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ASME B18.6.4 · Types 1, F, 23, 25 · DIN 7513

Thread Cutting Screws Manufacturer in India

Cut a clean thread in a plain hole, with no tap. We make thread cutting screws with every ASME cutting point (Types D, F, G, T, BF and BT) and metric DIN 7513 screws, in case-hardened steel, 410 and 18-8 stainless. Below: the six points, full dimension tables, hole sizes and thread engagement, and a hole and length finder.

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  • ISO 9001:2015 certified manufacturer
  • No tapping step
  • Inch and metric
  • Steel, 410 & 18-8
Zinc-plated slotted hex washer head thread cutting screws with a slotted cutting point
Sizes No. 0 – 1/2 in Points D, F, G, T, BF, BT Metric DIN 7513
Overview

Type F, 23 & 25 Screws (Thread Cutting Screws): Manufacturer & Exporter

A thread cutting screw is a tapping screw with a slot or flutes in its tapered point. The edges cut the mating thread as the screw turns in, and the chips leave through the flute, so a plain drilled or cored hole needs no tap.

Exotic Alloy manufactures thread cutting screws in Mumbai, India, for makers of castings, enclosures, appliances and machinery, and exports them to Argentina, Latin America, the Gulf, Africa and Europe.

Cut, form or drill?

A cutting screw removes material; a thread forming screw pushes it aside; a self-drilling screw makes its own hole first. This page covers the cutting family: the six ASME points, metric DIN 7513, the hole each needs and the length that lets the point clear the part.

ASME B18.6.4 Type 1 / F / 23 / 25 DIN 7513 UNC & UNF Steel, 410, 18-8
Thread cutting screw at a glance
Also called
Self-tapping thread cutting screw
Inch
ASME B18.6.4 (now in B18.6.3): D, F, G, T, BF, BT
Metric
DIN 7513 (2016); DIN 7516 (withdrawn)
Hole
Drilled or cored, larger than a tap drill
Steel screws
Case hardened, HRC 45 min surface
Related
Thread forming, self-drilling, pan head
No. 10-24 by 1/2 inch slotted hex washer head thread cutting screw, Type D (Type 1), drawn to scale: washer 0.384 to 0.414 inch across, head 0.105 to 0.120 inch high, 5/16 inch hexagon, 24 threads per inch, and a tapered point 0.146 to 0.188 inch long ending at a 0.148 inch point diameter, with one cutting slot washer .384–.414 head .105–.120 L 1/2 (from the bearing face) s .146–.188 dp .148 24 threads / in (UNC) cutting slot (Type D: one face on the axis) tapered lead 5/16 hex (.305–.312) slotted, indented hex washer head Determinant length 11/32 (90° heads) Min. torsional strength 56 lb-in (Types 1, F, 23) EXOTIC ALLOY
A No. 10-24 × 1/2 slotted hex washer head thread cutting screw with a single-slot Type D (Type 1) point, the style in our photo. Thread and point from ASME B18.6.4, head from ASME B18.6.3 Table 32; drawn at mean sizes.
Specification

Thread Cutting Screw Specification

The range we manufacture and supply.

Inch standardASME B18.6.4-1998, now ASME B18.6.3 (same tables)
Metric standardsDIN 7513:2016 forms A and B; DIN 7516 cross recessed
PointsD (Type 1), F, G, T (Type 23), BF, BT (Type 25)
SizesNo. 2 to 1/2 in (machine thread); No. 0 to 1/2 in (spaced); M2.5–M8
ThreadsUNC / UNF; spaced (Type B); ISO metric
HeadsHex washer, hex, pan, round, flat, oval, cheese, truss
MaterialsCase-hardened carbon steel; 410 stainless; 18-8 stainless
FinishZinc plated (clear, yellow, black); stainless plain
CertificationMill certificate; EN 10204 3.1 on request
PackingBoxes of 100 to 5,000; bulk cartons
Point types

Type 1, F, G, 23, BF & 25 Cutting Points

Four points on a machine screw thread, two on the coarser spaced thread.

