How to choose the right drill for an anchor?

Anchor bolts can be installed in any wall: concrete, brick, etc. To attach such a bolt, you will need to clear the hole. The diameter of the hole should usually match the diameter of the bolt itself. In your case, when the diameter of the anchor is 10 millimeters, you need to drill a hole with a no smaller diameter. In this case, a 10 mm drill will do.

But one nuance should be taken into account. To accurately determine which drill to take, you will need to use a caliper to measure the actual diameter of the anchor bolt along with the thread. Sometimes it happens that the marking indicates one value, for example, 10 mm, but in reality the diameter of the bolt along with the thread differs by 1 millimeter. And that means the hole should be a little larger.

If you don’t have a caliper, you can use this method: use a thread to measure the circumference of the bolt, and then use the formula - Circumference (length) = 3.14 * diameter - to calculate the diameter value. That is, to calculate the diameter, you need to divide the resulting circle (its length) by 3.14.

The main thing when installing an anchor bolt is to avoid its deformation. If you can’t insert the anchor normally, then you need to check the hole: its diameter, the presence of debris, etc.

Fastening medium-weight products

Objects weighing between 5–10 kg are secured with impact dowels Ø8 mm, a drill Ø8 mm, but always with a Pobedit tip. The fastener should extend into the wall cavity by 6 cm, and if the ceiling is 8 cm. To secure an object weighing up to 10 kg, 4 fasteners should be used.

Read also: How to unscrew a screw with a broken head

Material hardness

Brinell hardness is a characteristic that allows you to determine the hardness of a material.

Stainless steel fasteners are also equipped with special markings on the top of the fastener.

Type of steel A2 or A4 and tensile strength - 50, 70, 80, examples: A2-70, A4-80. Fasteners that have a clearly defined thread are color-coded for A2 in green and for A4 in red. The value for the yield strength is not specified.

For example, a value of 70 is the most standard and demonstrates the maximum strength of stainless steel fasteners.

Maximum fluidity for stainless steel hardware, often only a reference value.

The fluidity in this case will be 250 N/mm2 for A2-70 and about 300 N/mm2 for A4-80.

The approximate increase will be no more than 40%. In other words, this type of steel perfectly changes shape before irreparable deformation occurs.

Old domestic measurement methods according to GOST did not allow paying due attention to the maximum permissible loads on bolts, so the produced hardware was significantly lower in quality compared to modern ones.

An example to calculate the load on a material as accurately as possible using strength classification:

M12 fastening with strength 8.8, size d2 = 10.7 mm and maximum section length 89.87 mm2. In this case, the maximum permissible degree of load will be: (8*8*10)*89.87;0) = 57520 Newton.

Load chart for carbon steel and stainless steel bolts.

ST-4.6		ST-8.8		A2-70		A4-80
THREAD	d2, mm	Area 62, tt2	Max. load, Newton	Working load, kg	Max. load, Newton	Working load, kg	Max. load, Newton	Working load, kg	Max. load, Newton	Working load, kg
M1	0,8	0,5	121	322	10	126	151
M2	1,7	2,27	544	20	1 452	70	567	20	681	30
M3	2,6	5,31	1 274	60	3 396	160	1 327	60	1 592	70
M4	3,5	9,62	2 308	110	6 154	300	2 404	120	2 885	140
M5	4,4	15,2	3 647	180	9 726	480	3 799	180	4 559	220
M6	5,3	22,05	5 292	260	14 112	700	5 513	270	6 615	330
M8	7,1	39,57	9 497	470	25 326	1 260	9 893	490	11 872	590
M10	8,9	62,18	14 923	740	39 795	1 980	15 545	770	18 654	930
M12	10,7	89,87	21 570	1 070	57 520	2 870	22 469	1 120	26 962	1 340
M14	12,6	124,63	29 910	1 490	79 761	3 980	31 157	1 550	37 388	1 860
M16	14,6	167,33	40159	2 000	107 092	5 350	41 833	2 090	50199	2 500
M20	18,3	262,89	63 093	3 150	168 249	8 410	65 722	3 280	78 867	3 940
M24	21,9	376,49	90 359	4 510	240 956	12 040	94 123	4 700	112 948	5 640
M27	24,9	486,71	116 810	5 840	311 493	15 570	121 677	6 080	146 012	7 300
M30	27,6	597,98	143 516	7170	382 708	19130	149 495	7 470	179 394	8 960

We present to your attention an updated table of maximum loads on stainless materials and high-strength connections.

