A lathe center, often shortened to center, is a tool that has been ground to a point to accurately position a workpiece on an axis. They usually have an included angle of 60°, but in heavy machining situations an angle of 75° is used.^[1]

The primary use of a center is to ensure concentric work is produced; this allows the workpiece to be transferred between machining (or inspection) operations without any loss of accuracy. A part may be turned in a lathe, sent off for hardening and tempering and then ground between centers in a cylindrical grinder. The preservation of concentricity between the turning and grinding operations is crucial for quality work.

A center is also used to support longer workpieces where the cutting forces would deflect the work excessively, reducing the finish and accuracy of the workpiece, or creating a hazardous situation.

A center lathe has applications anywhere that a centered workpiece may be used; this is not limited to lathe usage but may include setups in dividing heads, cylindrical grinders, tool and cutter grinders or other related equipment. The term between centers refers to any machining operation where the job needs to be performed using centers.

A center is inserted into a matching hole drilled by a center drill. The hole is conical near and at the surface, and cylindrical, deeper.

2 days ago Lathe machines such as manual, CNC and vertical turning lathe machines are repaired. Emergency, on-site and complete repairing services are available. Industries served include aerospace, automotive, bearing manufacturers, ceramics, medical, military, defense, petrochemical, semiconductor, woodworking and production manufacturing. Lathe machines such as manual, CNC and vertical turning lathe machines are repaired. Emergency, on-site and complete repairing services are available. Industries served include aerospace, automotive, bearing manufacturers, ceramics, medical, military, defense, petrochemical, semiconductor, woodworking and production manufacturing.

Dead center (and live center)[edit]

A dead center (one that does not turn freely, i.e., dead) may be used to support the workpiece at either the fixed or rotating end of the machine. When used in the fixed position, a dead center produces friction between the workpiece and center, due to the rotation of the workpiece. Lubrication is therefore required between the center and workpiece to prevent friction welding from occurring. Additionally the tip of the center may have an insert of cemented carbide which will reduce the friction slightly and allow for faster speeds. Dead centers are typically fully hardened to prevent damage to the important mating surfaces of the taper and to preserve the 60° angle of the nose. As tungsten carbide is much harder than steel, a carbide-tipped center has greater wear resistance than a steel center.

When turning between centres, a 'dead centre' is used in the headstock as well as the tailstock. As the one in the headstock revolves with the work, this centre is known as a live centre.

Soft center[edit]

Soft centers are a special version of the dead center in which the nose is deliberately left soft (unhardened) so that it may be readily machined to the correct angle prior to usage. This operation is performed on the headstock center to ensure that the center's axis is aligned with the spindle's axis.

Running or revolving center[edit]

A revolving center, also known as a rotating center or running center in some countries, is constructed so that the 60° center runs in its own bearings and is used at the non-driven or tailstock end of a machine.^[2] It allows higher turning speeds without the need for separate lubrication, and also greater clamping pressures. CNC lathes use this type of center almost exclusively and they may be used for general machining operations as well. Spring-loaded centers are designed to compensate for center variations, without damage to the work piece or center tip. This assures the operator of uniform constant tension while machining. Some live centers also have interchangeable shafts. This is valuable when situations require a design other than a 60° male tip. A live center, which may be hard or soft, is a plain center placed in the revolving mandrel; it moves and is therefore live.

Pipe center[edit]

A pipe center, also known as a bull nose center is a type of live center which has a large diameter conical nose rather than a sharp point. This allows the center to be used in the bore of a pipe or other workpiece with a large interior diameter. While a pipe center ensures the workpiece remains concentric, its main advantage is that it supports the workpiece securely, and can be used for parts whose larger inner diameter prevents the use of a normal pointed center. Thin-walled material such as pipes easily collapses if excessive force is used at the chuck end.

Cup center[edit]

There are two types of cup centers. The woodworking variety is a variation of the traditional live center. This type of cup center has a central point like a normal live center and also has a ring surrounding it. The ring supports the softer material around the center point and prevents the wood from splitting under pressure from the central point. A different variety of cup center is used for metalworking. The metalworking variety of cup center has a tapered hole rather than a conical point. It supports the part by making contact with the outside diameter of the end of the part, rather than using a center hole.

Drive center[edit]

A drive center, also known as a grip center, is used in the driving end of a machine (headstock). It is often used in woodworking or where softer materials are machined.

