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SPINNING TOOLS ( DEVICE )

( OLD )

The bowls, stems and feet of cups,and hollow vessels of almost any profile may be produced from discs of sheet metal by burnishing them to shape on a lathe. This process is known as spinning. It is applicable to shapes which are circular in plan: though the form of the work produced may, of course, be afterwards altered by the use of snarling irons, or by shaping and planishing it on a suitable stake. Thus, the general form could have been produced on the spinning lathe, the flutes or lobes being afterwards snarled and hammered out. But, primarily, spinning is employed for shapes which are circular in plan, whatever their profile may be. The process is in very general use among manufacturing silversmiths, to whom the ease with which a number of exactly similar copies of a shape may be produced is of importance. It has, however, little interest for the artist, for to him variety and a less mechanical form than that so generally adopted commercially will naturally appeal.

(Maryon H.,Metalwork and enamelling: a practical treatise on gold and silversmiths' work and their allied crafts, page 104)

( NEW / BETTER )

Spinning is a process which a metal disc a spun at controlled speeds on a machine similar to a machine latte. The disc  is held between a mandrel, secured to a chuck and a follower attached to the tailstock. The mandrel corresponds the inside contour of the part to be produced. Power is used to revolve the mandrel, disc and tailstock follower.

Spinning tools can be made by brazing steel balls to suitable shanks. On one such tool the ball should be ground flat on one side,  as shown. Tools can also can shaped by filing steel rods to a more or less blunt point in the lathe. The ends must be hardned, polished with emergy cloth and burnished to mirror brightness on a buffing wheel with pumice stone or other fine abrasive.

( James A. Brown, Modern manufacturing processes, p.111 )

( Popular Science, September 1941, p. 181 )

DOUBLE ACTION DRAWING ( PROCESS )

( OLD )

The blankholding requirements for large panels, which comprimise the majority of exterior body panels, necessitates the use of double-action drawing to achieve proper control of metal movement. Many smaller, irregular shaped parts that present difficult problems in metal control are drawn by this method. In double-action drawing, punch is mounted on the inner slide of the press and the blankholder is mounted on anouter slide. The part is usually drawn open side up.

(Lascoe O.D., Handbook of Fabrication Processes, pg.193, Kayra Ermutlu)

( NEW / BETTER )

In doble action drawing operations the press has two slides acting from above: the drawing slide with the draw punch and the blank holder slide with the blank holder. The blankholder slides transfers the blankholding force via the blankholder onto the blank and the draw die. The die and the ejector are located in the lower die on the press bed.

During forming, the blank holder brings the sheet metal into contact against the die, the punch descends from above into the die and shapes the part while the sheet metal can flow without any wrinkling out of the blankholding area. In this case, the drawing process is carried out with a fixed blank holder and moving punch. In double action drawing operations, the drawing slide can only apply a pressing force.

( Schuler GmbH, Metal forming handbook, p. 159 )

MACHINE GAS CUTTING (  METHOD )

( OLD )
Avariety of gas cutting machines has been developped, also. These hold and guide the cutting torch mechanically and advance it over the work at absolutely uniform speed. In this way, cuts of much higher quality and accuracy are obtained at reduced cost.
(Oxyacetylene Welding and Oxygen Cutting İnstruction Course, p.56)

( NEW / BETTER )

 These machines cuts the parts by gas. For one thing , the oxi-acetlyne cutting torch, commonly called the gas cutting torch, is basically a high temperature flame that is augmented by high pressure stream of oxygen which “oxidizes” steel. Since aluminum, brass, copper,  and stainless steel will not oxidize or rust, these metals could not be cut with a gas cutting torch. This process make the cutting much more speedy and also qualified.

( Richard Finch,  Performance Welding Handbook, p.134 )

RESISTANCE WELDING  (PROCESS)

( OLD )

Resistance welding (RW) is a group of fusion-welding processes thai uses a combination of heat and pressure to accomplish coalescence, the heat being generated by electrical resistance to current flow at the junction to be welded. The principal components in resistance welding are shown in Figure 31.12 for a resistance spot-weiding operation, the most widely used process in the group. The components include workparts to be welded (usually sheet metal parts), two opposing electrodes, a means of applying pressure to squeeze the parts between the electrodes, and an AC power supply from which a controlled current can be applied. The operation results in a fused zone between the two parts, called a weld nugget in spot welding.By comparison to arc welding, resistance welding uses no shielding gases, flux, or filler metal; and the electrodes that conduct electrical power to the process are noncon-sumable. RW is classified as fusion welding because the applied heat almost always causes melting of the faying surfaces. However, there are exceptions. Some welding operations based on resistance heating use temperatures below the melting points of the base metals, so fusion does not occur.

(Mikell P.Groover, Fundamentals of Modern Manufacturing , materials,processes, and systems third edition page 716)

( NEW / BETTER )

 Resistance welding is the fast, modern, scientific counterpart of man’s oldest method of joining metals, hammering red hot pieces together at a forge. Resistance to electricity at the surface to be joined supplies the heat and gives this form of welding its name.

Manuel or mechanical pressure takes the place of hammering. The process was improved greatly during the war and is now speeding production and cutting costs in many civilian industries.

Resistance welding requires no extra metal, and the joining takes place when the metal is plastic but not molten, at lower temperatures than in arc welding. Resistance welding is ideal for joining chromium- nickel stainless steels, for heat is applied only briefly and its adverse effects on metal minimized. Electronic tubes do most of the timing. Once controls have been adjusted for the work being hadled, most resistance welding machines could be run by girls in boby socks.

 ( Popular Science Mar 1946, p. 108 )

SPOT WELDING ( Method )

( OLD )

Spot welding is the best-known resistance welding method. It is used for joining thin sheet materials (up to 3 + 3 mm) by overlap joints, and is widely used, e.g. in the automotive industry. An ordinary private car can have up to 5 000 spot-welded joints. The high current, in combination with a rapid heating time, means that the thermal energy input is efficiently used: very little is conducted away to the surrounding metal. Spot welding therefore has several advantages over other methods of welding sheet metal, such as:

- Little deformation of the workpiece, as the thermal energy is more or less restricted to the immediate vicinity of the weld.

- Very high rate of production for mechanised processes.

- Easy to automate, with high consistency, which is therefore suitable for mass production.

- Low energy requirement and little pollution.

- Fast: resistance welding of 1 + 1 mm sheet, for example, takes 0.20 s.

- No filler materials required.

- Little special training required.

- Less environmental impact than when welding with an arc.

Two electrodes clamp the two sheets of metal together with a considerable force, while passing a high current through the metal. Thermal energy is produced as the current passes the electrical contact resistance between the two sheets.

(Weman K., Welding processes handbook, p. 80)

( NEW / BETTER )

 Spot welding is the most common of the various resistance welding processes.In this process,  the weld is produced by the heat obtained at the interface between the work pieces. This heat is due to the resistance to the flow electric current though the workpieces which are held together by pressure from the electrode.  The size and shape of the formed weldsare controlled somewhat by the size and contour of the electrodes.

The welding time is controlled by a timer built into the machine. The timer controls four different steps :

-       -  Squeeze time, or the time between the first application of electrode force and the first application of welding current.

-      -   Weld time or the actual time the current flows

-      -   Hold time or the period during which the electrode force is applied and the welding current is shut off.

-       -  Off period or the time during which the electrodes are not contacting the workpieces

( Larry F. Jeffus, Welding: principles and applications, P. 694 )