SCREW – ON COPIER | MODEL CONSTRUCTION

Fixture is used for manufacturing propellers boat on lathes Тb-4 and TV-7. Using the tool it is possible to produce propellers of aluminum alloy (D16T), brass and plastics. Moreover, the production of screw blanks of alloy D16T takes up to 10 minutes, and made of brass — up to 40 minutes. The diameter of the screws up to 50 mm Number of blades — 3. You can do two – and four-bladed screws, but this requires modification of the spindle and tracer. The fixture consists of a housing, which is attached to the copier. In case the spindle is inserted, it is secured to the arm and disc. In a lathe Chuck clamped to the mill.

The casing is made of Steel 45. In the housing there is a hole with a diameter of 25 mm used for installation of the spindle. For attachment of the housing to the tool post of the machine on the lateral surface of the milled shelf. In the back of the case has a window, enabling the movement of the handle. The window can be closed by copier. Six holes for screws M5 and mark the holes of the copier.

The copier is made of Steel 10KP 1.5 mm thick. the Modelers, as a rule, necessary screws right and left rotation, so you will need two replacement copier under the “right” and “left” screw. These copiers will be in a different location of the groove for the handle, which performed particularly carefully. First on the plate prior to its bending it is necessary to mark and cut the groove with allowance for processing, that is, its width should be 9,5—9,8 mm. Final fit it on the handle to make Assembly of the copier housing. This should fix the copier on the housing, insert the spindle. The beginning of the groove of the copier to expand so that you can insert the handle through the copier into the hole of the spindle. Then gradually widen the groove so the handle without gaps and jamming moved on it as it rotates with the spindle.

Fixture Assembly:

1 – body, 2 — copy, 3 – feeler arm, 4 — 3 spindle, 5 — blank, 6 — cutter 7 — screw M8 mounting arm copier, 8 — M8 screws mounting the workpiece, 9 — screws M5.

Adjustment (extension) can be made only on one side of the groove. The inclination of the groove can be selected depending on pitch; in the drawing, it corresponds to a step equal to 48 mm. in the calculation of the angle the screw diameter is taken equal to 60 mm — diameter casing.

The handle is used for rotation and simultaneous feed of the spindle. It is made of Steel 45; one end through the slot on the copier inserted into one of the holes of the spindle and fastened with M8 screws.

The spindle used for the workpiece feed screw for a mill. On the front end of the spindle has a hole 0 25 mm, in which the workpiece is inserted and clamped in the spindle with three bolts M8. At the rear end of the spindle has three holes 08 mm located at an angle of 120°, which must be maintained as accurately as possible. For the manufacture of two-bladed propeller, it is necessary to drill one through hole, and four-for — four holes under an angle of 90E. Material — Steel 45.

Workpiece screw (disc) turned from alloy D16T, brass or plastic. The diameter is selected depending on the diameter of the screw. The blank has a shank diameter of 25 mm, which is inserted into the spindle. At the other end there is a cylindrical ledge — the future hub of the screw. Accordingly, its diameter must be equal to the diameter of the hub.

Mill — end standard. The diameter is selected depending on the screw pitch and number of visits. Due to the fact that the distance between the rotor blades changes depending on the diameter, the mill must grind pattern. To make a pattern with sufficient accuracy can be graphed. For this we need to plot the helical sweep surfaces.

On the vertical axis scale is the step of the screw N, while the horizontal circumference of the screw, starting from the outer diameter (ABOUT) and ending with the diameter of the hub (TH) with an interval of 5… 10 mm. Connecting the point a with all points on the horizontal axis, we obtain the schedule scan or spiral surfaces a graph of the angles of the blades in different diameters.

The pitch is divided ia the number of blades, in this case three cut. From points A1 and A2 lines are parallel to the lines AB, AV, AG, etc. the Distance between parallel lines is equal to the distance between the rotor blades, which can be determined more precisely by the formula:

The distance between the blades given without taking into account their thickness, therefore, the sizes it is necessary to reduce the thickness of the blade. For three-bladed propeller with a pitch of 48 mm cutter diameter equal to 14 mm.

The order of work. For the manufacture of screw is needed to secure the fixture in the tool post of the machine, the cutter — cartridge; insert the screw blank into the spindle and tighten its bolts; using the handle to withdraw the spindle in the rearward position; handles longitudinal and cross feed of the machine to bring the blank to the cutter, as shown; turn on the machine (rpm — 60…7ОО); gently pressing the lever, start the cut grooves; and cutting through the groove to the end, to bring the arm to its original position, loosen the lock bolt to move the lever in the next hole of the spindle and repeat the operation of milling.

If, after slotting the thickness of the blades is greater than normal, the cutting should be repeated, achieving the desired thickness of the transverse feeding of the caliper of the machine.

In the manufacture of the “left” screws to begin cutting the slots you should be especially careful, because the cutter and blank are rotated towards each other, so that there may occur jamming.

After the grooves are cut and the workpiece acquired the form of a screw, must be inserted in the Chuck of the lathe and drilling the hole for the propeller shaft, and then cutting cutter “screw” cut into the screws.

A. KOLOTOVKIN, head of ship modeling circle, g. Klintsy, Bryansk.

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