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A pot magnet is a permanent magnet encased in a steel shell, which is sometimes called a pot, hence the name ‘pot’ magnet.

A permanent magnet emits a magnetic field without the need for any electricity. For more information, see: Magnets glossary.

The steel shell helps the pot magnet by increasing its holding power and providing the magnet with added strength and stability.

Pot magnets are often used as magnetic bases and magnetic holders for large supermarket ceiling signs.

There are six forms of pot magnet: bi-pole, countersunk, through hole (cylindrical hole), internal threaded, threaded bushing and stud.

According to the classification of raw magnetic materials, pot magnet have four categories: Neodymium pot magnets, ferrite pot magnets, alnico pot magnets and smco pot magnets.

According to the classification of steel shell, pot magnet have two categories: Pot Magnets with Stamping Shell and Pot Magnets with Machinery Shell.

Waterproof function, you need to use encapsulated pot magnet by rubber coating.

There are many ways to use a pot magnet. To illustrate their applicability, here are a few examples:

Magnetic light fittings

Internal threaded stud pot magnets can be used as part of a light fitting for a magnetic down light. The magnet is attached to the end of the light to hold it onto the metal in a ceiling.

Exhibition display signs

Countersunk pot magnets can be used to attach an exhibition display sign to a stand for marketing purposes, e.g. at a trade show.

Holders

Internal threaded pot magnets with the added hook accessory can be used to hang items such as mugs to a fridge door.

Magnetic bases

Deep internal threaded pot magnets can be used as a magnetic base for gauges e.g. an articulated gauging arm. An articulated gauging arm is used to precisely position objects within metrology (the science of measurement).

Door stops

Internal threaded stud pot magnets can be used as door stops to protect the door from closing all the way to the wall by holding it open.

Tow lights

Through hole pot magnets can be attached to the bottom of a tow light to enable the user to attach the tow light to the car to warn other road users that their car has broken down.

Jigs

Bi-pole pot magnets can be used as jigs. A jig is a custom-made tool created to control another tool’s movements. The bi-pole pot magnet is press-fitted or glued in place on the jig to help hold a non-ferromagnetic material, such as a piece of wood, onto a ferromagnetic surface whilst it is being drilled into.

Magnet

A pot magnet’s magnetic face is only exposed on one side of the steel pot.
The north pole of a pot magnet is in the centre of the magnet, with the south pole around the outside edge.
The configuration of the magnetic poles creates a closed circuit when the magnet is attached to a ferromagnetic material, providing a stronger hold. A closed circuit is where the magnetic field is trapped within the ferromagnetic material when it becomes attached to the magnet.

This type of magnetisation does lead to the magnetic field being strong, but not far reaching, as the lines only run parallel to the magnet. Therefore, the pot magnet can only attract ferromagnetic materials when they are very close to the magnetic face.

Steel shell on a pot magnet

The steel shell is a casing for the magnet and protects it from any chipping or cracking from contact with a hard surface, and any demagnetising effects.
The steel pot provides strength for the magnet, which would otherwise be very brittle, and allows threaded holes and studs to be inserted.
The steel shell helps the magnetic field become up to thirty two times stronger than other magnets by concentrating it to only one magnetic face. This means it can hold large objects such as supermarket signs from a ceiling without any additional support.

Because of its steel shell, a pot magnet can be inserted into ferromagnetic objects, such as jigs and fixtures, as, unlike other magnets, it will not suffer any demagnetising effects.
Some varieties of pot magnet can also be encased in a brass or plastic shell. The brass and plastic provide the magnet with a non-ferromagnetic shell which increases the magnetic field when a pot magnet is not supplied with a spacer. This only occurs in American pot magnets, as brass or plastic shells are not currently available in this country.

Pot magnet spacer

A spacer acts as a barrier in-between the magnet and the steel shell to avoid any demagnetising effects the steel may have on the magnet.
A spacer in a pot magnet can either be made of brass or plastic.

