1842.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



373 



the works of tlie ancients and moderns was extensive, and he was so feelingly 

 alive to pro|iortion of parts and the effects of light and shade, and of contrast 

 and barmony in colour, that he was continually studying the difterent parts 

 of his buildings up to the moment of their completion, not being satisfied 

 until he had tried every modification which could tend to improve them. 

 Mr. Goldicutt published some ^^ews in Rome, and a series of etchings of 

 views in Italy and Sicily. He was the author of an elegant work on the 

 paintings in the Pompeian buildings, and of ^n interesting small volume in 

 illustration of Ileriot's Hospital at Edinburgh, the plates of which he etched 

 bimself. 



He has left a widow and 5 sons to lament his irreparable loss, and lies 

 buried in the New Cemetery at Kensal Green. The death of such an artist 

 is a loss to bis family, to his friends, and the public. Mr. Goldicutt was 

 Surveyor for the District of St. Clement's Danes, and St. Mary le Strand, and 

 one of the Justices and Commissioners of Sewers for Westminster and Mid- 

 dlesex. 



PATENT GUIDE SCREW STOCK, 

 Manufactured by Joseph Whitworth & Co. of Uonchesler 



A. the top plate, fastened Ly screws, a, a, n. B, a stationary die. C, C. 

 moving dies. D, a sliding piece with inclined sides for moving the dies. E, a 

 nut for drawing up the piece D. 



The guide stock is entirely new in principle, and will cut a screw scarcely 

 inferior to that obtained in a slide lathe from a true guide. The name,has 

 been chosen from this circumstance, as expressing the peculiar feature^of the 

 invention. The thread produced is not only true and of the exact pitch 

 required, but perfectly formed throughout, being cut clean without distortion 

 of the metal. 



Iq all these respects the advantage of the guide over the common stock is 

 remarkable. The latter, it is well known, will not cut a screw in any degree 

 perfect. The thread, besides being irregular, is never of the right pitch. It 

 is also more or less swollen by the violence done to the metal, so that the 

 diameter of the screw is often considerably greater than that of the blank 

 shaft on which it is cut. These defects are attended with the most serious 

 practical inconvenience. They often render it extremely ditlicult to obtain a 

 fit between the screw and nut, and consequently occasion a considerable 

 sacrifice of time and labour. They necessarily impair, in a very great degree, 

 the efficiency of the screw bolt, which cannot possess either the strength or 

 mechanical power which it would have if the thread were cut true and clean. 

 The defects in question are variously modified according to the size of the 

 master tap used in cutting the dies. If they have been cut by a master tap 

 double the depth of the thread larger in diameter than the shaft to be 

 screwed, they will act very well at first, and the thread will he started true ; 

 but as the operation proceeds, they become altogether unsteady and uncertain 

 in their action. If, on the other hand, they have been cut by a master tap 

 of the same size as the shaft to be screwed, the thread is made untrue in its 



origin. They first touch the shaft 

 only on the extreme points of their 

 outer edges, as shown in the annexed 

 sketch. They have neither sufficient 

 guide, nor steady abutment, till the 

 operation is on the point of being 

 completed. It is not unusual to em- 

 ploy a master tap of an intermediate 

 s/ze. In this case, however, it is ob- 



vious, the dies will combine, in a modified degree, the defects peculiar to 

 each of the cases before mentioned. 



In the guide stock this perplexity is entirely obviated, and the dies act 

 with full advantage from the commencement of the operation to its conclu- 

 sion. They are cut by a master tap double the depth of the thread larger in 

 diameter than the screw blank; while their general form, and the direction 

 in which they are moved forward, are such as to preserve their cutting power 

 and steadiness of action undiminished to the full depth of the thread. 



The plan of the guide stock will be easily understood from the sketch 

 prefixed. The interior of the stock is shown in dotted lines through the top 

 plate A. B is a stationary die ; C C arc moving dies, brought up by a piece 

 D, sliding in a recess in the stock, and bearing with a distinct incline against 

 the back of each die. The piece D is drawn up by a nut E, on the outside 

 of the stock. 



The dies having been cut by a full-sized master tap, as before mentioned, 

 the curve made by their outer edges is that of the blank shaft they are in- 

 tended to screw. Hence in starting the thread, they bear at all points of 

 the common curve, and the impression made by indentation is the exact copy 

 of the thread of the die. The parts indented serve as a steady guide to the 

 dies in cutting round the blank shaft. A groove in the stationary die facili- 

 tates the operation. Four cutting edges are brought into action at points of 

 the circumference nearly equidistant, so that by little more than a quarter 

 turn the thread is completely started round the shaft. The difficulty involved 

 in the operation by the common stock is entirely removed. 



After starting the thread, the stationary die serves principally as a guide 

 and abutment for the others. The moving dies are peculiar in their form 

 and direction, both peculiarities depending on the position of the arc in the 

 shank of the die. The tn o sides have each a different inclination to the arc. 

 As the dies move forward, one side becomes prominent towards the screw 

 shaft, and its cutting edge continues in contact with the thread, till it is 

 formed to the full depth required. The prominent sides of the moving dies 

 are those turned towards each other. 



The direction of the common die is necessarily towards the axis of the 

 screw shaft. In the guide stock the direction of the moving dies is that of 

 two planes, meeting beyond the centre of the stock, in a line parallel to the 

 a.xis of the screw shaft, and considerably behind it. This direction is deter- 

 mined by reference to the change which takes place in the relative position 

 of the screw shaft, as the thread is cut deeper. One of the three dies being 

 stationary, there must necessarily be a constant change in the position of 

 the screw shaft in relation to the two others, the ttfect of which, if not coun- 

 teracted, would be to deprive the cutting edges of the requisite prominence. 

 By giving them the direction before mentioned, the proper degree of promi- 

 nence is secured, notwithstanding the change of position. The latter, when 

 combined with the eccentricity of the dies, so far from being any impediment 

 to their action, materially assists it. The neniy formed thread is thereby 

 kept in contact with the dies for some distance behind their cutting edges, 

 affording them the same kind of support throughout the operation which 

 they have at its commencement, when, as before observed, the curve made 

 by their outer edges is coincident with that of the screw blank. This con- 

 tinued support, which is necessary to steady their action, could not he ob- 

 tained without a change in the position of the screw shaft. They would 

 otherwise acquire too much clearance, as they form the thread deeper, and 

 their cutting edges would be apt to dig. 



The steadiness of the guide stock, and its easy action in screwing, are 

 equally remarkable. In using it, not one half the force consumed by the 

 common stock is required. The inner edges of the moving dies (which 

 principally act in cutting out the metal,) are filed oft" to an acute angle. This 

 enables them to cut with extreme ease, and without in any degree distorting 

 the thread, while they take off shavings similar to those cut in a lathe. Their 

 action in cutting is in effect the same as that of a chasing tool, to which they 

 bear an obvious resemblance in form. They may aha be sharpened or. a 

 grindstone in the same manner. 



A practical difficulty has hitherto attended the use of the screw stock, 

 arising from the wear of the taps and dies. The tap becomes less in diameter 

 and consequently taps the hole too small, while the opposite effect takes 

 place with the dies, which, being unable to cut a full-sized thread, leave the 

 screw too large. The only mode of counteracting this two-fold error, so as 

 to obtain a fit between the screw and nut, is by forcing the dies forward, fill 

 they have reduced the diameter of the screw a proportionate quantity. From 

 what has been before observed, it is evident that this cannot be done in the 

 case of common dies without injury to the thread. In using the guide stock, 

 on the contrary, it is attended with no disadvantage. Lest the diiiaeter of 



