Loosening Screws, repairing Threads
You know the story: the sun's shining and you're all set to take off on a weekend tour, just as soon as you've replaced one small thing on your bike.
And then disaster strikes. You can't budge that one final screw fastening the part you want to change... or the head simply shears off and you're left with an embedded shank... or the wretched thing emerges along with the mating thread in the form of a miserable little spiral.
No matter what's going through your head at a moment like this, don't give in to your rage! Right now you need to keep your cool to avoid more serious damage. Before you do anything rash, first get yourself a cold beer, or whatever will calm your nerves in the circumstances, and take a minute to inspect your misfortune.
Stripped screw heads
If the slotted head or cross-head of a screw no longer provides adequate grip for a normal screwdriver to apply enough force to unscrew it, it's best to stop before you do even more damage to the screw. In such situations it's better to use an impact driver. This tool transforms the blow of a hammer into a very powerful rotational force, without damaging the head of the screw. Every motorbike toolbox should have one.
Set the impact driver to "Loosen".
A suitable bit and a couple of measured blows with a large hammer (at least 300 g) on the tool will loosen screws that are overtightened or seized up due to rust with damaged heads!
In general, a simple blow on the screw head using a screwdriver and hammer, combined with penetrating oil (e.g. WD-40), will always help to loosen up any rust in the thread. If the screw or nut is visibly rusty, you should give the penetrating oil time to work before proceeding. Of course, a hammer or impact driver is not the thing for delicate components. The key to loosening chewed up screws is always to choose the tool that fits best. Screwdriver blades should fit optimally and not be rounded with wear. Hex bolts should be loosened with a ratchet and socket with flank-drive (included in most socket wrench sets in the Louis range).
Other loosening methods
If you can get to it, firmly grip the head of the screw with a good slip-joint pliers and try to turn it slowly. You need to use your strength here; don't let the tool slip.
Stripped hexagon socket screws can be loosened by driving in a tri-square bit with a hammer and turning it with the ratchet. Of course this may damage the tri-square bit, but our main concern is to loosen the screw!
With a hammer and a small chisel, you can try to shift the head of the screw from the side.
Still no joy? Or if using a hammer is not an option on a delicate component, then try to make a deep, grippy slot in the head of the screw with a hacksaw and a key file so that it will accept a strong slotted screwdriver. If the screw is seated in aluminium, heat can help loosen it (see next section "Stubborn threaded bolts").
If all else fails, you must remove the head of the screw with a drill. Always drill in the centre; predrill first with a small bit and then to the diameter of the screw thread. Remember, you just want to remove the head initially, so don't drill too deep. Later you can decide how best to remove the threaded shank that's left behind. If the thread is intact, it can usually be easily gripped with a slip-joint pliers and unscrewed.
You can split rusted-on or stripped nuts from the side with a nut splitter. You can also use a file, hacksaw or angle grinder. Do not angle-grind into the thread! Take care not to do damage around the nut. Cover or tape off surrounding surfaces for protection. If you can access the nut, and the bolt is easy to replace, you can simply remove it by sawing it off flush (between the nut and the washer). This is often the quickest method. Always protect the surrounding area from the sawblade.
Damaged countersunk screws that no tool can grip or move can be removed with a screw extractor, if they have a diameter of 6 mm or more. You must drill into the screw in the exact centre and, in particular, to the right diameter (see screw extractor packaging). If you do not succeed in drilling exactly centrally, the outlook is dim – so leave the job for a professional if you are not confident of your abilities. Also take care not to put excessive strain on a small screw extractor: if it breaks off, you will have a piece of hardened steel stuck in the screw, which is particularly difficult to remove. Of course, screw extractors can also be used on stubborn studs. They are suitable only for right-hand threads, not for left hand threads.
Stubborn threaded bolts.
