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advice on a milling machine--with a different twist

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  • advice on a milling machine--with a different twist

    Hello,

    I am seriously new to both HSM and this forum. I have never personally looked at, or used, a milling machine. However, I bought a lathe several years ago and have long wanted a milling machine to go with it and do things I just can't accomplish on a lathe.

    I have looked at archived discussions on milling machines and opinions regarding used BP versus new/used Taiwan or Chinese machines, and they have been informative.

    The thing that is apparently never discussed, though, is what features/accessories/capabilities I should look for, regardless of the pedigree of the machine.

    For example, I get the impression that a machine with a 9x42 table and axis movements of 10-12" vertical and Z, with about 32-36" X is probably the spec most people would recommend. It won't do any good to ask me beforehand what I am going to use the machine for, since I really have no idea. I don't want to put out the money, only to find that I got something too small or too restrictive.

    How about DRO? Seems like not quite, but close to, a necessity. Power drive(s) for axis movement? Likely not a necessity, but how high is it on the "really want it" list? I saw a thread once that said you should avoid R8, if feasible, and go with 40 or 50 for tool mounting, as they were much more rigid and less prone to deflection. I don't exactly know what 40 and 50 mean, but have seen at least one machine with "30" versus R8. Is the difference significant for someone not operating a pay-for-hire machine shop? Again, I don't know what I might use the machine for, but it might be interesting to try milling an engine head or block--as a "for instance".

    Since I live in Albuquerque, many of the (relatively) good options for a used BP are probably not available to me. Likely, the Asian imports, whether new or used, are going to be more readily available. Other than relying on the word of the seller, what options are there for assessing the value and usefulness of a used machine? Granted, it will be somewhat difficult to go (probably) to the Los Angeles area to personally examine a machine, but if I did, what would I want to look for?

    I realize this is pretty long-winded, but I wanted to ask things that I normally don't see addressed in discussions of the merits of US versus Taiwan versus Chinese machines.

    Thanks for your help,

    JC

  • #2
    9x42 is a good size table...pretty much all the machines that size will have similar table travels. One nice thing about the Wells Index machines is they seem to have 1" more quill travel than all the others, which is advantageous for boring operations.

    Spindle taper....the R8 will be the most common. Buy a set of collets and you're ready to work with whatever round shank cutting tools you want...but you're limited to 1" diameter tools I beleive. With a CAT40 or CAT50 spindle, the toolholders are much larger and beefier, and will enable you to run large facemills will much less deflection than you'd get out of the same tool with a 1" shank or R8 shank on it. If all you'll ever do is run endmills or possibly a smaller flycutter, I wouldn't worry about it. You're probably not going to find much in the used machine market with a CAT40 or CAT50 spindle...most will be R8. I have a Tree 2UVR, which uses a quickchange system that will accept up to 3/4" tooling...while I enjoy not having to deal with a drawbar to change tools, the 3/4" max tool size kind of limits my selection when it comes to anything other than endmills. R8 tooling is cheap and available everywhere. CAT toolholders aren't cheap, but are available everywhere. If you don't see yourself running a 8" facemill to resurface cylinder heads or engine blocks, I'd probably go with the R8 for simplicity sake.

    A powerfeed on the X axis is useful for long cuts or for finishing where you need a uniform finish. A DRO is not a necessity, but is a huge timesaver. For example: Without the DRO, to drill a bolt circle in a part, I used to make a fixture to clamp the part to my rotary table, then remove the vise from the mill, bolt the rotary table to the mill, fixture the part, find center, offset the radius, and start drilling and cranking the rotab around. With a DRO, I clamp the part in the vise or next to the vise, find center, then program the bolt pattern into the DRO...and it tells me where to go to drill each hole. I recently had to learn how to use this feature of my DRO because I had a part that would not fit on my rotary table.

    I used to set up dial indicators to measure exact table movements, now I just watch the DRO. I wouldn't be without one ever again.

    Depending on how you plan on converting to 3 phase, the decision on what type of head to get is important. If you're using a VFD, then I'd get a step pulley head and simply use the VFD to adjust your speeds. If you have a rotary phase converter, then I'd look for a vari-drive head. The step pulley is going to be less problematic.
    Last edited by lbhsbz; 12-27-2012, 01:41 PM.

