There are several ways to mark center holes, but the most widely used are: a) marking using a marking compass (Fig. 105, a) and b) marking using a center-picker fig. 105, d). Before marking, the ends are usually chalked up so that the risks that determine the position of the center holes are more noticeable. Then proceed to markup.

Marking with a caliper

The legs of the marking compass (Fig. 105, a) are placed at a distance approximately equal to the radius of the part. A curved leg is applied to the circumference of the butt of the part, clamped in a vice, and an pointed leg draws an arc near the center of the butt. Then, three more arcs are carried out in the same way, each time moving the curved leg of the compass approximately on the circumference of the butt. The drawn four arcs form a curvilinear quadrilateral. If the compass legs are separated by a distance exceeding the radius, then the risks form a figure, as shown in fig. 105, b, and if at a distance less than the radius, then as in fig. 105, c.

Figure 105. Marking and naming of the centering hole: a - marking with a marking compass, b and c - marking risks, d - marking with a center-finder, g - centering nosing

The center of the hole should be in the center of the resulting quadrilateral. It is marked on the eye and then peg, as shown in fig. 105, d.

Center Markup

Marking with the help of a center-finder (Fig. 105, d). Attaching the center-viewer to the end of the part, scribing it at risk, then turning the part or center-searcher about 90 ° and carrying out the second risk. The intersection of the remarks oO determines the position of the center hole. The same is done on the other end.

Hole punching

The centering holes are shown in fig. 105, d. The center punch should be installed vertically, but in no way inclined. In the latter case, when hit with a hammer, the punch will shift from the intended point; in addition, it is possible for the punch to jump off the workpiece and the turner may damage the arm.

In details with a diameter of up to 40 mm, it is better to pin the center without marking using a special device called a bell (fig. 106). The device is installed on the end of the part vertically and a hammer on the core of the bell mark the place

Instruction card number 1

Topic “Using the marking tool”

1. Purpose and efficiency of the card application

The card is intended for organizing the work of students to perform training exercises:

Applying scratches using a metal measuring line and scriber.

Coreing

Using marking compasses.

The use of centro searchers.

Use of flightmask.

Sharpening and refilling marking tools.

2. Equipment, tools and fixtures

Metal measuring rulers, scriber, compasses marking single-needle rails, vertical rulers, center-detectors, square-center-detectors, sliding center-detectors, center pins, mechanical centerpieces, hammers with a metalwork 200 g, wooden blocks, a marking plate, sharpening machine , sharpening angle check templates, grinding bars .

3. Instructive instructions

Pic.1

Exercise 1.Scratching with metal measuring rulers and scriber

1. Attach a ruler to the workpiece.
Press the ruler to the workpiece tightly with three fingers of your left hand so that there is no gap between it and the workpiece.

2. Take a scoop and hold at risk.

Scriber to take in his right hand, like a pencil, and, without interrupting the movement, hold the risk of the required length. When carrying out risks, the scriber should be pressed tightly against the ruler, deviating from it by a small angle.

Pic2

Fig. 3

Exercise 2. Coreing

1. Roll a simple tuck at risk.

Take the center punch in your left hand with three fingers: thumb, index and ring fingers.

Slightly tilting the punch "away", set its edge exactly on risk.

Position the center punch perpendicular to the marked plane and apply a gentle blow to the head with a marking hammer.

In the same sequence to do the following core cavities (Fig. 2).

Observe the following rules for the sintering of marking markings:

when threading long scratches (150 mm and more) the distance between the recesses should be 25-30 mm;

for short scratches (less than 150 mm), the distance between the recesses should be 10-15 mm;

lines of small circles (0 to 15 mm) to be threaded at four mutually perpendicular points;

lines of large circles (0 more than 15 mm) coil evenly in 6-8 places;

arcs in mates will be twisted with shorter intervals between grooves than on straight lines;

the junction points and the intersections of the scratches are mandatory.

2. Screw on the spring with a center punch.

Take the center punch in the right hand. Slightly tilting the punch "away", set its edge exactly on risk. Having set the center punch vertically, push it down (fig. 3),

Fig. four

Fig. five

Exercise 3. Using marking compass

1. Set the compass legs to size.

Take the marking compass in your left hand and slightly release the clamping screw.

Set one leg of the compass point on the tenth division of the ruler, and the second - on the division greater than the specified by 10 mm.

Fasten the clamping screw, holding the compass by the leg, into which the clamping screw is screwed.

Check the set size on the ruler (Fig. 4).

Note. The use of compasses with a weakened joint is prohibited.

2. Draw an arc.

Apply two mutually perpendicular risks (axes) on the workpiece.

Screw the intersection point of the axes,

Set the compass legs to the size of the arc radius.

Place the point of one (stationary) leg into the core hole made and, slightly pressing both legs to the surface of the part, with the other (movable) leg draw an arc of a given length on the part.

When conducting an arc, the compass should be tilted slightly in the direction of motion (Fig. 5)

Fig. 6

Fig. 7

Fig. eight

Exercise 4. Using centro searchers

1. Mark the center with a center punch.

Note. A center-pivot center marks the centers only at the ends of the cylindrical parts.

Install a center pitch detector on the end of a cylindrical part. Holding the centerfinder in an upright position with your left hand, strike the center punch with a hammer (Fig. 6).

2. Outline the center withusing the center square finder.

Note. With the help of the square detector, centers are found only at the ends of the cylindrical parts.

Install the square-finder on the end of the part in this way; so that the corner bars touch the part. Holding the square-finder with your left hand, hold a scriber at risk on the end of the part.

Rotate the square about 90 ° and hold a second risk, the intersection of which with the first one will give the center of the end face - ABOUT.

