial bore d4. The stud in our photo has a slot in one end instead of the spigot.

Dimensions

Waisted Stud Dimensions & Length Constants

SizeWaist dsThread b
type L / K / Z		Spigot d1 / flats s / z2Second spigot dp
z3 KU / ZU		Bore d4Centre hole
M128.520 / 13 / 278 / 7 / 48 (11 / 7)–A1.6
M161223 / 16 / 3112 / 10 / 512 (14 / 8)–A1.6
M201528 / 20 / 3614 / 11 / 613 (16 / 9)–A1.6
M241832 / 24 / 4214 / 11 / 616 (17 / 8)–A1.6
M2720.535 / 27 / 4718 / 13 / 618 (19 / 10)–A1.6
M302339 / 30 / 5018 / 13 / 621 (19 / 12)–A2.5
M3325.542 / 33 / 5325 / 22 / 924 (21 / 14)–A2.5
M3627.545 / 36 / 5725 / 22 / 926 (23 / 14)–A2.5
M3930.548 / 39 / 6028 / 24 / 1030 (23 / 14)–A2.5
M4232.552 / 42 / 6428 / 24 / 1032 (24 / 15)–A2.5
M4535.555 / 45 / 6632 / 27 / 1134 (25 / 15)–A2.5
M4837.558 / 48 / 7032 / 27 / 1137 (26 / 19)–A2.5
M524162 / 52 / 7436 / 30 / 1240 (26 / 18)–A2.5
M5644– / 56 / 7940 / 32 / 1345 (28 / 19)–A2.5
M6451– / 64 / 8842 / 36 / 1452 (28 / 20)18A4
M72 × 658.5– / 72 / 9550 / 41 / 1556 (28 / 20)25A4
M80 × 666– / 80 / 10350 / 41 / 1563 (28 / 19)25A4
M90 × 675– / 90 / 11250 / 41 / 1574 (28 / 20)25A4
M100 × 684– / 100 / 12250 / 41 / 1586 (28 / 19)25A4
M110 × 692.5– / 110 / 13250 / 41 / 1597 (28 / 19)25A6.3
(M120 × 6)102– / 120 / 14250 / 41 / 15105 (30 / 20)25A6.3
M125 × 8106– / 125 / –50 / 41 / 15–25A6.3
M140 × 8118– / 140 / –65 / 55 / 18–36A6.3
(M150 × 8)127– / 150 / –65 / 55 / 18–36A6.3
M160 × 8136– / 160 / –65 / 55 / 18–36A6.3
(M170 × 8)145– / 170 / –65 / 55 / 18–36A6.3
M180 × 8154– / 180 / –65 / 55 / 18–36A6.3

DIN 2510-3 (1971), mm. ds waist; b thread at both ends for types L, K and Z (KU as K, ZU as Z); spigot d1 with flats s, length z2; second spigot dp with length z3 on KU and ZU; axial bore d4 from M64; centre holes form A. Sizes in brackets to be avoided.

Sizec1c2c3 minc4c5c6c7c8 min
M121412163018281617
M161816203521331921
M2022.520.5244125392325
M242724294629442730
M273027325132493033
M3033.530.5365636543436
M3336.533.5396139593739
M364037436542634043
M394340466745654345
M4246.543.5497248704649
M4549.546.5527551734951
M485349568256805455
M52–*53608659845759
M5661.557.5649164896263
M6470667310072987071
M72 × 6787481108801067878
M80 × 6868289115871138585
M90 × 6969299124971229594
M100 × 6106101109133106131104103
M110 × 6116111119142115140113112
(M120 × 6)126121129153124151122121

DIN 2510-1, mm, for the stud length rules in section 06. *M52 c1 is misprinted in the copy we hold, so it is left out; ask us for M52 types L and K with NF nuts.

SizeReduced body ds1 min
UNC / UNF / 8UN, in		Full body ds maxMetric sizeds1 min
mm
1/4 in.213 / .223 / –0.2500M65.21
3/8 in.329 / .343 / –0.3750M87.04
1/2 in.444 / .462 / –0.5000M108.86
5/8 in.559 / .583 / –0.6250M1210.68
3/4 in.677 / .703 / –0.7500M1614.5
7/8 in.795 / .822 / –0.8750M2018.16
1 in.910 / .938 / –1.0000M2421.8
1-1/4 in1.148 / 1.188 / 1.1601.2500M3027.46
1-1/2 in1.381 / 1.438 / 1.4091.5000M3633.12
2 in1.843 / – / 1.9092.0000M4238.78
2-1/2 in2.324 / – / 2.4082.5000M4844.43
3 in2.824 / – / 2.9083.0000M6459.74
3-1/2 in3.323 / – / 3.4073.5000M8075.74
4 in3.823 / – / 3.9074.0000M10095.72

ASME B18.31.2 (inch) and B18.31.1M (metric) reduced body studs; ds1 minimum, which sits just below the basic pitch diameter. Inch reduced body maximum = full body minimum.

