Centers Technical Information
Centers are used to accurately position a workpiece about its point or axis between a lathe chuck or head stock spindle and tail stock spindle. Enables the workpiece torotate or revolve and helps to ensure concentric work
Types of Centers
Live (Revolving) Centers: Revolve with their workpiece. They hold ball bearings inside that allow the center to prevent wearing to its ends. Live centers allow more force,higher turning speeds (without separate lubrication) and tighter gripping on work than plain centers, further reducing sideways movement during turning operations.
Live Centers are available with Standard Points or Extended Points:
Standard Point Live Centers: Offer increased rigidity over extended points, although tool clearance may not be as strong.
Extended Point Live Centers: Are recommended for operations whereby exceptional tool clearance is your top priority.
Bull Nose and Spring Loaded Live Centers:
Bull Nose Live Centers: Feature a shallower end than do plain centers, enabling the center to hold tubing, pipe or hollow shafts.
Spring Loaded Live Centers: Expands lengthwise to compensate for thermal distortion during the cutting operation.
Live Center Applications
CNC Heavy Duty: CNC lathes
Super Accurate: Grinding
Spring Type: Light/medium-duty work
Heavy Duty/ Extra Heavy Duty: Large parts
Triple Bearing: Medium-duty work
Double Bearing: Light-duty work
Quad-Bearing: Heavy loads
Bull Nose: Parts with large center holes
Dead (Plain) Centers
Dead (Plain) Centers: Do not rotate and provide workpiece support at either the fixed or rotating end of a machine. Within the fixed position, dead centers create frictionbetween the workpiece and the center, requiring lubrication to prevent friction welding.
Dead Centers can be Half Centers or Full Centers:
Half Dead Centers: Are used specifically for facing, as they allow a cutting tool to face the end of the work without bumping into the center. They are best used foradditional wheel clearance when grinding small parts with diameters smaller than that of the dead center. Half dead centers come either with a full carbon steelconstruction or with carbide tips.
Full Dead Centers: Are ideal for grinding and sometimes in turning applications requiring a high degree of precision
Center Tapers: A taper that provides a connection between a tool, arbor, or center and its mating part to ensure and maintain accurate alignment between the parts;permits easy separation of parts.
There are three primary center taper families:
Morse Tapers: Are self-holding standard tapers largely used on small cutting tools such as end mills, drills and reamers and, sometimes, machine spindles. MorseTapers come in eight standard sizes identified by a number between 0 and 7. The taper itself is roughly 5/8�? per foot.
Jarno Tapers: Are standard tapers with 0.600-inch taper per foot used on some machine tools Jarno Tapers range from 2 to 20. The diameter of the big end ininches is always the taper size divided by 8, the small end is always the taper size divided by 10 and the length is the taper size divided by 2. A Jarno #7, forexample, measures 0.875�? (7/8) across the big end. The small end measures 0.700�? (7/10) and the length is 3.5�? (7/2).
Brown & Sharpe (B&S) Tapers: Brown & Sharpe tapers are alternatives to the more-commonly seen Morse tapers. Like the Morse, these have a series of sizes, from1 to 18, with 7, 9 and 11 being the most common. Actual taper on these is within a close range of .500�? per foot.
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