Truss Head Screws Manufacturer in India | Modified Truss Head Screws

Overview

Modified Truss Head Screws & Truss Head Machine Screws: Manufacturer & Supplier

A truss head is a wide, low dome. The big bearing face holds thin sheet without pulling through and covers slotted or oversized holes, while the low profile keeps clear of covers and moving parts.

Exotic Alloy manufactures truss head screws in Mumbai, India, for steel framing, HVAC, electrical and cabinet makers. We stock across India and supply New Zealand, Australia, the Gulf and Africa. Heads are cold formed with the Phillips recess, drill points are formed on the blank, and threads are rolled before case hardening.

Machine screw or self-drilling

Truss head machine screws follow ASME B18.6.3 and go into a nut or tapped hole. Truss and modified truss self-drilling screws, like the one in our photo, drill, tap and fasten steel in one step; their threads and points follow SAE J78. For hex-head drill screws see self-drilling screws.

ASME B18.6.3 SAE J78 Modified truss #2 / #3 points Phillips

Truss head screw at a glance

Head: Wide, low dome; flat bearing face
vs round: 16–32 % wider, 12–23 % lower
Drive: Phillips PH 1–4; slotted to order
Points: #2 (thin), #3 (medium steel)
Length: Measured from under the head
Related: Round head, pan head, self-drilling

No. 8-18 × 3/4″ modified truss self-drilling screw, drawn to scale. Thread, point protrusion allowance and torsional strength from SAE J78; the head shows typical modified truss dimensions; the drill point is simplified.

Specification

Truss Head Screw Specification

The range we manufacture and supply.

StandardsASME B18.6.3 (truss head machine screws); SAE J78 (self-drilling, types BSD and CSD)

Size rangeMachine screws No. 2 to 1/2″; self-drilling No. 4 to 1/4″

HeadsTruss; modified truss (wafer) for framing screws

ThreadUNC / UNF (machine); spaced BSD or machine-pitch CSD (self-drilling)

DrivePhillips; slotted and square to order

Drill point#2 and #3; heavier points to order

MaterialsCase-hardened carbon steel; 410 and 18-8 stainless; brass (machine screws)

FinishZinc plated (clear or yellow), black phosphate; stainless plain

CertificationMill certificate; hardness and torsion test report; EN 10204 3.1

PackingBoxes of 100 to 5000, bulk cartons, collated strips to order

Head types

Truss vs Round, Binding & Modified Truss Heads

At No. 8: the further right, the wider and lower the head.

No. 8 heads at the same scale. Round, binding and truss from ASME B18.6.3; the modified truss shows typical self-drilling screw dimensions, which vary slightly between makers.

Size	Truss A / H max	Round A / H max	Truss is wider by	Truss is lower by
No. 2	.194 / .053	.162 / .069	20 %	23 %
No. 3	.226 / .061	.187 / .078	21 %	22 %
No. 4	.257 / .069	.211 / .086	22 %	20 %
No. 5	.289 / .078	.236 / .095	22 %	18 %
No. 6	.321 / .086	.260 / .103	23 %	17 %
No. 8	.384 / .102	.309 / .120	24 %	15 %
No. 10	.448 / .118	.359 / .137	25 %	14 %
No. 12	.511 / .134	.408 / .153	25 %	12 %
1/4″	.573 / .150	.472 / .175	21 %	14 %
5/16″	.698 / .183	.590 / .216	18 %	15 %
3/8″	.823 / .215	.708 / .256	16 %	16 %
1/2″	1.073 / .280	.813 / .355	32 %	21 %

ASME B18.6.3 maximum values, inches; percentages are our calculation.

Dimensions

Truss Head Screw Dimensions

The twelve ASME B18.6.3 truss head sizes at the same scale, Phillips recess top view and side profile.

Size	A head dia. max / min	H head height max / min	J slot width max / min	T slot depth max / min	UNC / UNF TPI
No. 2	.194 / .180	.053 / .044	.031 / .023	.031 / .022	56 / 64
No. 3	.226 / .211	.061 / .051	.035 / .027	.036 / .026	48 / 56
No. 4	.257 / .241	.069 / .059	.039 / .031	.040 / .030	40 / 48
No. 5	.289 / .272	.078 / .066	.043 / .035	.045 / .034	40 / 44
No. 6	.321 / .303	.086 / .074	.048 / .039	.050 / .037	32 / 40
No. 8	.384 / .364	.102 / .088	.054 / .045	.058 / .045	32 / 36
No. 10	.448 / .425	.118 / .103	.060 / .050	.068 / .053	24 / 32
No. 12	.511 / .487	.134 / .118	.067 / .056	.077 / .061	24 / 28
1/4″	.573 / .546	.150 / .133	.075 / .064	.087 / .070	20 / 28
5/16″	.698 / .666	.183 / .162	.084 / .072	.106 / .085	18 / 24
3/8″	.823 / .787	.215 / .191	.094 / .081	.124 / .100	16 / 24
1/2″	1.073 / 1.028	.280 / .250	.106 / .091	.161 / .131	13 / 20

ASME B18.6.3 truss heads for machine screws, slotted, inches.