At the point of intersection of the troughs, make a core cavity (Fig. 7).

3. Find the center of the hole using the sliding center finder.

Note. With the help of a sliding center-finder, the centers of the holes are found.

Tightly insert a wooden bar with a plate made of white tin into the hole so that the plane of the plate is 4--5 mm below the end plane of the part.

Spread the center-finder legs to a size approximately equal to the radius of the hole.

While pressing the bent leg of the center-viewer to the inner surface of the hole, make a notch on the plate of four mutually perpendicular positions.

Identify the “by eye” center inside the four serif arcs and thread it.

Check the accuracy of marking the center of the hole and, if necessary, repeat the marking (Fig. 8).

Fig. 9

Fig. ten

Exercise 5. The use of flight

1. Set the needle to the required size.

Set rehimes on the razmetochnoy plate, the rod / reymasa positioned vertically 2 - horizontally (fig. 9)

Scale up the rack and using a vertical ruler 8, preset it to the required size, then fix it on the rack with a clamping screw 4.

Rotating set screw 5 on the basis of flightmas, precisely set the tip of the scriber to the required size.

2. Hold on the details of the risk of flight.

Carry out the risk of a smooth continuous movement, pressing the base of the plane to the marking plate

The raymasa scriber should be tilted in the direction of movement by 60-70 ° with respect to the plane being marked, while maintaining a constant inclination (Fig. 10).

Fig. eleven

Fig. 12

Fig. 13

Exercise 6. Sharpening and refueling marking tools

1. Sharpen (fill) scriber.

Check the size of the gap between the handcuff of the sharpening machine and the periphery of the grinding wheel, and if it exceeds 2-3 mm, make the appropriate adjustment (installation).

Lower the protective screen and, by pressing the “Start” button, turn on the machine.

Take the scriber in both hands and, resting his left hand on the handkerchief, position the scriber at a slight angle to the end surface of the grinding wheel.

Rotate the scriber slightly, sharpen it at a length of 12-15 mm (Fig. 11).

2. Sharpen (fill) center punch.

Adjust the gap between the arm and the circle, lower the protective screen and turn on the machine.

Take the center punch in both hands and position it at an angle of 50-60 ° to the horizontal axis of the circle. To sharpen the center punch on the periphery of the circle, turning it around the axis.

Check the grinding angle with a template, which should be equal to 60-70 ° (Fig. 12).

3. Sharpen and tuck in (to bring) the caliper leg.

Bring compass legs together. Turn on the machine. Sharpen the legs of the compass from four sides to a square over a length of 15-20 mm so that the tips of both legs converge into one point.

Fill (bring) the compass legs alternately on the bar with longitudinal movements (Fig. 13).

Among the plumbing tools, there is one of such useful and simple hand tools as the punch. In this article we will talk in detail about this instrument, consider its purpose and types, and also focus on those details that should be remembered when buying a center punch in the store. Well, let's look at all this right now.

What is a center punch and what is it for?

As already mentioned, the punch is a hand tool designed for plumbing. So, it is used to mark the central holes (the so-called "cores"), which are necessary for the initial installation of the drill, or another visual mark. Externally, the punch is a metal rod having a circular cross section. One of the ends of the tool is the working part, and it is made in the form of a cone, whose angle at the top is 100-120 °.

The process that is performed during the work with this tool is called “coreing”. It consists in blows applied by a hammer from the opposite part of the tool’s tool, the so-called butt pad. The use of this tool helps to avoid several unpleasant things - with its help, the drill slippage from the drilling point is excluded, and the corener helps to more accurately perform the drilling process, etc.

You can buy a center punch in almost any store of plumbing and manual equipment. On the counter, it is easy to recognize it by the cylindrical shape, at the beginning of which there is a striker, and at the end is a pointed cone. In the middle part of the tool, there are notches or stripes that help hold it tightly in your hands. To get a mark using a center punch, you need to install it with a tapered end to the mark point, and strike the hammer with a hammer. The material from which the punch is made, as a rule, is a solid tool steel, hardened by thermal means. Note that this tool is often called “core”, but this is an erroneous expression.

Types and types of center pins

As we have said, the punch is a hand tool. However, at the same time, there are also automatic punchs, the so-called “crossbows”. This type of instrument suggests a completely different design and device. Outwardly, such a punch looks like a screwdriver, in the handle of which there is a spring and platoon-trigger mechanisms. These mechanisms make the striker move, and, in fact, leave marks on the metal surface.

The advantage of this type of center punch is the fact that it can be used to apply marks with one hand without using percussion instruments, respectively, without using the other hand. Also, the advantage of this center is the ability to adjust the force of impact. This, in turn, allows you to adjust it in such a way as to leave marks even on the softest or most fragile materials and parts that require increased accuracy and care when processing. And, of course, the automatic punch will significantly increase the speed of marking.

Another type of this tool is the electric punch. Its design provides a solenoid, which draws in the tool's core, and then applies a striking action on the center punch pin. As well as the automatic center punch, it is very easy to use, but its design is already somewhat outdated, therefore it is not so often to meet a tool of this type.

Also, there are centers with special mandrels. They will allow the mechanic to very quickly form a mark at a given distance, for example, from the edge, or, conversely, from the center of the part. In short, such a punch allows you to set labels on surfaces that have any specific features.

To buy a center punch in a store, it is enough to pay attention to the material, look at its appearance, and look at the manufacturer. The tool from the known producer, is more preferable, than the center punch without any identification marks or distinctions. Therefore, pay close attention to these details, and then the tool will serve you for a very, very long time.

More articles from the section:

2.12; section 6