STEAM HAMMER, TOOLS, AND EXERCISES
=112. A Forging.=—A forging is an article made of metal, generally
steel or iron, and produced by heating and hammering. It may be used
for either practical or ornamental purposes. The various forgings
already described were made by methods such as the older class of
smiths practiced, and are called hand forgings. From a practical
standpoint these smiths were familiar with the characteristic
composition of metals and with the knowledge of how they should be
worked.
Many forgings are produced at present by machinery. The product is
satisfactory for most practical purposes, and is generally equal to
that made by hand. The machines used are the drop hammers, horizontal
and vertical presses, steam hammers, and numerous other devices. The
power used for operating them may be either steam, air, water, or
electricity.
=113. The Drop Hammer.=—The drop hammer is provided with a pair of dies
made of cast steel, one upper and one lower, having suitably shaped
depressions made in them for forming the forgings. The lower die is
held stationary on a solid foundation block, and the upper one is
secured to a heavy weight or hammer. This is raised perpendicularly and
allowed to drop upon the metal, which is held on the fixed die by the
smith, thus forming the forging.
If the work is small and simple, all depressions may be made in a
single pair of dies, and the forging can be completed with one hammer
and without changing the dies. Work somewhat complicated may require
two or more pairs of dies, with various shapes of depressions. The
stock is broken down or blocked out by the first pair and then
completed by the stamping and finishing dies. Larger pieces may require
also a number of pairs of dies, then an equal number of hammers may
be used, each fitted with a set of dies. The material is passed from
one to the other, and the work completed without changing dies, and
possibly without reheating the metal.
=114. Presses.=—Presses may be either horizontal or vertical and are
generally used for bending or pressing the metal into some desired
shape or form; they are quite convenient for producing duplicate and
accurate shapes. Forming-dies or blocks are also required here, but
they are generally made of cast iron, and their construction need not
be so accurate. After the presses have been properly adjusted, very
little skill is required in their operation,—simply the heating of the
material and placing it against a gauge or between the dies. One thrust
of the plunger will complete the operation.
=115. The Steam Hammer.=—The steam hammer was first recorded by Mr.
James Nasmyth in his “scheme book” on the 24th of November, 1839.
Although this was the exact date of its origin, he first saw it put
into practical use by the Creuzot Iron Works of France in 1842.
Nasmyth’s invention legally dates from June, 1842, when his patent was
procured.
Of the various machines that have been devised for the smith’s use, to
relieve him of the laboriousness of pounding metal into shape, there is
none that could take the place of this invention. Numerous shapes and
forms can be produced more accurately and rapidly by the employment of
the steam hammer than by the use of hand methods.
[Illustration: FIG. 101.—A STEAM HAMMER EQUIPPED WITH A FOOT LEVER.]
Before proceeding any further, a few words of warning and advice may
not be out of place. Although this invention is a great benefactor to
the smith, it is not possessed with human intelligence, nor is it a
respecter of persons. The power of steam will always exert its utmost
force when liberated, so do not let in too much steam at first. Unless
the material is held horizontally and flat on the die, the blow will
jar the hands badly and will bend the material. All tools such as
cutters and fullers should be held firmly but lightly, so that they may
adjust themselves to the die and the descending blow.
After the hammer has been put into motion, the blows will fall in a
perfectly routine manner. By his careful observation and a thorough
understanding of the necessary requirements, and by signals from the
smith, the hammer operator should regulate the force of the blows to
suit the smith’s convenience.
A caution pertaining to the tongs used for handling the material should
be carefully observed. Whenever work is to be forged with the steam
hammer, the material should be held with perfect-fitting tongs secured
by slipping a link over the handles; a few light blows delivered on the
link will tighten their grip.
=116. Steam Hammer Tools.=—First some necessary tools will be
explained, then exercises requiring their use will be given, followed
by a few operations where simple appliances are needed.
[Illustration: FIG. 102.—THE HACK OR CUTTER.]
=117. The hack or cutter= (Fig. 102) is used for nearly the same
purposes as the hot cutter already described. It should be made of
tool steel from 0.80 to 0.90 per cent carbon. The head or top is made
convex, as shown, and not more than 5/8 inch thick, tapering equally on
both sides to the cutting edge, which may be made either 3/16 or 1/4
inch thick. It should be ground straight and parallel to the top and
tempered to a dark blue.