Why waisted

Why a Thin Shank Keeps the Preload

Elastic stretch of an M24 stud shank at the same force, relative to a full body shank: full body 1.00, ASME reduced body 1.21 and DIN 2510 waisted shank 1.78, because stretch is inversely proportional to the shank area (452, 373 and 254 square millimetres) M24 shank: stretch at the same force, relative to a full body (shank area in mm²) 0× 0.5× 1× 1.5× 2× Full body d_s 24: area 452 mm2, stretch 1.00 x full body Full body, ds = 24 1.00× · 452 mm² ASME B18.31.1M reduced body d_s1 min 21.8: area 373 mm2, stretch 1.21 x full body ASME reduced body, 21.8 1.21× · 373 mm² DIN 2510 waist d_s 18: area 254 mm2, stretch 1.78 x full body DIN 2510 waist, 18 1.78× · 254 mm² Our calculation: stretch = F · l / (E · A); the same force and shank length for all three. A thinner shank stretches more, so the same settling of the joint costs a smaller share of the preload. EXOTIC ALLOY
The waisted M24 shank stretches 1.78 times as much as a full body at the same force. Hover a bar for the area.
  • Purpose: DIN 2510-1 uses waisted studs where preload and fatigue life must hold under changing mechanical and thermal loads.
  • Spring effect: more stretch per kN, so a given settling or thermal mismatch costs less preload.
  • Weakest part: the waist, at 67–81 % of the thread stress area, carries the highest stress.
  • Thread: DIN 2510-2 gives the stud thread extra clearance.
SizeWaist dsThread root d3
basic		ds / d3Waist area
mm²		Waist / stress area AsWaist / full body area
M128.59.850.865767 %50 %
M161213.550.8911372 %56 %
M201516.930.8917772 %56 %
M241820.320.8925472 %56 %
M302325.710.8941574 %59 %
M3627.531.090.8859473 %58 %
M4232.536.480.8983074 %60 %
M4837.541.870.90110475 %61 %
M564449.250.89152175 %62 %
M645156.640.90204376 %64 %
M80 × 66672.640.91342179 %68 %
M100 × 68492.640.91554279 %71 %
(M120 × 6)102112.640.91817180 %72 %
M160 × 8136150.190.911452780 %72 %

Our calculation from DIN 2510-3: d3 = d − 1.2269 P (ISO basic), As per ISO 898-1.

Assembly

DIN 2510 Assemblies & the Stud Length Rule

A DIN 2510 type L waisted stud M24 in a flanged joint with a 100 mm clamping length: the stud length l1 of 154 mm is the clamping length plus c1 of 27 mm at each end, which takes the nut and the stud end; the waisted shank lies inside the joint, the threads in the nuts c1 27 c1 27 clamping length 100 l1 = 100 + 2 × 27 = 154 mm (steps of 1 mm) NF nuts (schematic) waist inside the joint EXOTIC ALLOY
Type L M24 with NF nuts in a 100 mm joint. The stud length is the clamping length plus c1 at each end; the waist sits in the joint.
Stud typeExpansion sleeveNutsCentringStud length l1Length steps
L–NFby the studsclamping length + 2 c11 mm
LENFby studs and sleevesclamping length + 2 c11 mm
K–NFby the nutsclamping length + 2 c11 mm
KDTFby nuts and sleevesclamping length + 2 c21 mm
Z–NFby the studsclamping length + 2 c35 mm
ZENFby studs and sleevesclamping length + 2 c35 mm
KU–AF (cap)by the cap nutsclamping length + c4 + c51 mm
KUDBF (cap)by cap nuts and sleevesclamping length + c6 + c71 mm
ZU–AF (cap)by the studsclamping length + c4 + c85 mm
ZUEAF (cap)by studs and sleevesclamping length + c4 + c85 mm

DIN 2510-1 assembly examples; clamping length includes any expansion sleeves. NF and TF hexagon nuts, AF and BF cap nuts and the sleeves D and E belong to the DIN 2510 system.

Finder

Waisted Stud Length & Stretch Finder

DIN 2510 length for your joint, and what the waist does at your preload.

Stud & joint

Our calculation. Clamping length = everything clamped between the nuts, including expansion sleeves. Stud length l1 from DIN 2510-1: clamping length + the constants of the assembly, rounded up to 1 mm, or 5 mm for types Z and ZU. Rp0.2 = 0.2 % proof strength of your stud material at its working temperature; preload as a share of the waist yield force. Stretch = F · 100 / (E · A), E = 210 GPa, per 100 mm of shank.