It consists of a dead center surrounded by hardened teeth, which bite into a softer workpiece allowing the workpiece to be driven directly by the center. This allows the full diameter of the workpiece to be machined in a single operation, in contrast with the usual requirement where a carrier is attached to the workpiece at the driven end. The use of modified shell end mills in a drive center, instead of hardened pins, enables better gripping and prevents breakdown time due to pin stop.^{[citation needed]}

Spring center[edit]

A spring center is a metalworking lathe center for maintaining a cutting tool like a reamer or a tap, in axial alignment with a hole being worked on. It consists of a point backed by a spring to push the cutting tool into the workpiece.

References[edit]

1. ^International library of technology: Drilling; Lathe work; Boring-mill work; Working chilled iron; Bench, vise, and floor work; Erecting, 138, International Textbook, 1914, p. 21.
2. ^Culley, Ron (1997) [1988]. Fitting and machining. PO Box 12477, Melbourne, Victoria: RMIT Publications. ISBN0-7241-3819-6.CS1 maint: location (link)

At Dan's Machine Tool, Inc., we specialize in the repair and reconditioning of all types of metalworking equipment. Customers trust us to provide the critical repairs to their mills, lathes, iron workers, benders, and other machinery that keep production running. When a piece of equipment is down or not functioning properly, an experienced technician can make a visit to the customer’s facility in order to make an initial diagnosis. Depending on the severity of the issue, a repair may be made on-site or the equipment can be transferred to our facility.

For full rebuilds, equipment is cleaned, disassembled, and all components are evaluated for wear. Any belts, bushings, fasteners, and other wear parts are replaced as needed and structural repairs are completed to the frame and body. Ways can be ground parallel and hand scraped to factory tolerances. The machine can then be reassembled and tested to customer requirements. We can also repair and rebuild older equipment that most shops no longer support, including Bridgeport mills. Through our extensive used equipment network, we maintain a significant inventory of hard to find replacement parts salvaged from older machinery. For more information about our equipment repair and rebuilding capability, see the table below, or contact us directly.

Photo Gallery of Before & After Repairs & Rebuilds

LeBlond Lathe Rebuild

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Mori Seiki Lathe Repair & Rebuild

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Bridgeport Milling Machine Repair & Rebuild

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Project Showcase of Metalworking Equipment Repair & Rebuilds

Machines & Brands We Repair

Milling Machines

Acra
Bridgeport
Cincinnati
Clark

Kent
Jet
Lagun
All import milling machines

Lathes

Acra
Clark
Cadillac
Hardinge

Kent
Mori Seiki
LeBlond
Webb
All imported lathes

Surface Grinders

Boyar Schultz
Harig
Kent

Mitsui
All imports

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Metalworking Equipment Repair & Rebuilding Capabilities

Dan’s Machine Tool, Inc. offers Preventative Maintenance and Diagnostic Inspection for CNC and Manual Machinery:

MILLING MACHINES, GRINDERS, LATHES, BANDSAWS, DRILL PRESSES, PUNCH PRESSES, SHEAR AND BRAKES, ETC.

Our Preventative Maintenance can be performed Economically to Prevent equipment Breakdowns before they occur and notify you of potential Safety Issues!

The Maintenance and Diagnostic Inspection consist of multiple key steps that help prevent premature wear to vital components on your machinery. Our Diagnostic Inspection lets you know if your machinery is operating to Factory Tolerances and its full potential.

Our Preventative Maintenance and Diagnostic Inspection consist of:

Testing Axes, Spindles, Chucks, Tailstock, Leadscrews, Ball Screws and Bed Ways for excessive run out and backlash.

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Ensure lubrication and hydraulic systems are dispensing properly. Draining and refilling lubrication and hydraulic reservoirs with new Grease, Way Lube and or Hydraulic Fluids. Also check the old lubrications for contaminants!

Run machinery to ensure all feeds, gears, motors and spindles etc. are operating freely and properly.

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Check all electrical components, machinery conduit, on off switches, emergency switches and electrical cabinets to ensure operators safety!

During maintenance our mechanics will adjust gibs, lubrication fittings, handles, loose conduit and electrical connections. Also removing debris, excess grease and lubrication from the body and operating areas of the machinery.

Providing a complete diagnostic report to your company detailing findings.

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OUR TERMS: NET ON COMPLETION