Long cylindrical workpieces are mainly processed in the centers. To secure such a workpiece in the centers, you need to have center holes at its two ends. Therefore, the center holes provide a stable base for holding long workpieces at the centers.

Center holes can be without a safety cone or with a safety cone. The holes are made with an apex angle of 60°.

The safety cone of the center hole, which protects the main conical surface of the hole from accidental damage, is made with an apex angle of 120°.

Questions

1. What is the purpose of the center holes?
2. What center holes do you know?
3. What is the apex angle of the center hole safety cone?

Tools for marking and techniques for marking center holes

There are several ways to mark center holes using a marking compass, a center finder, or a device (bell).

Before marking, the ends are usually painted over with chalk or mortar. copper sulfate so that the marks that determine the position of the center holes are more noticeable. Then they mark it.

Marking using a marking compass

The legs of the compass are moved apart to a distance approximately equal to the radius of the part. A curved leg is applied to the circumference of the end of the part clamped in a vice, and an arc is drawn with a pointed leg near the center of the end.

Three more arcs are carried out in the same way, each time moving the curved leg of the compass by approximately 1/4 of the circumference of the end.

The drawn four arcs form a curvilinear quadrilateral.

The center of the hole should be in its middle. The center is marked by eye and then marked, as shown in the figure below.

Marking using a center finder

The accuracy of marking center holes is increased by using a center finder. It consists of two prisms that form the sides of the angle, a clamping device and, the edge of which runs along the bisector of the angle.

They mark it like this: put a ruler on the even end of the workpiece and draw a line along it with a scriber, then turn the center finder 90° and draw another line.

The intersection of the marks will be the center.

It is better to mark center holes in parts with a diameter of up to 40 mm using a special device called a bell. It consists of a body, a conical bell and a center punch that moves in the body.

They mark with a bell as follows: with a conical bell, the device is installed on the end of the workpiece and, hitting the center of the hole with a hammer, the center of the hole is marked.

Questions

1. Name the easiest way to mark the center hole and indicate its disadvantages.
2. What parts does the center finder consist of?
3. How do you mark the center holes with a center finder?
4. What parts does the bell consist of?
5. How do you mark the center holes with a bell?

“Plumbing”, I.G. Spiridonov,
G.P. Bufetov, V.G. Kopelevich

You can drill holes accurately only with a properly sharpened drill. With such a drill, both cutting edges work, and the chips exit through two spiral grooves. Chip output with a correctly sharpened drill The drill is sharpened so that the cutting edges are the same length, and the angle at the tip corresponds to the hardness of the metal (for different metals different angles what will be said...

Dividing a circle into equal parts. Marking according to the drawing.

Example. It is required to divide a circle whose radius is 200 mm into 13 equal parts.

According to the table, the number corresponding to 13 divisions is 0.4786. Multiplying 0.4786 by 200 mm, we get: 0.4786X200 = 95.72 mm.

Using a compass to plot the resulting distance on the marked circle, we divide it into 13 equal parts.

Table 22 Dividing a circle into equal parts

Marking according to the drawing. Marking wrench(Fig. 80) must be performed in the following sequence:

1. Study the drawing.

2. Check the workpiece.

Rice. 80. Examples of markings (planar) of a wrench

3. Paint over the markings with vitriol or chalk diluted to the consistency of milk.

4. Hammer the bar into the key mouth,

5. Draw a center line along the key.

6. Draw a circle according to the drawing and divide it into six parts.

7. Repeat the same operations on the second head of the key.

8. Apply all dimensions according to the drawing.

By “hinge addition” it is customary to understand the sequence of operations for attaching a hinge to the facade (door) of furniture. As a rule, we are talking about the so-called. four-hinged hinges, which are the most common in the production of cabinet furniture. To attach a four-hinged hinge to the facade, it is necessary to make a special one on the back side of the facade seat- a blind hole of a certain diameter and depth. How to properly attach a furniture hinge using a minimum set hand tools will be discussed in this article.

Required tool:

1. Construction corner (square).
2. Pencil.
3. Kerner (optional).
4. Metal drill with a diameter of 2 mm (optional).
5. Faustner drill with a diameter of 35 mm (or 26 mm for reduced hinges).
6. Electric drill.

