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moldmakingtechnology.com 33 4930 S. Lapeer Rd. • Orion Twp., MI 48359 U.S.A. Phone: (586) 573-9450 • Fax: (586) 573-9451 www.millstar.com Sales Inquiries Welcome Manufacturing versatility, engineering expertise and outstanding service support empower all areas of Millstar to deliver the precise cutting tool solution for any job in every market. • Latest in profile and contour milling technology • Shorter machining and lead times • Higher machining accuracy and true contouring results No matter what market you're in, you can count on Millstar's quality, precision cutting tool solutions to meet performance expectations. Contact Millstar today. Accomplished to Serve Every Market Preload: Bolts Offer a Frame of Reference Someone who is unfamiliar with demanding loads on a joint interface or unfamiliar with torque might fasten joints together without it. If problems develop, he or she may simply decide to use successively larger bolts until the bolt is large enough to make the joint tight enough. This very-large-bolt design may be "good enough" for the loads expected, but may be insufficient if loads are unexpectedly increased. For this type of non-preload- ed joint, any load on the bolt will cause some stretch, and the joint will always have some gap. Increasing bolt size to tackle this problem results in a much larger and heavier bolting system, which is limited depending on the allowable gap for the application. Most joints need zero gap, so this is problematic. To those familiar with torque, the use of large bolts will seem counter- productive. Instead, smaller, torqued bolts are recommended. Below the torqued load, the joint will not sepa- rate and will provide constant position. A torqued (preloaded) bolt will not stretch, will maintain full contact and will remain tight. Using a larger bolt with no torque interface can be made to work with some degree of success, however using a smaller bolt with a torqued interface is the preferred best practice. Thus, the key to good mating of parts is preloading the bolts. Bolt size and torque is chosen to meet and exceed application parameters so parts stay in contact with zero movement. A prop- erly designed bolted joint will have no movement under the planned loads, giving the joint a perfectly infinite operating window (zero movement) up to the preload amount. Can we do the same thing with moveable cores? Yes. Preload Cores Just as applying torque to a bolt provides an infinite processing window for the bolted joint, so too does preloading mold steel The key value in these systems is the ability to preload cores toward the fixed stops and to provide an infinite processing window to moveable cores when and where possible.