In joinery and carpentry, it is sometimes necessary to draw large circles. This can happen when cutting out round pieces of furniture, such as countertops, from wood paneling or sheet material. I mean cutting round billets from chipboard, chipboard, plywood, MDF. And in the construction business, when designing a design, figures are also cut out of drywall. For such markings, a large carpenter's compasses are required, but it may not be enough along the radius.

The fact is that the radius of a classic compass is limited by the length of the legs. And if you need to mark a circle with a large radius, for example, about a meter, then the standard tool will not help. For such work, you can make a device using parts that are sure to be found in any home workshop.

The main part of the tool is a rod made of wood, the length can be taken about 1 meter. For most works, this will be enough, however, the size is chosen as needed. The rod is better suited round, with a section of 20 mm. ... By the way, a thin handle for a light garden tool is well suited as a blank.

When choosing a diameter, you must immediately think about another important detail. A plastic tube will be put on the rod, and it should be slightly larger in inner diameter than the outer diameter of the rod.

Drill a hole on one side of the rod, the diameter is selected according to the diameter of the pencil. After that, we saw through the part with a hacksaw from the end along with the hole. We drill another hole across the cut for a clamping bolt with a wing. A working pencil will be clamped into this device.

Now we cut off a piece of plastic tube 100-150 mm long. , pierce with an awl or drill a hole through the tube in the center. Then, from the inside, we insert a thin nail into one hole, and expand the other and screw the pressure bolt into it. By the way, it is better to pick up a nail with a large flat head, so it will be more rigid.

We put all the details of the compass together, insert a pencil into the split end of the rod and hold it with a lamb. At the other end, we put on a tube with a central axis and tighten with a clamping bolt. We set the desired radius of the circle, the distance between the end of the pencil and the central axis and tighten the clamping bolt on the tube. This bolt will simultaneously press the head of the nail - the axis of the compass. Just do not pull it too much, it will quickly break.

By the way, if a circle needs to be drawn somewhere on a construction site, and there is no time to look for suitable parts, then a simplified version of the compass can also be used. We take a thin long rail, tape a pencil to one end with tape. We measure the required radius and nail a thin sharp nail, it should go through the slats and become the central axis. I think it's understandable that the tip of the nail and the sharpened end of the pencil should be on the same side of the rail. There is one inconvenience here, for accurate marking sometimes you have to pull out and break the nail several times, but in general you can work.

Topic from the site http://ostmaster.blogspot.ru/2012/10/blog-post_14.html

It was in the evening, there was something to do ...

Once I got tired of drawing circles using the well-known "compass" of the "plank with two nails" type ...

I decided to buy a compass - in the stationery there are school "goat's legs" that cannot draw a large circle, at least 50 cm, and even so flimsy that they bend during the process of drawing a circle (as schoolchildren draw something with them) ... I realized that this is not an option.

I looked on the websites of instrument stores in my city - there are no compasses (nicht circus ...). But I found a couple of Moscow online stores, where they offered me to buy a good compass for 3500-4000 rubles. : wacko: Why is this necessary ??? - I thought.

And I decided to make a compass with my own hands. By the way, the manufacturing process took - only one evening.

Compass materials

For the compass I used:

• square shaped tube - 15mm;
• M8 bolts with nuts and washers;
• M6 bolts with nuts and washers;
• printer shaft with a diameter of 3mm (any hardened bar will do).

DIY compass assembly

Check out these articles as well

I cut off two pieces of pipe, the length of your choice, but at least 1 meter each, I used 30cm. It all depends on which circles you draw ...

The edges of the profile are cut as shown in the photo below to insert the needle bolts. Those. 3 out of four sides are cut off from the profile so that there is a plate for drilling for the bolts of the needles.

And for the upper part - 6mm, tk. M6 bolts are used there.

The top bracket can be made of 1mm sheet steel.

A 6mm hole is drilled at the top of the bracket and an M6 bolt with two nuts is inserted into it - this is a handle for conveniently rotating the compass (see the photo at the bottom of the article).