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    • #3
      Hi, I bought a mill knowing nothing about it, I did'nt know anything at all and had only seen a horizontal mill at the school workshop in about 1962 (but I never saw it run).

      I bought a new Asian turret mill...

      Luxcut mill by aardvark_akubra, on Flickr

      I choose an R8 spindle, I also bought a milling vise, a rotary table and a divider head (I probably didnt really need the divider head).

      It has two axis DRO so I dont know what it would be like to be without one however I do a lot of things without using the DRO or even the feed screw graduations which I suppose would be seen as poor practice.

      I made a few mistakes, I bought an ER32 collet chuck (which mounts in the R8 spindle) and use that for all milling cutters, presumably there are R8 collets chucks would have been more rigid, but I dont really know what the difference would have been.

      One of the first things I made was a power feed for the X axis.
      Last edited by The Artful Bodger; 12-27-2012, 02:02 PM.

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      • #4
        Originally posted by lbhsbz View Post
        With a CAT40 or CAT50 spindle, the toolholders are much larger and beefier,
        And much more expensive!

        Without knowing what you want to use it for makes it difficult to determine your options. Many will only use R8 tool holders, like the Clarkson because the tool will not slip out, while others (myself included) use plain R8 collets without any trouble. If you aren't doing any time sensitive "for pay" work then you probably don't need heavy duty cutters that require the Cat series holders.

        Dro's are not a necessity unless you are older with failing eyes, they are a big help then but they are a real treat to use. They make using a mill much easier and faster but don't rely on them for an absolute positioning system, at least for real accurate work. There are to many places were errors can creep in, so use them to get close, measure with your mic and then finish cut. Worth getting if the money is there.

        As for other bells and whistles like power feed, they make the use of the mill easier and faster but as stated are not a necessity. If you can afford them then get them but don't go hungry to do it.
        The shortest distance between two points is a circle of infinite diameter.

        Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

        Southwestern Ontario. Canada

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        • #5
          i have an older bridgeport 1hp , 9x42 table 19'' z x 19y x 32X with a $400 dro on it and it will do anything i want . the slow gears (30rpm ish ) are great and it has up to 3000aswell . for the $400 get a dro.... saves 200 zeros , does bolt holes and lots more . $2000-3000 would get a great mill .

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          • #6
            Originally posted by jcaldwell View Post
            It won't do any good to ask me beforehand what I am going to use the machine for, since I really have no idea. I don't want to put out the money, only to find that I got something too small or too restrictive.
            You might consider the size of your lathe as an indicator of the size mill
            you may want to look for. If your lathe is on the small side, but fulfills
            your needs, perhaps a smaller mill would be a better fit for you.
            or if your lathe is larger and you routinely utilize it's capacity, a 9x42
            may not be big enough for you.
            Being your first mill, you may want something a little smaller, and not so
            intimidating (or expensive) to learn and make mistakes on.
            After you get some experience under your belt you'll be in a better position to
            to know what you need and want. At that point you can always sell your
            starter and get something better.
            Too large a mill can bring difficulites with doing small work, as well as
            unneccessary expense.
            I cut it twice, and it's still too short!
            Scott

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            • #7
              I would absolutely go for the ISO30 spindle over anything else (MT, R8). Tooling is available, the tool is easy and quick to change and the cost is quite low as they are a lot smaller than the ISO40 or 50 spindle tooling.

              If you don't get ISO30 taper, then R8 is an option. But whatever you do, don't get a MT spindle taper, it is more headaches than use.
              Amount of experience is in direct proportion to the value of broken equipment.

