Hi, i want to fix an arial to a wall. it comes with a metal bracket through which to use screws to put into plastic rawlplugs in the wall.
since i will need to take it down again in a few years; which screws should i use that are least likely to rust? here in london u.k. i have only ever seen 'brass' screws in the old style tapered shape with the single slot, which i dont think are suitable.
so would you please advise a novice which of the modern non tapered screws are easiest to get out in a few years please? (i.e. heads have not rusted up). thanks
the mechanical style (in the USA) is called sheet metal screws. They have a coarse thread similar to a wood screw, but have no taper, except right at the point. The drive comes in both slotted and Phillips.
Stainless steel will never rust but they are softer than galvanized and easier to strip if using a phillips head . Brass will work. For 3 years or less I would use plain old galvanized hex head with attached washer. Those may not be available in UK but I bet a pan head galvanized sheet metal screw is.
The size of the screw would be based on the weight it needs to support and the size of the mounting holes. Also are you attaching to brick? Or what surface?
I question that stainless steel is "softer" than galvanised steel, though I would agree that it is less pliable and resilient. Brass is much softer and comparatively weak and can easily snap with over-tightening. It is also expensive. You also run the risk of bi-metallic corrosion as it is a fine conductor. (Jobs that you thought were temporary have a nasty habit of becoming permanent, like girlfriends) I usually use Allen Key heads - but a Phillips in
8mm stainless and correct screwdriver bit you needs be a mighty strong guy to damage the head seriously. It is another matter with the screws used in proprietary plastic-plug fixings. This may something for the quality of Wurth's products. Not cheap ! We have used hundreds and hundreds of such stainless steel bolts and never, ever had damage. if they are taken out they go back in the box for re-use. For fixings that require a long throw from the wall such as pipes that are bent around a corner, I use cut lengths of 8mm stainess threaded rod. Put a dome nut on the end and and with a hex bit on your cordless you can drive them in. For added strength I put a stainless penny-washer and a nut tightened to the wall.
I did omit one important particular in my first description of this system - The bolt should only go about 15mm 3/8 inch past the point at which the plastic plug begins to split. If the bolts are too long they will mangle the plug. And again the hole in the masonary much be exact.
I have never tested such a fixing to destruction but I do have some
200+ kilo static loads hanging off two fixings only.
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