Improved fastener for palisade fencing

Abstract

A steel bolt 10 for use in constructing palisade fencing, consisting of: a fully or partly threaded shank 50 and a conical or frustoconical head 20, pointing away from the shank, the base of the head

Description

18 02 25 The present invention relates to an improved fastener for Palisade fencing such as to enable greater security and reduced material usage. Background Palisade fencing is a recognised category of security fencing which is visually distinct and is used where an effective physical barrier to entry is required to an area. In many locations that are at risk of theft, such as factories and warehouses, may often erect a palisade fence around the perimeter of the property / location. These fences are used to provide security to these locations. In general terms a palisade fences comprises a series of posts that are embedded in the ground. Between each post is a plurality of pales, comprising a slat with one or more points on the top end, and may have their lower end embedded in the ground also. Wherein the plurality of pales are connected together and to the posts, via one or more rails on the inside of the fence. Typically, there are two rails, one proximate the top end, below the pointed section, and a second proximate the bottom end of the pale. In most cases these palisade fences are made of steel, but other materials may also be possible. When constructing these fences, the pales are secured to the rails via a plurality of bolts, typically steel bolts. Such bolts may also have been used to secure the rails to the posts also. However, to improve the protection provided by the palisade fence, the nuts and bolts used to secure the fence together may include one or more security features. These features are designed to make it more difficult to remove the bolts within the fence, such as to dismantle it to gain access. Examples of such security features include the following: Shear off nuts, which comprise curved, or domed portion, with a traditional hexagonal nut attached to the outside of this curved portion. When securing these nuts into place, the nut is positioned so that the curved portion is the side closest the fence. The user may then use traditional tools on the hexagonal portion of the nut to secure the nut to the shank of a bolt. Once fastened into place the user may continue to tighten the nut, which will result in the hexagonal portion of the nut sheering off. This leaves only the curved portion of the nut in place, securing the fence. This means that the nut is difficult to remove as most conventional tools will struggle to grip the curved surface of the nut, with enough strength to apply the necessary force to remove the nut from the bolt. In use these bolts provide improved security as it is more difficult to dismantle the fence. However, it is noted that these fences often require many of these bolts, which will result in a lot of waste due to all the sheared off 18 02 25 portions. These portions may be dangerous to the environment, especially if animals or possibly even children should find them and swallow them. Therefore, the use of these bolt will require additional time and resources to clean the site where the fence is located. Another example of a palisade fence security feature can be found in GB2307493A. in this design a clamp is positioned between the pale and the rail, with the bolt securing the clamp to the rail, and the clamp holding the pale in place. The purpose of this design is that the head of the bolt would be hidden behind the pale. This would make it difficult to access the bolt head without a specialised tool. This like the shear off bolt make it harder to remove the nuts and bolts holding the fence together, thereby improving the overall security provided by the fence. Similarly, in GB2447556, the fence comprises an outer layer on the pale, and / or rail, wherein this outer layer has a recess for the bolt or nut. As with the other safety features these recesses obscure either the bolt head or the nut making it harder to access, and therefore more difficult to remove the bolts holding the fence together. The problem with such designs is that even though the bolts and nuts are more difficult to access and remove, it is still possible for thefts and other intruders to do so. Especially given that over time such intruders can acquire the specialist tools needed to remove these bolts with ease. Therefore, there is a need for improved security features for bolts and / or nuts that is not only hard to grip, or reach, but is also difficult, or even, impossible to remove particularly without simply destroying the fastener. Invention The present invention provides a steel bolt for use in constructing a palisade fence. Said bolt consisting of: a fully or partly threaded shank and a conical, or frustoconical, bolt head pointing away from the shank. Wherein the base of the head presents a bearing surface of greater radius than the shank. Such a bolt helps to provide improved security as the conical or frustoconical surface of the bolt head will be hard to grip with traditional tools, used to remove commonly used hexagonal headed bolts. As a result, the claimed bolts may require a speciality tool to remove, which is configured to grip the sloped or curved surfaces of the conical / frustoconical bolt head. As traditional tools, such as spanners or pliers, are configured to grip flat surfaces, therefore if such tools were used on the claimed bolt there would be only a small point of contact between the tool and the bolt head, meaning less force could be transferred to the bolt. Additionally, if the bolt head has curved surfaces there may be little friction between the bolt and the tool making it more difficult to grip the bolt. As 18 02 25 a result, an