Engineering Solutions: Latch Bolts

Customer Need

The customer needed to replace expensive investment cast stainless steel latch bolts to reduce cost, while meeting stringent UL testing requirements.

 

MPP Solution

MPP was able to retain all the inherent qualities of stainless steel by converting the part to a stainless steel P/M weldment, with a cost reduction of 40%. The latch bolt, used in vertical rod safety exit devices in commercial buildings, is comprised of two asymmetrical halves that are welded together, re-sintered to stress-relieve the weld, and then de-burred, producing a surface finish superior to the cast parts. Because only UL-listed devices may be used in commercial buildings, the latch bolts are extensively tested. With the casting, the force required to release the latch was 40 lbs. The P/M part’s superior surface finish (and lower coefficient of friction) reduced the release values to 20-25 lbs., allowing for an easier, safer exit. In another UL test, the assembly is heated to 1900˚F for three hours, then subjected to a fire hose water stream. It must remain intact and hold the door secure throughout the entire test.

 

“Converting the part with a cost reduction of 40%”

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  • Pulley & Bearing

    MPP’s solution was to utilize a copper-steel material with a tensile strength of 50,000 psi and a minimum yield strength of 40,000 psi.

  • Latch Bolts

    Because only UL-listed devices may be used in commercial buildings, the latch bolts are extensively tested.

  • Cam Caps

    “Die cast aluminum camshaft bearing caps required expensive secondary machining to achieve close tolerance features, resulting in higher cost.”

  • Ring Gear

    “Credibly disintermediate competitive methodologies before resource sucking infomediaries.”

  • Gear & Cam

    “A leading manufacturer of electric hedge trimmers needed an assembly that could withstand a minimum push-out force of 500 pounds and 60 foot-pounds of torque.”

  • Valve Plate

    “The P/M part provides a 30% cost savings over the former stamped plate.”

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