Category The Technique of FURNITURE MAKING

ESTIMATING THE COST OF MAN-HOURS IN HANDWORK

Where no previous records are available the proprietor must assess his own capabilities and those of his employees. Common joinery items are usually in softwood of fairly large dimensions, with no careful selection of materials and no elaborate detailing. In furniture, hardwoods require from 10 to 20 per cent more time to work, more time to cut the smaller joints, more time to finish off; and a cabinet-door only a quarter of the size of a standard softwood door might take twice as long to make. The only practical method, therefore, is to see the work as a whole and attempt an assessment of the hours required to make it in terms of one man’s working time; then to itemize the various operations, i. e...

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Costs of man-hours

The total cost of man-hours at the rates paid, plus overtime rates where applicable, plus health insurance, pensions, paid holidays, etc.

have to be considered. Here again these may be added to the hourly rate, or as percentage additions to the wage total. Strictly speaking, either method is not really accurate, for most of the charges remain the same whether a man works 40 or 60 hours a week; but the percentage addition is the simplest method.

Machine costs

The cost per running hour of each machine is arrived at in accordance with the following example:

Sawbench

Initial cost 400

Estimated life 20 years, depreciation

per year 40

Interest at 15 per cent per annum 60

Annual value 100 Annual cost of maintenance and repairs 30 Annual electric power consumed 40

Annual saw replacements, sharpeni...

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Appendix: Costing and estimating

Costing is the pricing of completed work taking into account not only all the direct expenses— materials, wages and insurances, fuel and power, machining costs, workshop expenses, etc.—but also a fair proportion of the indirect expenses—salaries, office expenses, rent, rates, depreciation, interest on capital, etc.— expressed as a percentage addition to the workshop cost. Estimating is the intelligent anticipation of what the total cost is likely to be, and as such must have a basis of actual costing experience. In other words good estimating is the product of sound judgment and careful appraisal of the amount of labour involved in the proposed work, in the light of past experience of other comparable work.

In costing and estimating for quantity production the work can be broken do...

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WOOD STAINS

These rightly require a complete textbook devoted to their manipulation, and therefore only general observations are possible here. Of the three categories, water, spirit/alcohol and oil, the water stains are most troublesome to apply but penetrate fairly deeply and yield the clearest finishes; they are therefore firm favourites with the hand-worker. The old tried recipes are still viable, i. e. Vandyke brown crystals dissolved in hot water with a little 0.880 ammonia to bite into the wood and a teaspoonful of household detergent to break down surface tensions; mahogany crystals for red staining, water black aniline dye and
potassium bichromate...

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Dulling methods

Contemporary finishes usually call for an egg­shell, matt or semi-matt surface in preference to a choked-grain full gloss. Most lacquers are available either as full gloss (burnishing lacquers), matt or semi-matt finishes, the matt appearance being obtained by incorporating silex powder of other additives to scatter the light. These matt finishes do, of course, cloud the wood to some degree, and in fact all dulled surfaces cannot be expected to show the clarity of a high gloss which acts as both mirror and magnifying glass. The after-dulling of gloss surfaces for an egg-shell gloss effect can also be done with finest grade steel wool, which must be skilfully applied to be effective, or with french – polishers’ pumice and petrol/gasoline...

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Synthetic lacquers

These include cold acid catalyst, polyurethane and polyester lacquers, all of which have greatly increased heat, water and spirit resistance, tough films and high gloss, particularly the latter which is extensively used for wireless and television cabinets as there is little if any sinkage, and the gloss is comparable with a vitriol (German) piano finish. Polyester lacquers are, however, unsuitable for small turnovers, for they require dual-feed sprays for intimate dispersal of the catalyst hardener throughout the lacquer, and the resin-dust in surfacing can be an industrial hazard if suitable precautions are not taken.

Acid catalyst lacquers

Originally phenolic resins were used, but modern formulas include urea formaldehyde, melamine and epoxy resins with alkyd plasticizers for increased ...

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French polish

This is a specialist craft and should not be attempted without proper training, for the whole secret lies in the minimum and not the maximum amount of polish applied for a full gloss, and thick coats unskilfully applied are no better than cheap varnish. It is often said that a good french-polisher is born and not made, and that not only can he equalize the colours of mixed woods but can actually make some pieces appear lighter by regulating the thickness of polish and therefore the refractive index. Commercial brands of polish incorporate various gums and synthetics for quick drying and build up...

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Wood finishing

The craft of staining, matching, hand and spray finishing is highly specialized and forms a separate trade; the following notes are therefore for general guidance only, and the reader is referred to the standard textbooks on the subject.

GENERAL NOTE

Furniture in general use must be polished to seal the pores of the wood, protect the surfaces, accentuate and enhance the beauty of the figure, create highlights and provide as much resistance against heat or spilt liquids as possible. Earliest polishing materials dating back to the time of the Pharaohs were probably nut, poppy and linseed oils, gums, resins, etc., and it was not until 1820 that the familiar french polish was introduced into England from France...

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Surface damage

Slight bruising of surfaces where the actual fibres are not fractured can often be lifted by the repeated application of a heated iron tip through a wet cloth, creating sufficient steam to swell the fibres up. Bruises in bare wood can also be lifted by flooding the bruise with methylated spirit and setting fire to it, but the wood must not be scorched. There is no guarantee that the bruises will be eradicated entirely, for much depends on the elasticity of the wood fibres and their ability to recover, but it is always worth a trial. Deeper scratches, dents and bad bruising will have to be cut out and plugged with wood or filled with hard stoppers, plastic wood, etc. coloured to match the finished work...

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DRAWER REPAIRS

Wear is inevitable in all moving parts, and drawers and drawer runners may require extensive renovation, especially if the drawer sides and runners are of soft pine. Figure 542:2 shows a typical old drawer with missing cock beads, dovetails loose, drawer sides worn and solid bottom split and shrunk out of its groove. The sides will have to be cut back (542:3, 4) and fresh pieces glued on. Solid bottoms which have split can be shot and reglued, with the joint toped with glued coarse canvas if necessary, and the width extended with a new piece to take the slotted screws. Loose dovetails will have to be knocked apart and reglued...

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