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R8 or 40 International taper?

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  • R8 or 40 International taper?

    Has anyone any views on which is best for a workshop doing mainly hobby stuff like building IC engines but occasionally doing farm jobs? I have decided to update my ancient vertical mill with MT3 spindle nose and have more or less narrowed the possibilities down to a very tidy 1999 Rambo (?) variable speed turret mill with DRO, power to x axis and knee, but with 3hp motor and R8 spindle, OR Excell Pinnacle turret mill, slightly less pristine but with 2 axis DRO, power to x, 5hp motor and 40 Int spindle, slightly dearer by £300 delivered. Both are around the £4000 mark delivered. Do I go for extremely tidy but with R8, or slightly less tidy but £300 more and with 40 Int? Any advice gratefully accepted! John.

  • #2
    My vote is for R8. I have been running full size CNC mills with R8 since 2001. The R8 tooling is cheap and plentiful, with lots of variety. I use mine every day as a business and I don't feel restricted in terms of metal removal rates. My mills are Bridgeport type heads with 3 hp motor.

    The 5 hp 40 taper will allow higher metal removal rates, but that is usually only a concern when running long run production on larger parts. MRR is a function of hp. When you go up in hp, you have to have everything else beefier to match.

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    • #3
      I'd go with the 40 taper! It's the most commony used size in industry and is common over here. It has better capacity when removing a lot of metal in a manual machine. R8 might be ok for endmills up to 20mm, but a decent size shell or face mill works much better in a 40 taper machine.
      Location- Rugby, Warwickshire. UK

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      • #4
        TBH I would go with 40 taper if you have a choice and a higher HP machine. New holders cost more than R8. But you will find a LOT of used 40 tooling for cheep and a lot less home shop competition. Check the used holders prices in your area.

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        • #5
          Think of the R8 as being slightly more convenient than your MT3, certainly tooling is easier to get. The 40 taper is a step up in power which you may not need, it is the most common production size, but the mills usually are bigger. I suppose it boils down how you value your time.

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          • #6
            Thanks everyone, but I'm still in a quandary! One of my concerns with R8 was the lack of driving dogs, all the torque being transmitted by the tightness of the taper. That presumably was the problem at some point in the past with my old MT3 machine, as the socket in the spindle is worn to the point of being inaccurate. Tooling isn't really an issue with either machine - I have a full set of ER32 collets and either machine can come with an ER32 collet chuck as part of the deal. I think I can get a Clarkson chuck thrown in with either too, and I have Imperial and metric collets for that too. One thing I've used a lot in the past is my boring head, but I think I'll be able to get either shank for it. That was one reason I was leaning towards 40 Int with its positive drive, as amongst other things I have bored 80 mm holes in steel when making a new stub axle for a farm implement.

            However, reading your comments it sounds as if, provided I'm happy to take my time - which I am - the R8 may be the one to go for, being the tidier of the two and slightly cheaper. Presumably the taper doesn't slip if the drawbar is tightened enough? Old Mart, anything is an improvement on my old lady, not least because I sometimes have to hit the drawbar so hard to release the tool that I worry about the spindle bearings!

            Thank you all for the input! John.

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            • #7
              The 40 taper lets you swap tools and not lose your Z height.

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              • #8
                Originally posted by John Fearnley View Post
                Thanks everyone, but I'm still in a quandary! One of my concerns with R8 was the lack of driving dogs, all the torque being transmitted by the tightness of the taper. That presumably was the problem at some point in the past with my old MT3 machine, a.
                thats the difference of a draw bar, no draw bar holding it in place. I'd go 40, more rigid. R8 is cheaper and more commonly available. My XLO was made with R8 or 40 and more than once I've thought of swapping it out next time I saw a 40.....but I've just so much R8 stuff. I've got a mill with 40 and other with 30 tapers and both are imo superior to R8 for robust holding power. my 40 has dogs btw
                .

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                • #9
                  rambaudi come in 40 and 50 taper, the 40 is an impressive mill, though if space permits, 50 taper is nice
                  Mark

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                  • #10
                    If your main goal is to hold the majority of the tooling with stubs in an ER32 collet I'd say that you'll be fine with an R-8. But if you'll have a variety of large shell mills, face mills and bore big holes like 80mm on a regular basis then the 40 taper could be a better option.
                    Chilliwack BC, Canada

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                    • #11
                      If you work your home machine as hard as I work mine, Get the cleaner machine and do with the R8 as thousands of others do.

                      That is, unless you just enjoy "big Iron", and I do! ;-)

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                      • #12
                        40 taper tooling secondhand seems to be cheaper in the UK than R8 - I would guess because industry buys new and hobbyists are after the R8, it being more common on "hobby size" mills - my Test 2U has 40 taper and used tooling has saved me more than I paid for the mill so far, as well as being heftier...
                        Like R8, there are several drawbar threads in use, M16, 5/6 Whit, 5/8 and 1/2 UNC...

                        Dave H. (the other one)
                        Rules are for the obedience of fools, and the guidance of wise men.

                        Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

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                        • #13
                          2 questions.
                          1. What brand is the old MT3 mill and whats wrong with it?
                          2. Whereabouts in Norfolk?
                          Thats actually 3 questions.
                          Regards,
                          ex Norfolk emigree.

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                          • #14
                            Go with the 40. Both would probably work great for you but seeing as how you're starting fresh and need tooling anyway, go for the bigger one. Unless of course the difference in quality, function and condition of the rest of the machine is a deal breaker.

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                            • #15
                              If your mill uses 40, get 40, if it uses R8, get R8. Everything I do is manual in a home shop environment, so R8 is perfectly fine for me. If I was to get an industrial CNC mill, without a doubt, 40 taper.

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