slotting width vs depth when profiling
Recently I've had to make some very long slots in SS sheet metal to cut out some shapes (in this case, T-shaped brackets, but it could be some random shape in general). The sheet metal was .090, and I started by trying a 4flute 1/8 end mill, but I found out pretty soon that it was eating up endmills pretty fast, probably due to poor chip clearance. Cutting the profile in multiple passes didn't seem to help that much. At his time, I was using mist coolant, but maybe next time I will try flood.
This kind of got me wondering, suppose you need to cut a slot of depth "x" in order to cut out a shape, and so the width of the slot doesn't matter. What should be the diameter of the end mill you should use? It seems that if you use a bigger end mill, it's effectively a less deep slot (as a fraction of it's width) and so the chip clearance issue is less severe.
Use a cutter with less teeth - preferably two - as it assists in chip removal. Also climb mill where possible.
I asked the guy at the place where I buy tools, and he said that the "4 flute for SS" rule overrides the "less flutes for slotting" rule.
Also, when I said profile, I didn't mean that I was just trimming along the outside, I mean that I had to cut a profile, i.e. specific shape. So in this case, there is no climb milling, as it is slotting all the way around ,although I put the climb side of the cut towards the piece.
I did try a 3 flute, and it was even worse
Last edited by beanbag; 05-01-2010 at 08:20 PM.
Slotting is just plain hard on a end mill. It is basically tool rub every revolution vs a climb cut when a nice bite gets made.
Use coolant, slow down a bit on rpm.
Could you have band sawed it close to profile.
One of the reasons for 2 flute is so that the 3rd or 4th flute does not deflect the endmill causing the next flute to bite deeper into the metal, makes a more accurate and more chatter free cut.
With metal that thin, Id wonder more about support/clamping while cutting. Chatter is not conductive to long tool life, and thin sheets are hard to support well and keep the helix from pulling up. a low helix endmill might help.. And then theres reverse helix endmills, but I have no idea how you are supposed to support the work to use those.
In the end, I did a bit of bandsawing, but there were some concave sections that were difficult to get to.