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ASME B18.6.8 · DIN 464 · DIN 653 · No. 6–1/2 in, M1–M10

Thumb Screws Manufacturer in India

Turn by hand, no tool needed. We make thumb screws to ASME B18.6.8 (Type A and Type B, regular and heavy) and knurled thumb screws to DIN 464 and DIN 653, in zinc-plated steel, brass and A2 / A4 stainless. Below: every head type, full dimension tables, the room each head needs and a clearance and length finder.

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  • ISO 9001:2015 certified manufacturer
  • Tool-free fastening
  • Inch and metric
  • Steel, brass & stainless
Stainless steel knurled thumb screw with collar
Inch No. 6 – 1/2 in Metric M1 – M10 Heads thumb, knurled
Overview

ASME B18.6.8 & DIN 464 Screws (Thumb Screws): Manufacturer & Stockist

A thumb screw has a head made for finger and thumb: a flat thumb head or a knurled knob. Panels, guards, fixtures and instruments can be opened and closed without looking for a tool.

Exotic Alloy manufactures thumb screws in Mumbai, India, and keeps common sizes in stock for machine builders, instrument and electronics makers, and maintenance teams. We supply across India and export to Norway, Scandinavia, the Gulf and Africa.

Thumb, knurled or wing?

Flat thumb heads (ASME Types A and B) and knurled heads (DIN 464 and DIN 653) are covered here. For the full DIN knurled range see knurled head screws; for two-wing heads with a longer lever see butterfly (wing) screws.

ASME B18.6.8 Type A & B DIN 464 / 653 Tool-free A2 / A4, brass
Thumb screw at a glance
Inch
ASME B18.6.8 Type A; Type B regular and heavy
Formerly
ASME B18.17; also IFI 156
Metric
DIN 464 high knurled, DIN 653 low knurled
Length
From the bearing face
Tightened
By hand (DIN 464 also slotted)
Related
Knurled, wing screws, thumb nuts
DIN 464 M6 by 16 knurled thumb screw, high type with collar, drawn to scale: knurled head 24 mm across and 5 mm high, collar 12 mm across, total head height 15 mm, metric thread M6 by 1 and length 16 mm measured from the bearing face; view from above showing the knurl dk 24 (knurl) k 5 h 15 ds 12 (collar) L 16 from the bearing face M6 × 1 from above: knurled rim dashed: collar ds below Thread length b 18 (DIN 464, M6) Lengths, DIN 464 M6 8–25 mm EXOTIC ALLOY
A DIN 464 M6 × 16 knurled thumb screw with collar, the style in our photo. Dimensions from DIN 464; knurl pattern schematic.
Specification

Thumb Screw Specification

The range we manufacture and supply.

Inch standardASME B18.6.8-2010 Type A, Type B regular, Type B heavy
Metric standardsDIN 464 (high, collar), DIN 653 (low)
SizesNo. 6–3/8 (A), No. 6–1/2 (B), No. 10–1/2 (B heavy); M1–M10
LengthsASME range per size; DIN 2–40 mm by size
ThreadUNC / UNF (No. 10: 24 or 32); ISO metric coarse
HeadsRound thumb on collar, flat dished thumb, knurled
MaterialsSteel; brass; stainless A2 / A4
FinishZinc plated; stainless and brass plain
CertificationMill certificate; EN 10204 3.1 on request
PackingBoxes of 50 to 1,000; bulk cartons
Head types

Type A, Type B & Knurled Thumb Screws

Three inch thumb heads and two metric knurled heads.

