3) Lathe Classification by size

-Lathes are classifield to size by largest diameter ( in inches) that may revolved; this is commonly called the swing of a lathe. The second factor is the total length between the centers, with the tailstock at the end of the ways.

-Lathes vary in size from 6-in (152.4mm) diameter swing to well over a 100-in (2.54m) diameter swing




THE LATHES MOST COMMONLY USED IN INDUSTRY HAVE A
10 TO 30 INCH (254-762 mm) DIAMETER SWING



Size and specificaion of lathe
The size of a lathe is usually specified by:

1. height of the centres measured from the lathe bed.
2. The swing of a workpiece diameter over bed : this is the maximum diameter of work that can be rotated on a lathe.
3. The maximum distance between the centres: this is the maximum length of a workpiece that can be mounted between the lathe centers.
4. The length of the bed : this indicated the approximate floor space occupied by a lathe.

For example, If a lathe size indicated by 356mm * 762mm * 1800mm means maximum diameter of a workpiece is 356mm, 762mm, is the length between the lathe centres and 1800mm is the length of the lathe bed.




More information, refer
page 128
http://books.google.com.my/books?id=oDAvCF_tbXMC&pg=PA128&dq=lathe+classification+by+size&sig=ACfU3U03KVmm6A-P4yPjQbNTAvx79DxbFg#PPA123,M1