What is the best way to drill a bolt. How to drill a hardened bolt: several ways

During repairs, sometimes trouble happens - something breaks. Sometimes a broken part leads to trouble with a large device. For example, a broken bolt in the cylinder block. A broken bolt causes a lot of trouble. Especially when it broke down in a place where access is limited.

Easy option

The first thing to do is not to panic. Generally. A broken bolt can almost always be removed, the main thing is to act correctly.

Secondly - to examine the "scene". If it breaks when unscrewing - fill it with WD40, brilliant green or brake fluid - it is required that the broken off piece otkis along the thread. You can try to anneal the thread with a blowtorch - you need to look according to the circumstances. Let's see where it broke. When a broken piece sticks out above the part, you are very lucky - you can try to unscrew it. If there is such an opportunity, we wind two nuts, fix the lower one with the upper one. We unscrew the bottom nut - if the broken bolt left the whole thread, it should come out. There is not enough space for two nuts - we try to unscrew the thread with pliers. Another way is to make a cut in the middle with a grinder. As a result, we get a screw that you can try to unscrew with a screwdriver. If it works, the problem is solved. But more often the bolt breaks either flush with the part or inside it.

If it is broken at the detail level, try to unscrew it with your finger. In fact, when a broken bolt is inside the threaded hole, it is clean, and the screw simply broke due to metal fatigue or because it was pulled earlier - it can simply go from the finger. Or we pay attention to a chip - when a piece breaks off, a side always forms on the fracture plane - we substitute a chisel, a screwdriver - we try to unscrew it with light blows.

Such cases often happen when a non-threaded part is attracted to a stud or bolt - for example, a manifold to a cylinder block.

Difficult option

If it didn’t work out in these ways, we will drill. The main thing is that the broken bolt is not hardened. There are several ways to try before trying to drill out a broken bolt. The most elementary - we take a drill with a reverse and a drill. Sometimes such a trick takes place with an ordinary metal screw, with a drill at the end. We press on the broken residue, we try to unscrew it with small turns, accuracy is needed here - you need to turn it “tight”. If these methods fail, we move on to serious actions. When the diameter of the stud is small, you need to determine how to remove the chip - there is not enough space for two options.

Method one. With a small diameter drill, we make two holes in the fragment. Each against the other. We drill shallowly - about 5 - 10 mm, preferably away from the center. Then we take a snap ring puller, narrow-nose pliers, or simply insert two nails, clamp them with pliers - we try to unscrew them.

Method two. You need a special tool - an extractor. It is sold in tool stores. It is something like a cone drill, has a reverse thread, very hard hardened metal. First, we select a drill according to its diameter. Carefully mark the center of the stud with a core, we need it to drill a hole. You don't need to go deep - just drill a little deeper than the length of the extractor. Then we wrap the extractor, trying to unscrew the broken piece.

When no method has helped, the most remains difficult option- drill out. To do this, you need several different diameter sharp drills and a strong hand. The most important thing is to catch the center of the debris. As accurately as possible, we mark the center with a core, the accuracy of drilling depends on this. Then, with the smallest drill, we drill the broken one through.

It is important to drill exactly along the remainder, parallel to the wall, so that the holes are aligned on both sides. Then we take the next drill diameter and so on until we reach the wall of the hole. If you slightly missed the center of the hole - it happens. The main thing is to stop in time, leaving the whole thread. We take a chisel, a screwdriver or a nail, we crush the rest of the wall of the fragment inward. Then just pull the resulting lump out.

If you, by virtue of your profession or hobby, are engaged in the repair of equipment, you often face the question: - how to unscrew a broken bolt, part of which is in your hands, and the other remains in the thread?

In this article we will do short review ways to solve this problem. The choice of the method is up to you, as the skills and "arsenal" at hand are different for everyone. Let's start?!

Consider how to pull a broken bolt out of a thread with an extractor

For those who don't know, there are external and internal extractors. If the bolt is broken in such a way that it cannot be "grabbed" to, then the internal extractor may be the only solution to the problem.

The internal extractor resembles a tap. The shank (non-working part) is made "under the square"" for tools.

According to the type of working part, the extractors are divided into wedge-shaped, rod and screw (spiral).

The working part of the wedge-shaped extractor has the form of a cone with faces, the section of the rod extractor is the same along the entire length.

