70 FOREST UTILIZATION 



2. Do not try to fix a tooth fully at one time. 



Treat it gradually at five or six revolu- 

 tions of the saw. 



3. Proper speed for emery wheels at the rim 



is 4,500 feet per minute. 



4. After gumming remove the irregularities at 



the edges with a side file, since cracks in 

 saw are apt to start from them. 



5. Hammering becomes necessary when the 



use of emery wheels has caused the saw 



to expand ("let down") at the rim. 

 For small mills gumming with a file or a 



butt gammer is preferable to the use of 



emery wheel. 

 Soft wood requires more set or spread and 



less pitch than hard wood. 

 Swaging is also called upsetting or spread 



setting, 

 (g) Inserted tooth circular saws. 



1. The insertion into each socket of the rim 



consists of a holder and of a chisel point. 

 These points are extremely hard; still 

 they can be filed an<f swaged with the 

 help of specially constructed files. It 

 does not pay, however, to spend much 

 time in filing since new points are cheap, 

 and since they are readily inserted with 

 the help of a special wrench. 



Points are oiled before being inserted. 



When renewing one individual point be 

 sure to have it dressed down to corre- 

 spond to the line of old points. 



If the saw guide is not properly adjusted 

 it may touch the holder and smash the 

 saw. 



2. Advantages of inserted tooth saw are : 

 Less experience is required for dressing a 



saw. 



Less filing and gumming. 



Less saw repairs in backwoods. 



Diameter of saw remains unchanged dur- 

 ing its use. 



3. Disadvantages of inserted tooth saw are: 

 The saw kerf is very heavy. 



The teeth are large and hence few, so that 

 feed must be comparatively slow. 



The price of the inserted tooth saw is 

 higher than that of the solid tooth saw. 