intruder would find it difficult to remove the claimed bolts from the palisade fence, and therefore would not be able to make an entry point within the fence, to access the secured area within the fence. Additionally, in some cases, where the bolt has a conical head, the claimed bolt may act as an additional deterrent to intruders. As the points may cause harm to anyone who tries to grip and climb the fence, just like the points on the top of the palisade fence’s pales. In some cases, the pointed head may be made longer, compared to typical bolt head of the same size / diameter, to increase the chance of the intruder getting caught on the point. It is noted that the typical bolts for such fences are M8 bolts, which have a bolt head with a diameter of 13mm, shank diameter of 8mm and a bolt head width of 5-5.5mm. the bolt may use a smaller bolt head, such as a M6 bolt, to have a lower gradient for slope of the conical head, to decrease the angle at the tip of the head, so as to form a sharper point. However, it is noted that the long points, may be bent by an intruder, in order to provide a gripping surface, which may aid the intruder in removing the bolts from the fence. In other cases, the pointed head, or frustoconical head, may be made shallower, by increasing the gradient of the sloped surface of the bolt head. This results in the bolt head being smaller in length / width, compared to a typical bolt head of the same size, this further increases the difficulty required to grip the bolt head, as the thinner head provides an even smaller gripping surface. The increased gradient of the slope also helps to reduces the overall size of the bolt heads surface, again making the bolt harder to grip. It is noted that these shallower bolt heads may also be pointed as a deterrent, but the flatten frustoconical head may be preferable as they would provide a smaller gripping surface compared to the pointed bolt head, it is also noted that the broader points would be more difficult to flatten compared to the sharper point described above, though the broader points would also be less penetrative, and therefore less of a deterrent, providing another reason why the frustoconical shape may be preferable especially for the shallow bolt heads. It is also noted that these bolts may have a size larger that the typical bolt size, such as M12, so that the gradient of the bolt head can be increased further to provide a shallower bolt head, while still providing sufficient force to support the palisade fence. The claimed bolt may further comprise one or more gripping protrusions on the bearing surface of the bolt head. In particular, the surface of the bolt head that will be against the surface of the fence pale when the bolt is tightened, will comprise one or more protrusion that are configured to grip the surface of the fence pale. The purpose of such features is to prevent the bolt from turning when a nut is being tightened, onto the shank of the bolt, even when there is no tool gripping the bolt head. This way the user does not need to grip the bolt 18 02 25 head when fastening the bolt into place. This means that the conical, or frustoconical, shaped head of the bolt does not need to be gripped when constructing the fence, and thereby ensures the claimed bolt does not prevent the user from fastening the bolts into the palisade fence. In the preferred embodiment these protrusions are prismatic and angled, so that the protrusion only grips when tightening the bolt. Specifically, the one or more protrusions on the bearing surface of the bolt may be an angled prismatic shape, such as a wedge, configured to achieve this affect. Such protrusions are then positioned on the bearing surface so that the protrusions will grip the fence pale when the bolt is being tightened, thereby stopping the bolt from turning, and allowing the nut to be fastened to the bolt’s shank. However, these protrusions will be configured to not grip the fence when the bolt is rotated in the opposite direction, the direction that would loosen / unfasten the bolt. In the case of the wedge-shaped protrusion, they would be aligned around the circumference of the bolt head facing in a counter clockwise direction, so that the face of the wedge that is perpendicular to the bearing surface may grip the fence as the bolt is tightened / fastened into place. While the sloped, or angled surface of the wedge will not grip the surface of the fence, if the bolt is rotated in the opposite direction. Thereby making it easier to construct the fence, as described before, while also ensuring that these protrusions do not assist an intruder trying to remove the bolt. This is because the bolt may turn freely when someone turns the bolt or nut, in a direction to remove the bolt, unless the bolt is sufficiently gripped. It is noted that in the most preferable embodiment this prismatic protrusion would comprise an angle of 30°, or less, such as between 10 and 25°, to the bearing surface. As this relatively low angle helps to ensure that the sloped surface does not grip the fence surface. Also, this relatively low angle can help ensure that there is little space between the fence surface and the bearing surface, once the bolt is tightened as the low angle allows the protrusions to have a lower height, as such spaces / gaps may provide a means for the intruder to grip the bolt head, and thereby make it easier to remove the bolt. It is also understood that a steeper angled wedge would result in a larger space between the fence and the bolt head when the bolt is tightened, due to the protrusions having a greater height. However, it is also noted that the higher angle may provide additional friction to help the bolt head grip the fence when being loosened, even if the spacing between the bearing surface and the bolt head