Improvements in Drawing Iron and Steel Bars through Dies to Produce a. Smooth Surface Suitable for Shafting.
Year: 1886

page_text: Date of Application, 26th Oct., 1886.
Complete Left, 22nd July, 1887.
Complete Accepted, 23rd Aug., 1887.
Improvements in Drawing Iron and Steel Bars through Dies to
Produce a. Smooth Surface Suitable for Shafting.
I, BENJAMIN CHEW TILGHMAN, of South View, Altrincham, Cheshire, Engineer,
do hereby declare the nature of this invention to be as follows :---
My invention relates to the application of the process of drawing through dies to
the manufacture of bars of iron or steel suitable for shafting and other engineering
purposes requiring smoothness of surface.
Heretofore it has been found difficult to obtain by the drawing process a surface
smooth enough for such purposes. The bars as they come from the rolling mill
generally have a surface rough with scale and oxide, and when the scale is removed
by pickling, the cavities thereby made leave the surface nearly as rough as before.
Repeated drawings through dies will gradually make the surface smoother, but
many drawings and considerable reduction of diameter would be required to make the
surface sufficiently smooth, and in the case of bars of diameter suitable for shafting
and other engineering purposes, this would be a tedious and expensive operation.
Layers of scale sometimes go quite through a bar, and in such case they would appear
on the surface however much the bar had been drawn. Heretofore a separate
smoothing or polishing process has generally been applied after the bar has been
drawn.
My invention consists in covering the bar, before its final drawing to the desired
size, with a coating of softer metal (either tin or its alloys, or zinc, or copper or its
alloys), which will unite with or adhere to the iron or steel and fill up any cavities,
cracks or inequalities of its surface, and completely cover it.
The bar thus coated is drawn through one or more finishing dies, by which some
of the softer metal is, or may be, scraped off, and a thin and complete layer of it
adheres to the iron or steel and is extended with it by the compressive action of
the dies.
A smooth surface is thus obtained with only a few passages through the dies and
the layer of tin, zinc or copper protects the iron from rust and is more easily kept
clean.

page_text: A cheaper quality of iron can be used with the coating metal than would be
practicable without it.
The covering with tin or its alloys, or with zinc, is done by dipping the cleaned
bar into a bath of the melted metal as is well understood.
The copper may be put on by the known process of electro deposition.
The bars may be round, square, oblong or of any shape capable of being passed
through dies. If a commercial bar is fairly accurate in shape and not too rough in
surface, it may be coated before it is drawn, and a single drawing may then be
sufficient to finish it, but it is generally better to give a bar one or more preliminary
drawings before applying the coating metal, and then to give it a finishing draw.
I prefer that the drawings should be effected with the simultaneous application of
powerful longitudinal tension to the bar, as described in the provisional specification
filed by me on 20th July 1886, No. 9382, but this is not essential.
Dated this 26th day of October 1886.

page_text: Improvements in Drawing Iron and Steel Bars through Dies to
Produce a Smooth Surface Suitable for Shafting.
I, BENJAMIN CHEW TILGHMAN of Altrincham, Cheshire, Engineer, do hereby
declare the nature of this invention and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement :-
My invention relates to the application of the process of drawing through dies to
the manufacture of bars of iron and steel suitable for shafting and other engineering
purposes requiring smoothness of surface.
Heretofore it has been found difficult to obtain by the drawing process a surface
smooth enough for such purposes. The bars as they come from the rolling mill
generally have a surface rough with scale and oxide, and when the scale is removed by
pickling, the cavities thereby made leave the surface nearly as rough as before.
Repeated drawings through dies will gradually make the surface smoother, but many
drawings and considerable reduction of diameter would be required to make the
surface sufficiently smooth, and in the case of bars of diameter suitable for shafting
and other engineering purposes, this would be a tedious and expensive operation.
Layers of scale sometimes go quite through a bar and in such cases they would
appear on the surface, however much the bar had been drawn. Heretofore a separate
smoothing or polishing process has generally been applied after the bar has been
drawn.
My invention consists in covering the bar before its final drawing to the desired
size with a coating of softer metal, either tin or its alloys, or zinc, or copper or its
alloys, which will unite with or adhere to the iron or steel and fill up any cavities
cracks or inequalities of its surface and completely cover it. The bar thus coated is
drawn through one or more finishing dies by which some of the softer metal is, or
may be, scraped off and a thin and complete layer of it adheres to the iron or steel
and is extended with it by the compressive action of the dies. A smooth surface is
thus obtained with only a few passages through the dies and the layer of tin zinc or
copper protects the iron from rust and is more easily kept clean. The covering with
tin or its alloys, or with zinc, is done by dipping the cleaned bar into a bath of the
melted metal as is well understood; the copper may be put on by the known process
of electric deposit.
The bars may be round square oblong or of any shape capable of being passed
through dies. If a commercial bar is fairly accurate in shape and not too rough in
surface, it may be coated before it is drawn, and one or two drawings may then be
sufficient to finish it, but it is generally better to give a bar one or more preliminary
drawings before applying the coating metal, and then to give it a finishing draw.
I prefer that the drawings should be done with the simultaneous application of
powerful longitudinal tension to the bar, as described in the Patent granted to me
20th July 1886, No. 9382, but this is not essential.

page_text: -
The following is a method of carrying my invention into effect, taking for example
a round iron bar which is to be coated with tin and to be drawn so as to be suitable
for shafting. The bar is to be cleaned from scale and oxide by the usual process of
pickling filing and scrubbing so that it will readily and perfectly take the tin. Any
partly detached scales of metal are to be removed, as they would be likely to be made
more prominent by the action of the dies and thus damage the surface.
The bar is then to be tinned in the usual way. I have found it a good plan to heat
the bar in a bath of palm oil up to about the temperature of melting tin, and then to
dip it immediately into a bath of melted tin and rub it with a pad of asbestos cloth.
It is important that all parts of the surface should be tinned, and that a perfect union
or alloying of the iron and tin should take place. After the bar has been taken out of
the tin bath and the tin coating has solidified, it should be carefully examined, and
any holes or depressions in the surface should be filled up with tin by means of a
soldering iron or otherwise. The bar is then drawn through one or more dies until
the desired shape size and smoothness of surface have been obtained. The tin coating
seems to act to some extent as a lubricant and to lessen the friction and wear of the
dies. I prefer to use good commercial tin as the coating metal. Alloys of tin and
lead may be used if cheapness is desired. Zinc and copper produce similar effects but
are not so good as tin.
Having now particularly described and ascertained the nature of my said Invention
and in what manner the same is to be performed, I declare that what I claim is.
As a new article of manufacture, iron or steel bars suitable for shafting and other
engineering purposes which have had their surfaces coated with tin or its alloys, or
zinc, or copper or its alloys, and have afterwards been drawn through dies, substantially
as described.
Dated this Twenty first day of July 1887