The blade is about 2-1/4 or 2-1/2 inches wide, unless intended for
heavy forgings, when all dimensions should be increased. The width
of the blade should not be too great, however, for the broader the
cutter, the greater its liability to glance sidewise or turn over when
the blows are delivered upon it. The length of this cutter may be from
3-3/4 to 4 inches.
The handle may be about 28 inches long, approximately 3/4 inch in
diameter at _a_ and gradually tapered towards the end, where it is
about 1/2 inch. The portion indicated at _b_ is flattened to an oblong
section, as shown, to allow springing when the blows are delivered and
to prevent bruising the hands.
=118. The circular cutter= (Fig. 103) is made of the same material and
with a handle of similar dimensions and form as the hack. A section of
the cutting portion on _a-a_ is shown, and suitable dimensions given.
If convex ends are to be cut, the perpendicular side of the blade
should always be on the inner side of the curve, but on the outer side
for concave ends.
[Illustration: FIG. 103.—THE CIRCULAR CUTTER.]
An assortment of these cutters with various-sized arcs may be provided
to suit requirements, but quite frequently the curved cutting portion
is altered to suit the particular work at hand.
[Illustration: FIG. 104.—THE TRIMMING CHISEL.]
=119. The trimming chisel= (Fig. 104) is made quite similar to an
ordinary hot cutter and likewise provided with a wooden handle. It
should be strongly constructed, perfectly straight on one side, and not
too long from the cutting edge to the top to avoid its being turned
over when the blows are delivered upon it. The grinding should be done
on the tapered side only, with the cutting edge tempered to a dark blue.
=120. The cold cutter= (Fig. 105) is used for purposes similar to those
of the ordinary cold cutter. It should be strongly made in a triangular
form, as shown in the end view, also with a spring handle like that of
the hack. The top is made convex, and the sides taper to the cutting
edge, which should be ground equally from both sides. It should be
carefully tempered for cutting cold material.
[Illustration: FIG. 105.—THE COLD CUTTER.]
[Illustration: FIG. 106.—BREAKING COLD STOCK.]
In cutting stock with this tool, the material should be nicked
sufficiently deep on the exterior to allow it to be broken. By holding
the piece securely with the hammer, and the nicked portion even with
the edge of the dies, it may be broken off by a few blows from a
sledge. The steam hammer may also be used to break the stock when
nicked with the cold cutter. The piece should be placed on the lower
die of the hammer, as shown in Fig. 106, and broken by one or two sharp
blows from the hammer. A piece of round stock can be used instead of
the triangular piece of steel, with the same result. When material is
being broken in this way, see that no one is standing in a direct line
with the stock, as there is some liability of one or both pieces flying
in either direction.
[Illustration: FIG. 107.—CUTTING STOCK.]
When using the hack (Fig. 102) for cutting square stock, cut equally
from all sides, as shown at _a_, Fig. 107. This will produce smoother
ends than if it were cut unequally and will prevent the short end from
turning upward when the final blows are delivered. The fin or core
that is formed by the hack, shown at _b_, generally adheres to one of
the pieces, but it can be removed by using the trimming chisel in the
manner shown. These fins are commonly removed by the use of an ordinary
hot cutter and sledge.
The hack, if held perpendicularly, will not cut the end of either piece
square. If one end is to be cut square, the cutter should be held as
shown at _c_. Round material may be cut similarly, but to avoid marring
its circular section it may be held in a swage fitted to the hammer die.
Flat stock may be cut equally from both sides, or if it is cut nearly
through from one side, the operation can be completed by placing a
small piece of square untempered steel over the cut, as shown at _e_. A
sharp blow of the hammer will drive the steel through into the opening
and produce a straight, smooth cut.
When a semicircular end is to be produced, similar to that indicated by
the broken line at _d_, the circular cutter should be used. Here, also,
the cutting should be done equally from each side.
[Illustration: FIG. 108.—THE CHECKING TOOL OR SIDE FULLER.]
=121. The checking tool or side fuller= (Fig. 108) is made of tool
steel with a carbon content, the same as for the cutters. The handle
also is the same, with the exception of part _a_, which provides the
spring. Here, on account of its being used in two different positions,
a twisted form is much better, because the tool may spring in either
direction. From the end view you will notice that it has a triangular
section with one square corner and two curved ones.