Fostner drill (cutter) is a very common equipment, used to make blind (not through) holes in soft materials. When purchasing a Fostner drill for additive furniture hinges, you need to pay attention to several points. First, the needle (the central sharp tip) of the drill should be well centered (without noticeable runout). Secondly, the drill must have carbide (often called Pobedit) cutters, otherwise it will become dull very quickly. The length of the centering needle is a very important parameter. If the length of the needle is too long, there is a risk of drilling through the facade. If the length of the needle is insufficient, then the drill (when drilling hand drill by hand) will lead to the side. As a rule, the length of the needle of a new drill has to be reduced (ground down) by about 0.5 mm. Professional (machine) Fostner drills have a reduced needle length or do not have one at all, since they are intended for special filler machines or machining centers, where accuracy is ensured by other means. It is strongly recommended that before drilling into a façade, you do a test drill in a similar material of the same thickness.

Preparation.

The surface of the workbench on which the additive will be performed must be smooth, clean, and non-slip. Under the facade you can put, for example, a sheet of thin rubber, a piece of foamed polyethylene (a type of insulation) or several layers of stretch packaging film. It would not be superfluous to secure the façade with clamps. Do not forget about personal safety; use safety glasses when drilling.

Marking holes.

Marking is a responsible operation. The accuracy of the loop installation and the correctness of its operation depend on its accuracy. The figure below shows the dimensions for marking. Special attention a space of 21-22 mm should be given from the working (along which the hinges are attached) side of the facade. The other indentation (in the picture on the right/left) is not so important in terms of accuracy. The main thing is that the first and last hinges of the facade are located at distances from 70 to 150 mm from the sides of the facade adjacent to the working side. The total number of hinges on the facade can be two or more, depending on the size and weight of the facade.

Indents for marking.

Indentation 21 mm.

Indentation 100 mm.

Core drilling center.

After marking, everything is ready for drilling.

Drilling a hole for the hinge.

Before drilling, it is recommended to punch the center of the drill. Drilling must be done at a rotation speed of about 1500 rpm; too high speeds will lead to burning of the facade material, and the cutter will quickly become dull due to overheating. When drilling with a hand drill, it is recommended to perform light circular movements (describing a cone with the apex on the drill needle) of small amplitude, this will increase the efficiency of material sampling. Since the drilling depth is, by and large, controlled by eye, from time to time it is necessary to stop drilling and measure the depth (the easiest way to do this is using an existing loop). As a rule, a depth of 12 mm is sufficient.

Drill with Fostner bitdiameter 35 mm.

Drilling is complete.

Attaching hinges to the facade.

This is the simplest operation. To perform this, you need to insert a loop into drilled hole, level the hinge bowl area using a square, mark the fastening points with a pencil and, after preliminary core punching and/or drilling (with a drill about 2 mm in diameter), screw the hinge with two 3.5x16 mm self-tapping screws (the length of the screws depends on the thickness of the facade). Small installation inaccuracies (up to 1 mm) do not need to be corrected. With some experience, the hinge can be screwed on without marking, punching or drilling, but simply using the attached square.

Align with a square and mark the hinge mounting holes with a pencil.

Punching holes. No drilling was performed.

We looked at the principle of manually adding a loop, which can be done even at home. However, it is recommended to carry out the addition of loops using specialized equipment (even homemade), the most affordable option- ordinaryvertical type entry price category. This will significantly increase labor productivity and reduce the risk of damage to facades.

The easiest way to mark center holes is using a compass, one of the legs of which is bent inward. By spreading the legs of the compass so that the distance between them is approximately equal to the radius of the workpiece to be marked, and taking the compass right hand, press the end of the bent leg with the thumb of your left hand to the side surface of the part (Fig. 43, a), fixed in a vice. After this, using a sharp compass leg, four marks are applied to the end of the part (Fig. 43, b, c)

If the distance between the legs of the compass was set greater than the radius of the part, these marks will have the form shown in Fig. 43, b; if it was smaller than the radius of the part, the marks will have the form shown in Fig. 43, v. The center of the part in both cases lies inside these marks and can be easily identified by eye.

