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  • R 8

    What the upper and lower limits on the size of end mills that an R8 shank can go?

    I am getting a bigger mill and would like to know from peoples experiences of what is the true limits, not just the book.

    Many thanks,


  • #2

    Try to get a mill with a NT-40 or NT-50 or NSK-63 taper these are the three best from least to most desireable. You are unlikely to find an non-CNC mill with NSK-63 But I mention it in passing for your own eludication.

    Even an NT-30 machine is preferable to an R-8. NT40 & 50 is easy to get tooling for and there is almost no size limits - horsepower becomes your limiting factor. As such most machines with these spindles normally sport a 7 HP variable speed spindle or larger.

    On a Standard Bridgeport the largest facemill you should use is a 3" positive geometry & rake 4 insert facemill or a 1.5" triple insert (positive geometry & rake) endmill. This is really pushing the limits of the machine (presuming a 2 hp unit)


    • #3
      Well Jerry thats a good one,you can get endmills with a 3/4" reduced shank up to about 1-1/2" diameter maybe even 2",but you then begin to find the machines limits quickly,In a full sized b-port mill,cutting steel,I typically run no more than a 3/4 diameter endmill,but with light cuts I have run the 1-1/2"diameter,hp wise you can run fly cutters up to 3" and face mills up to 4" but thats pushing it.On aluminum you can go bigger.But beyond that its really starting to run up on rigidity,B-ports are pretty flexible,a bed type is more ridgid,but also more expensive.You can get a b-port type mill with a NT-30 or NT-40,but whats the point if the machine isn't rigid enough to run a cutter bigger than the R-8 can handle.You can however sometimes get a deal on a used b-port with the bigger taper because the R-8 spindle is more sought after.
      I just need one more tool,just one!