The nuts of the "wing" type are put on the bolts that hold the legs in the bracket, so that it is convenient to fix the position of the legs of the compass.

The lower M8 bolts are clamped in a vice, on the thread, close to the bolt head, a small cut is made with a round file - so it will be more convenient to drill them, then a 3mm hole is outlined and drilled to insert the needle

It is better to grind off the bolt heads by half so that the legs of the compass can touch as closely as possible.

And also, after inserting the needle, it is better to put a washer under the nut, otherwise the nut will rotate very badly on the needle.

For the needles, two pieces of a shaft from an old printer were used - a red-hot rod with a diameter of 3 mm.

As a result, during the evening of work (the other evening I took it apart and painted it), I got an excellent compass with great advantages and small disadvantages.

About the flaws of my compass

• the legs of the compass are not completely compressed due to the bolt heads, the needles do not close to zero, about 1 cm remains, i.e. the compass cannot draw very small circles, less than 1cm. This can be solved by increasing the width of the upper bracket so that the legs of the compass are attached at a greater distance from each other, but for myself I decided that I do not need circles less than 1 cm in diameter;
• the thickness of the profile pipe was not chosen very well, because it includes only an M8 bolt (when using an M10 bolt, 2.5 mm will already remain to the edges of the profile), in which you have to drill a 3 mm hole and when you tighten the nuts tightly, the bolt breaks in a thin place. I recommend using a 20 mm profile, into which you can safely insert an M10 bolt, which will increase the strength of the needles. But in my case, the tightening force is enough to hold the bolts, one needle securing bolt broke only when I decided to tighten it quite tightly with 2 keys: unsure:
• this compass can only draw with needles, and not with a pencil, but it is much more convenient to use a needle to mark circles on wood and sheet steel (it turns out a thin and precise line that is clearly visible), rather than a pencil. If desired, you can make devices for attaching a pencil to this compass.

Otherwise, the compass turned out to be wonderful and already helps me in my work. It is possible that in the future I will make a compass of version 2.0, where I will take into account all the shortcomings of the first version.

Update

On the advice of experienced people from the wonderful chipmaker.ru forum, the compass was modified - the legs were rotated 90 degrees, so that the bolt heads now do not touch, and the needles can be set at an angle - this is very convenient when drawing large circles. Thanks for the advice!

The last two photos show the already modified compasses.

Diy compass photo:

Quite often, a large compass is needed to work with curved wood and laminate blanks. It is used when it is necessary to cut circles or semicircles of large diameter, as well as in the manufacture of arched structures. Ordinary compasses, even with the use of nozzles, cannot provide such a large circle diameter, and even large joiner's compasses do not always cope. To solve this problem, you can do it yourself with a simple device for the formation of large-diameter circles.

The design of such a homemade compass is very simple, and everyone can make such a device. A round wooden rod 1-1.2 meters long is used as a base. The diameter of this rod can be anything, but the best option would be a size of 20-25 mm. With a thicker rod, a homemade compass will turn out to be too heavy and it will be inconvenient for work. You can buy these round rods at a joinery store or just go to the market and buy a thin shank for your garden tools.

A hole about the size of a regular pencil is drilled at one end of the wooden rod. Then, with a hacksaw, cut the rod along its axis. After that, you need to drill another hole (across the cut) for attaching the pencil. A bolt with a nut is threaded into this hole (it is better to take a clamping bolt, which has a convenient wing for twisting and unscrewing). If you are using a simple nut, you will need to use a wrench to clamp the pencil.

Then they take a plastic pipe of a suitable diameter (you can take a piece of pipe for hot water supply or heating). Its diameter is selected for the selected wooden rod, and the length can be in the range of 10-15 centimeters. In this tube, using a drill, two holes are drilled, into one of which a nail is inserted from the inside of the tube, and a clamping bolt is screwed into the second.

Now you can start assembling the compass. In the part that will describe the circle, a pencil is inserted into the intended hole, and a clamping bolt is screwed into the hole through the cut and with its help the cut is pulled together.

From the second end of the rod, a plastic cylinder with an inserted nail is put on it, which will act as the axis of a homemade compass.