Rice. 43. Marking the center hole with a compass (a) and the position of the resulting marks (b, c)

Marking of precision rolled workpieces, especially if the machining allowance is small, as well as machined parts that for some reason do not have center holes, should be done using a marking square (Fig. 44, a). Pins 1 and 2 are pressed into the short flange of this square at equal distances from its edge AA. Having placed such a square on the end of the part (Fig. 44, b), carry out the last mark. Then turn the square to an arbitrary angle and draw a second line (Fig. 44, c). The intersection of the marks will determine the center of the workpiece or part.

Rice. 44. Marking square (a) and marking (b, c) center holes using a square

Punching center holes. After marking the center holes, they are punched (Fig. 45, a). The error made in this case can be eliminated by shifting the marked center in the required direction, as shown in Fig. 45, b.

Rice. 45. Punching the center hole

Centering tools. Center holes are drilled twist drill(Fig. 46, a), the diameter of which is equal to the diameter of the cylindrical part of the center hole. The conical part of the center hole, drilled with a drill with a diameter of up to 1.5 mm, is formed by a countersink (Fig. 46, b). When the diameter of the cylindrical part of the hole is up to 6 mm, a countersink shown in Fig. is used to process the cone. 46, v. The countersink shown in Fig. 46, g, is used to obtain a center hole with a safety cone.

Rice. 46. ​​Centering tools

A center hole without a safety cone can be drilled much faster by using the combination center drill shown in Fig. 46, d, and the hole with a safety cone is a drill shown in Fig. 46, e.

Drilling center holes. Drilling center holes in small workpieces made of rolled material or previously turned material is carried out without marking. The workpiece is fixed in a self-centering chuck (Fig. 47, a). A drill chuck with a centering tool is inserted into the tailstock quill. Having drilled a center hole in one end of the workpiece, turn the workpiece over and drill a second hole.

Rice. 47. Drilling center holes

Marked and cored workpieces are centered like this. Instead of a front center, a chuck with a centering tool is inserted into the machine spindle. Having installed the workpiece as shown in Fig. 47, b, hold it with your left hand lateral surface(or even better, by a clamp secured in the middle of the part). By starting the machine and rotating the tailstock handwheel with your right hand, feed the workpiece onto the rotating centering tool. The second center hole is drilled in the same way.

In many factories, the centering of workpieces is carried out in procurement workshops (at warehouses) on special centering machines.

How to mark the alignment of a steel chimney when passing through the ceiling and roof?

To answer fully, it is advisable to know what stage you are at:

• the place for the heat generator is prepared, and you only need to install/install the chimney,
• build a house and select the exact location for the stove, going around the beams and rafters.

Anyway the right tool for such work there will be a simple construction plumb line. Even the best quality slatted levels and rules do not allow for accurate vertical markings over long distances. In addition, their “bubbles” only work in one plane, and we need a vertical axis in all directions.

If the marking is carried out from bottom to top “from the stove”, then you need to do the following:

We put a cross on the crate or on the roofing material(depending on where the marking went). Now you can create the outline of the passage and start cutting

This way you can find the axis, even if a passage unit is already installed in the ceiling. Please note that the axis point is also moved with a plumb line in the opposite direction: from the roof to the ceiling (and then to the stove).

An excellent tool for determining vertical axes is a laser plotter with a plumb line function. Such devices automatically level and provide an exceptionally clear axis above and below themselves (zenith and nadir). The builder can be installed on the stove, and the beam, for example, can be fired through a hole all the way to the roof. Or you can place it on the ceiling and send coaxial beams up and down.

Even household models will cope with the task perfectly. No markup assistant required

And there is another way of marking, but it will give not an axis, but a contour. Knowing where the pipe passes through the ceiling, and also having the ability to temporarily assemble the chimney, you can bring it to the roof using any levels for orientation in space. The top of the pipe is then wrapped with a sheet of cardboard. This wrap (sliding along the pipe) is lifted to the roof slope and an oblique cut is made on the cardboard, corresponding to the angle of inclination of the roof in this place. Then they again bring the cardboard imitation of the pipe to the slope and outline the junction with a marker.

This way you get a very precise hole (its shape, by the way, will resemble an ellipse), but do not forget that when making passes building structures it is necessary to create technological gaps.