Metal Spinning 6

Metal Spinning 6

and also gives the principal dimensions of a roller bearing for a

1¾-inch spindle. _A_ is a hardened steel bushing, which is driven into

the machine steel spindle. The parts _B_ are the hardened steel rollers

which travel in opposite directions. These rollers have a small amount

of friction, and this is distributed over a large area. A spindle

revolving at 2,300 revolutions per minute will not cause these rollers

to rotate very rapidly, while a ball bearing with balls traveling in a

channel 1½ inch or 2 inches in diameter would be traveling at the same

speed as the driving spindle. They also wear out rapidly as the end

strain is very great, it being necessary to force the center against

the metal with considerable pressure to keep it from slipping. _C_

is the hardened pin upon which the rollers revolve, and _D_ is the

hardened spindle on which the various back-centers are screwed. The

collar _E_ should either be flattened for a wrench, or a ⁵/₁₆-inch

hole, in which a wire can be inserted, should be drilled through the

spindle, so that it can be kept from rotating when screwing on the

back-centers. Some spinners prefer the spindle loose, so that it can

be withdrawn when changing the centers, while others prefer one with

considerable lateral motion, but not enough to permit of withdrawal. By

inserting a screw-point in the recess _F_, the center has considerable

lateral motion, but not enough to allow it to be withdrawn. This

recess is useful in that it helps to distribute the oil. All parts

should be hardened and drawn to a light straw color; they should

also be ground or lapped to a true fit after hardening. Back-centers

of this construction have been in use for over three years in one

establishment, and it has not been necessary to replace a single part.

 

[Illustration: Fig. 35. Detailed View of a Spinning-lathe Tailstock]

 

[Illustration: Fig. 36. Sectional View showing the Back-center and its

Double Roller Bearing]

 

 

Tools Used in Metal Spinning

 

Fig. 37 shows an attachment which is used to roll any bead or form.

This tool, when in use, is inserted in the tailstock spindle in place

of the regular center. It is adjustable for any diameter. The roll

illustrated is for making a sharp turn, but rounds and other forms are

used. The shell being spun by this tool should be held on a hollow

chuck. The roll is set at a point where the metal is to be turned over,

and by its use the curve may be governed and made uniform with less

skill than when the work is done by “air spinning.” In addition, the

spinning may be done in less time. This attachment, for some shapes,

makes the use of sectional chucks unnecessary.

 

[Illustration: Fig. 37. Attachment used for Rolling Sharp Turns and

Beads]

 

Fig. 38 shows several spinning tools, the heads of which were turned in

the lathe instead of being forged. This method of making spinning tools

is believed to be original. The spinners prefer them to the tools which

are forged in one piece, because the heads which are screwed to the

shanks are made of the best quality of steel, such as the high-speed

or self-hardening steel. The shapes are also better and the surfaces

more true. The heads of these tools are all threaded with standard

¼-inch, ⅜-inch and ½-inch pipe taps, according to the size. Obviously,

a spinner can have as many different shaped heads as may be required of

each of the sizes given, and only one handle. The tapering threads in

these heads insure that they will always screw on the shanks tightly no

matter how often they may be replaced. The ¼-inch size takes a ½-inch

cold rolled holder; the ⅜-inch, a ⅝-inch holder, and the ½-inch, a

¾-inch holder. These will be found large enough for the heaviest work.

The egg-shaped tool _A_ is a good form for roughing or breaking down,

as it has plenty of clearance on the heel, and a blunt point that will

not tear the metal. This tool is shown in four sizes. The ball or

spherical tool _B_ is a good one to use on curves and large sweeps.

The tool _C_ is elliptic, and is slightly different from _A_, as it

has a blunter point. One of these heads is shown at _D_ screwed onto

a reducer by which it is held in the lathe chuck while being turned.

These heads or points can also be turned while on the handle by using a

steady rest.

 

[Illustration: Fig. 38. Metal Spinning Tools with High-speed Steel

Removable Heads]

 

A group of trimmers, skimmers and edgers is shown in Fig. 39. Three

skimmers of the built-up type are illustrated, the shanks being of

machine steel and the blades being riveted to the holders. These

blades are made of either high-speed or regular steel. Skimmers

which are forged in the regular way from one piece of steel, are

shown at _B_. A number of edgers _C_, which are made of high-speed

or self-hardening steel, are also illustrated. These tools are used

without handles until they are worn down short, after which tangs are

forged on their ends and they are used in handles. Edgers are utilized

on all kinds of work for trimming the ends of the shells. The skimmer

is seldom used on metal chucks, but mostly in connection with wooden

chucks, where the metal cannot be smoothed down with a planisher.

