Dovetail form tools (center tool coated) that have been made from Carpenter Micro-Melt® Maxamet™ alloy.

May 31, 2001 - A Michigan producer of screw machine parts has tripled his tool life and slashed machine downtime for grinding at least one third by upgrading the tooling he was using to form the body of small stainless Type 303 hex valves.

The shop, which cuts various grades of stainless steels, brass and standard screw machine stock such as 12L14 and 12L15, wanted more parts productivity and more running time from the 9/16" multiple spindle Acme Gridley it was using to make the stainless valves.

Initially, the screw machine house was using dovetail form tools made from T15 high speed steel to size multiple diameters simultaneously. This alloy is a high-carbon tungsten-cobalt-vanadium tool steel that generally offers good abrasion resistance and red hardness.

When using the T15 tooling, however, the shop had to shut down its Acme Gridley every eight hours and grind off 0.040" of stock before the tools could be restored to service. The shop wanted to extend this interval between tool sharpening, thus reducing machine downtime.

Dave Nichols, president of Nichols Precision Tool, Inc., Madison Heights, MI, was consulted for help. Nichols is a specialized manufacturer of high speed tool steel and carbide cutting tools for screw machines and CNC equipment.

The toolmaker suggested making the form tools from Micro-Melt® Maxamet™ alloy, developed by Carpenter Technology Corporation. Maxamet alloy is a high-alloy content, super-hard high speed powder tool steel possessing properties intermediate between conventional high speed tool steels and cemented tungsten carbide. Balanced alloying additions give this alloy excellent wear resistance due to a high carbide volume, while maintaining good toughness at high hardness levels.

Form tools that were made from Maxamet alloy could be run for 12 hours - 50% longer than the T15 tools - before they needed re-sharpening. Then, the new tools needed only 0.020" of stock removed - half the amount required with the tools replaced - to be conditioned for renewed cutting. The longer time between tool maintenance and the savings in stock removed each time gave the shop up to a 300% increase in tool life. Machine downtime was reduced by 33%.

Flat spade drills that have been made from Carpenter Micro-Melt® Maxamet™ alloy.

While the shop machined its parts at the same speeds and feeds with both the T15 and the Maxamet alloy tooling, Nichols felt his customer could increase his speeds and get even more productivity without any noticeable loss in the Maxamet alloy tool life. When sharpening the new tools, he found very little edge breakdown.

Nichols is also planning to coat future Maxamet alloy form tools for this shop with titanium nitride and titanium carbonitride. He anticipated that these PVD coatings could increase tool life by two to three times. Maxamet alloy, in fact, offers a combination of high hardness, hot hardness and high temperature stability that makes it a good candidate for applications in which tools are coated prior to service.

When asked for a tooling recommendation, Nichols ruled out the use of tungsten carbide tools because he feared that, being comparatively brittle, carbide tools might crack due to the interrupted cut application, and cause a "wreck".

Carpenter's Maxamet alloy has consistently attained a room temperature hardness of HRC 70 minimum. This is distinctly above the maximum hardness achieved by conventional high speed steels, and approaches carbide hardness of HRC 75 and above, as converted from the HRA scale.

With its improved hardness, Maxamet alloy may be considered by shops that need to produce parts faster in order to stay competitive. It has been specially formulated to approximate the performance of carbide, but at lower cost.

Nichols receives his Maxamet alloy stock from Carpenter in flat plate up to 2" thick by 12" wide. To make his tools, he saws the material, then mills and/or turns, heat treats and grinds it. He uses rigid machinery and sharp, premium tooling to make his Maxamet alloy tools because the material is tougher to machine than conventional high speed tool steels. Carpenter notes that it does produce the alloy with sulfur levels up to 0.30% for tools requiring improved machinability.

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For additional information about Micro-Melt® Maxamet™ alloy contact:
Bud Carnes
Telephone: (610) 208-2579
FAX: (610) 736-8547
Email:  rcarnes@cartech.com

For additional information about Nichols Precision Tool contact:
Dave Nichols
Telephone: (248) 585-8055
www.nptformtools.com.