It is necessary to use a compass like this: set the required radius and fix the tube together with the nail-axis with the upper bolt. If the diameters of the wooden rod and tube are well matched, the head of the nail will also be tightened when clamping the tube. It is important not to overdo it when tightening the bolt; it is enough to slightly tighten it by hand.

For many homemade products, markings in the form of circles are required. Their diameter can be very different: from just a couple of centimeters to a meter or more. You can spend a lot of time to find suitable compasses. The old way of marking with a thread does not give the best results - the circles are crooked. The compass, which we propose to make with our own hands from scrap materials, is universal. With it, you can easily draw a circle and you can also easily change its diameter.

Materials (edit)

Before starting work, prepare:

• meter threaded rod M10;
• washers, 4 pcs .;
• nuts М10, 4 pcs .;
• nut М12, 1 pc .;
• screw;
• epoxy adhesive.

Step 1... A screw will become a needle for a homemade compass. It must be attached with epoxy glue to one of the outer edges of the large nut. For the convenience of work, you can clamp the nut itself in a vice. Take your time when gluing parts together. The self-tapping screw must be strictly perpendicular to the nut. It will take about 4 days for the glue to completely dry.

Step 2... Now you need to fix the resulting needle on the threaded rod. To do this, in the specified sequence, string on it:

• small nut;
• washer;
• self-tapping nut;
• washer;
• small nut.

Tighten the parts so that the nut and washer structure is strong and secure and holds the improvised needle in the position you want.

Step 3... At the second end of the threaded rod, according to the pattern you already know, you should fix the pencil. Place it between the washers and secure everything with nuts. The pencil itself must be hex. Round pencils will not hold. This has already been verified.

Everything. The compass is ready. To use it, you need to measure the length you need from the needle with a tape measure and twist the nuts with washers and a pencil to the indicated point.

What do we know from the history of kronzikul? The compasses we know from school are used to draw perfectly regular circles. The history of this instrument goes back more than one thousand years, as far as can be judged by the perfectly accurate circles that scientists-archaeologists see on the surfaces of ancient structures. During the excavation of the mounds of the ancient Gauls, in France, an ordinary compass made of iron was found. And during the excavations of Pompeii, scientists were surprised to find a slightly different instrument, it was about the same purpose, but very, very complexly arranged.

As it turned out, it has changed little since the days of the Roman Empire, in the same form it is produced and used in the modern world, although now there is even a digital caliper. This term is of foreign origin, consists of the German word "krone" - a crown and the Latin "circulus" - a circle. Belongs to the category of drawing and measuring instruments. It has two legs, most often of an arched shape, between which you can set the desired angle using a micrometric screw, which is also included in the design of the tool. The screw serves to adjust the desired distance between the legs. There is also a simplified version.

In the photo - for measuring the outer diameters and dimensions of parts.

Today, such a device is used in production to measure the outer diameters and dimensions of parts (one category of tools), as well as to determine the dimensions of the inner diameters of parts (other models of devices). In medicine, this instrument is also widely used in a variety of industries, but all of its varieties are associated with microscopic elements, for example, in dentistry or neurosurgery.

According to the method of obtaining data, mechanical and electronic models are distinguished.
This instrument, as a measuring device, does not need to be verified, because it is not included in the state register. To compare the dimensions of the parts of an object with the exemplary dimensions, just this type of caliper is used. So, having measured a detail with such a specific method, the data obtained are compared with the data of the samples, from which conclusions are drawn.

Calipers are also very convenient in turning, especially among woodworkers - indeed, when turning decorative parts made of wood, exact dimensions are often not too important and a tool that allows you to quickly estimate the size of a part or workpiece on the go is popular. Calipers are especially convenient when turning the same parts, and such a task for every turner regularly arises. The presence of several such tools is extremely speedy - you can pre-configure them for the main dimensions of the part and not be distracted by measuring with a ruler or caliper.

A simple caliper, like the one in the photo above, is not difficult to make on your own. It can be seen that the difficulty is only to find the right material, then a little simple plumbing work.