was the same, thereby reducing the beneficial effect of the protrusion as described above. Another aspect that may be used to provide improved security features to the bolt, is to use different classes of material for the bolt, nut and fence. In the preferable embodiment, the 18 02 25 bolt would have a property class of 4.8 or below according to ISO (RTM) 898. This value would be less than, or at most equal to the class for the material of the nut and the fence, while still being sufficiently strong to support the fence and not be easily broken by an intruder. By having a material with a lower class, the user can be sure that the protrusions of the bolt head do not wear, or dig into the fence pale, if the bolt is over tightened. As this may result in the protrusions stop the bolt from turning regardless of the direction the bolt is being turned. Meaning the bolt would grip the fence when it is being tightened, or loosened, thereby making it easier to remove the bolt. Additionally, by using a material with a lower class than the fence, and / or nut, this can allow the thread of the bolt to be worn away, either over time, or by over tightening the bolt. By wearing away a portion of the bolts thread, from the shank of the bolt, the user ensured that the nut on the bolt cannot grip the bolts thread, again making it more difficult for an intruder to remove the bolt. It is noted that the remaining thread, on the shank of the bolt, would hold the nut and fence pale in place, after the thread under the nut is worn. It should also be noted that if the bolt had a higher class than the nut, it would be the thread of the nut that is worn away, this may result in the nut becoming loose, or even falling off all together. Therefore, it is preferable for the nut and the bolt to be at least the same class, or if not, for the bolt to be in a lower class. As previously mentioned, the traditional bolt size for a palisade fence is M8, however the claimed bolt may be of various sizes, such as from M4 to M12 .most preferably sizes M6, M8 or M10, one above and below the standard size. As previously mentioned, by using different size bolt the user reduces the risk of an intruder having the correct tools for removing the bolt, additionally, the smaller M6 size would reduce the size of the gripping surfaces even further, making the bolt harder to remove. While, the larger radius of the M10 bolt, may allow the bolt head to be shallower when compared to the M8 bolt, while still being a sufficient size to tighten and grip the fence pale, again reducing the size of the gripping surface of the bolt head, making the bolt harder to remove. The invention comprises a kit of parts for constructing a palisade fence panel. This kit comprising: a plurality of bolts in accordance with the invention, a plurality of nuts for said bolts, two or more fence rails having apertures for fastening using said nuts and bolts a plurality of fence stiles / pales, having apertures for fastening using said nuts and bolts to said rails. Such kits may also include any specialised tools for use with the specific nuts and bolts within the kit. It is noted that with the fence simplistic design, only one such tool should be necessary to construct the entire fence. Therefore, providing an easy means for the user to improve the security within a desired area, with the aforementioned bolt features providing 18 02 25 improved security as the fence will be difficult to deconstruct, or to climb over, without the specific tool for the nuts and bolts of the kit, which may also be of a specific size and shape as mentioned earlier. Thereby providing the user with a simple kit with everything they need to construct the palisade fence. It is noted that the nuts within the kit may also be configured to provide improved security features. One example of such a nut, would be for the kit of parts to include shear off nuts. These shear off nuts comprise a rounded, or domed, portion which will fasten to the bolt shank, and is hard to grip due to its curved surface, this makes the bolt more difficult to unfasten, but not impossible with the appropriate tools. The nut also comprises a hexagonal portion which is used to tighten the nut, and is then broken off once the nut is fastened, so that the nut is easy to fasten during the initial construction, as the hexagonal portion can be gripped with traditional tools, such as a spanner, but once the hexagonal portion is removed only the rounded portion remains, which is very difficult to remove without a specialised tool. However, it is noted that these sheared off portions may cause issues to the user. Specifically, the sheared off portion, once removed, is simply waste material. These broken portions if not collected may litter the protected area, wherein they may be picked up, and possible eaten by any small animals or even children in that area, caused them harm. Therefore, the user would need to use additional time a resource to clear away the sheared off portions from the site. Additionally, the user may not want to incur the additional costs associated with the materials to make the shear off portions, as ultimately these portions are just wasted material, and / or the costs to clean up the sheared off portions. Therefore, it may be preferable to include curved, or domed, nuts with a tool configured to grip them, in place of the shearing hexagonal portion. Another potential safety feature for the nuts would be the choice of material for the nut, in comparison to the bolt, regardless of the nuts shape. The kit of parts comprises nuts made of a harder steel, one with a higher class, compared to the bolt. It may be necessary in any case to have a difference in strength between the nut and bolt, as this will allow more flexibility in one of the two components, which