Rubber cap and rubber coating on a pot magnet

Pot magnets can have a rubber coating on top of their steel shell which allows them to be used on surfaces where the user does not want the magnet to scratch, such as on a car roof.
You can apply the rubber coating yourself;

If the pot magnet does not have a rubber coating, there is the option to buy a rubber cap which is easy to press onto the magnet and to remove.
The rubber provides the pot magnet with friction which allows the magnet to be clamped on vertical surfaces so they will not easily slide off. However, the rubber cap or rubber coating on a pot magnet creates an air gap (see Magnets glossary for more information) meaning the holding capabilities of the magnet can be reduced.

A pot magnet works by attaching itself to ferromagnetic materials with the help of its magnetic field, or to non-ferromagnetic materials with the help of fittings (such as studs and threaded holes) on the top of its steel shell.

The steel shell on a pot magnet means that it can hold a greater amount of ferromagnetic material. This is because the steel pot causes the magnetic force to be contained within the shell on the ferromagnetic surface, making the magnetic pull stronger.

This is in comparison to a horseshoe magnet or bar magnet where the magnetic field lines are splayed around the magnet and are not focused on the surface the magnet is attaching itself to.

As the magnetic field is concentrated in one area, the magnet will not be allowed to attract ferromagnetic materials over a large air gap. This is because the magnetic field lines will not stretch out beyond the sides of the shell.

The pull force of a pot magnet attracts the ferromagnetic material to the magnet, holding it in place. The larger the pull force of the pot magnet, the more material it can attract.

A magnet’s pull force is determined by a number of different factors; for example, how the magnet has been coated and any damage which may have occurred to the surface of the magnet.

There are five types of pot magnet: countersunk, internal threaded, through hole, bi-pole and stud. The pot magnets vary in their attachments, which allow them to be connected to different types of objects, such as supermarket signs and articulated gauging arms.

Countersunk pot magnets

Countersunk pot magnets are a type of a pot magnet with a countersunk hole in the magnetic face. The countersunk hole has a flat top on one magnetic face which tapers at a 82 degree angle towards the top of the shell, in the shape of a cone.
The countersunk hole aids the magnet in its attachment to non-ferromagnetic materials with a countersunk screw.

Internal threaded pot magnets

Internal threaded pot magnets are a type of pot magnet with a threaded hole through the centre. An internal threaded hole is a cylindrical hole with continuous grooves, known as threads, in a spiral pattern around its inside wall.
Internal threaded pot magnets can be used as magnetic bases for gauges, for example, an articulated gauging arm.

Through hole pot magnets

Through hole pot magnets have a hole through the centre, known as a boss. The boss allows the magnet to be attached to non-ferromagnetic items with a bolt.
Through hole pot magnets can be used as retrieval magnets, which are used to pick up or retrieve ferromagnetic objects from hard-to-reach places. For example, you could use a retrieval magnet to pull a bicycle from a river.

Bi-pole pot magnets / Deep pot magnets

Bi-pole pot magnets have a thin magnet in the centre with two mild steel poles on either side, inside a shell. This is known as a sandwich magnet system.
A sandwich magnet system makes the bi-pole pot magnet thirty-two times stronger than a standard magnet, for example, a bar magnet.

Stud pot magnets

Stud pot magnets can either be a shallow or deep, and have a stud protruding from the top of the pot magnet’s case. The stud is the cylinder of stainless steel that protrudes from the surface of the magnet.
Stud pot magnets can be used to hold promotional signs from the ceilings of supermarkets.

There are four types of pot magnet according to magnetic material: neodymium pot, ferrite pot, smco pot and alnico pot. 

Neodymium pot magnets

Neodymium magnet elements: Neodymium Nd, Iron Fe, and Boron B
Neodymium magnets are made up of an alloy containing neodymium, iron, and boron.

They are the most common type of magnet available as they can produce the strongest magnetic field in a very small area due to the materials that make up the magnet being a stronger combination than any other.

Due to the magnetic force they produce, neodymium magnets can be used for any type of magnet from magnetic sweepers to magnetic discs.

ADVANTAGES
Advantages and disadvantages of magnetic materials

DISADVANTAGES
They corrode quickly, unless they are coated, due to their iron content
They start to demagnetise at anything above 80°C

Ferrite pot magnets

Ferrite elements: Strontium Sr, oxygen O, Carbon C, and Iron Fe
Ferrite is strontium hexaferrite SrO-6 (Fe203), which is an alloy made of strontium carbonate and iron oxide.
Ferrite magnets are also known as ‘ceramic magnets’ due to their brittle nature being very similar to porcelain.