The six ASME thread cutting points drawn at the same scale for size No. 10: Types D, F, G and T with the 24 threads per inch machine screw thread, and Types BF and BT with the 16 threads per inch spaced thread; each has a tapered blunt point, with one slot (D, G), several flutes (F, BF) or one wide flute (T, BT); end views show the cut seen from the point Type D Type 1 10-24 machine Type F   10-24 machine Type G   10-24 machine Type T Type 23 10-24 machine Type BF   10-16 spaced Type BT Type 25 10-16 spaced end Same scale, mean diameters; flute shapes and end views schematic (flute design is the maker’s option under ASME) EXOTIC ALLOY
The six ASME cutting points at the same scale, size No. 10. Every point is tapered and blunt; the slot or flutes run through the taper and the first full thread beyond it.
ASME typeAlso calledThreadPointTypical use
Type DType 1Machine screw (UNC / UNF)Tapered, blunt; single slot with one face on the screw axisSteel sheet, structural shapes, alloy steel, cast iron, brass, plastics
Type F–Machine screw (UNC / UNF)Tapered, blunt; several flutes forming multiple cutting edges and chip cavitiesHeavy-gauge sheet, aluminium, zinc and lead die castings, cast iron, brass, plastics
Type G–Machine screw (UNC / UNF)Tapered, blunt; single slot centred on the axis–
Type TType 23Machine screw (UNC / UNF)Tapered, blunt; single wide flute, 90–95° included, cutting edge above the axisCast iron, zinc and aluminium die castings, plastics; good chip clearing, low driving torque
Type BF–Spaced (Type B)Tapered, blunt; several flutes–
Type BTType 25Spaced (Type B)Tapered, blunt; single wide flute, 90–95° included, cutting edge above the axisMoulded or through holes in plastics and other soft materials

Point shapes from the ASME B18.6.4 drawings and notes; on Types T and BT the flute has a 90–95° included angle with the cutting edge above the axis. Typical uses from maker datasheets for Types 1, F, 23 and 25; we found none for G and BF. Trade names Type 1, 23 and 25 are supplier usage.

Dimensions

Thread Cutting Screw Dimensions

SizeMajor d
max / min		Point dp
ref.		Taper s, short
max / min		Taper s, long
max / min		Determinant L
90° / csk		Min. practical L
90° / csk		Torsion
min, lb-in
No. 2-56.0860 / .0813.068.062 / .045.080 / .0625/32 / 3/165/32 / 3/165
No. 2-64.0860 / .0816.070.055 / .039.070 / .0551/8 / 3/161/8 / 5/32–
No. 3-48.0990 / .0938.078.073 / .052.094 / .0733/16 / 7/325/32 / 7/32–
No. 3-56.0990 / .0942.081.062 / .045.080 / .0625/32 / 3/165/32 / 3/16–
No. 4-40.1120 / .1061.087.088 / .062.112 / .0887/32 / 1/43/16 / 1/413
No. 4-48.1120 / .1068.091.073 / .052.094 / .0733/16 / 7/325/32 / 7/32–
No. 5-40.1250 / .1191.100.088 / .062.112 / .0887/32 / 9/323/16 / 1/418
No. 5-44.1250 / .1195.102.080 / .057.102 / .0803/16 / 1/43/16 / 1/4–
No. 6-32.1380 / .1312.107.109 / .078.141 / .1091/4 / 5/161/4 / 5/1623
No. 6-40.1380 / .1321.113.088 / .062.112 / .0887/32 / 9/323/16 / 1/4–
No. 8-32.1640 / .1571.132.109 / .078.141 / .1091/4 / 11/321/4 / 5/1642
No. 8-36.1640 / .1577.136.097 / .069.125 / .0977/32 / 5/167/32 / 9/32–
No. 10-24.1900 / .1818.148.146 / .104.188 / .14611/32 / 7/165/16 / 13/3256
No. 10-32.1900 / .1831.158.109 / .078.141 / .1091/4 / 11/321/4 / 5/1674
No. 12-24.2160 / .2078.174.146 / .104.188 / .14611/32 / 7/165/16 / 13/3293
No. 12-28.2160 / .2085.180.125 / .089.161 / .1255/16 / 13/329/32 / 3/8–
1/4-20.2500 / .2408.200.175 / .125.225 / .17513/32 / 17/323/8 / 1/2140
1/4-28.2500 / .2425.214.125 / .089.161 / .1255/16 / 13/329/32 / 3/8–
5/16-18.3125 / .3026.257.194 / .139.250 / .19415/32 / 19/327/16 / 9/16306
5/16-24.3125 / .3042.271.146 / .104.188 / .14611/32 / 15/325/16 / 15/32–
3/8-16.3750 / .3643.312.219 / .156.281 / .2191/2 / 11/1615/32 / 5/8560
3/8-24.3750 / .3667.333.146 / .104.188 / .14611/32 / 1/25/16 / 1/2–
7/16-14.4375 / .4258.366.250 / .179.321 / .25019/32 / 3/49/16 / 23/32–
7/16-20.4375 / .4281.387.175 / .125.225 / .17513/32 / 9/163/8 / 17/32–
1/2-13.5000 / .4876.423.269 / .192.346 / .2695/8 / 25/3219/32 / 3/41075
1/2-20.5000 / .4906.450.175 / .125.225 / .17513/32 / 9/163/8 / 17/32–

