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Reconditioning of Large Buttress Screws

Barnes Industries specializes in the manufacture or reconditioning of large conventional lead screws, from Standard Acme or Trapezoidal Threads to special thread forms such as the Buttress thread. Superior Forge and Steel of Pittsburgh, PA, selected Barnes as their source for reconditioning and manufacturing 6.772 inch (172mm) diameter x 30.5 feet (9300mm) long buttress thread screws for their furnace lift system. Two screws operated as a matched set in the machine. Close control of tolerances during the threading operation was required to achieve this accuracy. We reconditioned their original buttress thread screws by re-cutting the threads and manufacturing new buttress nuts to be fitted to the screws according to the customer’s requirements. Engineering drawings were made while reconditioning the screws on an expedited basis.

Once the customer’s emergency needs were met, Barnes began manufacturing two new large buttress screws from our extensive inventory of high alloy steel on hand. We have 40 foot long bars of raw material up through 7 ¼ inch diameter, ready for processing your new lead screw.

After peeling and centerless grinding the bars to the finish diameter, the shafts are ready for thread whirling.

The buttress threads were whirled to finish size with matching leads on both screws for this special application.

Barnes has the precision equipment, highly trained personnel, and material on hand to give you the best possible delivery on any size conventional lead screw.

Product Description	Large Buttress Thread Lead Screws, 6.772 inch (172mm) Diameter by 30.5 feet (9300mm) long
Capabilities applied, processes	Large Capacity thread whirling Special thread forms and flank angles Matching leads between screws
Tightest Tolerances	Matched set of buttress screws Leads on two screws must match within .002 inch/foot over 341 inches of thread
Material Used	AISI 6150 HR, 7 ¼ inch diameter x 40 foot bars on hand-ready for processing
Material Processing	Steel Bars peeled to rough size Major diameter finish ground using 52 foot bar feed on a Cincinnati Centerless grinder
Thread Cutting Requirements	Large capacity thread whirling machine used Extensive steady rest support required Preliminary roughing cuts and straightening operations required Optical inspection of whirling tools to maintain buttress thread form Accurate hook-ups between whirled sections of thread
New Nut Processing	10.433 inch (265mm) diameter bronze buttress nut Threaded to fit buttress screw to customers required accuracy. Large capacity (28 inch diameter) lathes used for turning and chasing thread.
Application assistance	Engineering assistance available Special tooling design for non-standard buttress thread form Load and stress calculations to assure application reliability.
Industry for Use	Material Processing
Delivery Time	Reconditioned buttress screws – 6-8 weeks New buttress Screws- 8-10 weeks Expedited service available
Delivery Location	Ohio
Project Scope	Recondition two large buttress screws with matching leads and manufacture new nuts. Sketch screws for new spares. Design and build two large buttress screws and nuts with matched leads.