A convenient dimension for this tool is about 2-1/2 inches over all
from the square to the circular corners. It would be convenient to have
a smaller one also, of about 1-1/2 inches. The length of this tool
should correspond with that of the cutters.
In use, one of the circular corners of the checking tool is forced into
the metal, forming a triangular-shaped depression, as shown at _b_. Two
depressions are shown in this sketch in opposite directions to each
other, made by holding the tool in different positions and using both
the circular edges. The object of this operation is to set off the
rectangular portion _b_ so that the ends _c-c_ can be drawn out without
disturbing the center.
[Illustration: FIG. 109.—THE FULLER.]
=122. The fuller= (Fig. 109) is made with a handle like that of the
checking tool, but the portion used for fullering is made circular
in section and about 4 inches long. An assortment of sizes should be
provided, with diameters of 1, 1-1/2, and 2 inches. When smaller sizes
are needed, a bar of round steel may be conveniently substituted. These
tools may be properly termed top fullers, because they are generally
held on top of the metal and the blows are delivered from above, thus
forming depressions on one side only. Sometimes double depressions are
required directly opposite to each other. In such cases a short piece
of round metal, the same size as the fuller, is placed on the die
directly under the top fuller, with the metal between the two.
If the depressions are to be only semicircular, a short piece of
half-round material may be provided which is not liable to be
dislocated or jarred out of position on the die.
[Illustration: FIG. 110.—THE SPRING FULLERS.]
=123. The combined spring fullers= (Fig. 110) are very convenient for
making double depressions. They are similar to the single fuller,
but are flattened out at _a_ and _b_, so that they may be opened for
various sizes of stock.
[Illustration: FIG. 111.—THE COMBINATION FULLER AND SET.]
=124. The combination fuller and set= (Fig. 111) may be made with a
straight, round handle, but a twisted one is more desirable, because
the tool is frequently used in different positions. It should be made
of a quality of steel that will withstand severe hammering without
becoming battered. The heavy end which forms the tool is made about
1-1/2 by 2-1/2 inches; the corners on one side are left sharp and
square, while those opposite are made quarter-round. One side of this
tool may be made almost semicircular if it is intended to be used as a
fuller. The length may be about 4 inches.
[Illustration: FIG. 112.—DRAWING AND FINISHING WITH THE COMBINATION
FULLER AND SET.]
This tool is used as a fuller or set in drawing metal between
projections which have been formed by using the checking tool. In Fig.
112 the sections of metal, indicated by _a_ and _c_, are to be drawn
to smaller dimensions. This cannot be done with the hammer, because
these places are narrower than the width of the hammer dies. At _c_ the
fuller or set is being used flatwise, which is the better way, because
the two round corners will not cause galling. At _a_ it is shown in use
edgewise; but this should not be continued after the opening has been
enlarged sufficiently to use the tool as at _c_, unless perfectly sharp
corners are desired.
Another convenient use for this tool is for finishing a roughly drawn
tapered piece of metal, as at _d_. Here are shown the roughened tapered
surfaces, as they have been produced by the hammer, also the method of
using the set. If there is much of this kind of work to be done, it
would be advisable to provide a special tool with a circular side which
could be used solely as a flatter.
[Illustration: FIG. 113.—THE COMBINED TOP AND BOTTOM SWAGES.]
=125. The combined top and bottom swages= (Fig. 113) are also called
spring swages, because they are somewhat flexible at the connecting
loop, which keeps them in adjustment. The best material for these
swages, on account of the constant hammering to which they are
subjected, is a good quality of mild or soft steel. Much hammering has
a tendency to crystallize the metal and causes frequent breakage.
The heavy parts forming the swages ought to be well proportioned and
made from sufficiently heavy stock. The handles are drawn out from the
same material and welded, or merely stub ends may be drawn from this
material, and then flat stock welded on to form the handles. In either
case the edges should be swaged half-round previous to welding. The top
and bottom of the handles are not parallel with the upper and lower
parts of the swages, because the heavy parts only should receive hammer
blows.
The grooves should be perfect semicircles, with the exception of the
edges indicated at _e_, which should be slightly round, as shown. This
prevents metal from becoming lodged in the swages. If the metal sticks,
the smith will be unable to revolve it in the swages, and it will
become oblong in section. The corners on top of the upper swage should
be removed, as shown, so that the blows will be received more directly
through its center.
