VI. MACHINERY. 407 



2074. Model of Parallel Motion, consisting of three parts 

 only, which owing to the relative positions of the fixed centres and 

 joints is not liable to lateral deviation in practice. 



William Hayden. 



2075. Parallel Motion ; invented by the late Richard Roberts, 

 C.E., Manchester ; the peculiarity consists in the fixed centres 

 being in the plane of the parallelism. 



The Committee, Royal Museum, Peel Park, Salford. 



2076. McKay's patent Equilibrium Drilling Tools, with 

 specimens of work. Menzies Blagburn. 



This apparatus is designed to permit circular holes of any size to be bored 

 out Avith mathematical accuracy and absolute precision as to tbeir relative 

 positions. 



This object is attained by maintaining the centre point, around which the 

 cutters revolve, immovably fixed during tbe process of boring, while 1he 

 cutters are advanced, and are held in equilibrium with tbe centre points by a 

 hydraulic medium contained within tbe chambers of the tool, the pressure 

 being conveyed by the action of the feed given to the boring machine. 



This apparatus is exhibited for the purpose of showing how accurate work 

 can be obtained with a minimum of skilled labour and cost. 



2O76a. Isometric Drawing of an Expanding Mandril, 



or tool for fixing the tubes in the plates of boilers by expanding 

 the ends so that the tubes are firmly fixed in their places. 



W. H. Prosser. 



Invented and made by the late Richard Prosser of Birmingham in 1845. 

 Two of these expanders were sent to the United States in 1847 ; an im- 

 provement on them is now being imported from that country. 



2077. Bates' Anaglyptograph. Machine for producing 

 drawings or etchings in relief from models, coins, medals, &c. 



George Hogarth Makins. 



The machine consists of two portions : The first a solidly framed oblong 

 base, in which is fixed a long double screw, right-handed at one and left- 

 handed at the other half, and of 20 threads per inch ; rotation of this gives 

 opposite motion to two tables, upon the front one of which the object to be 

 copied is fixed, and upon the other the plate to receive the etching or draw- 

 ing. At the winch end of the screw is fixed a wheel cut with 100 teeth, and 

 also a stop arrangement by which any number of the teeth can be taken, and 

 thus equal partial turns given to the screw. 



The second portion of the machine is a framed apparatus carrying the 

 tracing and etching points. This is provided with wheels for travelling 

 across the base, and a groove is formed in the latter for their direction. The 

 tracing point is attached to a bar which in rising does so at an angle of 45. 

 In the centre of the bar is a piece which, being between friction wheels 

 attached to the diamond or etching point frame, will, as the bar rises by pass- 

 ing over any elevation in the object, cause the diamond frame to move at 

 right angles to the motion of the machine, and thus the line forming is curved 

 or waved just in proportion to the height of the elevation passed over; hence 

 the appearance of relief given to the etching. 