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              • #8
                The R8 spindle will probably do everything you want for home use. I have run Bridgeports (R8) professionally on a daily basis since 1980 and haven't had any problems with them not being rigid enough for any job that would normally be done on a Bridgy. I have also run the big Cincinnati, Milwaukee and several other brands of machines that take 40 and 50 taper tooling. When I bought my first CNC mill in 2001 I got it with a Bridgeport type head with R8 spindle. It is manual tool change. This is a prototype rather than production machine. I am still happy with this choice. For a production machine with automatic toolchanger I would get a 40 taper.
                The R8 tooling is cheap, small and lightweight. It is a common size. I am running the whole shop based on R8 and 5C (lathe and mill fixtures) with some ER collet sets that have R8 or 5C shanks.
                Kansas City area

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                • #9
                  A DRO falls under the heading of "very desirable".

                  I have an itty bitty mill (4x10) and a mid sized knee mill (8x26) . I added the DRO to the big one after using it for about 6 month of occasional hobby work. Before adding the DRO, it was a toss-up between choosing the small one or the big one for casual milling and drilling. The DRO makes it super easy to roughly find the center of a part, or to precisely find a point on the part. The small mill is now used more as a drill press and second op machine.

                  I want to add a power feed to the big one. Slow, consistent feeds are the key to a great finish. My hands are not calibrated that well.


                  Dan
                  At the end of the project, there is a profound difference between spare parts and extra parts.

                  Location: SF East Bay.

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                  • #10
                    I agree with the others, when choosing a mill, most any 9X42 will do the job in a hobby machine shop.

                    I would also choose an R8. A 2 axis DRO is almost a must; I can’t imagine not having one (Gear backlash can drive you crazy).

                    A power feed on the X axis is desirable but not a deal breaker.

                    If you have a choice of an Asian machine, then choose Taiwanese made over a machine made in China. Most Taiwan made machines have better quality control, and better fit and finish.

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                    • #11
                      If you can afford it then go for the 3 axis DRO, you will like it more in the end.
                      The shortest distance between two points is a circle of infinite diameter.

                      Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

                      Southwestern Ontario. Canada

                      Comment


                      • #12
                        Originally posted by Ron of Va View Post
                        I agree with the others, when choosing a mill, most any 9X42 will do the job in a hobby machine shop.

                        I would also choose an R8. A 2 axis DRO is almost a must; I can’t imagine not having one (Gear backlash can drive you crazy).

                        A power feed on the X axis is desirable but not a deal breaker.

                        If you have a choice of an Asian machine, then choose Taiwanese made over a machine made in China. Most Taiwan made machines have better quality control, and better fit and finish.


                        I agree for the most part but for home shop an 8 by 36 is plenty big,
                        and R-8 is a great economical choice with about zero setbacks for a home unit.
                        and like stated put what you save into a good DRO,
                        as far as a power feed on anything that is a luxury you can get by with no problem,
                        Go basic - then build - I went basic and have stayed basic,
                        My mill is always there when I need it but I haven't turned a handle on it in over three months...

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                        • #13
                          I learned on a mill without a DRO and can do anything I need to - BUT having a DRO is a great addition and one of those things I will eventually add to my Bridgeport. 3-axis is nice but 2-axis is likely good enough for any home shop. I also think having an X-axis powerfeed is almost a necessity for getting good finishes and good used ones can be found on Ebay for a pittance of new cost.

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                          • #14
                            One reason that I use in favor of ISO30 over R8 is also the fact of making your own tool holders etc. ISO30 is just one taper with threaded end and two slots on it, while R8 requires lots more material and dimensions.
                            Amount of experience is in direct proportion to the value of broken equipment.

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                            • #15
                              Originally posted by Jaakko Fagerlund View Post
                              I would absolutely go for the ISO30 spindle over anything else (MT, R8). Tooling is available, the tool is easy and quick to change and the cost is quite low as they are a lot smaller than the ISO40 or 50 spindle tooling.

                              If you don't get ISO30 taper, then R8 is an option. But whatever you do, don't get a MT spindle taper, it is more headaches than use.
                              From reading the replies and your suggestion to go for an ISO30 spindle, I get the impression that the 30, 40, and 50 spindle sizes may refer to mm diameters. Is that correct? If so, the ISO30 would hold tools up to about 1-1/4". Is that about right? There was mention of making ISO30 tool holders, with some taper and a threaded end. Though I like the idea of making my own tooling, I realize it would be much easier to use R8 collets. Are the ISO30 tools comparable in cost to R8?

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