536 REPORT—1896. 
(a and b) ; a temporary rivet or bolt is put through the hole c, and the 
ends intended to receive the half-nut device are clamped together as 
shown. A hole of the diameter of the core is then drilled across the two 
FIG. 7. 
bars at d, so that each bar receives one half of it. The clamp is then 
unscrewed, the bars are slightly separated, the tap is inserted between 
them, and the clamp screw tightened again gently. Of course now the 
two steel bars cannot meet, being prevented by the insertion of the tap. 
But the smooth end of the tap is now fixed in a chuck on a lathe, and is 
rotated forwards and backwards, while the clamp screw is tightened from 
time to time. This is carried on till the threads forming the half-nuts 
are complete. It is only necessary towards the end of the operation to 
separate the bars once or twice for the purpose of removing the bur 
which is raised by the operation. 
APPENDIX III. 
Working Dimensions in Millimetres and Thousandths of an Inch. 
By A. Le Neve Foster. 
| D ffer- 
External Diameter of | enceof Workin 
Diameter Core | Dia- Pitch Margin 
ee | meter 
ING eee oe SS ee Bs ae he, 
| | ag : 
' } | co 
mm. | inches | mm. inches mm. | mm. o-5 |; mm. mils, 
| | a 
Bar tacnsslvery a a | ue | 
0 6:0 236 48 | -189 ee 10 25-4 “O05 *002 
1 53 *209 4:22 | +166 1:08 9 28:2 *O5 ‘002 
2 47 185 S12 ay “972 81 31:4 04 *0016 
3 41 161 3°22 “127, ‘S76 73 34°8 “Ot ‘0016 
4 3°6 142 ZRE (LO "792 66 38°5 “O4 ‘0016 
5 3°2 “126 2:5 “O984 708 59 43 0 ‘03 ‘0012 
6 2:8 110 | 2:16 085 636 53 479 03 C012 
7 2°5 ‘098 1:92 ‘O76 575 48 52:9 03 ‘0012 
8 2°2 ‘O87 1°68 ‘066 ‘516 43 59:1 “02 “0008 
9 1:9 ‘O75 1:43 “0565 468 39 65:1 02 “0008 
10 i ter 067, 28 “0505 “420 35 726 ‘O02 “0008 