[Illustration: FIG. 114.—THE TOP AND BOTTOM SWAGES.]
=126. The top and bottom swages= (_A_ and _B_, Fig. 114) are made
separate, but of the same quality of material as those just described.
The handle of the top swage _A_, however, should be round, with a small
portion flattened, as shown. The bottom swage _B_ is constructed with
projecting lugs _d_, as shown. The distance between the lugs should be
equal to the width of the lower hammer die, over which the swage should
fit closely enough to prevent its displacement. The swages may be used
together or separately, as desired, the lower one being convenient for
cutting round material, as it prevents marring the sectional form of
the stock.
[Illustration: FIG. 115.—THE BEVEL OR TAPER TOOL.]
=127. The bevel or taper tool= (Fig. 115) is provided with lugs and
fits the hammer die. When constructed for general use, the pitch should
not be too great, because it may be increased by placing a short piece
of metal under one end, as shown, or decreased by inserting metal under
the opposite end. The heavy end should be made as nearly perpendicular
as possible, with the outer edge of the die. This tool is very handy
for drawing any tapering work, such as cold chisels, levers, keys, etc.
=128. The V block= (Fig. 116) was introduced by the inventor of the
steam hammer, and was used instead of a bottom swage. When large, round
sections are to be produced, and swages of the proper size are not
obtainable, this tool may be used.
[Illustration: FIG. 116.—THE V BLOCK.]
When round stock is drawn without a swage, only two portions directly
opposite to each other are acted on by the hammer, thus causing some
liability of producing an oblong section or a hollow centered forging.
These difficulties are avoided to a certain extent by the use of the V
block, because the force of the blow acts in three directions.
=129. The yoke or saddle= (Fig. 117) should be made of heavy flat
material bent into the form of a U, with the ends perfectly straight
and parallel. It should be provided with lugs fitted to the lower die
so that both sides will stand erect and at right angles to it, as at
_A_. The distance between the sides may be of any convenient width,
2-1/2 inches or more, depending upon the character of the work to be
done. Semicircular depressions should be made on the edges, as shown at
_e_.
[Illustration: FIG. 117.—THE YOKE OR SADDLE.]
Another view of the yoke is given at _B_, with one side removed. As
seen here, it is used to draw weldless or solid rings after the stock
has been blocked out and a sufficiently large hole has been punched
in it to allow it to be hung over the pin _p_, which rests in the
depressions previously mentioned. Hammer blows can be delivered on the
exterior of the stock, thus drawing it and increasing its diameter. As
this is increased, larger pins should be used, to produce a smoother
and more evenly drawn ring.
The yoke, shown at _C_, is being used as a bridge for drawing the ends
of a solid forged jaw. By using it for purposes like this, considerable
hand labor may be saved.
[Illustration: FIG. 118.—_A_, BOLSTER; _B_, A PLUG PUNCH IN POSITION
FOR USE.]
=130. Bolsters or collars= (_a_, Fig. 118) are used for punching holes,
upsetting metal for bolt heads, and similar operations. They should be
made of soft steel.
=131. Punches.=—At _b_, Fig. 118, a plug punch is shown in position on
the metal over a washer or bolster ready for punching. When properly
located, a few blows of the hammer will force the punch through the
metal and produce a smoothly finished hole.
Notice that the punch is made somewhat tapering, and that the heavier
portion is driven through first. Precaution should be taken not to have
the punch fit the bolster too closely or be too long, also to have it
directly over the hole in the bolster before attempting to drive it
through.
Holes can be punched with ordinary handle punches, but care should be
taken not to have them too long; even then a bolster or something must
be used, so that the punch can be driven clear through the metal and
not come in contact with the lower hammer die.
=132. Steam Hammer Work.=—The following exercises are known as machine
forgings. They will require the use of the steam or power hammer and
the tools just described. It will be necessary to know beforehand
what parts of the work are to be finished, so as to provide a proper
allowance at those places. The term “finished” means that the surface
is to be removed by the machinist, and the work made smooth and to the
required dimensions.
All machine drawings should designate the parts that require finishing,
by either the entire word or just the letter “F.” The symbol is more
convenient to use for only certain parts, but if the entire forging is
to be finished, it may be indicated by “finished all over.”
=133. Crank Shaft.=—Fig. 119. This is shown without dimensions or
finish marks. Select stock sufficiently heavy to produce a forging
equal to that shown at _b_.