ADVANTAGES
Cheap to manufacture
Can work in high temperatures
Corrosion resistant
Low cost

DISADVANTAGES
Hard and brittle so can break easily
Demagnetises at -10°C to -20°C

Smco pot magnets

Samarium cobalt magnet elements: Samarium Sm, and cobalt Co
Samarium cobalt magnets are an alloy of samarium and cobalt but can sometimes contain a small amount of either iron, copper, hafnium, zirconium, or praseodymium.
Samarium cobalt magnets are usually made into magnetic discs, bar magnets and pot magnets.

ADVANTAGES
Work at high temperatures, even at 300°C
Highly corrosion resistant so can be used under water

DISADVANTAGES
Are very brittle magnets so can chip and break easily
Expensive due to their cobalt content

Alnico pot magnets

Alnico magnet elements: Aluminium Al, Nickel Ni, Cobalt, Co, Iron Fe, and Copper Cu
Alnico magnets are made of a combination of aluminium, nickel, cobalt, iron and copper.
They can be identified by their traditional red coating; all except for a channel horseshoe magnet which is used for industrial uses, so does not require a coating.

ADVANTAGES
Operates at temperatures as high as 850°C
Corrosion resistant

DISADVANTAGES
Can only be made into round base magnets (shallow pot magnets), horseshoes magnets and long thin cylinder magnets
They are self demagnetising.

Pot magnets can be used in a variety of different ways. Each magnet has particular features which specialise them for these tasks.

Countersunk pot magnets

A countersunk pot magnet should be chosen when a pot magnet needs to be attached to a non-ferromagnetic material securely, for example, for an exhibition display sign.
This pot magnet would be an ideal choice, as the use of a countersunk screw to attach the magnet means that the pot magnet is not easily removed.

Internal threaded pot magnets

When choosing a pot magnet to be used as a magnetic base, the best type to choose would be an internal threaded pot magnet. This is because it allows you to attach your instrument, for example an articulated gauging arm, securely with the aid of a threaded hole.
The added depth of a deep internal threaded pot magnet also provides stability to the object when it is used as a magnetic base.
The depth of a deep internal threaded pot magnet can vary.

Through hole pot magnets

The best pot magnet to use as a retrieval magnet to collect ferromagnetic material, such as coins, from hard-to-reach places, would be a through hole pot magnet. This is because a piece of strong rope can be threaded through the boss (through hole) and tied to the magnet without affecting its magnetic ability

Bi-pole pot magnets (a subcategory of Deep pot magnets)

A bi-pole pot magnet is the ideal magnet to be used as a jig or fixture. A bi-pole pot magnet provides a higher magnetic pull than other magnets and can be easily glued into place. This allows the user to create a jig and provide a strong holding force for a fixture.

Stud pot magnets

A stud pot magnet should be chosen by a user who intends to use a pot magnet as a ceiling magnet.
A stud pot magnet has the ability to attach accessories such as hooks or eyebolts, which enables it to be used as a holder for supermarket signs that hang from the ceiling.

Shape

All pot magnets have two style shaped shells, its are a machine shell pot magnets and a stamping shell pot magnets.

They are not the same technology, materials are the same, is the metal steel.

Machine shell: It is machined out of the shell, steel casing : machine processing. so it’s top and bottom into a 90 degree angle.

Stamping shell: It is stamped out of the shell, steel casing : stamping processing. so it’s top and bottom into a R angle (arc angle ).

Holding Force

Holding force of machine shell pot magnets is stronger than holding force of stamping shell pot magnets.

A countersunk pot magnet is a pot magnet with a countersunk hole on its magnetic face.

The countersunk hole tapers inwards at an angle of 82 degrees, allowing the magnet to be attached to a surface with a countersunk screw, providing the screw has an 82 degree angled head.

Once attached, the screw should sit flush with the surface of the magnet.

Here, flush means that when the magnet has been sunk into an object, (e.g. a fridge door), the top of the screw and the magnet will be level with the surface, rather than protruding above like other types of screws would (e.g. on an internal threaded pot magnet).

