ROl TUMBLE ENGINEERING 83 



touch this punch mark, ami yuu will have one of the exact 



centers. 



Now, turn the engine over till it nears the other center, 

 and proceed exactly as before, remembering always to 

 place the straight end of tram exactly in same place in 

 block, and you will find botl renters as accurately 



! all the fine tools of an engine builder. 

 i arc now ready to proceed with the setting of your 

 id as you have both dead centers to work from, 

 > be able to do it, as you do not have to de- 

 pend on your eye to find them, and by the use of the tram 

 nrn your engine to exactly the same point every time 



to get a center. 



Remove the cap on the steam chest, place your engine 

 cad center and give your valve the necessary amount 

 of lead on the steam end. Now .e already stated 



\ve could not give you the proper amount of lead for 

 an engine. It is presumed that the maker of your en- 

 gine knew the amount best adapted to this engine, and 

 can ascertain his idea of this by first allowing, we 

 say, about one-sixteenth of an inch. Next bring 

 engine to the other center, and if the other end has 

 :han one-sixteenth, then you must conclude that he 

 :ded to allow less than one-sixteenth, but should it 

 more than this, it is evident that he intended more 

 than one-sixteenth lead; but in either case you must ad- 

 've so as to divide the space, in order to secure 