Five thumb screw heads at the same scale: ASME B18.6.8 Type A regular, Type B regular and Type B heavy for 1/4 inch, and DIN 464 high and DIN 653 low knurled thumb screws for M6; front views on top and edge views below, with head width and height ASME Type A regular, 1/4 in width 13.6 · height 15.9 ASME Type B regular, 1/4 in width 20.7 · height 12.7 ASME Type B heavy, 1/4 in width 25.9 · height 19.4 DIN 464 high knurled, M6 width 24.0 · height 15.0 DIN 653 low knurled, M6 width 24.0 · height 5.0 front edge Mean dimensions in mm, same scale; ASME head outlines schematic (shapes per the ASME drawings, values per the tables) EXOTIC ALLOY
Five thumb screw heads at the same scale, 1/4 in and M6. The heavy Type B head is the widest and thickest; DIN 653 is the lowest.
TypeStandardHeadSizes
Type A, regularASME B18.6.8 (= B18.17, IFI 156 Table 1)Thin round thumb head on a collar ENo. 6 to 3/8 in
Type B, regularASME B18.6.8 (= B18.17, IFI 156 Table 3)Wide flat head, rim C thicker than the dished centre D; no collarNo. 6 to 1/2 in
Type B, heavyASME B18.6.8 (= IFI 156 Table 4)As Type B, wider and thickerNo. 10 to 1/2 in
Knurled, highDIN 464Knurled head on a collar; also slottedM1 to M10
Knurled, lowDIN 653Knurled head onlyM1 to M10 (no M3.5)

ASME B18.6.8-2010 replaced ASME B18.17; the ASME Type B tables name low-carbon steel UNS G10060.

Dimensions

Thumb Screw Dimensions

Dimension letters of ASME B18.6.8 thumb screws shown on 1/4 inch screws: Type A with head width A, head height B, thumb thickness C and collar diameter E; Type B with head width A, head height B, rim thickness C and centre thickness D; length L from the bearing face A B L A B L E C C (rim) D (centre) Type A front Type A edge Type B front Type B edge 1/4 in thumb screws, ASME B18.6.8; outlines schematic, sizes to scale EXOTIC ALLOY
What the ASME letters mean, shown on 1/4 in screws.
LetterType AType B (regular, heavy)
AHead widthHead width
BHead height, bearing face to topHead height, bearing face to top
CThumb thicknessThickness at the rim
D–Thickness at the dished centre
ECollar diameter–
LLength from the bearing faceLength from the bearing face
SizeHead width A
max / min		Head height B
max / min		Thumb thickness C
max / min		Collar E
max / min		Lengths L
min–max
No. 6-32.31 / .29.33 / .31.05 / .04.25 / .23.25–.75
No. 8-32.36 / .34.38 / .36.06 / .05.31 / .29.38–.75
No. 10-24, 32.42 / .40.48 / .46.06 / .05.35 / .32.38–1.00
No. 12-24.48 / .46.54 / .52.06 / .05.40 / .38.38–1.00
1/4-20.55 / .52.64 / .61.07 / .05.47 / .44.50–1.50
5/16-18.70 / .67.78 / .75.09 / .07.59 / .56.50–1.50
3/8-16.83 / .80.95 / .92.11 / .09.76 / .71.75–2.00

ASME B18.6.8-2010 Type A regular, inch; identical in ASME B18.17-1968 and IFI 156 Table 1.

SizeHead width A
max / min		Head height B
max / min		Rim thickness C
max / min		Centre D
max / min		Lengths L
min–max
No. 6-32.45 / .43.28 / .26.08 / .06.03 / .02.25–1.00
No. 8-32.51 / .49.32 / .30.09 / .07.04 / .02.38–1.00
No. 10-24, 32.58 / .54.39 / .36.10 / .08.05 / .03.38–2.00
No. 12-24.71 / .67.45 / .43.11 / .09.05 / .03.38–2.00
1/4-20.83 / .80.52 / .48.16 / .14.06 / .03.50–2.50
5/16-18.96 / .91.64 / .60.17 / .14.09 / .06.50–3.00
3/8-161.09 / 1.03.71 / .67.22 / .18.11 / .08.75–3.00
7/16-141.40 / 1.35.96 / .91.27 / .24.14 / .111.00–4.00
1/2-131.54 / 1.461.09 / 1.03.33 / .29.15 / .111.00–4.00

ASME B18.6.8-2010 Type B regular, inch; identical in ASME B18.17-1968 and IFI 156 Table 3. D: thickness at the dished centre, as drawn.

