There are two general types of hollow concrete block machines on the market - those with a vertical face and those with a horizontal face. In making blocks with the vertical-faced machine, the face of the block is in a vertical position when moulded, and is simply lifted from the machine on its base-plate. The horizontal-faced (or face-down) block is made with the face down, the face-plate forming the bottom of the mould. The cores are withdrawn horizontally, or the mould is turned over and the core is taken out vertically; the block is then ready for removal. The principal difference in the two types of machine, is that, if it is desired to put a special facing on the block, it is more convenient to do it with a horizontal-faced machine. With the vertical-faced machine, the special facing is put on by the use of a parting plate. When the parting plate is removed, the two mixtures of concrete are bonded together by tamping the coarser material into the facing mixture.

Fig. 149 shows a Hercules machine. The foundation parts can be attached for making any length of block up to 6 feet. The illustration shows two moulds of different lengths attached. These machines are constructed of iron and steel, except that the pallets (the plates on which the blocks are taken from the machine) may be either wood or steel. This type of machine is the horizontal or facedown machine.

Another machine of the face-down type is shown in Fig. 150. This machine, the Ideal, is simple in construction and operation; they are portable, which makes them convenient to operate. In making blocks with this machine, the cores are removed by means of a lever, while the block is in the position in which it was made. The mould and block are then turned over, and the face- and end-plates are released, and the block removed on the pallet.

In Fig. 151 are shown a group of the various forms which may be made. The figure also illustrates the facility with which concrete may be utilized for ornamental as well as structural purposes.

Cement Brick Machines. Fig. 152 shows a machine for making cement brick. Ten bricks, 2 3/8 by 3 7/8 by 8 inches, are made at one operation. By using a machine in which the bricks are made on the side, a wetter mixture of concrete can be used than if they are made on the edge. The concrete usually consists of a mixture of 1 part Portland Cement and 4 parts sand. The curing of these bricks is the same as that for concrete blocks. In making these bricks, a number of wooden pallets are required, as the brick should not be removed from the pallet until the concrete has set.