To be additionally confident in the safety of the load, you can, without a twinge of conscience, divide the load in Newtons by thirty.

Stainless steel A2-50
THREAD	d2, mm	Area d2, mm2	Yield strength, MPa	Max. load, Newton	Working load, kg
M1	0,8	0,50	200	100
M2	1.7	2,27	200	454	20
M3	2,6	5,31	200	1 061	50
M4	3,5	9,62	200	1 923	90
M5	4,4	15,20	200	3 040	150
MB	5,3	22,05	200	4 410	220
M8	7,1	39,57	200	7 914	390
M10	8,9	62,18	200	12 436	620
M12	10,7	89,87	200	17 975	890
M14	12,6	124,63	200	24 925	1 240
M16	14,6	167,33	200	33 466	1 670
M20	18,3	262,89	200	52 578	2 620
M24	21,9	376,49	200	75 299	3 760
M27	24,9	486,71	200	97 342	4 860
MLO	27,6	597,98	200	119 596	5 970

Stainless steel A2-70
THREAD	62.mm	Area d2, mm2	Yield strength, MPa	Max. load, Newton	Working load, kg
M1	0,8	0,50	250	126
M2	1,7	2,27	250	567	20
M3	2,6	5,31	250	1 327	60
M4	3,5	9,62	250	2 404	120
M5	4,4	15,20	250	3 799	180
MB	5,3	22,05	250	5 513	270
M8	7,1	39,57	250	9 893	490
M10	8,9	62,18	250	15 545	770
M12	10,7	89,87	250	22 469	1 120
M14	12,6	124,63	250	31 157	1 550
M16	14,6	167,33	250	41 833	2 090
M20	18,3	262,89	250	65 722	3 280
M24	21,9	376,49	250	94 123	4 700
M27	24,9	486,71	250	121 677	6 080
MLO	27,6	597,98	250	149 495	7 470

Stainless steel A4-80
THREAD	12, mm	Area d2, mm2	Yield strength, MPa	Max. load, Newton	Working load, kg
M 1	0,8	0,50	300	151
M2	1,7	2,27	300	681	30
M3	2,6	5,31	300	1 592	70
M 4	3,5	9,62	300	2 885	140
M 5	4,4	15,20	300	4 559	220
MB	5,3	22,05	300	6 615	330
M 8	7,1	39,57	300	11 872	590
M10	8,9	62,18	300	18 654	930
M12	10,7	89,87	300	26 962	1 340
M14	12,6	124,63	300	37 388	1 860
M16	14,6	167,33	300	50199	2 500
M20	18,3	262,89	300	78 867	3 940
M24	21,9	376,49	300	112 948	5 640
M27	24,9	486,71	300	146 012	7 300
MLO	27,6	597,98	300	179 394	8 960

How to drill a brick wall

Drill into brick with a drill. simple process. An impact drill is used for work. If drilling is unstressed, the drilling process may take a long time.

It is very important that the tool operates at high power. Quantitative indicators of revolutions per minute are also important.

Indicators of more than 2,000 revolutions are considered the most acceptable.

Of course, to perform better work, a hammer drill is used. If it is not at hand, then use high-power drills. You don't need any tools to drill a hole. then special knowledge. The main thing is to follow a number of simple recommendations mentioned above. Sometimes you can stumble upon a burnt stone. It will be quite difficult to form a cavity in it. Such a brick is identified by the dust generated during operation. It becomes a pronounced black shade.

To create holes in burnt rocks, you need to turn on the drill at low speeds and set the impact function. You need to press very hard on the tool for the hammer function to work correctly.

It is also important to ensure that the drill does not overheat during operation. A severely overheated drill causes the edges of the drill to wear out quickly

For such purposes, a diamond-coated drill is most often used. This way the clutch is most effective. This leads to significant savings in physical effort and energy.

Sometimes situations arise when the hole made needs to be made of a significant diameter. For example, this could be a ventilation outlet. Such work will be very difficult to organize with ordinary tools. You will need powerful equipment and large crowns.

What to consider when choosing a drill for a dowel

Selecting a drill to create a hole in which the dowel will be fixed should take into account:

the material from which the wall itself is made, as well as its finishing;
expected loads of the fastener.

