Drill out a screw

Anyone who has had to deal with counter-threaded screws is likely to know the problem, or sooner or later - a torn screw or bolt that needs to be removed. If nothing works, the screw has to be drilled out. Which tools are recommended and how to drill a screw, you can read here in detail.

With screws, there can be various difficulties

In particular, screws which are provided with a mating thread, that is usually metric or imperial screws, tend under certain circumstances to demolish:

  • if rusted by corrosion
  • if the screws were tightened far before with too much torque
  • if no further measures have been taken to loosen the screws

Of course, a too tightened screw does not have to crack if it is to be unscrewed much later. Even when screwing the screw can already work. For mechanics is often the saying "Careful, after firmly comes off!" To hear. In rare cases, it may also be that when turning the screw is simply turned in the wrong direction. Especially left-hand threads are risky because they are rare.

Various options to release a broken screw

There are various approaches to releasing a broken screw or bolt. If the screw or the bolt is over, you can unscrew and lock two nuts. These can then be turned on if the screw is pretreated accordingly. What can and should be done on pretreatment, you can read below in the text.

Screw lock nuts or weld on

Usually a screw is so unfavorably broken off that it does not survive enough to turn on a nut, let alone two nuts. Then it can help if you weld the mother. Does not help, you can also use a screw extractor. Here is a guide to using a screw extractor.

Screw extractor with boring of the screw

Screw extractors are also not the ultimate solution. The problem: the Schraubenausdreher is tapered at the top and is screwed over the existing left-hand thread in the direction of rotation in the screw in which it actually dissolves (in conventional right-hand thread). That means that a hole must be drilled in the screw or the bolt.

The hook with Schraubenausdrehern

Now screw in the screw extractor, spread apart the remainder of the screw shaft through the conical course of the tool. This effect is reinforced with thinner screw shafts. As a result, the broken screw can then sit even tighter. The screw extractor then quickly snaps off and is now stuck in the remainder of the screw. Boring is now even more difficult because it is hardened steel.

Professional tool: toothed bolts that do not spread the screw

So you need a solution that makes sure your tool can not break. There are two tools here: a bolt extractor and special professional sets for unscrewing broken screws. The preparatory work is the same both times; You have to drill the screw.

Boring the screw

With both tools, it would be important to drill the hole as close to the center of the screw as possible. Bolt extractors usually come without additional accessories, which means that the preparation of the borehole is done without appropriate aids. First, the screw is grained. In the grit then a small metal drill is set and slowly drilled. Good creeping or cutting oil is also important for this. The grains must be really sharp and hard as well as the metal drill very sharp.

Drilling with guidance

The special professional sets make everything easier. They include drills of various sizes, associated turnbuckles driven into the bore, and union nuts over which the turnbuckles are then unscrewed. In addition, special guide tubes are included, which can be placed either on or in the threaded hole. This ensures that the hole is actually made in the middle of the shaft.

Drill turnbolt in drilled screw and turn out

The boring pin is provided with sharp webs, which make the diameter of the pin slightly larger than that of the associated drill. Then the pin is driven into the hole. When turning later, the pin sets like a gear. The advantage over the screw extractor: the remaining screw shaft is not spread. Almost every broken screw can be reliably removed.

Tips & Tricks

It is highly recommended to use a good rust remover, both when removing metal screws and especially when removing a broken screw. Also, if you drill the screw as described. Preferably you do not start immediately before drilling, but the day before. Also, heating the screw or bolt may help loosen.

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