The screw extractor is a cone with a left or right rotation thread.

The order of work is as follows:

When starting work directly on the car, make sure that the repair site is accessible for a drill, screwdriver, etc. Well, if the question is how to get a broken bolt out of a wheel hub, the repair area is open. But if you can’t “get” to the part, don’t be lazy and do the necessary disassembly, that is, dismantling everything in this case superfluous.

If you do not know how to unscrew a broken aluminum bolt, using an extractor will be the best solution.

It is better to buy extractors in ""extended"" sets, ie. complete with drills and guide sleeves for them.

But, unfortunately, such a tool is not always available in this moment or it cannot be used due to the design of a particular node.

If you have problems with broken edges, we recommend choosing fasteners best quality: https://avselectro-msk.ru/catalog/4976-bolty - bolts of suitable quality that can be bought in any quantities.

Alternative ways to unscrew a bolt with torn edges

Welding a nut as a way to unscrew a bolt without edges

This old tried and tested method led many out of a dead end during repairs.

specific case. Broken front suspension arm bolt on an old Suzuki Ignis. Moreover, the distance between the lugs of the arm of the lever did not allow either to hammer or screw the extractor into the fragment. Welding in this case is the most effective tool unscrew the broken bolt.

The essence of the reception is as follows.

We select a nut of a suitable diameter, put it on a broken bolt and weld it. If the bolt broke flush with the surface of the part, we fix the nut as accurately as possible in the center of the bolt. We cook. Carefully, without jerking, we unscrew the broken bolt by the nut.

Disconnect the battery terminals! Ensure the safety of wiring, hoses, plastic products from melting and burning!

Let's say that the extractor and welding are not available to you. Then, if the bolt broke in the thread, we apply

Drilling - a great opportunity to turn a bolt without edges

First of all, we calculate the diameter of the drill. The formula for a standard thread is simple - subtract the thread pitch from the diameter of the bolt (threaded part).

Next important point- how to avoid drift of the drill to the side? To prevent such trouble, there are conductors. The conductor (simplified) is a plate with holes. Guide bushings (sleeves) corresponding to the diameter of the drill are perpendicularly fixed in the holes. The conductor is fixed on the part, the sleeves are aligned with the holes with broken bolts. You can drill! It is the sleeve that will prevent the drill from deflecting.

The jig is indispensable if you need to remove a broken bolt from an aluminum part. Especially if it is the engine cylinder head.

You can also combine drilling with knocking out the remains of a broken bolt with a punch.

This technique is used if the threaded holes are through. Starting with a drill of the smallest diameter, we drill a chip. When the ""wall"" of it is sufficiently weakened, we remove it with a punch. Then we clean the thread with a tap.

In this way, you can, for example, get rid of fragments of the studs for attaching the exhaust pipe to the exhaust manifold on the VAZ2114-15 without removing the latter from the engine.

Heating to unscrew a bolt with stripped edges

Consider this situation - there are no extractors, welding, a conductor and good drills. How to pull out a bolt if it is broken?

You can solve the problem (and sometimes very successfully) by heating the parts red-hot. After cooling, they will become more pliable and may well be unscrewed with a chisel, center punch, etc. The described methods of unscrewing broken bolts are not an exhaustive, universal answer to problems of this kind. For clarity, watch the material in the video.

Thank you for your attention!

Do not rush to apply the "serious" tool. To begin with, spray WD-40 (as WD-40 is also used) on the bolt so that the liquid penetrates the thread as best as possible. After 10-15 minutes, we try to unscrew the bolt, there is a chance that the thread will turn off.


How to unscrew a stuck bolt if VD-40 does not help? Try to use larger tool, such as pliers, a large adjustable wrench or an impact wrench. In the most hopeless situations you can drill out the bolt completely (see below).

How to remove a broken bolt

There are not so many ways to unscrew a broken bolt. If possible (the remains of the bolt are not strongly recessed), then weld another bolt or nut to the bolt and turn it out in the usual way.
To unscrew broken bolts, an extractor (with a tenacious reverse thread) is used. We make a hole a couple of centimeters deep in the broken bolt and screw the extractor into it counterclockwise. When it is screwed in enough, it will pull the broken bolt along with it. Not difficult process shown in video:
The extractor is a highly professional thing and may not always be at hand. Therefore, most often it is necessary to drill out the whole broken bolt (see below).

