TIGHT JOINTS

Wanganui Chronicle, Volume LXXXIII, Issue 20104, 24 March 1928, Page 21 (Supplement)

TIGHT JOINTS

MINTS ON GASKETS

VARIETY OF MATERIALS Owing to the variety of purposes for which gaskets are used in different parts of a car, it is necessary to suit conditions. Thus some gaskets are required to withstand extreme heat conditions, some arc subjected to considerable pressure, while others operate under both heat and pressure. In every case the gasket is used to make a tight joint. Thin gaskets arc preferable to thick ones, and should always be used on joints that come together squarely. Metal to metal joints are the best, but as it is almost impossible to make both flanges meet absolutely square, it is necessary to interpose some kind of flexible material to compensate for inequalities of the surfaces. Gaskets which serve under the most severe conditions arc those under the cylinder head, those between the manifolds and the cylinder head or block, and those used between the exhaust manifold and the exhaust

As there is a high degree of heat and considerable pressure in all these cases, the gaskets arc made of a combination of asbestos and brass or asbestos and copper. The soft metal, combined with the heat-resisting, out compressible, asbestos, provides a gas-tight joint. In the absence of an asbestos-lined gasket, sheet lead may be used.

In these days of ready-made gaskets for all purposes, a firm that does not keep on hand a supply of the correct types and sizes of gaskets for all the cars it handles has little or no concern for its customers. No spare parts service is properly organised until it is stocked with joint material cut to size. The Type to Employ Cork and felt gaskets are employed in eases where it is necessary to make a joint oil-tight, such as around the lower half of th * crankcase. Oil leaks around these joints may often be traced to the gaskets not being properly fitted or that the bolts arc not drawn up sufficiently tight. At points where there is little or no heat, cardboard and heavy wrapping paper gaskets may be used.

It is advisable to use them at joints where water or petrol is to be confined. A leak is bound to occur if a damaged gasket is put back into position when re-assembling a unit that has been taken down. This particularly applies to paper, cork, and felt packing—.•■.ll of which arc easilv torn.

In the case of the copper asbestos •pc, the gasket can generally be used veral times before replacement is

If a new ready-made gasket for, sc< the cylinder head, is not available, a satisfactory packing may be made from wire-woven asbestos, which is sold in rolls. This material is manufactured from long-fibre asbestos and closely woven brass wire, impregnation with a heat and water resisting compound completing the process. A red compound on one side sticks to the flange when the joint is broken, while the graphite on the other side allows the joint to be easily taken apart.

Before fitting any gasket it is imperative to clean the two metal sur faces thoroughly.