SizeHead width A
max / min		Head height B
max / min		Rim thickness C
max / min		Centre D
max / min		Lengths L
min–max
No. 10-24.89 / .83.78 / .66.18 / .16.08 / .06.50–2.00
1/4-201.05 / .99.81 / .72.24 / .22.11 / .09.50–3.00
5/16-181.21 / 1.15.88 / .78.27 / .25.11 / .09.50–4.00
3/8-161.41 / 1.34.94 / .84.30 / .28.14 / .12.50–4.00
7/16-141.59 / 1.531.00 / .91.36 / .34.14 / .121.00–3.00
1/2-131.81 / 1.721.09 / .97.40 / .38.18 / .161.00–3.00

ASME B18.6.8-2010 Type B heavy, inch; identical in IFI 156 Table 4.

SizeKnurl dkKnurl height kDIN 464 collar dsDIN 464 head hDIN 464 lengthsDIN 653 lengths
M1 × 0.255.51.52.83.52–52–6
M1.2 × 0.2561.5342–52–8
M1.4 × 0.3723.54.72–63–10
M1.6 × 0.357.523.852–83–12
M2 × 0.4924.55.33–104–16
M2.5 × 0.45112.556.53–125–18
M3 × 0.5122.567.54–166–20
M3.5 × 0.614378.5––
M4 × 0.7163.589.55–188–25
M5 × 0.82041011.56–2010–30
M6 × 124512158–2512–30
M8 × 1.25306161812–2816–35
M10 × 1.5368202318–4020–40

DIN 464:2007 and DIN 653:2006, mm; both share the knurl dk and k. Lengths are the commercial range per size. Full DIN data, slot sizes and thread run-out on our knurled head page.

Choosing

Thumb, Knurled or Wing: Width & Height Compared

Room each head needs to turn, seen from above at the same scale: the head sweeps a circle as wide as the head, from about 13.6 mm for an ASME Type A 1/4 inch thumb screw to 24 mm for DIN 464 and DIN 653 M6 knurled screws and about 31.5 mm for a DIN 316 M6 wing screw 13.6 mm Type A thumb 1/4 in 20.7 mm Type B thumb reg. 1/4 in 25.9 mm Type B thumb heavy 1/4 in 24.0 mm DIN 464 high 24.0 mm DIN 653 low 31.5 mm DIN 316 wing M6 30.1 mm Type A wing reg. 1/4 in Seen from above: the head sweeps a circle as wide as the head (dashed); knurled heads are round already EXOTIC ALLOY
The circle each head sweeps, to scale. Wing screws need the most room; Type A thumb screws the least.
HeadWidth
swing / grip dia., mm		Height above part
mm		Character
ASME Type A thumb, 1/4 in13.615.9Thin round head on a collar
ASME Type B thumb, regular, 1/4 in20.712.7Wide flat head, dished
ASME Type B thumb, heavy, 1/4 in25.919.4Widest, thickest thumb head
DIN 464 knurled, high, M624.015.0Knurl plus collar
DIN 653 knurled, low, M624.05.0Knurl only, lowest profile
DIN 316 wing screw, M631.516.0For comparison: two wings
ASME Type A wing, regular, 1/4 in30.115.1For comparison: two wings

Mean values from ASME B18.6.8, DIN 464, DIN 653 and DIN 316, converted to mm. A wider head gives more leverage for the same finger force; a lower head stands out less.

Using them

Room to Turn, Length & Fit

  • Room: keep walls at least half the head width from the axis, plus room for finger and thumb.
  • Length: measured from the bearing face; parts clamped plus the thread engagement you need.
  • Standard lengths: ASME gives a range per size; DIN 464 and DIN 653 list commercial lengths.
  • Washer: a plain washer under the head protects painted or soft parts.
NeedBetter choice
Least room around the screwASME Type A thumb screw
Lowest headDIN 653 low knurled
Best grip with a thumb headASME Type B heavy
Hand and screwdriverDIN 464 slotted
Longest lever by handWing screw
Finder

Thumb Screw Clearance & Length Finder

Check the room to turn and find the shortest standard length.

Screw & space

Our calculation. Clamped = parts under the head; engaged = thread length you want in the tapped hole or nut; to wall = distance from the screw axis to the nearest wall or flange. Swing diameter = maximum head width (ASME A, DIN dk). Length = clamped + engaged, rounded up to the next DIN commercial length, or to the next 1/16 in inside the ASME length range.

