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Lapidary Tumbler (Barrel Part Only)

TitleLapidary Tumbler (Barrel Part Only)
Object NameLapidary Tumbler (Barrel Part Only)
Manufactured ByRobinson Plastics Corp.
Manufactured ForCraftools, Inc.
DescriptionThe hexagonal barrel is used for tumbling stones for up to 12 at a time. It was set with a hub into a base with a motor, and covered with a tight-fitting top. The barrel has a female tapered base which fits neatly over the hub (not pictured, permitting it to revolve and to be removed easily (unlike similar metal barrels). The barrel is reinforced by molded-in ribs on each side, and the hub has interior reinforcing ribs extending from the center of each shaft to each corner. The exterior corners are slightly recessed to provide corner clearance and to break any vacuum the might occur, making removal of the barrel difficult.
Date Manufactured1963
MaterialHigh Impact Polystyrene (HIPS)
Manufacturing ProcessInjection molded. A four-cavity family mold (main housing, hub, housing top, and tumbling barrel cover) was constructed to minimize costs, and to allow assembly and packing at the machine, eliminating later color matching problems and to limit shrinkage variations to permit a watertight seal. Given the collective size of the pieces it was decided to use a three-plate mold to allow molding the removable cover of the barrel together with the others. The cover was molded between the first and second plates while the other three parts were molded between the second and third plates. This design allows the cores which form the inside surfaces of the main housing to be pulled away at different times during the opening of the mold which insured the elimination of any possibility of the sticking which might occur in trying to pull the walls of the hub section of the main housing from a single cavity." When the mold was built, slight undercuts were placed in the runner system located between the first and second plates. This was done so that the runner system and the cover would stay with the first plate when the mold was opened. When the main housing and auxiliary sprue have been moved far enough out of the second plate (along with the threaded hub and its metal insert and the housing top section) a chain connecting the second and third plates actuates the knock-out pins and stripper plates forward of the third plate causing the two parts to fall free of the mold between the second and third plates of the mold. After all these parts have cleared the mold, a new threaded pin, which acted a loose mold component and formed the internal threads of the hub section, was snapped into place and the molding cycle repeated.
Number of Objects1
Accession Number2010_055.142
DonorGift of Irvin I. Rubin
Broad SubjectAppliances
For More InformationPlease address inquires to the Public Services Librarian, Special Collections Research Center, Syracuse University Library (e-mail:, tel. 315-443-2697).
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