The countersunk pot magnet has a countersunk hole which can be M3 to M14.

M3 to M14 stands for a metric countersunk hole which is 3mm (0.12″) to 14mm (0.55″) in diameter.

The screws used with a countersunk pot magnet need to be the same diameter as the countersunk hole. For example, you will need a screw that is 4mm (0.16″) in diameter to fit inside a 4mm (0.16″) diameter countersunk hole in a countersunk pot magnet.

Countersunk pot magnets can be used to hold any ferromagnetic material onto a non-ferromagnetic surface; for example, to attach an exhibition display sign to a stand for marketing purposes.

Countersunk pot magnets are usually measured diameter x depth. The size of the countersunk pot magnet always includes the size of the shell within the measurements.

Diameter

The diameter refers to the distance between the two widest points of the countersunk pot magnet. The diameter can range from 10mm (0.39″) to 76mm (3″).

Different diameters of countersunk pot magnets can be used for a large array of applications. For example, larger countersunk pot magnets are often used for holding large ferromagnetic materials closed or open such as heavy fridge doors, where the diameter will provide the magnet with an increased grip on the material.

For most applications, the diameter you choose will depend on the size of the item you wish to hold.

Depth

The depth of a countersunk pot magnet is the distance between the top of the shell and the magnetic face, and can range from 5mm (0.2″) to 19mm (0.75″).

The depth you choose will depend on the depth of non-ferromagnetic material you are attaching the magnet to and how much you wish the pot magnet to protrude from this.

A countersunk pot magnet with a smaller depth will create a cleaner, more slimline appearance, in comparison to one with a larger depth. If the magnet is being attached to a thin material such as an exhibition display sign, this may be preferable.

Magnetic pull

The magnetic pull of countersunk pot magnets ranges from 0.4kg (0.02lbs) to 164kg (361.56lbs).

The magnetic pull is the maximum weight of ferromagnetic material that the countersunk pot magnet can hold. This is not determined by the magnet’s overall size, but the material the magnet is made of. This means that a large magnet does not necessarily have a larger magnetic pull than a small magnet.

Summary

To summarise, when choosing a countersunk pot magnet, the most important considerations are the diameter and the depth. This is due to the effects these will have on the attachment of the countersunk pot magnet to a non-ferromagnetic material.

The larger the diameter, the greater the area of ferromagnetic material the magnet can hold onto. The depth, on the other hand, is dictated by the depth of material you are using.

Countersunk pot magnets can be attached to non-ferromagnetic materials with the help of a countersunk screw; for example, to hold heavy fridge doors open and closed.

To attach the countersunk pot magnet to a non-ferromagnetic material, you will need to do the following:

Equipment required:

22.23mm (0.88″) forstner drill bit
Cordless drill driver
12.7mm (0.5″) countersunk screw, such as a wood screw
19.05mm (0.75″) countersunk pot magnet
Slotted screwdriver

Countersunk pot magnet, countersunk screw, cordless drill driver, forstner drill bit

Step 1 – Drill hole

Use the cordless drill driver with the forstner drill bit attached to drill a flat-bottomed hole into a piece of non-ferromagnetic material, e.g. a piece of wood.

The forstner drill bit will produce a hole of a consistent depth with smooth sides, which is ideal to insert the countersunk pot magnet into.

A flat drill bit may also be used for this task, however it will not leave as neat a hole as the forstner drill bit due to its sharp pointed end

Step 2 – Insert countersunk magnet

Clear the hole of any wood chippings and insert the countersunk pot magnet with the countersunk hole facing upwards.

Step 3 – Fasten with screw

Fasten the countersunk magnet with the flat headed screws using a screwdriver. Continue doing this until the screw is flush (level) with the top of the countersunk pot magnet.

An internal threaded pot magnet is a type of pot magnet with a threaded hole through the centre.

An internal threaded hole is a cylindrical hole with continuous grooves, known as threads, in a spiral pattern around the inside wall of the hole.

The internal threaded hole allows the pot magnet to be attached to non-ferromagnetic materials which have corresponding grooves such as threaded bars or bolts. The internal threaded hole can fit M4 to M20 threaded studs and bolts.

