the scrooz blog

OK this need some clarifying, what measurements do we use in Australia to size screws and fasteners?

Well it seems we don’t really know whether to go metric or imperial so strangely enough we’ve decided to adopt a policy of ‘making it up as we go along’, let me elaborate …

European and most metricated countries use fully metric sizing for all metric fasteners and fully imperial sizes for all non-metric, for example a 6 x 50 coach screw is 6mm thick by 50mm long, imperial fasteners are usually also available in primarily metric countries and an example size for a bolt would be say 1/2″ x 2″ BSW (this means 1/2 inch thick by 2 inches long and the thread type is British Standard Whitworth, very important to get the thread type right for bolts as theres lots of different types). OK that’s that, imperial or metric and never mixed.

The US is primarily imperial with very few metric fasteners in mainstream use and so sizing is given the same as the BSW example in fractions of inches followed by the type e.g UNC, UNF etc.  Wood screws are pretty much always imperial so that would be say, 10g x 3 1/2″ (which is 10 guage thick and 3 and a 1/2 inches long, guage is the imperial measure of shank thickness). So anything with a g in the diameter is imperial and should be followed by the imperial length. Metric fasteners are termed the same as European as in diameter x length and metric and imperial are never mixed.

So, in Australia we like to complicate matters by using combinations of metric and imperial for the same fasteners, for example common wood screws would be 10-12 x 40 or 8-15 x 20, 20, this actually means 8 guage diameter (imperial) x 20mm long (metric) and just to complicate matters further we chuck the thread pitch in there which is the 12 or 15 in the examples. Clearly in years gone by we couldn’t decide whether to go with European or American standards for our hardware and so have just made our own up, its also probably due to the the fact that most Australian fasteners are imported from different regions giving this wide mix of product, this can be seen in most fastener companies stocks where a full range (as some of ours is) is split into both imperial and metric.

and the confusion continues …

This is a pretty common scenario, maybe your building a structural frame for your decking or even framing a house, whatever your project you suddenly find your self with a pile of structural grade timber and no bolts or fasteners to put it together … and maybe even less idea of which ones to to use. To make the right decision firstly you have to understand the basics of standard bolts, there are loads of different types and bolting technology is a massive subject but here we’ll just be talking about the basic types which mostly fall into 2 categories  :  high tensile and low tensile (or mild steel as they are often termed).

For our application, in timber, we’ll use low tensile and this would be the case 99.9% of the time, the reason for this choice is simple for 2 reasons, firstly, although high tensile bolts are of a much higher strength (as the name implies) there strength properties makes them less flexible than mild steel and as timber is an organic product that’s constantly moving, we want fasteners that will accommodate this movement and roll with the changes (so to speak), if the bolted joint isn’t allowed to flex it could snap a stiffer fastener or the local timber around the bolt. The second reason is a mild steel bolt is very strong and its pretty much guaranteed that most timber will break, way before the bolt will,  so using high tensile bolts for timber is complete overkill and wasted expense.

So OK low tensile it is, now which ones, well the main 2 choices are hexagon head bolts or cup head bolts aka coach bolts aka again carraige bolts. The wise choice is coach bolts as they are designed specifically for bolting timber sections together or timber to steelwork, the industry designation for these is actually ‘Cup Square Hex Bolt and Nut’ and the reason is all due to the shape, the head is a rounded cup shape with a square lug under it and a hex nut on the other end, its this lug and large cup head that makes this bolt so useful for timber as when you tighten them up the lug bites into the wood and locks it to stop it turning while you tighten up and the large surface area cup head stops it pulling through. You’ll find if you try and use a hex bolt its actually pretty difficult to fully tighten them, the head doesn’t lock so the whole assembly often turns, you can hold both sides with a spanner of course but you’ll quickly find the head burying into the timber and pushing the spanner off and leaving you in no mans land with with a half tight assembly that you can’t undo or tighten. click the pics for bigger images if you want a close up …

So there you go, for bolting timber together or timber to steel, use a low tensile (mild steel) or stainless steel (for maximum corrosion protection) coach or carraige bolt in either zinc plated for standard timber or hot dipped galvanised for treated timber, it what its designed for. Hex bolts are perfectly acceptable but you should use a washer both sides and be aware you will need access to both sides of the joint to hold and tighten.

