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Lathes

Hegner Lathes, built to the same high standards as the entirety of the Hegner range of machine tools.

HDB Lathe

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What makes the HDB a great lathe?



With so many seemingly similar machines and accessories on the market, even experienced turners may find it difficult to make an objective choice of equipment. We have listed here the main features that you will recognise as contributing to the quality and turning performance of any lathe and we explain how the Hegner design meets all of these important criteria. These are features that contribute directly to the lathe’s practical capabilities and your enjoyment in using it.

 

MAIN SHAFT BEARINGS: 

 

The HDB's double row angular contact bearings are easily adjusted to eliminate end float with this lock nut.Turning spindles that are mounted between centres places very little load on the main shaft bearings. The real test occurs when turning faceplate (or chuck) mounted work without support from the tailstock. Especially when the work extends out for some distance from the support of the front bearing (referred to as "overhang") will inadequacies be revealed. The common symptom of unwanted "float" in the shaft on these occasions is a noisy screech as the tool is applied to the work - and consequent difficulty in taking a clean cut.Single row ball bearings (with which the vast majority of lathes are fitted) necessarily have a limited amount of working "clearance", that is, free-play between the rolling elements and the inner and outer tracks. This translates into unwanted movement between the work and the tool. The HDB's bearing is a double row, angular contact ball bearing. Apart from its enormous load carrying capacity, it has the virtue of being adjustable to completely eliminate all trace of unwanted axial and radial float in the shaft assembly. It is pre-lubricated and sealed for life, so requires no maintenance. In practical terms, it means that the HDB enables you to undertake work that is far beyond the scope of similarly priced machines. Whether you are turning large or small pieces, the pleasure of being able to take the most delicate cuts and achieve the finest grain sheering finish without tool chatter must be experienced to be appreciated. 

Accurate alignment of the lathe’s headstock and tailstock centres is an important factor in lathe construction and affects two common areas of turning. Firstly, when the work is fixed in a chuck or on a faceplate at the headstock end and the tailcentre is brought up for additional support: or secondly, when drilling into the free end of the workpiece with a tailstock mounted drill. Misalignment of the centres in either case will create stresses that can only be relieved by the work loosening itself from its headstock fixing. (Strangely perhaps, accurate centre alignment is not relevant to good “between centre” performance, but it is nevertheless an indication of care in manufacturing.)

 

"The tailstock body incorporates two sprung ballbearing units...

The “kiss” test is a simple check of centre alignment carried out by bringing the head and tailstock together and observing that the centres meet. This is no guarantee however that the head and tailstock bores are in line with each other. The moment when a long hole boring auger emerges from the side of a lamp stem that you are drilling may be the first you know of the problem! Similarly, although a drill may be started into the work successfully because the tip is on the same axis line as the drive centre, drilling will become progressively more difficult and mechanically stressful if the bores are not parallel.

Without access to proper measuring equipment, a simple check is to carry out the “kiss” test with the tailstock in both the fully retracted and fully extended positions. If the tailstock bore is in line (the important bore in this case) there should be no appreciable deviation. Also check that operating the tailstock body and spindle clamps does not affect the accuracy of the setting through excessive clearance in the fit of the relative components.

 

... which take up the lateral working clearance between the slide faces and serve to locate the tailstock positively against rear-centre (datum) face of the bed."

Hegner’s design meets all of these requirements. The lathe bed is made from 4mm thick, rectangular box section steel, precision welded to form an immensely strong and rigid, one-piece structure. Its upper and inner bearing faces are then machine ground to provide a dimensionally perfect slide-way for the tailstock and cross slide assemblies. The tailstock body incorporates two sprung ballbearing units which take up the lateral working clearance between the slide faces and serve to locate the tailstock positively against rear-centre (datum) face of the bed. The practical effect is to ensure that the tailstock moves freely to any chosen position but never deviates from true, parallel alignment with the bed and mainshaft tuning axis. The tailstock spindle is also machine-ground to its finished dimension for a close tolerance fit in the tailstock body. Lateral pressure from the spindle clamp has no discernible effect on its centre alignment over the full 75mm travel. Bronze support bearings and a large diameter handwheel for the shaft make for a beautifully smooth operation. Drilling, long hole boring (through the hollow tailstock spindle) and support functions of the tailstock are as good as they can be. We also provide a twin bearing, industrial quality, live centre for the lathe. ( A poor quality centre can be the source of many problems such as spiral ribbing on planing cuts, vibration and so on.)

 

The HDB's Industrial quality centre converts easily from a standard revolving centre to a ring centre with the conversion ring supplied with the lathe.

CAPACITIES:

Large capacities may seldom be needed in everyday turning but there is no substitute for them when they are!  The HDB200XL will swing a full 16″ diameter by 40″ in length, between centres. Although, on the face of it, any lathe with a swivelling headstock can turn large diameters, tailstock support is very useful in the initial stages of shaping many pieces that will finally be held solely on a chuck or faceplate.  This is provided by the HDB in that its exceptional “swing over the bed” enables the tailstock to be used for supporting long overhangs from chuck or faceplate mounted work during initial rough shaping.  Additionally, when deciding how a large blank might be best mounted, it can first be loosely held between centres to establish its approximate centre of gravity or to determine what final mounting  position will preserve desirable features.

 

HDB Banjo at angle close up to central axis

The HDB200XL is ideal for producing fine work such as pens and thin spindles.  The toolrest holder is precision ground all along it’s underside allowing it to be secured in a wide range of positions, either at full extent to allow outboard turning to right up to the centre axis of the lathe.  For delicate work the HDB-TR6 150mm (6") Cranked Toolrest  can be positioned right up to the workpiece without hindering visibility or accessibility. 