Make two depressions with the checking tool, as shown, the distance _c_
between them corresponding with the dimension _a_ on the crank. Draw
the ends square and straight on the lower side, as shown at _d_, then
octagonal, and then round. In this way the fillets and shoulders will
be equal, as shown at _e_. The two ends should be swaged smooth and
round, then made perfectly straight and at right angles to the crank.
[Illustration: FIG. 119.—STEPS IN MAKING A CRANK SHAFT.]
=134. Connecting Rod.=—Fig. 120. The volume of the material required
for section _e_ must first be estimated. Then ascertain how many inches
of the selected material will be required to give this volume. This
will be the distance _b_ for the fullering shown at _a_. The sizes of
the fullers to be used should be the same as the required radii _r_.
Fuller in the depressions as shown, so that they will correspond with
the dimensions _g_, _h_, and _l_ of the finished rod. The metal between
_g_ and _h_ should then be drawn slightly tapered, as shown in the top
view, and to a uniform thickness _l_. The small end must now be drawn
to the proper size and trimmed with the circular cutter. Make the rod
perfectly straight, with the ends parallel to each other and to the rod.
[Illustration: FIG. 120.—STEPS IN MAKING A CONNECTING ROD.]
=135. Rod Strap.=—Fig. 121. This forging is begun by blocking out, as
shown at _B_, with _e_ a little greater than _h_ and plenty of stock at
_f_. The length _k_ must equal _l_, with a slight allowance of surplus
metal for the bending operation.
Sketch _C_ shows the method of bending. A forming block _m_ should
be provided for this, the width of which corresponds nearly with the
dimension _g_, and the thickness is somewhat greater than that at _d_.
The length may be equal to the inside length of the finished strap, but
it could be used if shorter. By placing this block perpendicularly on
the bottom die, with the forging resting on it and a small piece of
metal _n_ for a blocking on top of that, the upper die may be brought
down and a full head of steam turned on while the stroke lever is held
down. Both ends can be bent down simultaneously with sledges.
[Illustration: FIG. 121.—STEPS IN MAKING A ROD STRAP.]
After the bending, there may be required more or less labor with the
flatter and sledge to square it up in proper shape. Then the ends can
be cut off to equal lengths with the hack or hot cutter.
[Illustration: FIG. 122.—STEPS IN MAKING AN ECCENTRIC JAW.]
=136. Eccentric Jaw.=—_A_, Fig. 122. First form the depression _c_ with
the checking tool; then draw out the end _d_ to the form _e_ and punch
a hole at _f_ by using an oblong punch.
Then using the hack, carefully cut from both sides at the places
indicated by the broken lines at _f_. Any fin remaining after the
cutting can be removed with a hot cutter or the trimming chisel. The
ends forming the jaw can be drawn to the proper size by the use of
the yoke. The semicircular ends can also be cut by using the circular
cutter, but these ends will require some trimming with a hot cutter,
because all the work must be done from exterior sides.
=137. Hand Lever.=—_A_, Fig. 123. This illustrates and explains a
simple method of stamping which may be extended or adjusted to suit a
variety of forgings.
[Illustration: FIG. 123.—STEPS IN MAKING A HAND LEVER.]
In this case two stamping rings are made to suit the work at hand, as
follows: If the dimension _h_ is 2 inches and the thickness of the
lever _i_ is 1/2 inch, the rings must be made of 3/4-inch round stock,
and welded to an inside diameter corresponding with the dimension _k_.
First draw the material to correspond exactly with the dimension _k_ in
one direction and somewhat greater than that of _h_ in the opposite.
The latter dimension is made larger, to provide some excess metal for
the stamping operation, which is done in the following manner: Place
one of the rings centrally on the bottom die of the hammer, as shown
at _B_; lay the material on this, with the dimension _h_ perpendicular
and the proper distance from the end to provide enough metal for
forming the lever and handle. Then place the other ring on top of the
material directly above the lower one, and deliver blows on these
rings until the entire thickness almost corresponds with the desired
dimension _h_. The rings will be forced into the metal and form two
depressions, as shown at _C_. Next with a hot cutter or trimming chisel
remove the metal forming the corners _e_. Then draw out the lever
portion roughly, at first; by using the taper tool a uniform taper can
be produced correctly. Cut off the extra stock at the boss, and remove
the surplus metal which projects between the bosses as indicated at
_d_, and finish the end smoothly with a common top swage. The handle
portion can be formed at the anvil with top and bottom swages after the
end has been cut semicircular and to the desired length.