There’s lots of horror stories around with bolted joints so please use common sense when building anything structural, don’t just guess a size or use anything lying around for convenience and of course for any major structural application you should always consult a structural engineer to confirm your connections are adequate, and be aware that other forces may be applied to the bolts other than just the timber you can see. As a tip, to recognise a mild steel hex bolt it will have 4.6 stamped on the head (its the grade of steel), carraige bolts are not always stamped, dependant on the manufacturer.

An often asked question and the answer is …. none. The fact is plasterboard and drywall sheets are pretty weak materials, particularly for point loads where you can have all the load of a large item resting on a few small areas, a kitchen cabinet may actually only be fixed to the wall in 2 places for instance. So the ideal fixing for board materials will always be a wood, batten or coach screw of your preferred choice screwed directly through the board into the supporting structure, be that timber or metal battens/studs or maybe even masonry if the board has been bonded on, having said that if you have metal stud partition framing then the metal sections will be either hollow section or C section and therefore a cavity type expansion anchor would be more preferable such as hollow wall anchors.

To find the studs an electronic stud finder is a good idea but you can also use your ears and feel for the studs by gently tapping along the wall section, the stud will of course have more of a dull thud than the hollow areas and once you’ve found one or two then measuring off should get you near the rest, average stud width is 2″ (50mm) and distance between centres is usually 18″ (450mm) – 24″ (600mm).

If your building a new property or in the middle of some major renovation then its always worth considering lining the areas likely to have heavy loads fixed to them (kitchens or bathrooms) with plywood or similar before applying the plasterboard or adding extra studs and battens in strategic areas, this will give you the freedom to easily fix anything anywhere in the future and give a high strength anchoring area, remember, an empty kitchen cabinet is a lot lighter than a full one so you should consider the items final use not just its dry weight.

So in an ideal world all the internal framing of your wall will line up perfectly with where you want to put your fixings … OK in reality you might get lucky and the the odd one may be in the right position but the rest of your fixtures will have to go straight into the board. So which is best …. well here’s a quick rundown of the common types :

Hammer in drywall fixings, these are great for lightweight applications and really fast to install, simply hammer (tap) the anchor though the board and pop a screw in it, when you start tightening, the legs open up behind the board to give a solid fixing point.

Speed plugs or wall mate plasterboard anchors as they are often known, these are very easy to use and are inserted by simply screwing straight into the board, there’s no expansion or clamping action with these fixings with all the strength coming from the deep worm type threads cutting into the plasterboard, you then just use a standard wood screw fixed into the hollow centre section.

They are manufactured in corrosion resistant alloy and also nylon for non corrosive and non conductive electrical applications and ideal for light to medium weight fixing.

Butterfly plastic toggle anchors, these are highly underrated fixings which work exceptionally well, they work with a clamping action by collapsing the body and then pushing the fixing through a hole in the board, when a screw is inserted and tightened the wings fully open and clamp the back of the board to give a strong corrosion free anchor point.

Suitable for medium to heavy loads.

Hollow wall anchors, also termed brolly anchors are a steel body designed to open up into an umbrella shape when tightened, these are great fixings, and simple to install by inserting into a drilled hole and then expanded by either tightening of the supplied screw or using a specially designed pistol grip wall anchor tool, once it is locked in position you can attach the fixture.

They work on a clamping action behind the board rather than point loading and are therefore able to take considerable amounts of weight and are fine for medium to heavy loads, to give you some idea try and imagine pushing a closed umbrella through a letterbox, opening it and then trying to pull it back though …. good luck with that!

