When doing forging, it is necessary to take measurements rapidly - not an easy task with hot iron. Hence, gauges notched to different sizes are made of sheet iron, say 1/8 in. thick, the size of each notch being stamped above it, Fig. 255 being a gauge for round, Fig. 256 one for flat bars. - (English Mechanic.)
The following hints* may be found useful, especially in amateurs' shops where tools are not always in use: -
The wooden parts of tools, such as the stocks of planes and handles of chisels, are often made to have a nice appearance by French polishing; but this adds nothing to their durability. A much better plan is to let them soak in linseed oil for a week, and rub them with a cloth for a few minutes every day for a week or two. This produces a beautiful surface, and at the same time exerts a solidifying and preserving action on the wood.
1. Caoutchouc oil is said to have proved efficient in preventing rust, and to have been adopted by the German army. It only requires to be spread with a piece of flannel in a very thin layer over the metallic surface and allowed to dry up. Such a coating will afford security against all atmospheric influences, and will not show any cracks under the microscope after a year's standing. To remove it the article has simply to be treated with caoutchouc oil again, and washed again after 12-24 hours.
2. A solution of indiarubber in benzine has been used for years as a coating for steel, iron, and lead, and has been found a simple means of keeping them from oxidising. It can be easily applied with a brush, and is easily rubbed off. It should be made about the consistency of cream.
3. All steel articles can be perfectly preserved from rust by putting a lump' of freshly-burnt lime in the drawer or case in which they are kept. If the things are to be moved, as a gun in its case, for instance, put the lime in a muslin bag. .This is especially valuable for specimens of iron when fractared, for in a moderately dry place the lime will not want renewing for many yean, as it is capable of absorbing a large amount of moisture. Articles in use should be placed in a box nearly filled with thoroughly - slaked lime. Before using them rub well with a woollen cloth.
4. The following mixture forms an excellent brown coating for preventing iron and steel from rust: Dissolve 2 parts crystallised iron chloride, 2 antimony chloride, and 1 tannin in 4 of water, and apply with sponge or rag, and let dry. Then another coat of paint is applied, and again another if necessary, until the colour becomes as dark as desired. When dry it is washed with water, allowed to dry again, and the surface polished with boiled linseed oil. The antimony chloride must be as nearly neutral as possible.
5. To keep tools from rusting, take 1/2oz. camphor, dissolve in 1 lb. melted lard; take off the scum and mix in as much fine black-lead (graphite) as will give it an iron colour. Clean the tools and smear with this mixture. After 24 hours rub clean with a soft linen cloth. The tools will keep clean for months under ordinary circumstances.
6. Put 1 qt. freshly-slaked lime, 1/2 lb. washing soda, 1/2 lb. soft soap in a bucket and sufficient water to cover the articles; put in the tools as soon as possible after use and wipe them up next morning or let them remain until wanted.
7. Soft soap with half its weight in pearlash, 1 oz. of mixture in about 1 gal. boiling water, is in everyday use in most engineers' shops in the drip-cans used for turning long articles both in wrought iron and steel. The work, though constantly moist, does not rust, and bright nuts are immersed in it for days till wanted, and retain their polish.
8. Melt slowly together 6-8 oz* lard to 1 oz. rosin, stirring till cool; when it is semi-fluid it is ready for use. If too thick, it may be let down by coal-oil or benzine. Rubbed on bright surfaces ever so thinly it preserves the polish effectually, and may be readily rubbed off.
9. To protect metals from oxidation, polished iron or steel for instance, the requisite is to exclude air and moisture from the actual metallic surface; therefore, polished tools are usually kept in wrappings of oil-cloth and brown paper, and, thus protected, they will preserve a spotless face for an unlimited time. When these metals come to be of necessity exposed in being converted to use, it is necessary to protect them by means of some permanent dressing, and boiled linseed oil, which proves a lasting covering as it dries on, is one of the best preservatives, if not the best. But, in order to give it body, it should be thickened by the addition of some pigment, and the very best, because the most congenial of pigments is the ground oxide of the same metal, or in plain words, rusted iron reduced to an impalpable powder, for the dressing of iron and steel, which thus forms the pigment or oxide paint.
10. Slake a piece of quicklime with just water enough to cause it to crumble in a covered pot, and while hot add tallow to it and work into a paste, and use this to cover over bright work; it can be easily wiped off.
11. Olmstead's varnish is made by melting 2 oz. rosin in 1 lb. fresh sweet lard, melting the rosin first, and then -adding the lard and mixing thoroughly. This is applied to the metal, which should be warm, if possible, and perfectly cleaned; it is afterwards rubbed off. This has been well proved and tested for many years, and is especially well suited for planished and Russian iron surfaces which a slight rust is apt to injure very seriously.