[Illustration: FIG. 124.—STEPS IN MAKING A CONNECTING LEVER.]
=138. Connecting Lever.=—_A_, Fig. 124. After drawing the metal to an
appropriate dimension, fuller two depressions _b_ on opposite sides,
the proper distance from the end, to form the jaw. A single boss _c_
should be stamped with one ring, at the required distance from _b_
to provide the necessary amount of metal for the length _d_ of the
lever. Then remove the corners, as indicated by the broken lines. Begin
drawing the lever by using the combination set, and finish the flat
side with the hammer, producing the taper edge with the taper tool.
Punch a square hole in the jaw and remove the metal indicated by the
broken lines at _e_, with a hot cutter. Finish the jaw similar to the
eccentric jaw and the boss as in the previous exercise.
[Illustration: FIG. 125.—SOLID FORGED RING.]
=139. Solid Forged Ring.=—Fig. 125. This should be made of soft steel,
the dimensions being supplied by the instructor to suit the stock and
equipment at hand. The volume (see calculating rules and tables, pp.
197-206) of the forging must first be determined and some surplus
allowance for forging provided. The process of making the ring will be
found in the explanation of the use of the yoke in section 129.
[Illustration: FIG. 126.—PRODUCING DOUBLE AND SINGLE OFFSETS.]
=140. Double and Single Offsets.=—Fig. 126. The following exercises
are given to explain the use of simple appliances for producing work
accurately and rapidly. Examples similar to the four following ones
would require considerable care and skill if they were to be produced
without the use of the steam hammer.
At _a_ is shown a double offset bend, the depth of which, for
illustration, may be 1/2 inch. To produce this, place two pieces of
1/2-inch flat material, with _width corresponding_ to that of the
material to be bent, on the lower die, and sufficiently far apart
to allow the offsets to form between them. On these the material is
placed, and on top of that also, located midway between the 1/2-inch
supporting pieces, a third piece of 1/2-inch stock is placed. The
width of this should correspond with the required dimension at _a_ and
should be somewhat longer than the width of the material to be bent.
This arrangement is shown at _c_. By delivering a sufficiently heavy
blow upon them, the two offsets, will be formed simultaneously and
accurately.
[Illustration: FIG. 127.—SIMPLE METHODS FOR BENDING CLAMPS WITH A STEAM
HAMMER.]
In all operations of this kind the thickness of the lower forming
pieces should always correspond with the required depth of the offset,
and the corners should be ground round to prevent shearing or galling.
At _d_ is shown a single offset which can be produced in a similar way,
with the exception that here only two blocks are required. But the
forming corners of these should also be ground as previously stated,
and they are placed in position as shown at _e_.
Figure 127 shows the method of bending a semicircular pipe or rod
clamp. Here a piece of round stock _f_ is used above for stamping, but
as the lower blocks are easily displaced, it would be advisable to make
a stamping block like that shown at _g_. This could be used instead of
the two lower pieces. If the clamps were to be made square, then the
stamping block should be like the one shown at _h_, and the upper piece
as at _f_ should be made square.
QUESTIONS FOR REVIEW
What is a forging? Name the machines used in making forgings. Who
invented the steam hammer? How should material be held on the dies?
What tool is used in place of a hot cutter at the hammer? How can
a convex end be produced? Describe the special form of a trimming
chisel. How should metal be broken after it has been nicked with the
cold cutter? Describe the correct way of using a hack in cutting
square stock. Explain the use of a checking tool. Describe the
different fullers used at the hammer. Explain their uses. For what
is a combination fuller and set used? Describe the hammer swages.
The bevel or taper tool. What is it used for? What is the advantage
in the use of the V block? Describe the yoke. Explain its use. What
is the difference between a plug punch and a handle punch? How is a
bolster used for punching? What does the word “finished” mean on a
drawing? What hammer tools are brought into use in making a crank
shaft? In making the connecting rod? Describe how the hammer is used
in bending a rod strap. What tools are brought into use in making the
eccentric jaw? Describe the method of forming the bosses on the hand
lever. Explain some simple methods of bending work with the steam
hammer.