This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Fig. 14. Common Five-Knuckled Loose-Pin Butt.
Fig. 15. Steel Washer for Butt.
Fig. 16. Ball Bearings for Butt.
The protection against wearing of the knuckles may be by ball bearings, as above shown (Fig. 16), or, as in the more general practice, by bushings consisting of thin steel plates (as shown by the stippled part in Fig. 17) set in each face of each knuckle so that they receive all the wear and relieve the softer metal. In these plates are slight indentations (not stippled) which hold oil for an indefinite period. This oil lubricates the bearings. Often the - knuckles are bored out, and a steel cylinder inserted as a bushing.
When it is advisable to use real bronze for butts, expense should not be spared to get the best from a mechanical standpoint. It is always a safe rule to get the cheaper material with perfect workmanship, rather than expensive material of indifferent workmanship.
Fig. 17. Steel Plate Bushing Used between Butt Knuckles.
This does not add to the distinctness of the design, and only leaves the impression of a "well-broken" surface. It will be noted that, in general, the plainer the butt, the higher the price, and the highest grades of butts are rarely of the ornamental variety.
There is little ornamental value in the knuckles of a butt. A butt should, therefore, be of such a size as to project as little as possible beyond the door or frame. The only point to be carefully seen to, is that it shall extend outward far enough to throw the door clear of the trim or woodwork at the side. Thus the projection at a, Fig. I8, should be a trifle more than one-half the distance b, in order to carry the door, when opened back, clear of the side trim.
After the decision relative to the style of hinges or butts to be used is made, the closest attention should be given to the mechanism. A door in common use will wear its hinges with astonishing rapidity. Three hinges should always be used on a door. The third hinge, or the one at half the height, keeps the door from springing, and relieves the strain on the other two, so that the door is more easily operated; and it also gives 50 per cent additional wearing resistance.
The same reason for using loose-pin butts as above given for doors, apply to the hanging of all items swinging on upright bearings - such as cupboard doors, window-sash, etc.; and it is sometimes necessary to use much care in the selection, in order that the swinging parts may turn clear of all obstructions or fold back on themselves, as with inside blinds.
Where the swing is from horizontal bearings, the pins should always be fixed - that is, so made that they cannot be removed. In an upright position gravity holds them in place; but when put horizontally, the swinging of the sash works the pin loose, and in time it is apt to fall out and allow the sash to drop, this being the case particularly in swinging transom sash.
Besides the types of butts above referred to, there are many appliances properly classed under this head designed for special service, such as spring butts and double-acting butts.
Fig. 19. Cheap Type of Spring Butt.
Spring Butts. Spring butts are those in which a spring is placed so as to force the door closed when not held open by some other force.
These vary from the light type commonly used on wire-screen doors, costing from 10 to 15 cents a pair (Fig. 19), to heavy bronze butts with a high-grade metal spring in the joint, costing $5.00 a pair (Fig. 20), which can be regulated to give either a strong or a light reaction.
The disadvantages of this type are that they rack the door by constant slamming; they are much more expensive than butts of the same material without the spring; and when once installed, it is practically impossible to throw the spring out of service. For the light and cheaper work, a single spiral spring (Fig. 21), costing from 15 to 25 cents, can be used independently of the butt; it is easily unhooked when not needed.
Fig. 20. Heavy Bronze Spring Butt.
Fig. 21. Common Type of Spiral Spring for Doors.
Double=Acting Butts. The function of the double-acting butt is to allow the door to swing to both sides of the jamb. It is necessarily of the spring-butt type, above mentioned, but is double and is so set as to leave the door shut when at rest. There are no cheap types of this butt on the market, and the work required makes the best mechanism necessary. There are no appliances which can be substituted as in the case of simple single-spring hinges. In order to do the work satisfactorily, a very large hinge is required - too large to be ornamental - so that certain types are embedded in the'floor, out of sight; these are peculiarly adapted to heavy doors when the floors are of Mosaic so that the hinge can be firmly bedded in concrete.