Aerospace Castings

The nagging worry in Aerospace manufacture is that parts that fly must not fail. Sometimes this guarantee of performance is made at a sacrifice in design or machining cost. Hictol castings provide this insurance against failure with the added benefit of operation-saving close tolerances, like those on the castings described below.

Rocket Fin

These aluminum fins provide the only guidance for a non-military rocket with a range up to 50 miles. Spinning must be controlled within 2 r.p.m. max. Original design allowed 0.015 lean or bow in the leading and trailing edges and on the center-line. The rocket wouldn't fly with these tolerances. A hurry-up emergency meeting established that closer tolerances would be required and that a 100% inspection of all critical dimensions would be required. The checking fixture and an unusually accurate casting helped make the rocket a success. For proper aerodynamics, the leading and trailing edges had to be straight, and within the same plane as the center line at "A". Deviation of more than.005 in any of these conditions caused the rocket to spin and lose its course.

This view shows the checking fixture and phantom outline of the casting in position. The casting must drop easily into the fixture cavity, which is a reverse imSpression of the casting. No forcing or binding is permitted. A depth indicator is used to check each side along centerline "A" after the casting is in place.

Valve Plate - in type 416 stainless steel, heat treated to Rc 26-32 for jet engine fuel control pump. The four trapezoidal holes were cast to size, eliminated costly and difficult secondary operations. Go, No-Go gages were used to check each hole.

Clamp - Over 30,000 of these clamps, some in 410 stainless steel, some in 4140 alloy steel were cast to size and heat-treated to Rc 36 miniMLIm. Not a single casting was ever rejected for dimension, quality or any other reason.

Gimbal - thin walls, isolated bosses and stainless steel made for a difficult combination against which to guarantee tolerances on diameters and overall dimensions to @.015. Yet concentricity, boss locations and all tolerances were consistently maintained in production. A checking and scribing fixture was used in a 100% inspection which guaranteed the accuracy of every casting shipped.

Manifold - This steel part could have been described as 14 pounds of headache by the foundries that tried to make it. In addition to 100% x-ray per ASTM E71-52, Class 1, and 100% magnetic particle inspection, EpCo guaranteed that each casting would pass a 3500 psi pressure test.

The sample casting, which was approved for production by the customer, was shipped two weeks ahead of schedule and helped to bring a critical military program closer to schedule. Follow-on production was also shipped ahead of quoted delivery.

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