The skimmer is run over the metal lightly, taking a thin shaving and

smoothing the uneven surfaces. It requires considerable skill to

use this tool without wasting the metal. The surface of the work is

finished with emery cloth after skimming.

 

[Illustration: Fig. 39. Tools used for Trimming and Skimming Spun Work]

 

Figs. 40 and 41 show a number of spinning tools of various shapes. The

letters _A_ indicate the breaking-down or round-nosed tools of different

sizes. This type of tool, which is finished smooth and has a blunt

point, is used for forming corners and sharp angles, and it is the

tool most commonly used by spinners. The planishers and burnishers

_B_ are used on all convex surfaces and for finishing on metal chucks

where there is to be no skimming done. The tools _C_ are known as hook

or poker tools, and they are used to turn up beads or curves from the

inside of the shell. The holders having rollers are used for turning

over beads, the metal first being trimmed and turned to a vertical

position. The other shapes shown are irregular tools for special work

and they are not in daily use.

 

[Illustration: Fig. 40. A Group of Spinning Tools of Various Shapes]

 

[Illustration: Fig. 41. Another Group of Spinning Tools]

 

Two pairs of spinners’ pliers for turning over the edge of the metal

when making large curves are shown in Fig. 42. The wedge-shaped pieces

shown in this illustration are used when breaking down or roughing

shells to give a bearing to the metal in order to prevent it from

wrinkling or buckling when changing its formation. These pieces are

made of hard wood with the exception of the one to the right, which is

of steel. When one of these pieces is in use it is held in the left

hand at a point directly opposite the spinning tool, the metal being

between the two. Wood is preferable in most cases, as it does not

harden the metal blank.

 

[Illustration: Fig. 42. Spinners’ Pliers which are used for turning the

Edge of the Metal when making a Large Bend]

 

The tools shown in Fig. 43 are used in spinning steel. The round tools

are of drawn brass, and they can be used where the steel tools cannot,

for while a steel tool is perfection on brass, a brass tool is the only

thing on steel. It wears out, however, much more rapidly than one of

steel. The rolls shown in the center are used for breaking down steel

shells. These tools are hardened and have hardened roller bearings. The

handles are made of one-inch iron pipe, which is filled with lead to

give weight and strength.

 

[Illustration: Fig. 43. Some Spinning Tools used in Working Steel]

 

Hard wood tools that are used for breaking down large thin copper

blanks ranging from 2 to 5 feet in diameter are shown in Fig. 44. These

tools are also used where the surface that the tool will cover without

hardening the metal is important. Blanks which are broken down with

these tools are finished with the regular types.

 

The handles of spinning tools vary in diameter from 1¼ to 1¾ inch, and

in length from 16 inches to 20 inches. The tools should project from

the handles from 9 to 18 inches, and the total length of the tool and

handle should average from 30 to 34 inches.

 

[Illustration: Fig. 44. Wooden Tools which are used on Large Thin

Copper Blanks]

 

A group of wood working tools is shown in Fig. 45. These tools are

of the type commonly used by spinners for turning the various shapes

of wooden spinning chucks. As the tools illustrated are the kind

regularly used for wood turning by patternmakers and other wood-workers

generally, they will need no description.

 

[Illustration: Fig. 45. Wood-turning Tools which are used in turning

Spinning Chucks]

 

 

Preparation of the Metal

 

Brass, copper, and German silver should be pickled after annealing in

order to get the scale or oxide from the surface. There are furnaces

that anneal without scaling by excluding the air when heating, but

they are not in general use. A pickling bath may be made by using one

part of oil of vitriol (sulphuric acid) and five parts of water. The

shells can be put in hot, or the bath can be heated by a coil of lead

or copper pipe running through it. Steam in no case should enter the

bath, as the iron in the feed pipe will spoil the pickle. Any basket

or box that may be used to hold the shells in the pickle should not

contain any iron. If a box is used it should be held together with

copper nails. The pickle can be used cold, but it will take a little

longer time to remove the scale. As soon as the scale is free, which

will be in about half an hour, the shells should be removed or washed

thoroughly in running water. The shells should be allowed to dry before

the next operation, which is that of spinning. A lead-lined wooden

tank or an earthen jar may be used for holding the pickle. The pickle

which is used for steel should be about half as strong as that employed

for brass. After the work is in this pickle, the latter should be

brought to the boiling point, after which the pieces should be taken

out and washed. They are then replaced in the fire for a short time to

evaporate any acid that may remain after washing.

 

Finished brass articles may be given different shades by dipping them

in a solution consisting of one part aqua fortis (nitric acid) and two

parts oil of vitriol. This solution should stand seven or eight hours

to cool after mixing, and be kept in a crock immersed in a water bath.