Structural Steel Fastening System

Tension Control Bolts (TCB) comprise of a button head design bolt with a 12 point pintail, a high

strength hex nut, and a hardened flat washer. When installed with a dual socket electric shear

wrench, the outer socket applies the turning force to the nut while the inner socket holds the

bolt in place by gripping the 12 point spline pintail. When the forces reach or exceed the

designed tension the 12 point spline pintail will shear off, leaving the bolt and nut securing the

bolting application at the proper tension.

Installation procedure

Handling – Storage - installation

All structural fasteners should be protected from dirt and moisture at the job site. No

more than the amount of bolts to be used should be removed from the container.

Remaining bolts at the end of the day should be returned to the correct container. Dirty

/ oily / rusted or bolts that have been lubricated or been exposed to water after supply

bolts should not be used TCB’s are certified in the AJAX NATA laboratory, to achieve the

minimum tension requirements before shipping. Changes in the condition and the

addition of foreign matters may alter the results in the field.

Place all the bolts into the connection, with the washer under the nut in standard and

short slotted holes. For long slotted and oversized holes a washer should be placed

BOTH the head of the bolt and the nut. Washer and nut identification markings should

always face the opposite direction of the connection.

Bring all the fasteners in the connection to a SNUG TIGHT CONDITION, starting with the

most rigid part of the connection. And commence the installation procedure as

described above.

Determining Proper Bolt Length

To determine the proper length of the Fastener that is

required, refer to the chart for the proper length to be

added to the grip.

Bolt size Length Added to Grip

M12 20mm

M16 22mm

M20 25mm

M24 31mm

M27 38mm

M30 41mm

L = Bolt Length LG = Grip Length LA = Length added to Grip (as stated in the table above)

MINIMUM BOLT LENGTH REQUIRED = LG+LA

Tightening of TCB’s

Tension Control Bolts (TCB’s) are a simple and uncomplicated system that completely removes

the responsibility of attaining the correct preload in a given connection away from the erector.

The Shear wrench is light in weight / quite to use and requires minimal effort to achieve the

correct tension. For example to tighten a M20 for a friction joint connection requires

approximately 375-450Nm. A substantial force if hand tightened and extended time is installed

by an impact wrench.

Before commencement of preloading, the connected components shall be fitted together and

the bolt in the assembly shall be brought to a snug tight (finger tight) condition. This shall be

carried out for all bolts to be installed in the connection starting from the most rigid part of the

connection. In order to ensure that the preload in fully installed bolts meet the specified

minimum preload, the installation process consists of two tightening stages, the first stage

applies a bedding torque to ensure a firm contact between components. This can be

accomplished by:

1. Using the Shear wrench, but only snugging the bolts and not shearing off the splines.

There is distinct change in sound/tone of the wrench motor, when used this way. It

indicated that pre-tensioning has commenced and a bedding torque is being applied.

Once bedded, when the power trigger is disengaged the wrench gearing will backtrack /

reverse allowing the tool to be easily removed from the bolt.

2. Using a standard nut runner / impact wrench with a deep socket to pull all the surfaces

into contact without involving the bolt spline. (As the shear wrench is required for final

tightening, this is the least preferred option)

NOTE – If mating surfaces are SIGNIFICANTLY distorted or misaligned the “SLAVE” bolts should be used. TCB’s can be used as slave bolts, but they must be identified and replaced with new bolts once all bolts in the connection have been tightened and the mating surfaces are in contact.

The second tightening stage can only be achieved using the shear wrench. When the spline end

of the bolt shears off at the break neck, full preload has been achieved as shown previously.

About Shear Wrenches and maintenance

Shear wrenches are lightweight / non-impacting and extremely low noise tools, specially

designed for the use of tightening TCB’s the wrenches consist of both an INNER SOCKET

(engages with the 12 point spline) and the OUTER SOCKET (which engages the nut). Changing

the sockets is simple and quick, to set the wrench

with the correct spline and nut socket to suit the size of bolt to be installed. Detailed

instructions on the process are included with every shear wrench sold.

Shear wrenches are “Dumb tools”, that do not need calibration, but do require some

maintenance and must be handled carefully, to avoid damage.

Maintenance

Clean both inner and outer sockets to avoid build-up of foreign matter or debris / dirt.

Change the motors carbon brushes when necessary, drop in performance is an indicator

that the motors brushes have worn.

Do not carry the shear wrench by the electrical cable, most good quality shear wrenches

are sold with a protective case.

Ensure electrical cable and plug regularly – replace if damaged to avoid electrical shock.

Replace inner and outer sockets when worn.

Maintain the cleanliness of the wrench as would be the case with any other electrical

tool.

To maintain the shear wrench in good condition and service, return to AJAX

approximately every 6 months or 40,000 bolt installation.