In the drawing, a caliper with a measuring diameter of up to 180 mm.

What was used in the work.

Tool.
A set of ordinary locksmith tools, something for drilling holes. I used the simplest grinding drum installed in a wood lathe. I used a small angle grinder with a thin cutting disc and an electric sharpener. Stamps with numbers came in handy. A steel plate or anvil is indispensable.

Materials.
A piece of sheet steel of suitable thickness. Used stainless steel, 1.5 mm thick. It is desirable that the workpiece be flat, without dents. Medium abrasive paper. A bit of hardware.

So.
In the manufacture of the tool, several deviations from the drawing were made - the legs of the calipers were taken of the same thickness, instead of the rivet, I used the usual M6 screw. Practice has shown that two reinforced "body" washers and a washer-stopper allow the legs to move smoothly, with little effort. By tightening the nut, it can be adjusted.
I printed the drawing of the caliper leg on a printer on thick paper, adjusting the size to the required one. Cutting out, I got a template. The contour of the leg can be transferred to the workpiece using carbon paper.

All that is possible is cut off with a grinder. The difficulty is cutting out the inner radius. It had to be cut out with a very small "remnant" of a cutting disc.

After rough sawing, I finished the contour on a sharpener and a magic file.

Here, again, there is a problem with the inner radius. I solved it by making a small grinding drum from a birch block with a radius slightly less than the inner radius of the caliper leg. On the block, without removing it from the machine, I wound a sandpaper, fixed the ends with adhesive tape.

After fully refining the shape of the legs, holes were drilled for the hinge.

An M6 bolt of a suitable length was selected, the legs are fastened with an impromptu hinge. It turned out simply and quite efficiently, moreover, the effort with which the legs move can be adjusted.

You can recommend an alternative manufacturing option, more, hmm, classic - without dancing with angle grinders. A number of holes with a diameter of 4 ... 5 mm are drilled along the contour of the legs. A small chisel is used to cut through the bridges between the holes. Further the same.

The hardening of the working part of the legs is lowered and when using the tool not only for wood, it would be better to do it:
- heat the working parts of the legs to a length of 20 mm to a light cherry-red heat color and cool through a layer of oil in water;
- align the legs of the calipers after hardening and clean with an abrasive paper.

Some changes can be made in the described sequence of manufacturing the calipers.
If the blanks for the legs are small and it is inconvenient to mark them in a geometrical way, then two templates are made of thin sheet steel to mark them: one for drawing lines on which you will need to screw the centers for the auxiliary holes, and the second (smaller) one for marking the contour of the leg ... Previously, a template is imposed, which is a contour. First, auxiliary lines are applied on the workpiece according to the first template, and then the main ones according to the second template of smaller sizes. The latter is installed so that the lines of its contour are equally distant from the applied auxiliary contour lines for the centers of the auxiliary holes.

If the material for the caliper blank is 25X4 or 30X4 mm strips, then straight lines are marked on them, reproducing the shape and length of the legs in an unbent form. Then the strip is chopped off with a chisel on a plate or in a vice, retreating 0.5-1 mm from the marking line, and sawn off roughly. After that, the leg is heated and bent with hammer blows on a round mandrel, the dimensions of which correspond to the bending radius of the legs.

Finishing the calipers is the same as above.
With this method of manufacturing calipers, less time is spent, since there is no need to drill auxiliary holes along the contour of the workpiece. The latter method is used most often in the manufacture of an internal gauge, since bending the ends of its legs is very simple, while bending the legs of a caliper is a rather complicated operation that requires certain skills and abilities.

Caliper test and technical requirements. The caliper test consists in spreading and squeezing its legs. In this case, the movement in the hinge should be smooth, and the ends of the legs should converge tightly. The surfaces of the calipers must be clean, free of scratches, nicks and dents, and sharp edges blunted. The ends of the caliper legs should be hardened 20 mm to a hardness of HRC 40-50.

It remains to say that the tool in the arsenal of a wood turner is in great demand. Practice has shown that it is better to have several pieces. Used at the same time, a maximum of four.