Powder Steel Solves Broaching Problem

Changes in tooling material and design have helped Beretta USA Corp., Accokeek, Maryland, to significantly improve tool life, cut setup costs, increase productivity and improve quality in broaching hammers and barrels for its Model 92 and 96 series pistols.

Case Study From: 10/15/1998 Modern Machine Shop

Changes in tooling material and design have helped Beretta USA Corp., Accokeek, Maryland, to significantly improve tool life, cut setup costs, increase productivity and improve quality in broaching hammers and barrels for its Model 92 and 96 series pistols.

Broaches Inc., a Detroit manufacturer of precision cutting tools, came to the company's aid by redesigning critical broaches and making them with Micro-Melt T-15 alloy, a powder high-speed tool steel from Carpenter Technology Corp., Reading, Pennsylvania.

Beretta was having problems broaching the engagement of teeth of the hammer, using the original hammer broaches. A set of six tools was used to broach the surfaces of the 4140 steel hammer.

The original broaches were cumbersome and time-consuming when changing setup or tooling. On occasion, the broaches would prematurely wear out or chip.

Joe Nicoletti, Broaches, Inc., president, saw that the high-speed ram on the broach machine was running at up to 120 fpm under a relatively low power of three to five tons. This, he felt, was essentially a slabbing operation that caused vibration and chatter, and suggested the need to modify broach design.

He redesigned the roughing and finishing teeth to generate an off-angle cut and produce an improved profile with an edge-cutting tool. In the process, he also decided to make his broaches from the Micro-Melt T-15 alloy. This is a high-carbon, tungsten-cobalt-vanadium high-speed powder metal tool steel with excellent abrasion resistance and red hardness.

The advantages of this premium powder metal include ease of grinding, response to heat treatment, more uniform structure, greater wear resistance and improved toughness. Mr. Nicoletti went to the Carpenter alloy, he said, because of the high speed of the ram and the potential to improve parts productivity.

Results were described as impressive. The new broaches can now be set up in two hours, dramatically reducing setup time by 75 percent. With the design and alloy changes, the plant has been able to get three to four weeks of production before broach sharpening.

The quality and efficiency of the workstation also have been improved with this change. This improvement has helped Beretta to meet its production and quality requirements each month.

The manufacturer had to solve similar problems with M-4 rifling broaches used to put spiraling inside its gun barrels. Broaches from another company would produce no more than 60 barrels, resharpening to the end of the tool life.

Mr. Nicoletti, switching to the T-15 alloy, changed the stepping and configuration of the broach cutting teeth. The new tool was used to broach 4140 steel and Type 410 stainless steel barrels.

With the new design and tooling materials, Beretta has been able to broach 60 percent more barrels per sharpening and get ten additional sharpenings per broach.

Carpenter's T-15 alloy comes with minimal distortion characteristics because of the special processing it undergoes on Carpenter's hot rolling mill and rotary forge.

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