ASME B18.6.4-1998 Table 8 = ASME B18.6.3-2013 Table 44, inch. Screws of the determinant length and shorter have the short point taper, longer screws the long one. Torsion: minimum torsional strength from maker datasheets for Types 1, F and 23 (identical where listed).

SizeThreads
per inch		Major d
max / min		Minor d1
max / min		Point dp
ref.		Taper s
max / min		Min. practical L
90° / csk		Torsion
min, lb-in
No. 048.060 / .054.036 / .033.031.042 / .0311/8 / 1/8–
No. 142.075 / .069.049 / .046.044.048 / .0361/8 / 5/32–
No. 232.088 / .082.064 / .060.058.062 / .0475/32 / 3/164
No. 328.101 / .095.075 / .071.068.071 / .0543/16 / 7/32–
No. 424.114 / .108.086 / .082.079.083 / .0633/16 / 1/413
No. 520.130 / .123.094 / .090.087.100 / .0757/32 / 9/3218
No. 620.139 / .132.104 / .099.095.100 / .0751/4 / 9/3224
No. 719.154 / .147.115 / .109.105.105 / .0791/4 / 5/16–
No. 818.166 / .159.122 / .116.112.111 / .0839/32 / 11/3239
No. 1016.189 / .182.141 / .135.130.125 / .0945/16 / 3/856
No. 1214.215 / .208.164 / .157.152.143 / .10711/32 / 7/1688
1/4 in14.246 / .237.192 / .185.179.143 / .1073/8 / 1/2142
5/16 in12.315 / .306.244 / .236.230.167 / .12515/32 / 19/32290
3/8 in12.380 / .371.309 / .299.293.167 / .12517/32 / 11/16590
7/16 in10.440 / .429.359 / .349.343.200 / .1505/8 / 25/32–
1/2 in10.504 / .493.423 / .413.407.200 / .15011/16 / 27/32–

ASME B18.6.4-1998 Table 7 = ASME B18.6.3-2013 Table 43, inch. Torsion: Type 25 maker datasheet.

SizeAcross flats s
max / min A / min B		Across corners e
min A / B		Head height k
nom.		k grade A
max / min		k grade B
max / min
M4 × 0.77 / 6.78 / 6.647.66 / 7.52.82.925 / 2.6753 / 2.6
M5 × 0.88 / 7.78 / 7.648.79 / 8.633.53.65 / 3.353.74 / 3.26
M6 × 110 / 9.78 / 9.6411.05 / 10.8944.15 / 3.854.24 / 3.76
M8 × 1.2513 / 12.73 / 12.5714.38 / 14.25.35.45 / 5.155.54 / 5.06

DIN 7513:2016 form A, hexagon head, mm; head dimensions as ISO 4017.

