Convenient adjustable compass for marking on sheet steel from an old speaker

Metalworking work often requires precise marking of circles on sheet steel. An ordinary compass is of little help here, since its needle cannot be fixed in such a way. To do this, you need a specific tool that is easy to make with your own hands.

Materials:

• Pipe 25 mm;
• strip 20 mm;
• bearing;
• speaker magnet;
• stud M10-M12 with nuts;
• wing bolts M4-M6 with nuts;
• rod 4-6 mm.

Fixture manufacturing process

It is necessary to cut off a ring from the pipe that matches the width of the race of the selected bearing.

A piece of strip 50 mm long is welded to it, with a pre-drilled hole at the end with an 8-10 mm drill.

The bearing is pressed into the ring.

Next, we disassemble the speaker to remove the magnet. A metal insert is knocked out of it.

A bolt is inserted into the magnet and secured with a nut. Then the previously made part with the bearing is pressed.

The compass needle is made from a piece of a pin that matches the diameter of the inner race of the bearing. From one edge it needs to be drilled across and along to bring the holes together. The longitudinal thread is cut.

The second end should be sharpened to a cone.

Then the pin is inserted into the bearing and pressed on both sides with nuts. It needs to be adjusted so that the needle is level with the magnet.

Next, the compass rod is made. To do this, use a piece of thin tube 30-40 mm long, into which you can insert a marker or pencil.

A hole is drilled in the side and a nut is welded onto it. The rod itself must be welded to the tube, made from a thin rod that can freely pass into the transverse hole in the needle.

The rod is inserted into the needle and tightened from above with a screw and wing nut. A marker or pencil is placed into the tube and clamped in the same way.

The instrument is now ready for reconciliation. You need to stick a magnet to the surface so that the needle is located at the central point of the drawing. Then we adjust the radius with the barbell and draw a circle.

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