A Bolt with a Hexagon head is measured by the thread diameter and the length from under the head to the end.
The tensile strength of a bolt is indicated with a Class or a Grade.
The table below shows the approximate equivalents between a Class and a Grade
|Class 4.6 Mildsteel|
|Class 8.8 High Tensile||Grade 5 High Tensile|
|Class 10.9 High Tensile||Grade 8 High Tensile|
|Class 12.9 High Tensile||Grade 9 High Tensile|
No, there can be various Metric Fine thread pitches available.
We recommend the thread to always be measured with a thread gauge or checked with a nut to ensure the correct thread pitch is ordered.
We can cut any thread on a bolt in our specialised Workshop. Just advise us of the thread pitch and the length of the thread required and we can make it for you.
A Set Screw is a fully threaded bolt. It has a Hexagon head and has no plain shank. (Not to be confused with a Socket Set screw).
Most commonly available in Metric and in Class 4.6 Mildsteel & High Tensile Class 8.8, although also available in some sizes in Classes 10.9 & 12.9.
Set Screws are sold without the nuts because they are mainly used for in tapped holes with the longer Set screws being used for adjusting situations.
This can vary depending on the Length of the Bolt, and the Standard it is manufactured to.
The table below can be used as a general guide...
|Bolt Length||Thread Length Calculation|
|up to 125mm long||2 X Diameter + 6mm|
|up to 200mm long||2 X Diameter + 12mm|
|Over 200mm long||2 X Diameter + 25mm|
If the measurement of the thread or the Parallel Plain shank of the bolt is crucial, we highly recommend that you contact us and we can give you an accurate measurement.
We can also manufacture Bolts with specific thread lengths in our Workshop - contact us for a Quote.
Need a fitted bolt ? We can also make these for you.
You can use the Part Turn Tightening Method...
Nut Rotation from the Snug Tight condition.
|Nominal||Length of Bolt||Length of Bolt|
|Bolt||Nut Rotation||Nut Rotation|
|Diameter||1/2 turn||3/4 turn|
|M16||Up to 120mm||Over 120 up to 240mm|
|M20||Up to 120mm||Over 120 up to 240mm|
|M22||Up to 120mm||Over 120 up to 240mm|
|M24||Up to 160mm||Over 160 up to 350mm|
|M30||Up to 160mm||Over 160 up to 350mm|
|M36||Up to 160mm||Over 160 up to 350mm|
The Length of all Countersunk bolts and screws are measured overall - including the head.
This is because when installing, the head sinks into the material, therefore becoming part of the length.
A Socket Screw is a screw that has an Inner Hex drive and can be fastened with an Allen key or a hex Drive bit.
Available in the following head types...
Socket Head Cap Screws
Countersunk Socket Screws - length is measured overall, including the head
Button head Socket Screws
Socket Set Screws - also known as Grub Screws
Socket Shoulder Bolts - length is measured from under the head to the end of the shoulder.
The diameter of a Tension pin is measured by it's Hole size. It is not measured by the actual size of the pin.
M6 Tension pin Nominal Hole Size = 6.0mm Actual Diameter of pin = 6.7mm
Metric Taper pins are measured differently to Imperial Taper pins.
When measuring Metric Taper pins , the diameter is measured at the smallest end of the pin.
Metric Taper pins have a taper of 1:50
When measuring Imperial Taper pins, the diameter is measured at the largest end of the pin.
Imperial Taper pins have a taper of 1:48
The Length of a Clevis Pin is only the Effective Length
The length is measured from under the eye to the end of the shorter leg.
The diameters of Self tapping & Self drilling Screws are measured in Gauges rather than millimeters, below is a conversion table..
The thickness of a Washer is often measured in Gauges, here is a conversion table into millimetres.
|22 Gauge||0.75 mm|
|20 Gauge||0.95 mm|
|18 Gauge||1.2 mm|
|16 Gauge||1.6 mm|
|14 Gauge||2.0 mm|
|12 Gauge||2.5 mm|
|10 Gauge||3.0 mm|
When ordering U Bolts, we need to know the following measurements and information...
Material ie: Mildsteel, High Tensile & what grade, Stainless & what grade etc..
Material thickness ie: M10, M12 etc..
Centre ie: the measurement from the Centre of one leg to the centre of the other leg.
Overall length ie: from the outside top of the U bend, to the end of the legs.
Thread length ie: the length of thread on each leg.
Thread pitch for example: Metric Coarse, UNC, UNF etc...
We also need to know...
The Nominal Bore is the internal diameter of the pipe the U Bolt will fit.
There are four NZ Courier pick-ups from The Boltholder every day (Monday to Friday). Most destinations within the North Island can be reached overnight, and many within the same day.
We deliver three times a day to Hamilton, Rotorua and Tauranga, twice a day to Taupo and once a day to Auckland, Napier.
If your order is going to a rural address, expect to add one additional day to delivery times.
For larger orders, we use other Transport Companies.
If we don't stock the product you're looking for, we may very well be able to source it for you or fabricate it for you in our workshop.
We have an excellent network of suppliers, both within NZ and across the world from which we can source bolts and other products. Contact our Sales team and let us know what you're looking for.
No problem, you can either open an account by downloading our Credit Account Application form, or just let us know what you are after and we can email you an invoice and our bank account details for payment.
We accept Credit cards for any Email or Phone orders, subject to a 3% Credit card processing fee.
If you would like to pay on collection of goods, we only accept EFTPOS payments at our premises.