Long thin spindles can be supported by the HDB-ST Work Steady for HDB, simply clamped onto our standard toolrests and easily adjusted for a wide range of spindle diameters.

 

The headstock swivels through 360° and is locked with a 'kip' type handle

With the headstock swivelled 90° , or locked at any other convenient working position through 360° , diameters of up to 30″ can be turned.  The HDB’s cast iron headstock body, large diameter spindle nose (33mm x 3.5mm pitch thread) and widely spaced, deep-groove bearings (the wide spacing importantly serving to direct load forces radially) all combine to provide trouble free turning performance.  You will enjoy your time at the lathe and be able to give your full attention to the work in hand without distraction from mechanical shortcomings.

SPEED  CONTROL:

It seems logical to expect the force exerted by a moving object to be directly proportional to its speed.  In other words, doubling the speed should double the force.  In fact, the energy developed in a moving object increases as the square of the speed.  Conversely, reducing the speed reduces the forces generated by a far greater factor than one would logically expect.

 

The clearly laid out face of the HDB200XL electronic control box.

To translate this into a “real-life” situation that can be easily understood, consider the forces at work in a roughly circular work piece of about 12″ in diameter.  Imagine that is is turning at about 450rpm – typically the lowest speed available on a stepped pulley arrangement without variable speed control.  Ignoring the balanced portion of the work and simply calculating the effects of say a 2kg imbalance, at this speed the kinetic energy developed is about 56 joules.  Reducing the speed to 90rpm has the amazing effect of reducing the kinetic energy to just 2 ¼ joules!  The effects of imbalance are reduced by about 96%!  The value of being able to control speeds down to a very low setting is therefore evident.  Large and potentially out-of-balance work can be set to run at a low speed where the otherwise powerful (and sometimes dramatic) effects of imbalance are minimised or eliminated.   Turning is altogether a more relaxing and pleasant pastime under these circumstances.

The electronic speed control fitted to the HDB lathe gives a range of speeds from 90 to 3800rpm. Of course it is important that a reduction of turning speed is not accompanied by a lessening of the turning force (or torque).  Below a certain level, the electronic circuitry can only partly compensate for a loss of turning force as a result of reduction in motor speed.  Mechanical gearing through a three step pulley and belt system between the motor and the main shaft enables the HDB’s motor to keep at a “comfortable” speed to give high torque even at the lowest drive speeds.  All turning, from heavy faceplate to the very smallest spindle work are properly catered for.  You simply select the appropriate “high”,”middle” or “low” speed range and turn the control dial to whatever setting you want.  As mass and imbalance are removed during the turning process, the speed can  be safely increased just by turning the dial.

 

The "high" and "low" speed belt change

Some turning speeds and loads will be found to have sympathetic or harmonic resonance with the “natural frequency” of the lathe.  The effect can be that a comparatively small amount of imbalance in the work amplifies itself with each revolution and produces a disproportionate amount of vibration.  Here again, electronic speed control comes into its own as it is a simple matter to change the speed setting by the few rpm that is usually all that is required to get out of the resonant band.

 

Releasing the belt tension to change the speed range

Uniformly smooth acceleration and braking ramps eliminate the starting “snatch” of purely mechanical systems so that even the most delicate work (ultra-thin stemmed goblets for example) are unaffected by starting or stopping surges.  Another nice feature of the HDB’s electronic control is that the circuitry senses the varying braking force of the turning tool you are using.  It then automatically and instantaneously compensates to keep the work rotating at the preselected revolutions within the power available.

 

Functions on the control panel include switches for START/STOP; FORWARD /REVERSE and rotary dial for VARIABLE SPEED. Plus a substantial NO-VOLT MAINS SWITCH

Thermal overload protection and No-Volt Release are standard features.  (N.V.R. Automatically trips out the internal power connection in the event of an interruption of the power supply.  The lathe cannot the restart without a deliberate switching action from yourself.)  Functions on the control panel include switches for START/STOP; FORWARD/REVERSE and rotary dial for VARIABLE SPEED.

Yet another major benefit of the Hegner electronic system is that it is fitted with “filter” circuits to contain electrical noise from the powerful induction motor and prevent it feeding back into your electrical supply.

RUNNING ADJUSTMENTS:

 

 

Easy to use cam clamps, that require little pressure to operate, are used to lock both the cross-slide and the tailstock

Frequent adjustments in the position of the toolrest and cross-slide assembly are necessary during the course of most turning projects.  Here again, you will find that the Hegner clamps are a delight to use.  The cross-slide is secured by means of a high leverage, progressive cam that requires no more than fingertip pressure to lock the assembly immovably.  Also, once the clamp is released, the cross-slide assembly can be slid freely to any required position using just one hand.  The design eliminates the tendency for any part to bind on the bed as its position is adjusted.  Similarly, a precisely machined cam and piston-type cam follower sliding in a close tolerance cylinder (not just an eccentric bar with metal strap) is fitted in the tailstock body giving the same advantages – silky smooth slide and immovable clamping with minimal pressure.

 

Pulling down the handle you can reposition it out of the way

Headstock swivel for large diameter turning is effected by an adjustable (sprung spline type) handle under the headstock.  The headstock can be simply locked at any position through a full 360° facilitating unobstructed tool access to any part of the work piece whilst a comfortable working stance is maintained.

“Indexing” is the term used to refer to the feature that enables the lathes main shaft to be rotated and locked in equally spaced divisions. For example, it is useful to be able to lock the stem of a mug-tree in increments of 90° for drilling the four, radial holes required for its branches.  Spiral twists, flutes, reeds, decorative plugs of contrasting wood and so on, all need to be indexed in a similar way.  The HDB’s indexing facility enables the shaft to be locked in any of 24 rotational positions so that the work can be divided into 24, 12, 8, 6, 4, 3  or 2 segments.

 

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