Conceived by Harold Clisby in Australia during 1970, and first manufactured in that country by Ron Sher, by 1972 the rights had been passed to the American Sheerline Company (interesting details about the design and development of the lathe and commercial underpinning firm can be found here: http://sherline.com/about/sherline-history An early example of what was called at first the Sherline 3-inch Precision Lathe can be found towards the bottom of the page.
Under the control of the clever and hard-working Joe Martin, the lathe was further developed together with a range of small precision milling machines and numerous accessories. Today the lathe and associated products are widely exported and have a sound reputation for effective design and efficient working. Although a number of different models have been introduced, the basis of this well-engineered little lathe has remained essentially unchanged since its introduction with the result that the latest accessories can be used on  the earliest machine - and spare parts easily and reliably obtained. Some versions of the lathe and miller have also been rebranded for sale in Europe using the "Unimat" name.
For a long time, the Sherline product line was static, due to its founder's prolonged illness.  Joe Martin died a couple of years ago and, with his typically generous spirit,  willed the company to its employees - who, with great enterprise, are engaged in the production of additional, interesting accessories and working to improve the versatility of their lathes. They have introduced a double riser block, an extra thick cross slide and a new headstock that takes standard 3C collets, an automatic WW-type collet closer for light production work, a newly designed chuck, and additional CNC support.

Sherline Products
2350 Oak Ridge Way, Vista, VC 92083 USA
International Phone: 001-760-727-5857   Fax: 001-760-727-7857
Toll Free (orders only) 1-800-541-0735
http://www.sherline.com

Formed as an aluminium casting, the base of the Sherline lathe carries a steel bed machined with dovetail ways along its edges. The "leadscrew" runs down the centre of the bed, protected from swarf and engaging with the carriage via a "full nut"; this simple and reliable arrangement means, unfortunately, a lot of hand twirling by the operator to reposition the cutting tools on longer jobs, there being no quick-feed rack as on most larger lathes. The saddle is adjusted to the bed, and the cross slide to the saddle, by long tapered gib blocks - a more expensive but superior method to the usual row of small adjusting screws and loose, thin, flexible gib strips.
Non-backgeared, the box-form headstock casting carries a20 mm sealed-for-life bearings and is bolted to the bed but can be rotated on it, to a limited degree, to allow taper turning.
With a 0.4.5" (10 mm) bore, the  No. 1 Morse taper spindle with its 3/4" x 16 t.p.i thread is driven by a 100/240v 50/60 Hz motor (which adjusts automatically to voltage and Hz) through an electronic controller giving infinitely variable speeds from 70 to 2800 rpm. The drive from motor to headstock is via two-step pulleys, giving high and low speed ranges and effectively increasing the torque at lower rpm. - a very useful feature when trying to turn larger diameters in more resilient materials..

Offered in several forms, the basic Sherline lathe, the Model 4000 (or 4100 with metric graduations), is supplied as standard with a motor and speed controller, faceplate, drive dog for between-centres work, two centres (No. 0 Morse for the tailstock) a single cutting tool for the tool post and a simple cross slide - although a swivelling top slide (compound) is now available as an accessory. A ring-scroll three jaw chuck would be first on anyone's options list and, at around £80, this unit has found favour with owners of older miniature machine tools, where the  non-availability of reasonably-priced self-centring chucks has been a problem for many years.
A pleasing feature of the lathe is the provision of crisply engraved micrometer dials, with inch or metric graduations and with the option of an adjustable "zeroing type" which can be locked and unlocked by a screw on the face of the handwheel. These dials are not of the quick-setting friction-held type (which can, in practice, unless well engineered, be difficult to set up properly) but positive-locking ones which require a deliberate action on the part of the operator to use correctly. If fitted with these dials from new the Models become the 4500 (inch) and 4530 (metric).
A long-bed version of the lathe admitting 17" between centres is also produced, and fitted as standard with some of the more desirable extras - zeroing micrometer dials on the feedscrew and cross slide and a rocker type ("American" to British readers) adjustable-height toolpost in place of the standard unit.
One useful extra not included in the long-bed specification is the power feed attachment - a simple, constant-speed motor which drives the carriage under power from right to left at a steady 0.9" per minute. The unit is positioned to the left hand-side of the lathe and can be switched on and off electrically - or disengaged at any point in its travel by a mechanism included with the drive.
The newest Sherline lathes and millers incorporate two modifications:
       - the tailstock on the lathe is now locked to the bed by a screw, tightening vertically against an adjustable brass gib; this eliminates the tendency, caused by the split-base assembly used previously, for the tailstock spindle to be pulled out of alignment. The whole assembly is adjustable for wear - and the tailstock can also be removed for the fitting of a raiser block without having to remove the handwheel first.
       - the miller now features a simple rotating-locking lever that secures the Z-axis in a positive fashion without the need to find a wrench - it replaces a friction lock that previously tightened against the dovetail.
There are numerous third-party suppliers of CNC kits for Sherline lathes and millers, and the factory have recently introduced "CNC-ready" stepper-motor mounts to simplify installation of these fascinating toys.
Other computer controlled accessories are also in production - a self-contained CNC rotary indexer (P/N 8700) which can be used on millers of all sizes - with a linear version available to convert any of the lathe or miller feeds to a power drive..

One of the more unusual accessories for the Sherline in the Screwcutting Attachment. The lowest speed on the lathe being too fast for generating threads, this simple but effective substitute has been designed to overcome the problem. In order to use it the motor is removed and replaced by a large handwheel and, whilst it would be difficult to manufacture a thread of any length in hard steel, for occasional use on brass or aluminium it appears to be a very satisfactory arrangement.
With the changewheels supplied 31 unified threads from 10 to 80 t.p.i and 28 metric threads from .25 to 2.0 mm can be generated in both left and right-hand forms.
With fifteen changewheels included, the kit includes a mounting bracket, a dog-clutch arrangement to engage and disengage the drive (the operating handle for which can be seen on the front face of the unit, immediately below the headstock badge) and a handwheel. Fitted with this device both the inch and metric lathes can cut threads of the opposite persuasion. Being able to drive the spindle by hand has certain advantages in other machining operations as well - and the use of the handwheel is not, therefore, confined to just screwcutting use. The idea of a hand-powered spindle is not, of course, new and another lathe fitted with a similar mechanism was the little known Jason  - which was made in Norwich, England until the early 1970s.