You should also choose a drill depending on the diameter of the fasteners used. On the outer surface of factory-produced dowels, as a rule, there are markings that allow you to correctly select drills of the appropriate diameter for them.

Table 1. Selection of drill and screw for dowel

It is important to know not only how to choose a drill for a dowel, but also how to drill a hole correctly. If it is necessary to drill a hole in the wall for a dowel, the diameter of which is 10 mm, then first use a drill with a diameter of 8 mm and an impact drilling mode. After the hole is drilled, the tool is replaced with a drill with a diameter of 10 mm and is used without using the impact drilling mode. This approach will allow you to get a hole in the wall of the required diameter with smooth and neat edges.

If you need to drill a concrete wall, it is better to use a Pobedit drill, which can handle such a durable material without any problems. The selected cutting tool must be at least 3 mm longer than the dowel itself. If you neglect this requirement, the dowel will not completely fit into the resulting hole, in the final part of which dust and pieces of crumbled material, as a rule, accumulate. In addition, the shape of the bottom of the hole may not match the shape of the tip of the fastener.

Calculate the drilling depth with a margin relative to the dowel length

Methods for securing a dowel in a large hole

What should you do if the hole drilled in the wall is larger than the dowel? Professionals recommend following the following methods of fixing a dowel in a wall:

Using a repair cloth. It means a piece of special material that is wrapped around a dowel and then placed in a hole made in a brick, aerated concrete, or concrete wall. Before “wrapping”, the napkin must be moistened in water. Once the fastener is wrapped, it is driven into the gap. Next, you need to wait until it hardens - about two to three minutes. Then, you can insert a self-tapping screw, screw and other fastening devices.
Use a 2-component composition. It means a special type of glue, which contains polyurethane without styrene, which is safe for the human body. The package, which resembles a syringe, contains a 2-component composition.

Drilling for dowels

The hole for the dowels is made with an 8 mm drill.
Also, in order not to drill through the part, it is advisable to equip it with a depth limiter. At the end we drill with the same drill to a depth of 20 mm. Do not forget that during any work the drill must be strictly perpendicular to the plane of the part.

Of course, if you picked up a drill for the first time in your life, you won’t do very well. But this activity can be learned quite quickly.

In construction, there are many fasteners, for example, screws, nails, self-tapping screws. Sometimes it is difficult to understand from their name what they are talking about. For example, let’s take a fastening element such as a confirmat.

The word is unusual, but the meaning is simple. This is a furniture screw. It got its name from a German company. In our country, this fastener has become popular since 1990. The confirmat has its own characteristics and varieties, which we will discuss below.

Types of dowels

Dowel type Driva

Perhaps the most popular fastener for plasterboard sheets. It comes with or without a drill, metal or plastic. When making a hole for its fastening, use a drill with a diameter of 8 mm. The manufacturer declares the working shear load that gypsum board can withstand using this dowel is 25 kg, while the maximum load is up to 50 kg.

The popularity of the Driva dowel is due to its fairly high reliability and relatively low price. The strength of such fastening is achieved by distributing the load over a large area, which is ensured by the shape of the dowel.

Driva drywall dowel is simple and effective

Flat dowel nail

This dowel is made of fire-resistant steel, is quite simple and easy to use, since it does not require additional drilling and, accordingly, eliminates dust. It can be hammered into the drywall with a hammer or pressed in by hand if you can do it.

The principle of operation of a dowel-nail is that when a self-tapping screw is screwed into it, the initially flat front part opens up, forming a reliable stop.

It is used for sheets up to 12.5 mm thick inclusive. Self-tapping screws are chosen with a diameter of 3.5-5mm. The working load for pulling out, declared by the manufacturer, is 15 kg, for shearing - 30 kg, the maximum shear load, obtained experimentally, is 48 kg. Among other things, the dowel-nail is reusable, that is, it can be dismantled and mounted in another place several times.

The flat dowel-nail for drywall is very convenient to install, as it does not require drilling

Universal expansion dowel Butterfly

The butterfly dowel is suitable for both drywall and concrete bases. The hole for its installation is drilled with a drill with a diameter of 8 mm, the diameter of the complete self-tapping screw is 4.5 mm.