SizeHead dk
max / min		Head height k
max / min		Slot n
max / min		Slot depth t
min		Core hole dh
DIN 7513
M2.5 × 0.454.5 / 4.321.8 / 1.660.8 / 0.660.72.2
M3 × 0.55.5 / 5.322 / 1.861 / 0.860.852.7
M4 × 0.77 / 6.782.6 / 2.461.51 / 1.261.13.6
M5 × 0.88.5 / 8.283.3 / 3.121.51 / 1.261.34.5
M6 × 110 / 9.783.9 / 3.61.91 / 1.661.65.5
M8 × 1.2513 / 12.735 / 4.72.31 / 2.0627.4

DIN 7513:2016 form B, slotted cheese head, mm; head as ISO 1207. Core hole from DIN 7513:1995.

SizeCore hole dh% thread
with dh		Tap drill d − P
for comparison		DIN 7513 lengthsDIN 7516 lengths
M2.52.251 %2.05 (77 %)6–20–
M32.746 %2.5 (77 %)6–226–22
M43.644 %3.3 (77 %)8–258–25
M54.548 %4.2 (77 %)10–3010–30
M65.538 %5 (77 %)12–3512–35
M87.437 %6.75 (77 %)14–4014–40

DIN 7513:1995 (types A, BE, FE, GE; A from M3) and DIN 7516:1995 (cross recessed AE, DE, EE; withdrawn): commercial lengths and core holes, mm. % thread: our calculation.

Cut or form

Thread Cutting vs Thread Forming

Schematic sections through the wall of a hole: a thread cutting screw removes material, which leaves as chips through the flute, so the hole wall stays as it was beyond the thread; a thread forming screw displaces material sideways and up into the thread, with no chips Thread cutting material removed, chips leave by the flute drilled hole wall chips part screw side Thread forming material displaced, no chips original hole wall material pushed into the flanks part screw side Schematic, not to scale EXOTIC ALLOY
A cutting screw removes material; a forming screw moves it. The flute on a cutting screw gives the edge its rake and carries the chips away.
 Thread cuttingThread formingSelf-drilling
HoleDrilled or cored firstDrilled or cored firstNone: the point drills it
How the thread is madeCut; chips leave by the fluteMaterial displaced; no chipsDrilled, then tapped by the thread
Typical materialsCast iron, die castings, brass, plastics, heavy sheetDuctile metalsSteel sheet
StandardsASME D, F, G, T, BF, BT; DIN 7513 / 7516ASME A, AB, B, BP, C; DIN 7500ISO 15480–15483, SAE J78
Our pageThis pageThread formingSelf Drilling SMS
Holes & length

Hole Size, Thread Engagement & Length

Cutting screws want a bigger hole than a tap, and enough length for the point to clear.

