Feature Article

The author gives an overview of the most common hardness testing methods: Rockwell, Brinell, Vickers and Knoop.

An expert on heat treating write about the advantages and disadvantages of available approaches and systems: stainless steel foil, atmospherically controlled furnaces, pressure-quench vacuum furnaces and two-zone vacuum furnaces. There's also a sidebar on cryogenic treatment of metals.

Tips for deep-hole tapping in titanium and other aerospace-grade materials. Advice is provided by NIST and the International Titanium Association.

A new turning tool emits an electric signal when its insert reaches a predetermined wear point or breaks. Called Sensor Tool, sections of the coated insert are ablated by a laser, thereby creating an electronic circuit.

A look at the various types of CNC lathes available to shops contemplating stepping up from a manual machine. The pros and cons of the following lathes are discussed: combination, cutoff, slant-bed, twin-spindle and turn/mill. The author also touches on available options.

Part I: The author discusses how to maintain and repair machine tool spindles and what causes spindles to run out of round. Common sources of out-of-round spindles include loose bearings and improperly ground spacers. In-machine spindle repair is also discussed. Part II: There are three common ways to repair tapered toolholders: regrinding, replacing damaged material and chrome-plating.

Capability is determined by how well a process produces parts. Three measures of capability are important to a machinist: gage, machine and process. The author provides a detailed description of capability and suggests ways to quantify if a process is or isn't capable.

Cutting forces cause the boring bar to deflect, which can lead to vibration and damaged workpieces. The author gives an overview of available boring bars and offers guidelines for selecting one for a specific application.

Grinding burn is a general term used to describe various types of thermal damage that occur to the workpiece during grinding.

The author discusses three recent advancements in electrical discharge machining: the use of linear motors on EDMs, wire EDMs with an automatic slug-removal capability and dielectric fluid additives that yield finer part finishes.

DNC can mean either Direct Numeric Control or Distributed Numeric Control. Either way, a DNC links a shop's computers and machine tools and saves times. A DNC eliminates manual transcription of NC data, the downtime caused by shop personnel having to make programming entries and transporting part programs between engineering and their machines.

The use of shrink-fit toolholders continues to grow, mainly because, compared to conventional holders, they secure tools more tightly and extend the life of cutting tools. Article includes an overview of available systems and comments from users of shrink-fit holders.