TG&P stands for Turned, Ground & Polished. It describes a processing sequence used to produce round bar with a controlled outside diameter and finished surface.
The term describes how the bar is processed. It does not identify the steel grade, heat treatment condition, or a universal tolerance.
What Happens During Turning?
Turning removes material from the bar’s outer surface using a cutting tool. It can remove the original surface layer and reduce the diameter while leaving stock for subsequent grinding.
The amount removed depends on the incoming bar and the required finished dimensions.
What Happens During Grinding?
Grinding uses an abrasive wheel to remove material and control the outside diameter. For suitable round bars, centerless grinding supports the workpiece between a grinding wheel and a regulating wheel, with a work-rest blade beneath it.
The grinding operation is planned around the specified diameter, tolerance, roundness, and surface finish.
What Happens During Polishing?
Polishing refines the surface after grinding. It may also remove a small amount of material, which must be accounted for when controlling final size.
A polished surface does not automatically mean a mirror finish. The required roughness should be specified with its measurement parameter and units.
Does TG&P Guarantee Straightness?
No single straightness limit is defined by the TG&P name alone. Straightening may be included in bar preparation, but the required straightness and inspection method must be specified separately.
Diameter tolerance, roundness, straightness, and surface roughness describe different characteristics. Meeting one does not establish that the others have been met.
Is TG&P the Same as Centerless Ground Bar?
The terms describe different aspects of processing. TG&P identifies turning, grinding, and polishing as a sequence. Centerless grinding identifies a grinding method that can be used within that sequence.
A centerless ground bar may start from turned stock or another suitable starting condition. The terms are therefore not mutually exclusive.
How Does TG&P Differ from Cold Drawn Bar?
Cold drawing pulls material through a die to change its cross-section. Turning and grinding remove material from the outside surface.
Cold drawn stock can also undergo grinding and polishing. Compare the specified material condition, dimensions, and finish rather than assuming one label always provides better performance.
When Is TG&P Bar Useful?
TG&P bar can be useful for shafts, pins, rollers, and machining stock where outside diameter and surface finish matter. It may reduce later processing when the supplied bar already meets the relevant drawing requirements.
For bearing or linear-motion applications, hardness, surface condition, and dimensional requirements still need to be checked against the equipment specification.
Where Can You Request TG&P Bar?
For material availability, finished-bar requirements, and ordering information, visit our TG&P Bar & Precision Shafting Supply page.
If you already own material that needs diameter finishing, see our centerless grinding services.