in turn reduce the risk of one or both of the components snapping under the force they exert on each other, compared to when the components are made of the same material, or at least materials with the same strength according to ISO (RTM) 898. The reason it is preferable for the nut to be made from the harder material, is that over time the force exerted between the nut and the bolt will cause wear, specifically it will wear away the thread on both components. However, in the case where one of the components is made of a softer material, it is the softer material that will wear away first. In this scenario, if the nut was made of a softer material, the thread inside the nut would wear away, eventually causing the nut to become loose and no longer grip the 18 02 25 bolt, thereby becoming unfastened. However, in the case wherein the bolt is made of the softer material, it is noted that the thread on the shank of the bolt, in the area covered by the nut, would wear away. In this case the nut may still be held in place by the thread on the rest of the shank, before and after the nut, meaning the bolt is still fastened. And more importantly the nut would become harder to remove as it would not have the thread to grip onto. This may help improve security by making it more difficult, if not impossible, to remove the bolt. Of these two alternatives, the stronger nut would be preferable over the shear off nut, as there are no wasted materials. It is also noted that the harder nut may include other safety features, such as additional side, preferably so that the nut has an odd number of sides, or curved sides, these different shapes for the nut may make the nut harder to grip with traditional tools, which are designed for standard nuts, which typically have six or eight sides. Thus, making it harder for an intruder to remove the nut. As mentioned in the case of the claimed invention, it is preferable that the nut be made of a material that is harder than the bolt, in most cases both components would still be made of steel, as this material is relatively strong compared to other materials, as is less likely to rust or be worn away by adverse weather, especially as such fences would most likely be installed outdoors. Based on the standards for bolts set out in ISO (RTM) 898, is preferable that the bolt has property class 4.8 or below, as this would be enough to provide the necessary toughness to support the palisade fence, without risk of the bolt being too brittle, or the risk of the bolt damaging the fence due to its harder material wearing down the pale, or digging into the surface of the pale. By using lower values, the bolt may also have a slight amount of flexibility, compared to harder materials, making the bolt less susceptible to breaking under impact. Specifically, this may help prevent an intruder from removing the bolt by striking off the bolt head, it may also make it easier for a manufacture to form a bolt head with a curved surface as described earlier. With regards to this difference in toughness, between the bolt and the nut, it is preferably that the property class difference between the components is 1.0 or greater. This difference is enough to provide the above-mentioned effects, wherein the thread of the bolt may be worn away by the force exerted onto the bolt, by the nut. If the difference was any lower it may not be sufficient to have a notable difference in the wearing effect, leading to the situation wherein both the nut and bolt become worn, leading to the bolts unfastening. However, it is also noted that the preferable property class difference should also be in the range of 4.2 or less. For if the nut was any harder, relative to the bolt, there is a risk that after the thread of the bolt is worn away, the thread of the nut may burrow, or dig into the surface 18 02 25 of the bolt, and be sufficiently hard to create its own thread within the worn region. Thereby re-threading the bolt, making it easier for the bolt to be removed. Therefore, a property class difference between 1.0 and 4.2, provides the most preferable range, wherein the user can be assured that the thread of the bolt will be stripped first, without the risk of the nut rethreading the bolt. This, as mentioned, provides improved security as an intruder will not be able to remove the nut, when there is not thread for it to grip to. It is also noted that the thread of the bolt would only be stripped in the region within the nut, the thread on the rest of the bolt’s shank will help to hold the nut in place after the thread of the bolt has been stripped. Detailed description of the invention The present invention is illustrated by means of the following drawings show: figure 1, a fastener of the present invention figure 2, the bearing face of a fastener of the present invention figure 3, an illustration of a strict thread of a fastener of the present invention in use, List of the features of the present invention 10- bolt 20- conical / frustoconical bolt head 22- bearing surface of the bolt head 30- prismatic protrusions 40- bolt shank 50- bolt thread 60- worn / stripped thread Figure 1 depict an example bolt 10 in line with the present invention. Specifically, the figure depicts a steel bolt 10 with a frustoconical head 20, though it is noted that the bolt head 20 may also be conical with a point. The purpose of this head geometry is that the curved surface of the conical / frustoconical shape provides a bolt head 20 that is difficult to grip using traditional tools, such as spanners and pliers, as such tools are configured to grip the flat sides of a standard bolt head. Such head geometry will only provide a small point of contact, with traditional tool, when trying to grip the curved surface of the 18 02 25 conical / frustoconical bolt head 20. This means that