The internal threaded hole runs the entire length of the pot magnet allowing maximum thread contact between the internal threaded hole and a screw or bolt, for secure clamping. This allows the magnet to be used on dirty and uneven surfaces which a magnet may have found difficult to attract to normally.

An internal threaded pot magnet can come with one to four internal threaded holes.

If the pot magnet has four threaded holes, it is known as a limpet pot magnet, and can be used to fit onto a clamp mounting with bolts. This is often used to mount a camera onto a car for filming purposes.

Internal threaded pot magnets can be used as magnetic bases for gauges, for example, an articulated gauging arm.

An articulated gauging arm is used to precisely position objects within metrology (the science of measurement).

There are two types of internal threaded pot magnet: shallow internal threaded pot magnets and deep internal threaded pot magnets.

Shallow internal threaded pot magnets

Shallow internal threaded pot magnets are thin and flat, and often used when there is a restricted height such as hanging seasonal decorations, where the deep internal threaded pot magnet cannot be used without looking too obtrusive.

Deep internal threaded pot magnets

Deep internal threaded pot magnets on the other hand, are tall and thin with a depth of over 20mm (0.79″). They are used when there is no height restriction, e.g. retrieving large ferromagnetic objects from water or as a magnetic base for objects such as an articulated gauging arm.

To use an internal threaded pot magnet, you will need to use another non-ferromagnetic threaded object such as a bolt or accessory.

To attach the accessory or threaded bolt onto the internal threaded pot magnet, turn the non-ferromagnetic object clockwise into the internal threaded hole. The bolt needs to be twisted clockwise into the internal threaded hole to attach it.

To remove the internal threaded pot magnet, turn the non-ferromagnetic object or accessory anti-clockwise.

Various accessories are available for use with internal threaded pot magnets. They should have a threaded end which is screwed into the pot magnet’s threaded hole.

Hooks

Hooks can be used to hold doors open or to hold different items onto a ferromagnetic surface (for example, decorations, temporary wiring, or promotional signs).

The hooks available for an internal threaded pot magnet are all removable due to a thin external threaded stud on one end.

Some internal threaded pot magnets have a hook known as a jacking screw, which is thicker than a normal hook and set at a right angle.The jacking screw is positioned in the centre of the magnet in order to prise the magnet away from ferromagnetic material, when it has a magnetic pull of more than 100kg (220.46lbs).

The thickness of the jacking screw provides strength to the hook, making it ideal for this purpose, whereas a normal hook would be too thin.

Eyebolts

An eyebolt is a type of threaded bolt with a loop on one end, and is designed to attach hooks, cables, or ropes.

Eyebolt attachments for internal threaded pot magnets are used to hang cables from ferromagnetic materials. For example, an M5 (5mm (0.2″)) eyebolt is ideal for holding thick rope or cable.

Ball knobs

Ball knobs are similar in appearance to door knobs. They have a thin threaded stud for attaching to an internal threaded pot magnet and a wide flat top for the user to hold.

Ball knob accessories can be used to aid the opening of ferromagnetic doors by providing a handle for the ferromagnetic surface.

Internal threaded pot magnets are always measured diameter x depth. The size of the shell is usually included within the measurements.

Shallow internal threaded pot magnets

Diameter

The diameter refers to the distance between the two widest points of the magnet and ranges from 19mm (0.75″) to 100mm (3.9″).

The diameter you choose will depend on the size of the object the pot magnet is needed to hold, (e.g. a set of keys).

An internal threaded pot magnet with a smaller diameter may provide a more aesthetically appealing end result, compared with an internal threaded pot magnet with a large diameter.

Depth

The depth of a shallow internal threaded pot magnet is the distance between the top of the shell and the magnetic face. This usually increases as the diameter does, and can range from 7mm (0.28″) to 20mm (0.79″).

Magnetic pull

The magnetic pull ranges from 3.6kg (7.9lbs) to 55kg (121.25lbs).

The magnetic pull is the maximum weight of ferromagnetic material the internal threaded pot magnet can hold. This is not determined by its overall size, but by the material the magnet is made from. This means that a large magnet does not necessarily have a larger magnetic pull than a small magnet.

Summary

To summarise, when purchasing an internal threaded pot magnet, the key thing to look out for is the diameter, as this has the greatest effect visually on the end product.