Size	M recess dia. ref	G penetration gauging depth, max / min	Phillips driver
No. 2	.097	.052 / .034	PH 1
No. 3	.103	.059 / .042	PH 1
No. 4	.105	.062 / .044	PH 1
No. 5	.121	.078 / .060	PH 1
No. 6	.151	.073 / .048	PH 2
No. 8	.166	.088 / .063	PH 2
No. 10	.181	.104 / .079	PH 2
No. 12	.241	.111 / .086	PH 3
1/4″	.256	.126 / .101	PH 3
5/16″	.345	.173 / .148	PH 4
3/8″	.376	.206 / .182	PH 4
1/2″	.437	.268 / .243	PH 4

ASME B18.6.3 truss heads with Phillips recess, inches.

Size	Threads per inch	Major dia. max / min	Minor dia. max / min	P protrusion #2 / #3 point	Min. length pan / truss head, #2 / #3	Min. torsional strength, lb-in
No. 4	24	.114 / .110	.086 / .082	.163 / –	5/16″ / –	14
No. 6	20	.139 / .135	.104 / .099	.190 / .220	5/16″ / 3/8″	24
No. 8	18	.166 / .161	.122 / .116	.211 / .251	3/8″ / 7/16″	42
No. 10	16	.189 / .183	.141 / .135	.235 / .300	7/16″ / 1/2″	61
No. 12	14	.215 / .209	.164 / .157	.283 / .353	1/2″ / 1/2″	92
1/4″	14	.246 / .240	.192 / .185	.318 / .393	1/2″ / 1/2″	150

SAE J78 type BSD self-drilling screws (spaced thread), inches. Minimum practical lengths for heads with a flat bearing face, such as truss and pan heads. Torsional strength for steel screws.

Size	Threads per inch	Major dia. max / min	P protrusion #2 / #3 point	Min. torsional strength, lb-in
No. 4	40	.112 / .107	.130 / –	14
No. 6	32	.138 / .133	.152 / .172	24
No. 8	32	.164 / .159	.162 / .202	48
No. 10	24	.190 / .183	.193 / .258	65
No. 12	24	.216 / .209	.223 / .293	100
1/4″	20	.250 / .243	.275 / .350	156

SAE J78 type CSD self-drilling screws with machine-screw thread pitch, for thicker material, inches.

Drill points

Choosing the Drill Point for Truss Head Self-Drilling Screws

The drill point must cut right through the steel before the first thread engages. If the thread reaches the metal while the point is still drilling, the screw tries to advance faster than it drills and the point breaks or the thread strips. That is why each point has a protrusion allowance and a working thickness range.

The steel being drilled should also be at least 10 to 20 Rockwell hardness points softer than the screw. Hardened 410 stainless drills harder material than 18-8 stainless.

Screw size	Drill point	Steel thickness min – max, in	Steel thickness min – max, mm
No. 4	#2	.035 – .080	0.9 – 2.0
No. 6	#2	.035 – .090	0.9 – 2.3
No. 8	#2	.035 – .100	0.9 – 2.5
No. 10	#2	.035 – .110	0.9 – 2.8
No. 10	#3	.110 – .175	2.8 – 4.4
No. 12	#3	.110 – .210	2.8 – 5.3
1/4″	#3	.110 – .220	2.8 – 5.6

Type BSD selection guide from the SAE J78 chart. A guide only: check heavier steel, hard material or special coatings with us.

Installation

Driving Truss Head Self-Drilling Screws

Screw gun

Use a screw gun with a depth stop or clutch and a good PH 2 bit.

Square to the work

Hold the screw upright and press firmly while the point drills.

Clamp the layers

Hold the sheets tight so they do not lift apart as the thread starts.

Right length

Material thickness plus the protrusion allowance, then the next standard length.

Do not over-drive

Stop when the head seats; over-driving strips the thread in thin sheet.

Mind the hardness

Hard or very thick steel needs a heavier point or a pilot hole.

Calculator

Self-Drilling Screw Point & Length Finder

Enter the screw size, the steel to drill and anything fixed on top. The finder chooses the drill point and the shortest standard length that lets the point finish drilling.

Joint

Screw size

Units

Steel to drill (total)

Other material on top

Point ranges from the SAE J78 type BSD selection chart; length = steel + top layer + protrusion allowance P, rounded up to a standard length and not shorter than the J78 minimum practical length. A guide only.