it is more difficult for an intruder to remove the bolt 10, especially as the claimed bolts 10 are configured to be used to construct a palisade fence, which the user may use to provide protection to a specific site. The user may be provided with a specialised tool configured to grip the conical / frustoconical bolt head 20. It is noted that as the bolt 10 are likely to be used within a perimeter fence, in particular a palisade fence which comprises one or more point on the top of the fence’s pales to deter intruders from climbing over the fence, it may be preferable to use a conical bolt head. For such bolts would provide additional sharp points to act as a deterrent to intruders. It is noted that in a typical palisade fence design each pale would be attached to two rails, one proximate the top, pointed end, of the pale and one proximate the bottom end of the pale. Therefore, if the user were to use such pointed bolts, it may be preferable that they are only used on the rail proximate the pointed end of the pale. This is because, if the pointed bolts are used on the lower rail, they may harm anyone who comes need to the fence, such as bystanders and possibly the user themselves. For this reason, the user may choose to use the frustoconical bolts 10 for at least the lower rail. It is also noted that the surface of the pointed bolt heads may be easier to grip, specifically the surface proximate the point, for if the point is long, the tip of the point may be flatted providing a flat surface that can be easily gripped grip. Therefore, it may be preferable to use a bolt 10 with a frustoconical shape bolt head 20, which does not have a point, as there is no area that can be gripped easily without a specialised tool, and though these bolts 10 do not act as a deterrent to the same degree as the pointed bolts, they also do not pose a risk to other people, or animals, near the fence. Another factor that may help improve the security provide by the disclosed bolts, may be to use shallower bolt heads, these bolts heads 20 may have a conical or frustoconical head geometry. These shallow bolt heads have curved surfaces with steeper gradients, which results in a bolt head 20 that is thinner and flatter than a typical bolt head of the same size. These shallow bolts improve security as they have even less area to grip, and therefore are more difficult to remove, and may even have a point to act as a deterrent. Note that if the shallow bolt has a point it may act as a deterrent, but the shallow shape will result in a broader point that will be more difficult to flatten, thereby providing both a deterrent in the form of the point and a surface that is as hard to grip as that of the frustoconical shape bolt head. It is noted that in order to securely fasten these bolts 10, the user may require specialised tools designed to fit the shape of the bolt head 20, to hold it in place, while a nut is then 18 02 25 secured to the threaded shank 40 of the bolt 10. Such tools may comprise a ring or loop that is configured to securely fasten around the circumference on the bolt head 20, and may be adjustable to couple to different points of the bolt head 20 and / or different sized bolts 10. However, another possibility may be to use features on the bearing surface 22 of the bolt head 20, to hold the bolt in place while it is fastened. Note that the bearing surface 22, is the surface of the bolt head 20 that touches / rests against the surface of the fence pale. These features may be in the form of protrusions 30, that may be configured to grip onto the surface of the pale. These features help to prevent the bolt 10 from turning as it is being fastened. However, if an intruder has access to the nut attached to the bolt 10, these same features may make it easier for the bolt 10 to be removed, as the features will also stop the bolt from turning when the nut is being loosened / remove, thereby removing the need to grip the curved surface of the bolt head 20. To prevent this, it is preferable that the protrusion 30 comprise a prismatic shape, such as the wedge shape depicted in Figure 1, that will only prevent turning in one direction. To be specific the wedge shape protrusion 30 would be aligned around the circumference of the bearing surface 22 facing in a direction, so that the flat side of the wedge, perpendicular to the bearing surface 22, will grip the pale to prevent the bolt 10 from turning when it is being fastened. While the sloped surfaces, will not grip the pale when the bolt 10 is being unfastened, allowing the bolt 10 to rotate with the nut, in a manner to prevent the nut being removed. It is noted that it is preferable for these protrusions 30 to have a relatively low angle, of 30 degrees or less, as this will reduce the friction created by the sloped / angled side of the protrusion 30, reducing the risk of the bolt 10 gripping the pales when the nut is being removed. Additionally, it is noted that these protrusions 30 may result in there being a space, or gap, between the bolt head 20 and the pale, when the bolt is fastened. It is noted that this space may make it easier for intruders to grip, or even remove, the bolt head 20 in order to remove the bolts 10 from the fence. Therefore, another reason why a low angle is preferable, as this will allow the protrusions 30 to be relatively low, or flat, so as to create a minimal gap between the bolt head 20 and the pale. The gap may be removed entirely if the bolt head 20 was made of a sufficiently strong material, so that the protrusions 30 burrows, or dig, into the fence pale. However, this does run the risk of the protrusions 30 becoming stuck within the pale, resulting in the same issue wherein the protrusions 30 hold the bolt 10 still even when the nut is being removed, therefore the use of shallow protrusions