Among detachable connections, threaded connections are especially common. They allow, if necessary, to disassemble the assembly into parts without damage, and then reassemble them again. For this reason, all kinds of thread-cutting devices are designed and produced in large quantities, both by industry and by numerous craftsmen.
Below we consider a variant of a thread-cutting machine based on an electric motor and, mounted on its axis, a friction unregulated drive in the form of a rubber-coated bushing.
Required accessories
In order not to be distracted from work, you should purchase, find and prepare:
- two ferrous metal plates measuring 150×120×20 mm with a hole in the center at the top with a diameter of 30 mm;
- two steel disks with a diameter of 200 mm, a thickness of 10 mm with a single-sided hub with an outer diameter of 40 mm and an internal hole of 25+ mm with three radial holes with M8 threads;
- two copper or brass bushings with outer and inner diameters of 30+ mm and 25+ mm, respectively, for pressing into the holes of plates 150x120x20 mm;
- blank for the main axle made of steel 400 m long and 25+ mm in diameter after turning;
- two sections of pipe 100 mm long and with a diameter of: outer – 40 mm, inner – 25+ mm;
- two steel rods 300 mm long and 25 mm in diameter (final size) with a blind hole at one end with an M10 thread;
- one steel plate 180 mm wide, 150 mm high, 8 mm thick with a triangular recess in the center at the top for the tap to exit and two holes at the edges at the bottom for M10 bolts;
- two steel angles 35×35 mm, 150 mm long with two holes at the edges for an M8 bolt;
- two steel corners 35×35 mm, 500 mm long with ends beveled at 45°;
- the same length 400 mm;
- steel sheet measuring 500×400×3 mm;
- motor switch;
- collet chuck from an electric drill;
- hardware (bolts, nuts, washers on M8 and M10).
Equipment and tools
To prepare parts and assemble the threading machine we will need:
- lathe;
- grinder;
- bench vice;
- welding machine;
- wrenches;
- punch and hammer;
- oiler with lubricating oil;
- liquid for degreasing surfaces;
- dye;
- spray gun, etc.
The process of preparing parts and assembling the machine
Some parts are completely ready for assembly, others require some further work.
1. On the grinder we finally finish (remove burrs, round and grind) all the edges and surfaces of the 150x120x20 mm plates, which will perform the main power function in the machine, giving consistency in size and the necessary rigidity to the system as a whole.
2. We clamp the copper bushings into the chuck of the lathe and adjust the bore diameter to a size that is guaranteed to ensure their tight fit in the holes intended for them.
3.We press in the bushings using a bench vice, ensuring that they are completely seated in the holes intended for them, until the shoulders of the bushings rest against the surface of the plates.
4. Install the workpiece for the main axis of the machine on the lathe. To ensure minimal radial runout of the workpiece during turning, remove the rear support of the lathe and temporarily place a chuck with a centering drill in its place and, turning on the machine, make a recess at the end of the workpiece for the rear support of the lathe.
5. We carry out external turning of the workpiece, controlling the diameter with a caliper so as not to weaken the future main axis. Having achieved the specified size, we check the free sliding of the axis along the bushing of the power support of the threading machine. If it is not sufficient, turn on the lathe and grind the bushing to the axle.
6. We grind the working end of the axle under the seat of the collet chuck, degrease it with the help of an appropriate liquid and secure the chuck.
7. By turning on a lathe, we align the surfaces of the disks that will interact with the rubber-coated drive bushing, and achieve the required diameter of the hole in the hub. We check the accuracy by inserting the axis and turning it, with simultaneous axial movement. These movements must be performed without jamming or jamming.
8. We lay corners along the perimeter of the base of the machine, join them in the corners and weld them together and to the base sheet.
9. On one edge of the base we install the main axis with two supports, between which there are two driven disks for working and idling. We try on guides with tubes and an electric motor with a friction (rubber-coated) bushing mounted on its axis.
10.Once again we check the correctness and accuracy of the layout and, using a welding machine, weld the power supports of the main axis to the base of the machine. After this, we once again check the freedom of rotation of the axle in the supports and its movement back and forth.
11. On the outer sides of the front power support, in places where it interfaces with the base, flush with its front edge, we weld cylindrical guides along which the guide rods will move.
12. We mark the shelves of the corners for the electric motor, mark with a center punch the locations of the holes for mounting the motor and drill them for M8 bolts. We install the corners with the motor attached to them, check the accuracy of the installation (perpendicularity of the motor axis to the main axis of the machine) and weld the corners to the base.
13. Then we again disassemble the layout of the machine and paint the parts, excluding those that interact with each other (axle, bushings, guides, working surfaces of disks, etc.). Let the paint dry and proceed to the final assembly of the machine, lubricating the rubbing surfaces with machine oil.
14. We fix the electric motor in the verified place and install the guides in place. We screw a panel with a slot for a tap to their front ends. We tighten the bolts securing the discs to the main axle against longitudinal displacement, lightly pressing them against the drive friction bushing.
15. Assemble and close the motor switch cover. The thread cutting machine is completely ready for use.
16. We check its performance by alternately cutting threads in the holes for M5, M6 and M8, pre-lubricating the taps. When pressing on the supporting surface with the part in which the thread is drilled, the tool rotates to the right and cuts the thread.When pulling back a threaded part, the tap begins to rotate to the left and disengages with the resulting thread.
Watch detailed video
Watch detailed video instructions on how to make a thread-cutting machine with your own hands.