Internal threaded pot magnets are always measured diameter x depth. The size of the shell is usually included within the measurements.

Deep internal threaded pot magnets

Diameter

The diameter refers to the distance between the two widest points of the magnet and ranges from 6mm (0.24″) to 80mm (3.15″).

Depth

The depth of a deep internal threaded pot magnet is the distance between the top of the shell and the magnetic face. It can range from 20mm (0.79″) to 65mm (2.56″).

Magnetic pull

The magnetic pull ranges from 0.2kg (0.44lbs) to 155kg (341.72lbs).

Summary

The size of deep internal threaded pot magnet you choose depends upon the size of the non-ferromagnetic material you are attaching it to.

The size of the pot magnet needs to be sufficient enough to hold onto the object without becoming unstable. For example, for a large and heavy gauge, you will need a large depth and diameter pot magnet in order to stop the object from falling over.

A through hole pot magnet is a pot magnet with a large hole through the centre, known as the boss. The boss allows the magnet to be attached to non-ferromagnetic items with a bolt.

The boss is wide enough to accommodate the bolts without them touching the magnet. This allows the bolt to be attached to a non-ferromagnetic material very tightly, as clamping directly onto the magnet could break it, as it is very brittle.

The boss in a through hole pot magnet can be M4 to M20. This stands for a through hole which is 4mm (0.16”) to 20mm (0.79”) in diameter. However, this only refers to the size of the through hole rather than the size of the bolt which can be attached. This is because some through hole pot magnets provide a larger air gap between the magnet and the bolt to stop the two from touching.

The size of the bolts which can be attached to a through hole pot magnet depends upon the diameter of the hole in the top of the pot magnet’s shell. This hole can fit M3 to M12 bolts – which stands for a bolt which is 3mm (0.12”) to 12mm (0.47”) in diameter.

The bolts used with a through hole pot magnet need to be the same diameter as the shell’s through hole. For example, you will need a bolt that is 4mm (0.16″) in diameter to fit inside a 4mm (0.16″) diameter through hole in a through hole pot magnet.

Through hole pot magnets can be used as retrieval magnets, which are magnets used to pick up or retrieve ferromagnetic objects from hard-to-reach places, (e.g. underwater). This is useful for treasure hunters hoping to find money at the bottom of a river.

Through hole pot magnets can also be attached to the bottom of tow lights to enable users to attach the tow light to a car to warn other road users that the car has broken down.

Attaching a screw to a through hole pot magnet

To use a through hole pot magnet, a bolt needs to be placed through the hole until the head touches the top of the steel shell, with the magnetic face pointing outwards away from the ferromagnetic surface.

Screw in a through hole pot magnet

The bolt is then attached to the ferromagnetic material with a nut to hold it securely in position. The through hole pot magnet will now be ready to use.

Diameter and depth of a through hole pot magnet

Through hole pot magnets are always measured as their diameter x depth. The size of the through hole pot magnet always includes the size of the shell within the measurements.

Diameter

The diameter refers to the distance between the two widest points of the through hole pot magnet. The diameter ranges from 14mm (0.55″) to 100mm (3.9″).

The diameter you choose will depend on the role the through hole pot magnet is used for. If the through hole pot magnet is used as a retrieval magnet then the user will require a large diameter. This is because a large diameter through hole pot magnet will be able to secure the ferromagnetic material in a hard-to-reach place more securely than one with a small diameter.

Depth

The depth of a through hole pot magnet is the distance between the top of the shell and the magnetic face. It can range from 3.6mm (0.14″) to 22mm (0.87″).

Magnetic pull

The magnetic pull of through hole pot magnets ranges from 5.2kg (11.46lbs) to 164kg (361.56lbs).

The magnetic pull of a through hole pot magnet refers to the maximum weight of ferromagnetic material that the pot magnet can hold. It is determined by the materials the pot magnet is made from, rather than its overall size and depth. For more information, see page What are magnets made of?

To summarise, when purchasing a through hole pot magnet, the key thing to look out for is the diameter and the magnetic pull of the magnet. These are the two greatest variants of a through hole pot magnet and can affect the amount of ferromagnetic material it can hold securely. For example, a magnet with a large diameter and magnetic pull will allow the magnet to retrieve ferromagnetic materials from underwater.