would be preferable. Figure 2 provides a clearer view of the above-mentioned prismatic protrusions 30, on the bearing surface 22 of the bolt head 20, the image also shows the threaded shank 40 of the bolt, and also shows a small unthreaded portion of the shank 40 proximate the bearing 18 02 25 surface 22. It is noted that depending on the thickness, or structure of the fence pale, the bolt shank 40 may comprise an unthreaded portion proximate the bolt head 20. This is because the shape of the fence pale may mean that it is not practical, or possible to fasten the nut on the bolt 10 all the way to the bolt head 20. Therefore, the thread 50 on the shank 40 should end at the point the nut would be expected to reach when the fence in constructed. A reason for this is that this excess thread not only uses more material, but may also provide a means to grip the bolt 10, or more likely, the excess thread may grip the fence pale, producing more friction on the bolt 10, thereby making it easier to stop the bolt from turning, when loosening the nut on said bolt 10. However, if this region of the bolt is unthreaded, or smooth, not only is it more difficult to grip, but it would produce little to no friction against the fence pale, thereby making more difficult to remove the bolt 10. Figure 3 depicts yet another possible security feature for the claimed bolt 10. In the depicted example the bolt shank 40 comprises a worn portion 60, this worn portion 60 is a part of the bolt shank 40 where the thread 50 on the shank 40 has been worn down, and may even been worn away entirely. This effect may be achieved by choosing specific materials for both the bolt 10 and the nut. In particular the bolt 10 may be made of a softer material compared to the nut used to fasten the bolt. This way over time the nut will wear down the thread 50 of the bolt 10 directly under the nut. It is noted that the thread 50 on the shank 40 of the bolt 10 next to the nut may help to hold the nut in place once the thread is worn. Additionally, the user my accelerate the wearing of the bolt’s thread 50 by overturning the nut once the bolt 10 is fastened, as this action allows the harder nut to grind down the bolt’s thread 50. Once the bolt thread 50 is worn away, an intruder will find it more difficult to loosen the nut from the bolt 10, as the nut will spin loosely with not grip on the bolt thread 50, thereby improving the security of the fence. It is noted that, in the case of the invention, the softness of the material of the nut and bolt 10 may be determined by the property class of the material used to make each component, as defined in ISO (RTM) 989. Specifically, the material used to form the nut should be of a higher property class than the bolt 10. Preferably this difference in class would be at least 1.0 or more, because if the difference is any less the effect of the property class would be negligible. In such cases, wherein the difference in between the property class is less than 1.0, the force between the nut and the bolt 10 may result in some wear on both components, and would be insufficient to wear the thread completely. It is noted that if the thread is worn from the nut, then there may be little to no force holding the nut in place, especially when the thread has worn from both the nut and the bolt 10. This would mean that the nut would be loose and may even cause the bolt 10 to unfasten completely, making it easier for an intruder to remove the bolts 10 from the fence. It is also noted that when the property class 18 02 25 of the nut and bolt are the same, or have a difference below 1.0, there is a risk that the force exerted on these components may crack, and may even break, one or both components. Therefore, it is preferable for at least one of the components to be softer, this way there is enough flexibility to prevent this cracking from occurring, and for the reasons above it is preferable that the bolt 10 be the softer component. It is also noted that it is preferable for the property class difference between the nut and the bolt 10 to be less than 4.2. For in the cases wherein the difference is above this limit, there is a possibility that once the harder nut wears away the bolt’s thread 50, the thread of the nut may dig into the worn region, after this the nut may rethread the bolt’s shank 40. This would allow the nut to again grip the bolt 10, making it easier to remove the nut. It is also noted that if the bolt 10 is too soft, an intruder may be able to break off the bolt head 20, for example with a hammer or cutting tool, in order to remove the bolt 10, or the fence pale the bolt was fastened to. Therefore, by keeping the difference in the property class below 4.2, the user can ensure that the bolt 10 is sufficiently strong to support the fence, and cannot be easily broken by an intruder, and also ensuring that the bolt is not soft enough that it can be threaded by the thread of the nut, allowing the above mentioned wearing of the bolt thread to occur, as depicted in Figure 3. By incorporating some or all of the aforementioned features, the claimed invention provides a bolt 10, that improves on the security of currently used security fences, in particular palisade fences. As the claimed invention provide a bolt that can be used to securely fasten the pales of the palisade fence to one or more rails that support said fence. Wherein the bolt 10 comprises a bolt head geometry which is hard to grip with conventional tools, as their curved surface cannot be gripped, therefore these bolts 10 cannot be easily removed. The bolt 10 may also comprise a thread 50, designed to be worn away by the nut securing the bolt 10. Once the thread is worn away the nut may not be able to grip the bolt’s shank 40 and therefore cannot be removed from the bolt 10. 18 02 25