Result

#2

drill point

3/8

in screw length

Point range:0.035–0.100″ steel

Length needed:0.286″ (7.3 mm)

Protrusion P:0.211″

Min. torsional strength:42 lb-in

Driver:PH 2

Materials

Truss Head Screw Materials & Hardness

Self-drilling screw	Material	Hardness	Use
Carbon steel	AISI 1016–1024, case hardened	Case HRC 52–58; core HRC 32–40	Steel framing, ducts, general sheet metal
410 stainless	Martensitic, hardened and tempered	Case HRC 55 min; core HRC 38–42	Outdoor steel, harder material
18-8 stainless	Austenitic	About HRB 90 to HRC 25	Corrosion resistance in softer materials

Values from the SAE J78 chart. Truss head machine screws are made in 18-8 and 316 stainless, brass and zinc-plated low-carbon steel.

Carbon steel

1018 · 1022

Case-hardened drill screws, as in the photo.

1018 1022

410 stainless

Hardenable

Stainless that still drills steel.

410

18-8 stainless

304 · 305

Machine screws and corrosion-resistant fixings.

304 305

316 stainless

Marine grade

Truss head machine screws for wet areas.

316 316L

Manufacturing

How Our Truss Head Screws Are Made

1

Wire

Low-carbon steel or stainless wire, certified by heat.

2

Heading

Wide truss dome and Phillips recess formed in one blow.

3

Point forming

Drill point formed on the blank for self-drilling screws.

4

Thread rolling

Spaced BSD, machine-pitch CSD or UNC / UNF threads.

5

Case hardening

Hard case for drilling, tough core for torsion.

6

Plating & testing

Zinc plating, then hardness, torsion and drill tests.

Applications

Where Our Truss Head Screws Are Used

Steel stud framing

Stud-to-track connections with modified truss drill screws.

HVAC ducting

Duct seams, hangers and plenum panels.

Electrical

Boxes, trays and panels in sheet steel.

Trailers & vehicle bodies

Thin skins on steel frames with wide heads.

Cabinets & enclosures

Low heads that clear doors and drawers.

Machine covers

Truss head machine screws on guards and housings.

Quality & testing

Truss Head Screw Inspection & Certification

Check	Method	Applied to
Head diameter & height	Micrometer: A, H	Every lot
Phillips recess	Penetration gauge	Every lot
Thread	Major and minor diameter; ring gauges for machine screws	Every lot
Hardness	Case and core Rockwell	Every heat-treatment lot
Torsional strength	Torque to failure against the J78 minimum	Self-drilling lots
Drill test	Drill-through time on test plate	Self-drilling lots

Every shipment includes

Mill certificate with heat number
Dimensional and hardness report
Lot number on every box

On request

EN 10204 3.1 certificate
Torsion and drill test report
Salt spray test for plated lots

FAQ

Truss Head Screw Questions, Answered

A truss head screw has an extra-wide, low, rounded head. The large bearing face holds thin sheet and covers oversized holes, and the low profile clears moving parts. Inch truss head machine screws are made to ASME B18.6.3; a No. 10 truss head is up to 0.448 in across and 0.118 in high, against 0.359 in and 0.137 in for a round head.

A wider, flatter variant of the truss head used on self-drilling and tapping screws, especially for steel stud framing. A typical No. 8 modified truss head is 0.426 to 0.446 in across and 0.082 to 0.098 in high, against 0.364 to 0.384 in across for the standard No. 8 truss head. Dimensions vary slightly between makers.

The truss head is the widest and lowest of the three. In ASME B18.6.3 the truss head is 16 to 32 percent wider and 12 to 23 percent lower than the round head of the same size. Choose truss for thin sheet and soft materials, pan for a general-purpose head, and round for a traditional look.

It depends on the steel thickness. As a guide from SAE J78 type BSD charts: a #2 point drills 0.035 to 0.100 in (No. 8) or 0.035 to 0.110 in (No. 10), and a #3 point drills 0.110 to 0.175 in (No. 10) or 0.110 to 0.210 in (No. 12). Heavier steel needs a #4 or #5 point.

Long enough that the drill point has finished drilling before the threads start to engage. Add the protrusion allowance to the total thickness being fastened: for a No. 8-18 screw with a #2 point the allowance is 0.211 in. Our finder adds it up and picks the next standard length.

410 stainless drill screws are hardened and drill harder material than 18-8 stainless drill screws, which are chosen mainly for corrosion resistance. As a rule, the material being drilled should be at least 10 to 20 Rockwell hardness points softer than the screw.

For ASME B18.6.3 Phillips truss heads: PH 1 for No. 2 to No. 5, PH 2 for No. 6 to No. 10, PH 3 for No. 12 and 1/4 in, and PH 4 for 5/16 to 1/2 in. No. 8 framing screws normally take a PH 2 bit.

Self-drilling screws are made in case-hardened carbon steel (zinc plated, like the screw in our photo), hardened 410 stainless or 18-8 stainless. Truss head machine screws are made in 18-8 and 316 stainless, brass and zinc-plated steel.