A bi-pole pot magnet has a thin magnet in the centre with two mild steel poles on either side, surrounded by a shell, hence its name. This is known as a sandwich magnet system.

A sandwich magnet system makes the bi-pole pot magnet thirty-two times stronger than a standard magnet, such as a bar magnet. The two steel poles on the sides of the magnet concentrate the magnetic field lines, making the magnet stronger.

The bi-pole pot magnet does not have a way of attaching itself to non-ferromagnetic materials, and this is known as blind-ended. This means that bi-pole pot magnets either have to be glued into place or used in a press fit installation.

Press-fit installations

A press-fit installation, also known as an interference fit, is where friction holds two objects together without any other means of fastening. This is used in applications where the magnet is not meant to be easily removed, such as a jig or fixture.

A jig is a custom-made tool created to control another tool’s movements, whereas a fixture holds a tool in an exact position.

The bi-pole magnet is press-fitted or glued in place on the jig to help hold a non-ferromagnetic material, such as a piece of wood, onto a ferromagnetic surface whilst it is being drilled.

Bi-pole pot magnets can be attached to non-ferromagnetic materials with the help of glue, to create a jig or fixture, for example.

To attach the bi-pole pot magnet to a non-ferromagnetic material you will need to do the following:

Equipment required:
super glue, cordless drill driver, forstner drill bit, and a bi-pole pot magnet
22.23mm (0.88″) forstner drill bit
Cordless drill driver
Cyanoacrylate glue (also known as super glue)
19.05mm (0.75″) Bi-pole pot magnet

Step 1 – Drill hole

Use the cordless drill driver with the forstner drill bit attached to drill a flat-bottomed hole into a piece of non-ferromagnetic material, (e.g. wood).

The forstner drill bit will produce a hole of a consistent depth with smooth sides, which is ideal to insert the bi-pole pot magnet into.

A flat drill bit may also be used for this task, however it will not leave as neat a hole as the forstner drill bit due to its sharp pointed end.

Step 2 – Apply glue

Apply glue to the bottom of the bi-pole magnet.

Step 3 – Insert magnet

Clear the hole of any wood chippings and insert the bi-pole pot magnet with the magnetic face pointing upwards.

Hold the magnet in place for 2-3 minutes until a secure hold between the glue and the non-ferromagnetic material is achieved.

Bi-pole pot magnets are always measured diameter x depth. The size always includes the shell within the measurements.

Diameter

The diameter refers to the distance between the two widest points of the bi-pole pot magnet, and ranges from 6mm (0.24″) to 32mm (1.26″).

The diameter you choose will depend on the size of the fixture or jig you are creating. If you are creating a small jig or fixture, then you may require a bi-pole pot magnet with a smaller diameter, to make the fixture or jig more slimline.

Depth

The depth of a bi-pole pot magnet is the distance between the top of the shell and the magnetic face. It can range from 20mm (0.79″) to 40mm (1.57″).

The depth you choose will depend on the depth of the non-ferromagnetic material you are attaching the bi-pole pot magnet to.

If you are creating a jig out of wood with a 20mm (0.79″) depth, then you could use a bi-pole magnet with a 20mm (0.79″) depth, however you will not be able to use a 40mm (1.57″) depth bi-pole magnet as this will be too large.

Magnetic pull

The magnetic pull of bi-pole pot magnets ranges from 1kg (2.2lbs) to 71.4kg (157.4lbs).

The magnetic pull is the maximum weight of ferromagnetic material the bi-pole pot magnet can hold. This is not determined by its overall size, but the material the magnet is made from. This means that a large magnet does not necessarily have a larger magnetic pull than a small magnet.

Summary

To summarise, when purchasing a bi-pole pot magnet, the key thing to look out for is the depth and diameter as these are determined by the size of the fixture or jig you intend to use.

Internal threaded stud pot magnet and an external threaded stud pot magnet

A stud pot magnet has a stud (cylinder of stainless steel) protruding from the top of its steel shell.

Stud pot magnets can be used as antenna mounts on car roofs, or to hang promotional signs from the ceiling of supermarkets, or to be the light fitting for a magnetic down light.

