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The old mill/drill vs small knee mill dilemma!

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  • #76
    Originally posted by Pfowler67 View Post
    Some great points I think tom_d
    I was hooding the belt changes would become easier over time and it sounds like an non issue to me. Like you say, adding vfd and 3 phase is always an option later on. I think having a more solid machine from the get go is more important for me.


    Originally posted by BCRider View Post
    One other factor. You're obviously going to be doing a lot of work in aluminium. And that generally calls for higher spindle speeds. I see that the Oxford only goes up to 1970 where the Aricas runs up to 3000RPM. And the Busy Bee knee mill is in the middle at 2520. This will be a factor you need to consider as well. Especially if you want to run with solid carbide end mills where they seem to get their best finish when used at higher speeds.
    Easy solution to both of these: 2 speed 3450/1750 RPM three phase motor. I tend to move move between 660 and 1120 RPM all the time on the bridgeport, but rarely anything much else. I would use a 2 speed motor all the time.

    Do the little knee mills have a backgear?
    21" Royersford Excelsior CamelBack Drillpress Restoration
    1943 Sidney 16x54 Lathe Restoration

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    • #77
      Originally posted by The Metal Butcher View Post
      Easy solution to both of these: 2 speed 3450/1750 RPM three phase motor. I tend to move move between 660 and 1120 RPM all the time on the bridgeport, but rarely anything much else. I would use a 2 speed motor all the time.

      Do the little knee mills have a backgear?
      no backgear on these knee or bench mills.

      A standard 1750rpm inverter duty 3ph motor plus 3 or 4 pulley ratios would cover a very wide range of speeds within a conservative 40-100Hz frequency range for the motor. My treadmill motor equiped 6x26 can go down to 30-40rpm with enough torque to use a 1" drill in stainless (mill didn't like it though) and up to 3500rpm to use a 1mm endmill in aluminum (I didn't like that much, could barely see the thing), with just 3 pulley ratios. I have another one if I shift the pulley on the motor shaft, as the spindle has 4 ratios but the motor shaft only has 3 - there used to be a jack shaft in between which I removed.

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      • #78
        Originally posted by Hopefuldave View Post
        If the RF45 is a round-column mill, I'd hate the head going out of alignment if raising or lowering it, knee mill would be my choice.
        If the RF45 comes with more extras at the same price, it's because it's a cheaper machine, built to a lower price. Basically it's a drill press with an XY table on it.

        Dave H. (the other one)
        RF45's are all dovetail ways on the Z. Rong Fu and all the knockoffs make round column mills, but they're not the '45 model.

        Having owned an RF45 knockoff, and since I currently own a G0759 Griz, I will say that having a knee mill with a ram that you can swing to clear the table, so that you can hang long work over the end and mount to an angle plate is something I miss sorely. I often curse the limited Z travel of my machine, especially if I'm doing anything with a long tool holder. Having a belt drive would drive me crazy, although I would redo the motor to be run off a VFD and have adjustable frequency, so speed changes would be less of an issue.

        If the RF45 style machine has proper NSK bearings in the spindle, that is a big plus and probably an indicator of some level of relative quality. My RF45 came from a guy who was relatively new at importing them to the US at the time, and it was of known lower quality for a very low price. Fit and finish was not great and it was always frustrating. I should have bought a used boat anchor 2J bridgeport, because all in I spent the same amount of money, did a VFD and inverter grade motor on the RF, and had 1/4 the machine in terms of capability.

        -paul

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        • #79
          All great points thanks guys. BCrider, thanks for sticking up for me on the our lack of used machines issue here in BC. It’s sparse! One point though as I’ve mentioned, you may be looking at the wrong spec for the busy bee machine. See the KBC spec as I’ve included earlier. 3200rpm is plenty for me, as I currently make do with just over 2000rpm on my current machine and haven’t had an issue. I use pretty small carbide end mills at times and have been happy with results. 3200 will be great.
          just found a barely used busy bee knee on Craigslist. It’s one without a picture - why do people do that?! Emailed him and it looks mint. Trying to get him to seek it separately to his lathe. (Nice 12x36 lathe with it, 9500$ for both)

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          • #80
            Get the knee mill. I have used both over my 50 years in shop. Don't be seduced by add-ons and attachments. You will not regret getting the knee mill, I cannot say the same for the mill/drill.

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            • #81
              Thanks Profkanz . That’s what I wanted to hear!

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              • #82
                What about this one?

                ​​​​​​https://www.ebay.com/itm/Bridgeport-...IAAOSwGmtejoAb

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                • #83
                  Originally posted by Ringo View Post
                  What about this one?

                  ​​​​​​https://www.ebay.com/itm/Bridgeport-...IAAOSwGmtejoAb
                  I love a Bport like everyone else, but a 1/2 HP mt3 round ram that probably needs rebuilding is a lot less desirable than an RF45 to me, even as a big, old tool lover.

                  Edit: and wow, somehow sold ASAP. Okay...
                  21" Royersford Excelsior CamelBack Drillpress Restoration
                  1943 Sidney 16x54 Lathe Restoration

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                  • #84
                    As best I could tell from the pics, that machine still showing some flaking & scraping on the ways. the table was not beat up or milled into.
                    My gut feeling tells me that was a good machine. that might be a classic example of the old american iron 1/2hp vs the new import 1/2hp.

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                    • #85
                      You must have missed the NO CANADiANS in bold in the ebay description

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                      • #86
                        Yeah sorry Ringo, that’s not for me. Can’t go over the border and it won’t fit in my space. All my tooling is r8...
                        Thanks though. Anyone sees a used 8x30 or similar knee mill though, let me know!

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                        • #87
                          I also hate to think how much it would cost to ship a B'port from Illinois to the West Coast.....
                          Chilliwack BC, Canada

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                          • #88
                            Over a grand? I paid around 260€ to ship a mill from Sweden to Finland, closer distance. I guess this would be more akin to shipping something from Germany or France.

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                            • #89
                              Hello all!

                              I ended up posting an ad on Craigslist (looking to buy) and recently received a nice email from a guy just down the road in Vancouver, who is selling his 'pristine' KBC branded machine. So I went to see it yesterday and it really is awesome! He wants $2500 CAD for it so i'm really excited to be going to collect it on wednesday. Check out the pics and see what you all think. All the ways are beautifully clean and the spindle is like new. All very smooth and tight throughout.
                              My next challenge will be to dismantle it, drive it home to Whistler and lug it down the 15 steps at the front of my place, through three 30" doorways and into my shop. Wish me luck!
                              Taking the machine to pieces will also be a great opportunity to give it a thorough clean and get it running as I like.
                              Attached Files

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                              • #90
                                PS, I will also be adding 3 axis DRO with the money I have saved from buying used.
                                Does anyone have any brands of glass scale DRO that they can recommend?

                                Thanks!

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