How to unscrew a bolt with torn edges

The easiest way to remove a broken bolt is to use pliers or wrench. But not always the availability of free space allows the use of such a tool.


Another way is to make a notch on the bolt head with a grinder or a chisel so that it is possible unscrew the bolt with a screwdriver(impact screwdriver). Doesn't fit? Place a screwdriver at an angle to the bolt and hit it with a hammer so as to create rotary motion bolt counterclockwise.


You can also use welding. We stick an electrode inside the head and weld the head and head of the bolt(or secret) medium current. Unscrew until cool. Another secret you can try to unscrew close-diameter head of 12 facets. First heat the head, and when it cools down, it will more tightly wrap around the secret around the circumference.

Drill bolt completely

A universal way to remove a bolt or its remnants. You will need a drill and a cobalt or pobedite drill. In the process of drilling, do not let the drill overheat, periodically cool it with water or oil. Select the drill diameter so that the thread is not damaged during drilling.
Recall that sometimes the bolt may have a reverse thread, try unscrewing it clockwise. Have you encountered bolts that did not want to get out? In what way did you manage to solve the problem? By the way, do you know how

When screwing in a bolt, many of us sometimes encounter the fact that the head of the bolt breaks off, even if we are dealing with a high-quality fastener. And when such a nuisance happens, not everyone knows how to unscrew a broken bolt without damaging the parts that it connects. There are a few standard options such a situation and the algorithms of actions in case of their occurrence will also be standard.

Situation one: part of the thread sticks out above the surface

This is the easiest case. To solve this problem, we take an adjustable wrench and, after appropriate settings, carefully unscrew the bolt. To make the screwed piece of iron give in better, you can take a penetrating lubricant and apply it to the protruding part. Then make a few light blows on the fragment - this is so that the lubricant is better absorbed inside to the thread. After 5-10 minutes, the rod can be removed.

Situation two: the bolt broke at the same level with the surface or even below it

But here, too, the task of how to unscrew a broken bolt is quite doable. Solving it with a wrench is not worth it - there is simply nothing to grab onto. Therefore, be patient and try some of the action algorithms we offer. Ways to solve the problem are more complex and require patience, but it is possible to complete them.

You can make a groove for a screwdriver: if it is ordinary, then the slot should be deeper, and if it is cross-shaped, then the groove can not be too deep, because a Phillips screwdriver has a larger area of ​​adhesion to the surface than a regular one. Most often, this method solves the problem of how to unscrew a broken bolt. But there are times when the iron rod is tightly jammed and the screwdriver can not cope with it. In such situations, you need to take drastic measures and drill a hole in the rod for a smaller bolt and make a thread in it.

Such an operation will require an electric drill and a set of drills of different diameters and a tap. If you screw a small bolt into the chip, then it will be enough just to get it with the help of wrench. In such severe cases this method usually works, but here you need to remember: there must be a reverse thread inside the rod.

Drilling the bolt according to the rules

Not all home craftsmen know how to drill a broken bolt correctly. Meanwhile, certain recommendations must be followed so as not to worsen the situation. The hole is drilled very carefully and exactly in the center, otherwise you will strip the thread when unscrewing (note that broken screws, nails and studs are removed according to the same principle. If all the steps were performed correctly, any stuck fastener easily brought to the surface. AT difficult cases the hole must be gradually expanded using drills of various diameters, moving from smaller to larger. When the walls of the rod become thinner, they can be broken and pulled out with tweezers.

A torn hat can be attached

This is a method from the category of "need for invention is cunning." We take a nut whose diameter is at least 1 millimeter larger than the diameter of the rod and simply weld it to the fragment. During welding, the metal should warm up properly and expand. We connect the rod and the nut, we get a knot that needs to be poured with water. When the knot has cooled, you can carefully unscrew the chip.

Thus, we learned what methods exist for extracting broken fasteners. We hope that they will help you solve this small but annoying problem that sometimes arises in the practice of home craftsmen. But it is better that you get strong and unbreakable bolts, studs and screws.

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Video: How to remove a broken bolt

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“Everything new is well forgotten old” - this is how the saying goes, and it’s hard not to agree with this. Increasingly, people are returning to the knowledge of their ancestors, and this knowledge is becoming more and more popular every day.