Result
154
mm stud length l1
117.6
kN preload
Rule:100 + 2 × 27
Thread at each end:32 mm
Waist ds / area:18 mm / 254 mm²
Stress, waist / thread As:462 / 333 MPa
Stretch per 100 mm, waist:0.220 mm
Full body, same force:0.124 mm (×1.78)
Designation:DIN 2510-3 type L stud M24 × 154

Materials

Waisted Stud Materials

MaterialGradesWhere
Heat-resistant Cr-Mo-V steel21CrMoV5-7 (EN 10269); ASTM A193 B16Turbine casings, hot flanges
Cr-Mo alloy steel42CrMo4 (EN 10269); ASTM A193 B7Valves, compressors, pressure equipment
Stainless steel304, 316 types; A193 B8, B8MCorrosive service, as in the photo
Nickel alloysInconel 718, A-286, Nimonic 80AHighest temperatures
Alloy steel
B7 · B16 · 42CrMo4

Most waisted studs.

41404340
Stainless
304 · 316

As in the photo.

304316
Nickel alloys
718 · A-286

Hot sections.

Inconel 718A-286
Manufacturing

How Our Waisted Studs Are Made

1

Bar

Heat-treated alloy bar, certified by heat.

2

Turn

Centre holes, waist and transitions turned.

3

Polish

Waist and transitions finished smooth.

4

Thread

Threads rolled or cut to DIN 2510-2.

5

Spigot

Spigot and flats milled; bore from M64.

6

Inspect

Crack testing, marking and packing.

Applications

Where Our Reduced Shank Studs Are Used

Steam & gas turbines

Casing joints that heat up and cool down.

Valves

High-pressure, high-temperature bonnets.

Pressure vessels

Hot flanges and covers.

Power plant piping

Flanged joints in steam lines.

Compressors & engines

Joints under cyclic loads.

Chemical reactors

Covers with thermal cycling.

Quality & testing

Waisted Stud Inspection & Certification

CheckMethodApplied to
Waist diameterMicrometer at several pointsEvery stud
ThreadsRing gauges to DIN 2510-2Every lot
Surface of waistVisual and roughnessEvery stud
CracksMagnetic particle or dye penetrantAs ordered
MechanicalTensile, impact, hardnessEvery heat-treat lot
MaterialPMI / chemical analysisAlloys

Every shipment includes

  • EN 10204 3.1 certificate with heat number
  • Dimensional report with waist diameters
  • Identification on every stud

On request

  • EN 10204 3.2 with third-party inspection
  • Elevated-temperature tests
  • Crack test reports
FAQ

Reduced Shank Stud Questions, Answered

A stud whose plain shank is thinner than the thread. DIN 2510 waisted studs have a shank of about 0.86 to 0.92 times the thread root diameter; ASME B18.31.2 reduced body studs have a shank close to the pitch diameter. The thinner shank stretches more under load.

DIN 2510-1 names the purpose: to keep the preload and the life of a bolted joint under changing mechanical and thermal loads. A thinner shank stretches more for the same preload, so settling of the joint and temperature changes take away a smaller share of it.

They differ in thread length and ends. For M24, type L has 32 mm threads, K and KU 24 mm, Z and ZU 42 mm. All have a spigot with two flats on one end; KU and ZU have a second, round spigot at the other end and are used with cap nuts.

DIN 2510-1 gives it as the clamping length plus constants for the ends: for type L or K with NF nuts, l1 = clamping length + 2 c1 in steps of 1 mm; type Z uses 2 c3 in steps of 5 mm. For an M24 type L stud and a 100 mm clamping length that is 100 + 2 x 27 = 154 mm.

About 0.86 to 0.92 times the basic thread root diameter: 18 mm for M24, 51 mm for M64. Its area is 67 to 81 % of the thread stress area, so the waist is the most highly stressed part of the stud and does most of the stretching.

An ASME reduced body stud has a shank about equal to the pitch diameter, for 1/2-13 UNC at least 0.444 in. A DIN 2510 waisted stud is much thinner. For M24 the shank area is 373 square millimetres on a reduced body stud and 254 on a waisted stud, against 452 for a full body.

Sleeves fitted between the nut and the flange, which count in the clamping length. DIN 2510-1 shows type K studs with sleeves D and TF nuts, and types L and Z with sleeves E and NF nuts; type KU studs can also take sleeves D with BF cap nuts.

We make them in heat-resistant alloy steels such as 21CrMoV5-7 and 42CrMo4 to EN 10269, in ASTM A193 B16 and B7, in stainless steel and in nickel alloys. The stud in our photo is stainless, with a slot in one end.
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