The fixture is designed without a preliminary marking to make notches in the hubs of the propeller blades.
The base is cut out or milled from steel or aluminum. Margins of 10 mm from the upper end of the workpiece bore through hole Ø 8 mm for focusing with long head. Perpendicular to the top plane to install the lock, make another hole Ø 4.1 mm, 4 mm offset from the axis to the left. Focus and a dividing head are machined together. The diameter of the focus of 7.95 (hole in base). Bevel the cut end under a three – or tetrahedron to entering into the shaft hole in the hub, the verge hold it in position, preventing its turning.
The circumference of the dividing heads divide into three equal parts and draw a short risks. Then divide the circumference into four equal parts and slide risks longer. On the basis of take one risk at the top for fixing the shaft stops. When you turn the dividing head to match mark the hub at the same time rotated to the desired angle.
The retainer is inserted into the drilled hole for him at the top of the base. Then to a depth of half its diameter round file make the hole exactly on the shaft it stops, and at the upper end of threaded M4 under the lamb. When screwing the lamb, the latch will rise and due to it made in the hole tightly pressed to the ground and complete with dividing head.
A movable stop — rod Ø 4 mm with drilled from one end a hole, which includes the top of the hub, presses it and stop screw. Both stops are placed on the same axis.
For convenience, you need to make a sheet metal thickness of 0.8—1 mm squares, with the most common step angles of 40, 30, 25°. They have a slot through which the guide edge move along the axis of the hub. Along the hypotenuse of the square has a bent down edge guide for focus hacksaw.
Before processing the slots, the fixture is clamped in the vise. To saw through grooves can be on the lathe. The squares in sham case is not necessary. The fixture can be mounted to the caliper and rotate with it the desired angle.
S. PETROV, head of laboratory of ship modeling Cricut, Khabarovsk