Il6 SCIENCE OF SUCCESSFUL THRESHING 



hammer, and with light blows bead the tube all around, 

 moving the tool slightly at each blow. The beading tool 

 may be used when there is water in the boiler, but care 

 must be taken to use only very light blows of the hammer 

 or the concussion will be transmitted by the water and 

 loosen other tubes. Having water in the boiler when 

 beading the tubes has the advantage of showing the leaks 

 so that it may be known when the tube is tight. If the 

 leaks be more serious, it will be necessary to use an ex- 

 pander. The expander requires considerable care and 

 some experience to use, and in the hands of an inexper- 

 ienced or careless workman, may cause great damage 

 by distorting the flue sheet, or rolling the tubes thin and 

 worthless. In using the roller expander, place the flange 

 against the tube sheet and drive the pin in with a few light 

 blows. Then turn it back and forth with a wrench until 

 it loosens. Drive the pin in again, and repeat the opera- 

 tion several times. The roller expander may be used when 

 there is water in the boiler. If a spring or plug expander 

 be used, be sure that it is the right size, and is made to fit 

 the thickness of the flue sheet in your boiler. This is very 

 important. To use the spring expander, place it within 

 the tube with the shoulder well up against the tube sheet. 

 Drive in the taper pin with a few light blows and then 

 jar it out by striking it on the side. Repeat several times, 

 turning the expander a little each time, until it has made a 

 complete revolution. The spring expander cannot be used 



