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The old mill/drill vs small knee mill dilemma!

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  • #16
    I notice that on the mill/drill you can tilt the head either way, much like on Doozer's Clausing. In addition to the normal raising/lowering in Z. It seems to have all the same motions available, and a DRO... so like I said, square column and all I would be quite tempted.
    25 miles north of Buffalo NY, USA


    • #17
      Well, if I was going to CNC convert one between the two, I would go with the Mill/Drill. If not, the knee mill.


      • #18
        Originally posted by Pfowler67 View Post
        I guess my main concern with the knee mill now is the belt changing. I think I’ll be able to live with this , but it’s hard to tell until I’m using it of course.
        Belt changes on a mill aren't a big deal, it goes fast and easy - nothing like the pain of having to use change gears every time you want to adjust the feed on a lathe, for example.
        Location: North Central Texas


        • #19
          I've got a question for the gallery: on a RF dovetail column can you take a cut with that axis in motion, or only move, lock off, and then use the quill? The quill on my round column Jet 16 is a bit loose after 28 years, I fear it was too many cuts taken without locking the quill, thinking it didn't make a difference if I wasn't hitting a target depth. If I had a knee the quill would be locked off for all but actual drilling so there'd be no side loading of it.

          As for belt vs gear, on the belt you can always swap the motor for a 3 phase and add a VFD speed control. Many new mills actually come that way now. If you go low speed enough to lose power, you can always then change the belt speed. I have VFDs on my mill, lathe and drill press.

          For those who always say get a Bridgeport sized machine, some of us physically can't. I have neither the access not height in my basement shop, but I can bring either of these machines down in pieces. The nice thing about low joists is that you can set up a hoist wherever you want!
          Location: Jersey City NJ USA


          • #20
            My question is what's your budget? Are you going to put 5,000 dollars in a import mill?
            If so then spend 2,000 on a used Bridgeport and use the other 3,000 for delivery setup and tooling.

            I have the asian version of that knee mill in 6x26 size. Belt changes are not a really big deal to me.
            If you got some choices in your tooling, then the belt changes come less often:
            example, if you got a mix of HSS and carbide cutters, if the current belt is too fast for HSS, then install a carbide equivalent.
            if the belts are turning fast, then use smaller diameter bit,
            if the belts are turning too slow, then use larger size bit
            this is not a fix-all but this slows down my belt changes a lot.


            • #21
              I think the Busy Bee Tool is expensive but most used full size knee mills in Ontario (I'm assuming that's where you live) are clapped out. Hardly any shop sells a good knee mill so you have to be patient and do a lot of looking. $2000 will not get you a mill in good condition here unless you spend the next year looking for one or you know somebody who knows somebody.


              • #22
                Just to pile on a little. I have a knee mill similar to the Craftex, made in Taiwan around 1979. I've noticed over the years that there are several different sizes and models that look the same. Some have more Z than others. Some have more spindle travel.

                I've used the knee mill for many years and find that it's a nice sturdy machine. I've made wide and deep passes just to test how much material I can remove, and was quite surprised. The downside of this machine is that the swing is limited by the column to spindle distance. The head is not mounted on a ram and will not move in and out like it does on a BP. I have mine "tricked out" with a DRO and 3 ph motor with VFD. Belts were not a problem, I just wanted the option of slower (and faster) speeds.
                At the end of the project, there is a profound difference between spare parts and left over parts.

                Location: SF East Bay.


                • #23
                  Originally posted by danlb View Post
                  Just to pile on a little.
                  Pile ain't deep enough, let me add more !!!

                  Cleveland Ohio isn't that far from parts of Ontario... closer than BC for sure. HGR is a huge used tool sales place that has a LOT of used Bridgeport mills for sale. Something on the order of a hundred. Prices range from $1274 to $7000 (US). Quality ranges from clapped out to "oh wow". The salespeople are friendly, but they won't put an indicator on the spindle and measure TIR for you. However, you can go wander the amazingly huge warehouse floor for a few hours and take all the measurements you want. Sometimes you can even power up a tool if there are the appropriate plugs, etc. They also run a sort of reverse auction. They want to get rid of stuff so they start with a high price, and then keep lowering the price until it sells. I got a 3' x 4' granite surface plate for $100 that way.


                  There are a number of people around Cleveland who make money by buying decent tools from HGR (or at auction) and rebuilding them and selling them. They will provide you with specs such as TIR on the spindle, backlash, etc. Some even offer 90 day warranties. That's how I got my Bridgeport from Varney Machine. Really nice guy, gave me guaranties on table flatness, etc. He also repainted it, put in new bearings, etc. When I showed up he sold me all sorts of tooling at bargain prices, too. Unfortunately for you he's getting out of manual machining and rebuilding mostly CNC stuff nowadays. Still, an email might turn up something. Or maybe you could pay him to buy a machine and refurbish it for you... That would get you a good machine at a decent price.



