When square heads are used, judgment must be used in tightening the bolts which held the knives. They should not be drawn so tight that the bolt is strained and weakened. The average man with a regular wrench exerts a force of 1600 times the diameter of the bolt. Square heads should never be used for flat surfaces at high speeds. Use Good Bolts.
Alloy steel makes the safest and best bolts for square heads.
They should be of the same size and weight so they will be balanced. They should not touch the bottom. Many accidents have resulted from this cause. The workman thinks he has the knife held firmly to its place, but the pressure is at the end of the bolt and not at the head. If there is a minute space between the knife and head, shavings will drive under and break the strongest bolt that can be made.