Percentage of thread for thread cutting screw holes compared with tap drills: the ASME drive-test holes for Types D, F, G and T give about 21 to 67 percent of thread in inch sizes, and the DIN 7513 core holes about 37 to 51 percent in metric sizes, while ordinary tap drills give about 69 to 78 percent 0 10 20 30 40 50 60 70 80 90 100 % of thread, = (d − hole) / (1.299 P) Inch, Types D F G T No. 2-56 56 No. 3-48 67 No. 4-40 49 No. 6-32 44 No. 8-32 42 No. 10-24 31 No. 12-24 31 1/4-20 34 5/16-18 31 3/8-16 21 Metric, DIN 7513 / 7516 M2.5 51 M3 46 M4 44 M5 48 M6 38 M8 37 thread cutting screw hole tap drill for the same thread EXOTIC ALLOY
The standard holes for thread cutting screws leave a shallower thread than a tap drill. Inch: ASME B18.6.3 drive-test holes; metric: DIN 7513 core holes. Percentages are our calculation.
SizeTest plate
thickness, in		Test hole
drill, in		% thread
test hole		Tap drill
for comparison		% thread
tap drill		Torsion
min, lb-in
No. 2-56.0760–.0800#49 (.0730)56 %#50 (.0700)69 %5
No. 3-48.0920–.0960#46 (.0810)67 %#47 (.0785)76 %–
No. 4-40.1070–.1110#41 (.0960)49 %#43 (.0890)71 %13
No. 5-40.1070–.1110see note–#38 (.1015)72 %18
No. 6-32.1385–.1425#31 (.1200)44 %#36 (.1065)78 %23
No. 8-32.1380–.1420#26 (.1470)42 %#29 (.1360)69 %42
No. 10-24.1845–.1905#17 (.1730)31 %#25 (.1495)75 %56
No. 12-24.1845–.1905#8 (.1990)31 %#16 (.1770)72 %93
1/4-20.2470–.2530#1 (.2280)34 %#7 (.2010)75 %140
5/16-18.3095–.3155L (.2900)31 %F (.2570)77 %306
3/8-16.3720–.3780T (.3580)21 %5/16″ (.3125)77 %560
No. 10-32.1845–.1905#16 (.1770)32 %#21 (.1590)76 %74
1/4-28.2470–.2530A (.2340)34 %#3 (.2130)80 %–
5/16-24.3095–.3155M (.2950)32 %I (.2720)75 %–
3/8-24.3720–.3780T (.3580)31 %Q (.3320)79 %–

ASME B18.6.3-2013 Table 48, Types D, F, G, T: test plate and hole for the drive test, inch. The 5-40 row is not shown: its drill (No. 37 = 0.104 in) and hole (0.1010 in) disagree. Tap drills for comparison; % thread = threads per inch × (d − hole) / 0.01299 (our calculation). Torsion from maker datasheets.

  • Hole: start from the test hole or the DIN core hole and confirm it by trial in your material.
  • Length: parts under the head + tapped thickness + point taper s, so full threads fill the part.
  • Taper s: short taper up to the determinant length, long taper above it (ASME note).
  • Blind holes: drill deeper than the screw reaches, leaving room for the point and the chips.
ProblemLikely cause
Very high driving torqueHole too small, or chips packing a blind hole
Screw strips outHole too large, or too little thread length
Head twists offTorque above the torsional strength
Point will not cutPart not 10–20 Rockwell points softer than the screw
Finder

Thread Cutting Screw Hole & Length Finder

Thread engagement for your hole, and the shortest length that lets the point clear the part.

Screw & joint

Our calculation. Clamped = parts under the head; tapped = the part the screw threads into. Hole default: ASME drive-test hole (inch, where listed) or DIN 7513 core hole (metric). % thread = (d − hole) / (1.299 P); for the spaced thread, share of the thread depth between major and minor diameter. Inch length = parts under the head + tapped part + point taper s, not less than the minimum practical length (ASME B18.6.4). Metric: the shortest DIN length that reaches through the part; add the tapered lead.

Result
42
% of thread
3/8
in, next 1/16 in
Minimum length:0.329 in
Point taper s used:0.141 in (long)
Point diameter:0.132 in
Torsional strength, min:42 lb-in
Designation:No. 8-32 × 3/8 thread cutting screw

Materials

Thread Cutting Screw Materials & Hardness

MaterialHeat treatmentHardnessNotes
Carbon steel, AISI 1016–1024Case hardened, liquid quenched, tempered at 650 °F (343 °C) minSurface HRC 45 min; core HRC 28–38Zinc plated; the standard choice
410 stainless1850–1950 °F (1010–1066 °C), quenched; tempered at 525 °F (274 °C) minCore HRC 38–42Hardened stainless (Type F datasheet)
18-8 stainlessNot hardened by heat treatmentHRB 90 to HRC 20Best corrosion resistance; softer materials
Carbon steel screw sizeCase depth, in
No. 4 to No. 60.002–0.007
No. 8 to No. 120.004–0.009
1/4 in and larger0.005–0.011

The material being tapped should be at least 10 to 20 Rockwell points softer than the screw. Stainless screws resist corrosion better, 18-8 more than 410. DIN 7513 screws are heat treated. Values from maker datasheets that quote the ASME B18.6.4 tables.