                  (No financial interest in HGR or Varney, they won't give me a kickback, etc.)


                  • #24
                    Originally posted by Doozer View Post

                    When I was 25 years old, I bought this Clausing 8520.….

                    Not trying to jack OP's thread here, but do you have any write ups on this head conversion you can point me to Doozer?

                    Neighbor across the street from me has a real nice 8520, except for the bent spindle. Original head with MT2.

                    This looks like it'd be a perfect solution....and all the more reason for me to buy it from him.


                    • #25
                      Just to add to the confusion I will suggest a euro style mill.

                      But an RF-45.. That's what Stefan G uses to great effect for his work. It's got a dovetail column and not round one AFAIK. So I don't see how the spot/drill/ream issue is a problem like was mentioned above unless it was a round column, maybe those exist and I don't know, I am not really into chinese machinery.



                      • #26
                        Thanks everyone. I live in Whistler, BC, so unfortunately travelling to Ontario to shop for a Bridgeport isn’t really a possibility. My shop is pretty small too, around 200 square feet, so I think anything larger than the two machines I have mentioned would be over kill. Add this to having to navigate through three 30” doorways after coming down a flight of steps to the front door and I’m pretty sure a Bridgeport would be a little much. I think also I’d just prefer to buy new or newish as I’m not sure I have enough experience to restore a classic machine.

                        I really appreciate all your help though.

                        It seems like there are pros and cons to both machines and in some ways it comes down to so level of personal preference. I imagine an RF would be ample machine for most of my needs, but I can’t help thinking I’d be happier in the long run if I got an 8x30 knee and modified it along the way to suit my needs (DRO would be a must for me from the get go). I’ll keep my eye on the used market and hope I get lucky and if not, there’s always Busy bee - assuming they don’t go back up to the full 7k price, which makes 5k sound like a good deal! And it’s made in Taiwan, at least not China.


                        • #27
                          Originally posted by Pfowler67 View Post
                          I can see the knee being a very handy feature for keeping things aligned accurately. Tooling isn’t too much of a concern mattthemuppet, as I have a smaller mill/drill with r8 spindle so have collets, vice, rotary table and loads more already.

                          I guess my main concern with the knee mill now is the belt changing. I think I’ll be able to live with this , but it’s hard to tell until I’m using it of course.
                          If you already have a small mill-drill, why by another? I've used an 8520 at work, and own a Rockwell, which is a little bit bigger. The only drawback I've found with those machines is the limited amount of quill travel for drilling operations when compared to a full size Bridgeport. The smaller size when dealing with limited home shop space more than makes up for it though, and having the convenience of an accurate knee makes quill travel a non issue. As for changing speed with v belts, once you've done it a few times it's darn near as fast as throwing some levers. And the belt drive is nice and quiet. If speed change did become a concern, these are low horsepower applications so swapping over to a 3 phase motor and a vfd shouldn't be a budget buster.


                          • #28
                            Originally posted by Dan_the_Chemist View Post

                            This simple sequence of operations was impossible on my RF-45

                            1) spot drill for a hole
                            2) drill the hole
                            3) ream to final dimension

                            That's because of the difference between the spot drill length (1.5") and the reamer length (7"). I had to move the head in the Z direction, and that meant losing alignment. Oh, I could sort of get it aligned again, but it was always sort of by feel.

                            When I got my rebuilt Bridgeport I remembered why machining could be fun. Not only did it keep alignment, it's much more solid. I used to feel that the RF was standing between me and doing precise work. Now the only thing standing between me and precise work is my own bad habits.
                            Much like what I was doing yesterday, a round-column mill wold have driven me to the point of breaking things out of frustration, not to mention misalignment! All I was doing was mounting a 4-jaw on a backplate: stubby spot drill to start, long series drill , 8mm drill to size and finally counterbore - all very different lengths! Made me glad I had a few 40-taper/ER-collet holders for quick changes, too.

                            Not having a quill on the vertical head, I had to power feed the knee - kinder to my old bones and no worries when breaking through

                            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


                            • #29
                              Originally posted by Barefoot View Post

                              Not trying to jack OP's thread here, but do you have any write ups on this head conversion you can point me to Doozer?

                              Neighbor across the street from me has a real nice 8520, except for the bent spindle. Original head with MT2.

                              This looks like it'd be a perfect solution....and all the more reason for me to buy it from him.
                              these guys specialize in that, they sell complete machines already setup.
                              call them and get more info



                              • #30
                                I like the Busy Bee best even though the other one has got more useful extras. What matters most in the long term is whether the capacity is big enough for your needs. At the museum, we have a round column drill mill and a Tom senior knee mill. The DM has greater capacity, but the TS is nicer to use, hopefully we will keep both.