Spring toggle anchors, operate on a similar umbrella type principle, these fixings are spring loaded so you push the fixing through a drilled hole and it snaps open so the wings are inside the wall and then simply tighten the screw to secure the fixture, you need to be careful with these that you don’t undo the screw completely as the toggle section is not captive and will just fall into the wall to be lost forever, suitable for light to medium loads.

Gravity toggle anchors as the name suggest work on gravity, you push the anchor through the board and turn it, the toggle then drops down at 90 degrees to the screw so when you tighten it up it clamps the back of the board, a simple to use fixing which works very well with medium to heavy fixtures.

So just to summarise, if you can fix into a stud then that’s the way to go, if not, theres plenty of choice of board fixings all doing a similar excellent job allbeit in slightly different ways and as for the best well its mostly down to your own preference, try the different types out and see what you think, personally I’m a speed plug, butterfly toggle and hollow wall anchor fan, but that’s just me.

As an extra trade tip if you find you simply cannot get any fixing to hold as the hole in the plasterboard just keeps getting bigger with every attempt or the fixing is pulling out due to the weight of the fixture then use expanding sealing foam in the hole and completely fill the cavity around the damaged area, re drill your hole one size down and carefully and insert a nylon wall plug, position your fixture, screw straight into the plug and there you go … job done. c49wy25qih

Heres a handy screws conversion table to quickly help you convert metric screw sizes and diameters to imperial guage and vice versa, guaranteed to save all that headscratching. Print it out and stick it in your toolbox …. you never know when you might need it. I’ll be happy to post another for bolts and threaded fasteners shortly.

Ever wondered why your screwdriver slips when your trying to tighten a screw or just rips the head up until you can’t get a screwdriver in it at all. Well, chances are your using the wrong screwdriver, it may look the same but its not, all screws have a particular drive system and a particular size so if you don’t pick the right driver and size then you’ll never get a secure fit and that where your problems start, particularly as the screw gets tighter into whatever your fixing into. The most common mistake is mixing up pozi drive and phillips as they both look the same at first glance but if you look closer at the pozi drive image, you’ll see its a cross with a kind of star shape over the top whereas the phillips is just a cross. This identifier is stamped on every screw from all manufacturers and although they may look very similar, these drives are vastly different internally due to the mating angles and the way the cross is cut. Try it, get a pozi screw with a phillips screwdriver or vice versa, test fit them and you’ll see although its close it just doesn’t quite fit properly, now try with a pozi screwdriver and immediately you’ll see and feel the difference … snug as a bug and particularly important if you use cordless screwdrivers where a lot of instant pressure is put on the screw head.

Phillips drive is the most common drive system found in Australia with the most common sizes of driver for phillips and pozidrive being No2’s which tend to cover 8 and 10 guage screws, No 1’s are mostly 6 guage and below and No3 usually 12 guage and over. Slotted drivers tend to be sized in mm based on the long length across the screw head as do hex head drivers. Torx drivers are slightly different and are usually sized as TX10, TX15,TX20 etc etc and square drivers, which are excellent for driving into hard timbers, are again sized in No1, No2 and No3 with No2 being most popular. So if you use the right size driver for the right screw you’ll be amazed how easy fastening screws in has suddenly become …

Hello everyone and a warm welcome to our online hardware and fastener blog.

So what’s it about? …  well hopefully it will be a fairly light hearted way of passing on some general info about fasteners along with plenty of hints and tips on how to use them, stuff which is well known to us in the industry but maybe not too obvious generally. We’ll be chatting about allsorts such as how to size fasteners properly and what do all the various sizes and codes mean, how to recognise different grades of steel, what the different plating finishes are, what to use to fix timber to bricks, and so on. Its all designed to educate you guys a little more about the fastener and hardware industry and take away some of the mystery about which fixings and fasteners to use for your projects, we hope you find it useful and of course we’ll be passing on any interesting scrooz news as we go, if theres anything specific you’d like to know then leave us a comment or drop us an email through our main site.

thanks