Stripped screw heads or bolts are often a sign of a deeper-seated problem: usually the bolt won't budge because it is rusted tight or the thread is damaged. So first try penetrating oil, leaving it to soak overnight! What you do next depends on how much of the bolt is left to grip: if there is enough thread for two nuts, put them on, lock them tightly and try to twist the bolt out. If there isn't enough thread for that, try the slip-joint pliers. Grip as firmly as possible with the pliers and try to twist the bolt... if this doesn't work, it's better to leave it and use the rest of the thread to weld on a good screw and twist it instead! If welding is not an option, you can try a screw extractor. If the bolt is seated in aluminium, heat can greatly help to loosen it, as hot aluminium expands more than steel. However, make sure there are no rubber shaft seal rings, O-rings, rubber gaskets or anything else heat-sensitive nearby, or else they would have to be replaced. If possible, take off housing cover to warm it up and lay it on a hotplate. If using a gas torch, always heat the bolt with a circular movement; never hold the flame stationary on one spot. If you are dealing with painted aluminium, use a hot air gun from a DIY store, instead of a torch, and avoid excessive heat. 100–150 degrees Celsius is enough to loosen a bolt (as a guide: oil evaporates at 200 degrees, water at a little over 100 degrees Celsius). If high-strength threadlock adhesive was applied to a bolt, it must generally be loosened with heat, even if it is a steel/steel connection. Loctite high strength requires as much as 300 degrees Celsius.
If nothing works, you have to weigh up your options, especially if the stubborn bolt is in the engine.
Engine refurbishers are able to remove bolts by using a strong electric current to make them disintegrate, leaving the surrounding aluminium undamaged – and the thread!
Drilling out always entails repairing the thread (see next section) or cutting the next-largest thread. In this case, it is essential to drill straight and in the exact centre. You may have to leave a job like this to a professional because if you don't drill correctly and are left with an ugly crater, you really do have a problem. The only solution is then to weld the whole thing and rethread. However, the thread in the welded material will not have the same strength as the original.
Repair thread with Helicoil
The patented "V Coil" thread insert does a good, durable job of repairing a damaged internal thread. V Coil has the advantage over steel threaded inserts that is does not loosen even under constant thermal loading, which makes this product ideal for repairing spark plug threads, for example. Each V Coil repair kit contains the spiral inserts plus a bit for drilling the hole, a special thread cutter and a tool for screwing in the inserts properly (Fig. 10-12). Crucial to your success is that any remnants of the bolt are properly removed so that you have a clean, straight hole to cut the new V Coil thread. For that reason, if you are not confident of your abilities, leave the repair to a vehicle workshop. As an example, unless you have an extremely well-trained eye and a deft touch, it will be difficult at the first attempt to drill centrally and at the correct angle to make the thread of the manifold mount on the cylinder head while it is installed on your motorbike. If in doubt, you should definitely uninstall the part so that you can align it properly under a bench drill, and spare yourself the nuisance of a crooked, botched thread!
Avoid trouble with faulty threads
Prevention is better than cure, as anyone who has ever had to deal with any of the problems described will tell you. And prevention is quite easy, actually. Always use tools that are in good condition. Get rid of worn screwdrivers,wrenches and other tools out of your toolbox. The trouble they will give is sure to outweigh any satisfaction you may take from saving money in the short term... You should have a good selection of slotted and cross-head screwdrivers or bits so that you can work with properly fitting tools at all times. You will find all you need in our range. You should also get yourself a set of bits for your impact driver.
You can avoid damaging hex bolts by using ratchet sockets with a flank-drive, in particular. All Rothewald socket wrench sets in our range have them. When installing, always make sure that the thread is clean! To clean the thread, use brake cleaner or compressed air. With just a tiny amount of copper paste, the thread will be much less prone to seize. And copper paste, unlike grease, does not reduce connection strength at all. Always use copper paste on stainless steel screws in aluminium. If a screw coated with copper paste falls in the dirt, it must be cleaned with special care (use brake cleaner). Always insert screws, and spark plugs in particular, with care. If you feel resistance during insertion, unscrew again immediately, and find the cause! Often, the thread can be saved by recutting it or repairing it with a thread file. If in doubt, ask your vehicle workshop.
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The Louis Technical Centre
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These tips for DIY mechanics contain general recommendations that may not apply to all vehicles or all individual components. As local conditions may vary considerably, we are unable to guarantee the correctness of information in these tips for DIY mechanics.
Thank you for your understanding.
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