HSS Tool Grinding---Again

[jocat54]

I have another question about grinding HSS toolbits, what is the importance of grinding the top relief? I don't grind the top relief and the bits seem to cut fine and leave a decent finish. The reason for not grinding the top relief is that I don't do it worth a flip and usually end up starting all over so I just quit doing it and things seem okay. I know I am missing something here.

 

[GK1918]

Without more info, my wild guess would be it depends on the tool holder. If I remember
they will produce this rake around 16 degress thereabouts. Thats if you are using
the origional lantern tool post, then there are holders that have -0- rake. I know
when I grind them a little backwards of the normal,I grind this rake first then the sides
that way the point that does the cutting is sharp. Most do the sides then the top,
thats where I used to mess up usually ruining where its spose to be sharp. So my bet
is you are using them Armstrong William many more with a built in rake, but when
treading you will have to grind the top flat to get rid of this built in rake.
Makes sense to me. I dont use lanterns any more I gave all that stuff to my shaper.

 

[DMS]

Depends on what you are cutting. With brass and cast iron you don't want top or side rake, the tool cuts with more of a scraping action. Aluminum and plastics tend to give a better finish with more rake. Steel is a compromise between a good finish and an edge that holds up. I would say, if it works for you, and you get a decent finish, don't sweat it.