There are three types of stud pot magnet: internal threaded studs, external threaded studs, and plain studs.

Internal threaded studs

An internal threaded stud is a plain stud with an internal threaded centre. The added thread length inside the stud allows a more secure hold with a threaded bolt than without the stud, as on an internal threaded pot magnet.

The internal threaded hole allows the pot magnet to be attached to non-ferromagnetic materials which have corresponding grooves such as threaded bars, bolts, or hooks. The internal threaded hole can fit M4 to M20 threaded hooks and bolts.

Internal threaded stud pot magnets can come with a hook attachment.

When a hook is attached to an internal threaded stud pot magnet, the two are known as a ceiling magnet. This is often used to hang promotional signs to supermarket ceilings.

Internal threaded stud pot magnets are also known as female threaded pot magnets. They can attach themselves to external threaded stud pot magnets, which are also known as male threaded pot magnets. This is particularly useful for storage as it allows the two pot magnets to be stored together without one demagnetising the other (see Magnets glossary).

External threaded studs

External threaded studs have continuous grooves, known as threads, in a spiral pattern around the outside. They can either be screwed into a threaded hole or placed through a plain hole and then held in place with a nut.

Plain studs

A plain stud is a stud without any threads or markings. As it has no threads, the plain stud is riveted to non-ferromagnetic materials.

“Riveting” is achieved by punching the stud into the material with a rivet gun. This causes the top of the stud to bend into an umbrella shape, holding the stud pot magnet in place.

Each type of stud pot magnet requires a slightly different method for use. Read on to find out more…

Plain stud pot magnets

To use a plain stud pot magnet you will need a riveter to create a hole in the non-ferromagnetic material you are attaching the magnet to.

Step 1 – Position magnet

First, place the plain stud pot magnet through the hole in the non-ferromagnetic material.

Step 2 – Rivet in place

Then, on the side of the material where the stud is protruding, use the riveter to punch the stud into an umbrella shape, holding the magnet securely in place.

External threaded stud pot magnets

There are two ways to use a threaded stud pot magnet, either by screwing it into a threaded hole or by using a nut.

Screwing into place

For this method, the stud of the external threaded pot magnet needs to be inserted into the threaded hole. To attach with a screw, turn the stud pot magnet clockwise whilst applying pressure. Make sure you keep turning until the stud cannot be tightening any further.

To remove the external threaded stud pot magnet, simply turn the stud pot magnet anti-clockwise.

Nut

A nut is used when a threaded hole is not available.

First, push the external threaded stud through the hole in the non-ferromagnetic material. Next, place a nut on the end of the stud and turn it clockwise until the nut is attached securely to the external threaded stud.

Internal threaded stud pot magnets

To use an internal threaded stud, an external threaded stud or bolt is required. This external threaded stud needs to be turned clockwise into an internal threaded hole to attach securely.

Stud pot magnets are always measured diameter x depth. The size always includes the shell within the measurements.

Diameter

The diameter refers to the distance between the two widest points of the stud pot magnet. It ranges from 10mm (0.39″) to 125mm (4.9″).

The diameter you choose will depend on where the stud pot magnet is going to be used.

For example, if the magnet is going to be used for promotional ceiling signs or light fittings, the diameter should be larger, as the magnet needs greater contact with the ferromagnetic material to provide a secure hold.

Depth

The depth of a stud pot magnet is the distance from the top of the stud to the magnetic face, and can range from 5mm (0.2″) to 70mm (2.8″).

The depth you choose will depend on the amount of space available for the stud pot magnet. If there is a limited height available, then a magnet with a depth of less than 20mm (0.79″) would be ideal.

Magnetic pull

The magnetic pull of stud pot magnets ranges from 0.8kg (1.8lbs) to 164kg (361.56lbs).

The magnetic pull is the maximum weight of ferromagnetic material the stud pot magnet can hold. This is not determined by its overall size, but the material the magnet is made from. This means that a large magnet does not necessarily have a larger magnetic pull than a small magnet.

Summary

To summarise, when purchasing a stud pot magnet, the key thing to look out for is the depth and diameter. These affect the tool’s ability to hold non-ferromagnetic material to a ferromagnetic surface (e.g. a down light to a steel ceiling).