Result
24
mm swing diameter
10
mm length
Room beyond the head:8 mm
Head height above the part:15 mm
Length needed:9 mm
Standard range:8–25 mm
Designation:DIN 464 M6 × 10

Materials

Thumb Screw Materials & Finishes

MaterialFinishWhere
Low-carbon steel (ASME Type B: UNS G10060)Zinc platedIndoor machinery, fixtures and panels
Stainless A2 (304)PlainInstruments, food equipment, as in the photo
Stainless A4 (316)PlainOutdoor, marine and washdown
BrassNaturalElectrical and decorative uses
Low-carbon steel
1006 · 1010

Zinc-plated thumb screws.

10101018
Stainless
A2 / A4

As in the photo.

304316
Brass
CuZn

Non-magnetic, decorative.

Brass grades
Manufacturing

How Our Thumb Screws Are Made

1

Material

Wire or bar, certified by heat.

2

Head

Thumb head formed; knurled heads headed or turned.

3

Knurl or trim

Knurl rolled; thumb heads trimmed and edges rounded.

4

Thread

Thread rolled.

5

Finishing

Zinc plating, or cleaning and passivation.

6

Packing

Counted boxes, lot-labelled.

Applications

Where Our Thumb Screws Are Used

Panels & enclosures

Access covers opened for service.

Instruments

Adjusters and clamps on lab and optical equipment.

Jigs & fixtures

Stops and quick clamps.

Electronics

Rack equipment, cards and connectors.

Food machinery

Stainless screws on parts removed for cleaning.

Machine guards

Guards opened for setting and cleaning.

Quality & testing

Thumb Screw Inspection & Certification

CheckMethodApplied to
Head width and heightCallipers to ASME / DINEvery lot
Thumb thickness, collarCallipersEvery lot
Knurl, burrs, edgesVisualEvery lot
ThreadRing gaugesEvery lot
LengthHeight gaugeEvery lot
MaterialPMI / chemical analysisStainless and brass

Every shipment includes

  • Mill certificate with heat number
  • Dimensional report
  • Lot number on every box

On request

  • EN 10204 3.1 certificate
  • Salt spray test for plated lots
  • RoHS declaration
FAQ

Thumb Screw Questions, Answered

A screw with a head shaped to be turned between finger and thumb, so no tool is needed. Inch thumb screws are standardised in ASME B18.6.8 as Type A, a thin round head on a collar, and Type B, a wide flat dished head in regular and heavy series. Metric knurled thumb screws follow DIN 464 (high, with collar) and DIN 653 (low).

Type A has a thin round thumb head standing on a collar under the head. Type B has a wider flat head that is thicker at the rim than at the dished centre, and no collar; it comes in regular and heavy series. For 1/4 in the head is 0.52 to 0.55 in wide on Type A, 0.80 to 0.83 in on Type B regular and 0.99 to 1.05 in on Type B heavy.

A thumb screw has a single flat or round head gripped like a coin, a wing screw has two wings that give a longer lever. A 1/4 in ASME Type A regular wing screw spreads 1.12 to 1.25 in, wider than even the heavy Type B thumb screw at 0.99 to 1.05 in, so thumb screws need less room around them.

Both have the same knurled head diameter and knurl height. DIN 464 is the high type with a collar under the knurl, DIN 653 the low type without a collar. For M6 the knurl is 24 mm across and 5 mm high; DIN 464 adds a 12 mm collar for a total head height of 15 mm.

From the bearing face under the head or collar to the end of the screw. ASME B18.6.8 gives a length range for each size, for example 0.50 to 1.50 in for a 1/4 in Type A thumb screw; DIN 464 M6 is listed from 8 to 25 mm and DIN 653 M6 from 12 to 30 mm.

A circle as wide as the head, plus room for the fingers. That is about 14 mm for a 1/4 in Type A, 21 mm for Type B regular, 26 mm for Type B heavy and 24 mm for an M6 knurled thumb screw.

The knurled DIN 464 thumb screw is also made with a slot, with slot width and depth given in DIN 464, so it can be finished with a screwdriver; the old slotted DIN 465 is withdrawn. Plain thumb screws are made to be turned by hand.

Steel, zinc plated; the ASME B18.6.8 Type B tables name low-carbon steel UNS G10060. We also make thumb screws in brass and in A2 and A4 stainless steel; the screw in our photo is stainless.
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