Carbon steel
Case hardened

Zinc plated, as in the photo.

10181022
410 stainless
Hardenable

Stainless that still cuts metal.

410
18-8 stainless
304 · 305

For plastics and soft metals.

304305
Manufacturing

How Our Thread Cutting Screws Are Made

1

Wire

AISI 1016–1024 or stainless, certified by heat.

2

Heading

Head cold formed; slot or recess formed.

3

Thread & point

Thread rolled; tapered point slotted or fluted through the first full thread.

4

Hardening

Case hardened and tempered (steel), hardened (410).

5

Plating

Zinc plating with hydrogen embrittlement relief.

6

Testing

Hardness, drive and torsion tests per lot.

Applications

Where Our Thread Cutting Screws Are Used

Die castings

Zinc and aluminium housings and covers.

Cast iron

Pump, valve and machine castings.

Electrical

Enclosures, panels and cabinets.

Appliances

Plastic and metal parts, Type 25 in moulded holes.

Automotive

Brackets on heavy-gauge sheet and castings.

Machinery

Guards and covers on structural sections.

Quality & testing

Thread Cutting Screw Inspection & Certification

CheckMethodApplied to
Head and lengthCallipers, gauges to ASME / DINEvery lot
Thread and pointMajor diameter, point diameter, taper lengthEvery lot
Slot or flutesVisual, through the first full threadEvery lot
Surface and core hardnessRockwell / micro-hardnessEvery heat-treatment lot
Case depthMicro-sectionEvery heat-treatment lot
Drive testInto the ASME test plate and holeEvery lot
Torsional strengthTorque to failureEvery lot

Every shipment includes

  • Mill certificate with heat number
  • Hardness and drive test report
  • Lot number on every box

On request

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

Thread Cutting Screw Questions, Answered

A tapping screw with slots or flutes at its point. Their edges cut a mating thread in a pre-drilled or cored hole, removing material as chips, much like a tap. ASME B18.6.4, now part of ASME B18.6.3, defines Types D, F, G and T with machine screw threads and Types BF and BT with spaced threads; metric thread cutting screws follow DIN 7513.

A thread cutting screw removes material and the chips leave through its flutes. A thread forming screw displaces the material into a thread without making chips. Cutting screws are used in materials such as cast iron, die castings and plastics, and the Type 23 design drives with low tightening torque.

They are common trade names for ASME types: Type 1 is Type D, Type 23 is Type T and Type 25 is Type BT. Types D, F, G and T have machine screw threads (UNC or UNF); Types BF and BT have the coarser spaced thread.

A larger hole than a tap drill. In the ASME drive test an 8-32 Type D, F, G or T screw goes into a No. 26 drill hole of 0.147 in, about 42 percent of thread, where an 8-32 tap uses a No. 29 drill (0.136 in, about 69 percent). DIN 7513 gives a 4.5 mm core hole for M5. Confirm the hole by trial in your material.

Long enough that the tapered point passes right through the tapped part: length at least the parts under the head plus the tapped thickness plus the point taper length s. For 8-32 the taper is at most 0.109 in on screws up to 1/4 in long and 0.141 in on longer screws.

Yes, if the hole is deeper than the screw reaches, so that the tapered point and the chips carried by the flutes have room below the full thread.

Mostly case-hardened carbon steel, AISI 1016 to 1024, with a surface hardness of at least HRC 45 and a core of HRC 28 to 38; also hardened 410 stainless and 18-8 stainless. The material being tapped should be at least 10 to 20 Rockwell points softer than the screw.

No. DIN 7513 screws have an ISO metric thread and cutting flutes that run from the point to the head. ASME thread cutting screws are inch sizes whose slots or flutes run through the tapered point and the first full thread beyond it.
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