Spur drivers
Spur drivers
EXPERT KNOWLEDGE SPUR DRIVERS
What is the difference between Spur drivers and centre punch?
When turning long timber, the workpiece is clamped "between the tips" of the Spur drivers and centre punch (Live centres / moving centre punch tip). The Spur drivers transmits the rotation of the spindle, which is driven by the motor, to the workpiece. The centre point holds the workpiece in the horizontal axis and must rotate or move with it, it must not hinder the rotary movement.
Today, the so-called Four-tooth spur drivers are the standard for long wood turning. As the name suggests, its four prongs press into the face of the workpiece and reliably transfer the rotation. Four-tooth spur drivers usually have a point in the centre that facilitates precise positioning in the centre. This tip can also be removed on many models, e.g. to enable the workpiece to be drilled through.
With the so-called multi-point face drivers, a ring with many smaller points transfers the torque to the workpiece. They are somewhat safer and more versatile than 2-prong or 4-prong Spur drivers and offer greater precision. The large number of teeth also makes it easier to reposition the workpiece at a later date.
What is a Morse taper?
A Morse taper is a Type of connection between two components. The outer taper of one component fits precisely into the inner taper of the other component. The mating surfaces are manufactured very precisely and adhere to each other due to this precise fit (static friction). The name comes from its inventor, Stephen Morse. This connection is preferably used for clamping drills, but also for milling machines and lathes. On lathes, both the Spur drivers are connected to the spindle and the centre punch to the quill by a Morse taper. Morse tapers in the sizes MK2 and MK3 are common. When selecting accessories, make sure you choose the right size!
What is the purpose of a safety catch on lathes?
The Thread on the spindle side (M33 x 3.5 DIN 800) of a Lathes is designed so that the screwed-on clamping accessories tighten during turning. If the direction of rotation is changed (e.g. in order to use the external turning device) or a heavy workpiece is braked too quickly, the clamping accessory may come loose unintentionally. The run-out protection or a run-out protection ring (ASR) prevents the Chucks, Faceplates etc. from coming loose when the Lathes is running backwards or when a larger turned part is braked. Both the spindle of the lathes and the chucks must have a corresponding safety groove in accordance with the Euro standard (ASR).
Selection of driver sizes
The diameter of the Spur drivers (e.g. 13 mm, 22 mm or 32 mm) must be adapted to the workpiece diameter, e.g. the diameter of a staircase spindle. The more clamping surface is available, the larger the diameter should be selected. Smaller diameters are often offered with MK2 tapers as standard. If you want to use smaller accessories on a large lathe with MK3, there are suitable adapters (Morse taper reducing sleeves).
Why are there Spur drivers with and without forcing nuts?
To change the Spur drivers, the Morse taper fit can be loosened again. To do this, the Morse taper must be pressed out of the fit of the spindle bore. Most lathes have a so-called Hollow spindle (standard today) for this purpose, in which the fitting connection can be released or ejected by inserting a rod on the outside of the lathe. Disadvantage: if space is limited, the lathes often stands against the wall and it is not possible to insert a bar. In addition, not every lathes has a hollow spindle. If the Spur drivers are equipped with a forcing nut, the fit can be loosened by turning with a spanner. Disadvantage: Versions with a forcing nut are rare and more expensive, as the manufacturing effort is higher.
Do I always have to switch between Chucks and Spur drivers?
That depends on your chucks. There are also Spur drivers that you can insert into the centre of a Chucks so that you do not have to dismantle the chuck. Bear in mind, however, that chucks with a larger diameter can be a hindrance when turning long timber and increase the risk of injury.
What do I use a support ring on the centre punch for?
The support ring (e.g. from Hager) is attached to the centre point. The support ring has a cutting edge that grips into the wood and creates a wider contact surface. This means that the tip only penetrates the wood until the support ring makes contact or cuts into it slightly. The wood cannot split any further in the longitudinal direction. The support ring is used when turning longer and more delicate woods.
What is a Live centres system?
The Live centres system from Oneway is basically a Live centres with support ring or a Spur drivers set for different clamping situations. The support ring is permanently installed here. A cone or a larger tip can also be screwed onto the centre punch. The cone can be mounted as an inner or outer cone and enables the clamping of balls, for example, and minimises damage to the surface. The large cone tip makes it easier to clamp parts that have already been drilled (e.g. small cans, vases and lamp bases).
