Lathe dog

Lathe[1] Dog is also widely known as Lathe Carrier. It is a device made up of Iron Cast that is used to provide a firm connection between the workpiece and headstock spindle mounted between the centre. It clamps around the workpiece and allows the machine spindle rotary motion to be transmitted to the workpiece. Carrier is mostly used while turning between centres on a lathe, however, it may also be used on dividing heads or any similar conditions. Lathe Dog is used in conjunction with a Face Plate and drive plates. The plate is mounted directly onto the machine spindle and drive pin is attached to the plate. Carrier and workpiece are inserted between the centre and the legs of the carrier resting against drive pin.  

Straight leg carriers. The setup shows the drive plate, workpiece and carrier setup between centers on lathe
Bent tail lathe dog hooked on chuck jaw.

Lathe dog is used when you are using centres in the head stock and tail stock. A faceplate is put in the headstock as well. A lathe dog is a tool that is bent to 90 degrees with its one end consists of a loop and a setscrew. The end with the setscrew and loop slid over the work and tightened while the other end captures a slot in the faceplate which drives the carrier and workpiece.

The objective of Lathe Dog Invention:

The primary objective behind the invention of the lathe dog is to provide stable balanced safety to push an operator's hand or arm out the possible path of the danger using a sliding contact produced by a rotary camming operation of the lathe dog mounted on a workpiece.

The principal objective of the carrier obtained by the provision of a safety as lathe dog have an off-centre opening for receiving a workpiece. Lathe Dog is usually in the form of a disc which have smooth outer surface. It has screw set installed through the surface to secure the workpiece.

Another objective of the invention of carrier is to provide safety. Lathe dog is in the form of a smooth surface plate have an eccentrically opening for the mounting of a workpiece. Which has detachable insert members fitted in the opening. These are secured by set screws and central opening of different size to receive the workpiece and make the carrier to be used with workpieces of different sizes and shapes.

Function of Lathe Dog:

Lathe Carrier is a clamp that fixes workpiece and its some of the most common functions are:

  • It is used to hold the workpiece securely for even and smooth turning while providing the full support and grip.
  • It is made of robust and rigid high grade cast iron material for maximum strength.
  • Lathe Carrier is provided with the square head screw.
  • It is used in conjunction with plates, these act as a driving device while turning between centres.
  • A ‘V’ groove in the body assist in the clamping of round jobs.
  • It is supplied in different shapes or types.

In 1895, Armstrong invented the Lathe Tool Holders that replaced the large hand-forged cutters with holders. It enables the machinist no longer needed to be a blacksmith to operate as machinist has to be able to forge his cutter bits earlier. Armstrong supplied the drive dogs so the machinist no longer needed blacksmith work.

Types of Lathe Dog:

Mounted between the centre Lathe Dogs or Carrier provides a firm connection that permits the workpiece to be set at the same speed as spindle under the strain cutting. Turning between centres is considered old fashioned while it is the most basic and precise method of turning parts in a lathe machine. It allows us to take the work in and out of lathe without using precision as parts can be reversed to machine different ends. There are various types of Lathe Dog[2] and the most important or widely used which is worth mentioning are:

  • Straight Tail & Bent-Tail Lathe Dog
  • Safety Clamp Lathe Dog
  • Heavy Duty Lathe Dog

Straight Tail & Bent Tail Lathe Dog:

Straight Tail & Bent Tail Lathe dog requires U-Clip bolted to the faceplate. Clamps fit in a wide range of sizes and often the only turning carrier in some of the kits. Some Tail Lathe dog comes with a single clamping screw while double screws most commonly are on large size dogs.

Tail Lathe Dog is most commonly used for round workpieces and available with the square head set screws or headless sets screws. Bent Tail dogs are designed around a window that results in series. The window is the length of the tail from the centre and the length of the bent tail. Overall proportion size is necessary to prevent excessive vibration and it must be strong enough for expected torque

Tail Lathe Dog is used in precision turning and driven by stud in the drive plate. It is used in conjunction with driving plates, these act as driving devices while turning material between centres.

Safety Clamp Type Lathe Dog:

Safety Clamp is designed with safety top and bottom clamping plates. These safety grips plates provide a positive grip during turning of the workpiece.

Clamp Type Lathe Dog:

Clamp type lathe dog is designed with a clamping plate and adjustable screws. These clamping plates and screws hold a wide range of diameters of work as it is provided with a ‘V’ groove and adjustable nuts and bolts. Clamp type lathe carrier may be used to hold square and rectangular sectioned rods as well. They are also very useful to hold small diameter jobs because of the provision of the ‘V’ groove.

Safety & Precautions:

All the lathe operators, beginners or even professional must be constantly aware of the safety hazard associated with the using of Lathe Machine and Lathe Dogs specifically

Ignorance and Carelessness are two great risks to personal safety, Other hazard can be related to mechanical working with the lathe dogs. Proper uniform or correct dress is important. Removal of rings and watches, roll sleeves above elbows is also mandatory for safety.

  • Never lean on the lathe Machine.
  • Never place your tools on the lathe Machine work area. Use a wide board with a cleat on each side to lay on the ways or a separate table.
  • Do not attempt to measure the workpiece when the machine is working, and it is turning.
  • Never file lathe workpiece except if it has a handle.
  • Always stop the lathe machine before making any adjustments.
  • Always wear eye protectives to protect your eyes.
  • Protect the lathe ways with a block of wood while installing a chuck.
  • Always make sure where is the emergency stop so you may know it before operating the lathe machine.
  • Always use a brush or similar tools to remove chips; never use your hands.
  • Protect the lathe ways when grinding or filing and handle sharp cutters and drills with special care.
  • Always Change the spindle machine when the lathe stops completely.

Ignorance and Carelessness are two great risks to personal safety; other hazards can be related to mechanical working with lathe dogs. Proper uniform or correct dress is important. Removal of rings and watches, roll sleeves above elbows is also mandatory for safety.

Lathe Dog or Carrier is one of the important parts of the Lathe Machine which not only helpful in handling the machine safely but it also provides accuracy and perfection.



See also

References
  1. "Devices Used in Lathe Operation | Machine Tools | Industrial Engineering". Engineering Notes India. 2017-07-24. Retrieved 2020-12-06.
  2. "Lathe carriers – My Tutorial World". Retrieved 2020-12-06.
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