Sentence:  These are all the shoulders that will be necessary, unless when the reversing motion is used, and in that case, two more square or polygonal parts "w w", must be formed for the external ratchet-wheels N and O to be fixed upon, and these wheels may be secured in their places by the washers "x x", which may be screwed on, or, what is better, be made secure by <WSD>crosswedge</WSD>-keys driven through them, as shewn in the figure. 
Meaning of the word marked with <WSD> tags:  A wedge that is driven crosswise.