Min Max Min Max Min Max

M16 x 50 9 ≥8 10 26 M20 x 50 9 ≥8 10 21 M24 x 60 9 ≥8 10 25

M16 x 60 9 ≥8 10 36 M20 x 60 9 ≥8 10 31 M24 x 70 9 ≥8 10 35

M16 x 70 19 ≥17 20 46 M20 x 70 19 ≥17 20 41 M24 x 80 19 ≥17 20 45

M16 x 80 19 ≥17 20 56 M20 x 80 19 ≥17 20 51 M24 x 90 19 ≥17 20 55

M16 x 90 29 ≥27 30 66 M20 x 90 29 ≥27 30 61 M24 x 100 29 ≥27 30 65

M20 x 100 29 ≥27 30 71 M24 x 120 29 ≥27 30 85

grip length grip length grip lengthShank

lengthSizeSize

Shank

length

Shank

lengthSize

Base Mat

thickness

MAX

Base Mat

thickness

MAX

Base Mat

thickness

MAX

Other diameters and lengths avalaible on request (M12 / M27 / M30 ) upto 190mm in length

Base material is the thickness of the steel in contact with the head of the bolt. This ensures that the shank of the bolt is through the shear plane to provide

the maximum design shear capacity. If Base material is thinner Shear capacity is as determined through the threaded section capacities.

Dimension of Standard TCB (Tension Control Bolts) to EN 14399-10

All dimensions in millimeters

M12 M16 M20 M24 M27 M30

1.75 2.00 2.50 3.00 3.00 3.50

nom 12.00 16.00 20.00 24.00 27.00 30.00

max 12.70 16.70 20.84 24.84 27.84 30.84

min 11.30 15.30 19.16 23.16 26.16 29.16

Max Bearing Diameter (Dw) min 20 26 33 41 46 50

Min Bearing Diameter (Dk) min 21 27 34 43 48 52

nom 8 10 13 15 17 19

max 8.8 10.8 13.9 15.9 17.9 20.0

min 7.2 9.2 12.1 14.1 16.1 18.0

Under Head Radius (r ) min 1.2 1.2 1.5 1.5 2.0 2.0

Head Radius ( R ) min 18 20 22 25 27 30

12 point spline Length (F1) min 11 13 15 16 19 21

Length to control groove (F2) max 16 18 20 21.5 24 26

max 8.0 11.6 14.4 17.1 19.3 21.4

min 7.4 11.0 13.8 16.5 18.7 20.8

Spline AC (Eb) min 8.36 12.43 15.60 18.65 21.13 23.5

Incolmplete thread (Ua)

Size

Pitch

Head height (k)

Spline AF (Sb)

Incomplete Thread U ≤ 2*Pitch

Shank Dia (Ds)

Dimension of HRD Nut to EN 14399-10

All dimensions in millimeters

M12 M16 M20 M24 M27 M30

1.75 2.00 2.50 3.00 3.00 3.50

max

min 20.10 24.90 29.50 38.00 42.80 46.60

max 22.00 27.00 32.00 41.00 46.00 50.00

min 21.16 26.16 31.00 40.00 45.00 49.00

Nut AC ( e ) min 23.91 29.56 35.03 45.20 50.85 55.37

Nom 12.00 16.00 20.00 24.00 27.00 30.00

min 11.65 15.65 19.35 23.35 26.35 29.35

max 12.35 16.35 20.65 24.65 27.65 30.65

max 0.8 0.8 0.8 0.8 0.8 0.8

min 0.4 0.4 0.4 0.4 0.4 0.4

="S" Nut AF actual

Nut Thickness (m)

Size

Pitch

Bearing Washer (dw)

Nut AF (s)

Bearing Washer thickness ©

Dimension of Washer to JSS II 09 (F35)

All dimensions in millimeters

M12 M16 M20 M24 M27 M30

max 13.70 17.70 21.80 25.80 28.80 32.00

min 13.00 17.00 21.00 25.00 28.00 31.00

max 26.00 32.00 40.00 48.00 54.80 60.00

min 25.20 31.00 39.00 47.00 56.00 58.80

max 3.60 5.00 5.00 6.70 6.70 8.70

min 2.80 4.00 4.00 5.30 5.30 7.30

Internal Diameter (d)

Outside Diameter (D)

Thickness (t)

Size

Tension Control Assemblies comparison: Button Head vs Hex Head Ninety nine percent of all TCB bolts are manufactured or produced with a button head design

which incorporates a larger bearing surface than the hex head design. In structural applications

the hardened, flat, bearing surface under the bolt head is in contact with a softer steel beam

surface which is generally rough with mill scale, blast cleaned, or primer coated. These surfaces

will have a higher friction coefficient than the hardened surface of the bolt, thus preventing

rotation. Therefore with the AJAX button head which has 40% more bearing surface than a hex

head, there is less chance of rotation because there is 40% more resistance and clamping force

being distributed between the bolt head and the structural member.

The lower friction coefficient inherent in the hex head design has a

greater chance of rotation in installation, thus resulting in decreased

torque and causing the tip to shear before minimum tension is

achieved. This could mean having to remove the assembly and

reinstalling a new assembly.

41-45 Mills Road Braeside, Melbourne Australia www.ajaxfast.com.au Tel: +61-3-9586-6666