One of the important possibilities of this process is in the repairing of defective castings fresh from the foundry. Even in the most careful foundry practice the scrap heap is always a very expensive mountain to the foundryman. If he can keep down the heap he can increase his profits. With the oxy-acetylene flame all kinds of defects of castings can be repaired. Broken pieces can be put together an imperfect pieces built up and repaired. As with other repair work, a preheating torch or furnace would be needed for pieces of any size, even though they were of low-carbon steel. After the acetylene flame had done its work, an annealing furnace would be necessary. Both the oxy-acetylene process and the thermit process (see page 121) offer a solution for the economical reduction of the scrap heap.

Fig. 56. - Welded aluminum engine bed.

But there is one serious limitation to the possibility of using the oxy-acetylene flame or thermit to repair a new casting. Such a casting cannot honestly be called new. The repair may make it stronger than a perfect piece, but the fact remains that it is a repaired piece. The foundryman may or may not tell his customer what he is selling him, according to his standard of honesty. It may be difficult to convince that customer that he is getting a first-class article and should pay full price for it. Many customers would not accept it under any sort of guarantee. Again, it might be equally damaging to the foundryman if it became known that he sold as perfect castings which had to be repaired, if he did so without telling the customer. Again, it is poor practice for the printer, the potter, the foundryman, etc., to accept knockdown prices for a doubtful product, and so admit its inferiority.

Fig. 57. - Welded auto frame. Weld is at the white line near the base of the steering handle.

The fact remains that this flame offers a fairly cheap way of redeeming defective castings. The founder must use his judgment in employing it.