For the butterfly dowel, we recommend using self-tapping screws without missing threads, since when screwing in, having reached the smooth neck, the self-tapping screw will begin to scroll, and the dowel will not take the desired shape as a stop.

In general, the plastic butterfly dowel works approximately the same as the others, creating a stop behind the gypsum board when screwing in the self-tapping screw. The shape of this stop is somewhat reminiscent of a butterfly, hence the name of the fastening element. The calculated working load on the dowel is 25 kg, the maximum load is 55 kg.

The Butterfly dowel for drywall is the most popular because it is equally inexpensive, convenient and effective.

Dowel Molly

The Molly dowel, or rather the Molly anchor (after all, it is an independent fastening unit that does not require an additional screw) is another popular type of fastening for drywall, made of metal. This dowel, unlike the previous ones, is available in various sizes and, accordingly, for various loads.

For example, for Molly of the minimum size marked 4/16/38 (4 is the diameter of the screw, 16 is the length of the neck and the maximum thickness of the sheet for which it can be used, 38 is the total length of the element), the working load is 25 kg, the limit for cutting is 47kg.

To make holes for Molly, choose a drill 2 times larger than the diameter of the neck (the first number in the marking), that is, for a four it will be 8 mm, for a six it will be 12, etc.

To install the Molly dowel, you need a special tool that brings the fastening element into “combat readiness”. With its help, the screw is slightly pulled towards itself, while the hooks bend. Then you can turn the screw with a screwdriver, bending the hooks until they stop. All this should be done by inserting a dowel into a hole in the drywall.

If there is no special tool, you can activate the anchor using wire cutters (side cutters) or even a regular flat-head screwdriver.

Molly dowel for drywall - a solution for professionals

Fischer plastic twist dowel

When a self-tapping screw is screwed into such a dowel, the latter twists, forming a stop behind a sheet of drywall, hence the name of the fastening element. The drilling diameter for such a dowel is 8 mm, the screw diameter is 5 mm.

When tightening a self-tapping screw, the main task is not to pinch too hard, otherwise it will begin to rotate and the fastener will need to be re-done. For this reason, when using a screwdriver for tightening, set it to the minimum speed.

The working load for tearing off a twisting dowel is 10 kg, for shearing - 25 kg, crash load - 70 kg.

Twistable plastic dowel for drywall - an interesting and effective solution, backed by Fisher reliability

Bolt Load Calculation

The bolt head markings usually contain the following information:

manufacturer's mark (JX, THE, L, WT, etc.);
strength class;
arrow “counterclockwise” (if left-hand thread).

The first digit indicates the nominal tensile strength (tensile strength): 1/100 MPa (1/100 N/mm²;

1/10 kg/mm²). Example: (strength class 9.8) 9*10=900 MPa (900 N/mm²; 91.71 kg/mm²).

The second number indicates the percentage of yield strength to tensile strength (tensile strength): 1/10%. Example: (strength class 9.8) 9*8=720 MPa (720 N/mm²; 73.37 kg/mm²).

The yield strength value is the maximum permissible working load of the bolt, above which irreversible deformation occurs. When calculating the load, 1/2 or 1/3 of the yield strength is used, with a double or triple safety margin, respectively.

According to the current international classification, high-strength bolts include products whose tensile strength is greater than or equal to 800 MPa (800 N/mm²; 81.52 kg/mm²). Accordingly, starting from 8.8 for bolts and 8 for nuts.

Examples of material flow

An example would be a common kitchen fork. By bending it in one direction, you can get a completely different object, which means its fluidity is disrupted, which leads to deformation. In this case, the material only deformed, but did not break, which indicates a high degree of elasticity of the steel. Conclusion: maximum strength is much higher than yield.

Other kitchen equipment, such as a knife, will break if you try to change its shape. Conclusion: the knife has the same fluidity and strength; such a product can be called fragile, despite the fact that it is made of steel.

A similar practical example would be screwing in a nut: the bolt itself increases in length only after a certain amount of action is applied to it. If the outcome of the experiment is unfavorable, the thread on the fastener may break.

The percentage of elongation is an average indicator that demonstrates the length of the deformed part before the onset of failure. Figuratively, we can call this kind of bolts flexible, meaning precisely the ability to elongate.

The technical terminology for this is quite simple: elongation is nothing more than the percentage of increase in a sample compared to its original size.