Claims

1. A kit of parts for constructing a palisade fence panel, the kit comprising:a plurality of bolts (10) consisting of:a fully or partly threaded shank (40) anda conical or frustoconical head (20), pointing away from the shank (40), so that the point of the conical or frustoconical head (20) extends away from the shank (40);the base of the conical or frustoconical head (20) comprises a bearing surface (22) of greater radius than the shank (40);a plurality of nuts for said bolts (10);two or more fence rails having apertures for fastening using said nuts and bolts (10) to a plurality offence stiles / pales;that plurality of stiles having apertures for fastening using said nuts and bolts (10) to said railswherein the bolt (10) is of a softer steel than the nut.

2. The kit of any of claim 1 wherein the bolt has a property class 4.8 or below according to / SO (RTM) 898.

3. The kit of parts of claim 1 wherein the bolt (10) has property class 4.8 or below according to ISO (RTM) 898 and the nut has a higher property class.

4. The kit of parts of claim 3 wherein the property class difference is 1.0 or greater.

5. The kit of parts of claim 4 wherein the property class difference is 4.2 or less.

6. The kit of parts of any of claims 1 to 5 wherein the nuts are shear off nuts.

7. The kit of any of claim 1 to 6 wherein the bolt (10) bearing surface (22) of the conical orfrustoconical head (20) comprises gripping protrusions (30)), that extend away from the conical or frustoconical head (20).

8. The kit of claim 7 wherein the protrusions (30) are prismatic and angled for gripping upon tightening.

9. The kit of claim 8 wherein the prismatic protrusion (30) is angled at 30° to the bearing surface (22).

10. The kit of any preceding claim, the bolt being of size M6, M8 or M10.LD

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