Therming is a technique used by woodturners to simultaneously create multiple copies of spindles and table legs. [1] Often described as off-center spindle turning, therming is also known as drum turning and barrel turning. [1] Therming allows a woodturner to make exact duplicates of three, four or however many spindles a therming rig can hold. Figure 1 shows multiple identical, partially completed spindles mounted on a therming rig. Note that all outer surfaces of the items being turned are curved. By rotating each spindle in the therming rig, all of the sides can be turned to individual contours to create unique shapes. For a four-sided turning, each side would be rotated 90 degrees after completing a side. Each spindle must be rotated the same amount in the rig to maintain similarity. Shapes with three, four and five sides are typical. Historically, the technique was used to produce table legs and balusters, usually with four sides. [1] Therming dates back to the 18th Century and is mentioned in a letter to Thomas Jefferson from Nathaniel Colley, dated 22 January 1791 on the delivery of tables from London with therm’d legs. [2]
Therming rigs can be made with a center shaft or just with end plates as shown in Figures 2 and 3. A therming rig includes individual turning blanks separated by gaps when mounted between end plates. These gaps result in a process called ‘turning air’, as shown in Figure 4, where the cutting action occurs intermittently as the turning blanks rotate past the cutting tool. Production therming rigs often hold 20 or more spindles at a time. An article on 'Angular Turning on the Lathe', published in the Summer of 1998 in 'American Woodturner' magazine, provides descriptions of the techniques used for turning multiple spindles. [3] [4]
Description of the Therming technique for making a therming rig and creating a three-legged stool
The router is a power tool with a flat base and a rotating blade extending past the base. The spindle may be driven by an electric motor or by a pneumatic motor. It routs an area in hard material, such as wood or plastic. Routers are used most often in woodworking, especially cabinetry. They may be handheld or affixed to router tables. Some woodworkers consider the router one of the most versatile power tools.
A lathe is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, and turning, with tools that are applied to the workpiece to create an object with symmetry about that axis.
Metalworking is the process of shaping and reshaping metals to create useful objects, parts, assemblies, and large scale structures. As a term it covers a wide and diverse range of processes, skills, and tools for producing objects on every scale: from huge ships, buildings, and bridges down to precise engine parts and delicate jewelry.
Woodturning is the craft of using the wood lathe with hand-held tools to cut a shape that is symmetrical around the axis of rotation. Like the potter's wheel, the wood lathe is a simple mechanism which can generate a variety of forms. The operator is known as a turner, and the skills needed to use the tools were traditionally known as turnery. In pre-industrial England, these skills were sufficiently difficult to be known as 'the misterie' of the turners guild. The skills to use the tools by hand, without a fixed point of contact with the wood, distinguish woodturning and the wood lathe from the machinists lathe, or metal-working lathe.
A chuck is a specialized type of clamp used to hold an object with radial symmetry, especially a cylinder. In drills and mills it holds the rotating tool whereas in lathes it holds the rotating workpiece. On a lathe the chuck is mounted on the spindle which rotates within the headstock. For some purposes an additional chuck may be mounted on the non-rotating tailstock.
Turning is a machining process in which a cutting tool, typically a non-rotary tool bit, describes a helix toolpath by moving more or less linearly while the workpiece rotates.
Spindle turning, or turning between centers, is a woodturning method referring to a piece of wood on a wood lathe that is being turned on its center axis.
Lathe 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.
A metal lathe or metalworking lathe is a large class of lathes designed for precisely machining relatively hard materials. They were originally designed to machine metals; however, with the advent of plastics and other materials, and with their inherent versatility, they are used in a wide range of applications, and a broad range of materials. In machining jargon, where the larger context is already understood, they are usually simply called lathes, or else referred to by more-specific subtype names. These rigid machine tools remove material from a rotating workpiece via the movements of various cutting tools, such as tool bits and drill bits.
An indexing head, also known as a dividing head or spiral head, is a specialized tool that allows a workpiece to be circularly indexed; that is, easily and precisely rotated to preset angles or circular divisions. Indexing heads are usually used on the tables of milling machines, but may be used on many other machine tools including drill presses, grinders, and boring machines. Common jobs for a dividing head include machining the flutes of a milling cutter, cutting the teeth of a gear, milling curved slots, or drilling a bolt hole circle around the circumference of a part.
In machining, boring is the process of enlarging a hole that has already been drilled by means of a single-point cutting tool, such as in boring a gun barrel or an engine cylinder. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. Boring can be viewed as the internal-diameter counterpart to turning, which cuts external diameters.
Segmented turning, also known as polychromatic turning, is a form of woodturning on a lathe where the initial workpiece is composed of multiple parts glued together. The process involves gluing several pieces of wood to create patterns and visual effects in turned projects.
In engineering, a dog is a tool or part of a tool that prevents movement or imparts movement by offering physical obstruction or engagement of some kind. It may hold another object in place by blocking it, clamping it, or otherwise obstructing its movement. Or it may couple various parts together so that they move in unison – the primary example of this being a flexible drive to mate two shafts in order to transmit torque. Some devices use dog clutches to lock together two spinning components. In a manual transmission, the dog clutches, or "dogs" lock the selected gear to the shaft it rotates on. Unless the dog is engaged, the gear will simply freewheel on the shaft.
A screw-cutting lathe is a machine capable of cutting very accurate screw threads via single-point screw-cutting, which is the process of guiding the linear motion of the tool bit in a precisely known ratio to the rotating motion of the workpiece. This is accomplished by gearing the leadscrew to the spindle with a certain gear ratio for each thread pitch. Every degree of spindle rotation is matched by a certain distance of linear tool travel, depending on the desired thread pitch.
Grinding is an abrasive machining process that uses a grinding wheel as the cutting tool.
Bar stock, also (colloquially) known as blank, slug or billet, is a common form of raw purified metal, used by industry to manufacture metal parts and products. Bar stock is available in a variety of extrusion shapes and lengths. The most common shapes are round, rectangular, square and hexagonal or hex. A bar is characterised by an "enclosed invariant convex cross-section", meaning that pipes, angle stock and objects with varying diameter are not considered bar stock.
Threading is the process of creating a screw thread. More screw threads are produced each year than any other machine element. There are many methods of generating threads, including subtractive methods ; deformative or transformative methods ; additive methods ; or combinations thereof.
Ornamental turning is a type of turning, a craft that involves cutting of a work mounted in a lathe. The work can be made of any material that is suitable for being cut in this way, such as wood, bone, ivory or metal. Plain turning is work executed on a lathe where a transverse section through any part of the work comprises a plain circle. Ornamental turning, also called Complex turning, is executed on a lathe with attachments which convert that plain circular section to variants of outline; these range from a simple series of cuts taken at intervals around the work to non-circular movements whereby the whole of the circular shape is removed to give a completely different form. Such shapes are achieved by various means, the principal ones being:
In metalworking and woodworking, an automatic lathe is a lathe with an automatically controlled cutting process. Automatic lathes were first developed in the 1870s and were mechanically controlled. From the advent of NC and CNC in the 1950s, the term automatic lathe has generally been used for only mechanically controlled lathes, although some manufacturers market Swiss-type CNC lathes as 'automatic'.
Milling is the process of machining using rotary cutters to remove material by advancing a cutter into a work piece. This may be done varying direction on one or several axes, cutter head speed, and pressure. Milling covers a wide variety of different operations and machines, on scales from small individual parts to large, heavy-duty gang milling operations. It is one of the most commonly used processes for machining custom parts to precise tolerances.