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  • Have a mill but no lathe-

    Turn your mill table into a lathe bed. A couple things I've watched recently kind of clicked me into this- sometimes you see a dividing head or rotary table mounted on the mill table. When the spindle is horizontal, the configuration is right. When you see a chuck mounted onto it- bingo, there's your headstock. The table and the slots can be used to slide a tool post carriage along, and the t-slots can be used to set the degree of friction, lock the carriage, or keep it from jumping off. If at least one of the slots is an even width across its length, which is a reasonable assumption, then you have a guide edge for the carriage. The tailstock can be just another fixture which makes use of the slots for alignment and mounting. It doesn't take much imagination to see how to run the carriage back and forth using either a rack and pinion, or a lead screw. If the mill table has a slot on the front side, it can be used to secure carriage stops, or to mount the rack or bushings and lead screw.

    You could carry the concept as far as you wanted- set it up for threading, move the headstock back and forth with a lead screw and mill while turning- lots of possibilities. I can see a way to mill eccentrics easily if the spindle housing can pivot up and down. What a project this would be!
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    I can mill stuff in my lathe.
    Andy

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    • #3
      You could just put the lathe tool in the mill spindle and use the bed of the mill to move the work along under the cutting tool with the X axis leadscrew.

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      • #4
        With a chuck or a face plate mounted on the spindle of my horizontal mill I could easily have the equivalent of an 18" swing lathe. Could be useful for facing something with a large diameter, but I only have 10" of cross travel available for turning.

        Tom
        Tom - Spotsylvania, VA

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        • #5
          You could just put the lathe tool in the mill spindle and use the bed of the mill to move the work along under the cutting tool with the X axis leadscrew.
          Isn't that called milling?
          Tom - Spotsylvania, VA

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          • #6
            Originally posted by flathead4 View Post
            Isn't that called milling?
            Not if the tool is not spinning. I think he is talking about spinning the work in the rotary table/dividing head, and holding the lathe tool in the mill spindle.

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            • #7
              Originally posted by flathead4 View Post
              With a chuck or a face plate mounted on the spindle of my horizontal mill I could easily have the equivalent of an 18" swing lathe. Could be useful for facing something with a large diameter, but I only have 10" of cross travel available for turning.

              Tom
              Dave at Calypso Ventures has a Mach3 screen set available for doing something similar in a vertical mill.

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              • #8
                You could actually put threads on a rod with this setup?

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                • #9
                  A mill as a lathe is a very practical idea - but I would not get too carried away with it - if you want to do long pieces that need a tailstock or you want to thread then life will start to get complicated real fast - why?
                  the main reason is because your going to want to use your mill half the time, and your lathe the other half - so set up and tear down gets tedious

                  If all you have to do is flop the head back up and re-tram it's one thing - but bolting piece upon piece and all the re-doing will get old real quick...

                  I use my Mill as a lathe all the time - but I only do small hub work or anything that's not too long - but that's about 85% of what I need a lathe for so it's worth it...




                  The pic above is my mill in lathe mode, i usually have the rotary table in the middle of my mills table and my vise at the end - all's it takes for me to put it in lathe mode is flop the head down and tram - remove RT and clamp QCTP in vice... still a little hassle but to me it's worth it having one machine that basically does the job of two - my friends got 3 lathes I can use if I need too so it's a wise economical choice for me...

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                  • #10
                    Me too when the swing is too big for my lathes

                    http://i273.photobucket.com/albums/j...tolathe001.jpg
                    The difficult done right away. the impossible takes a little time.

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                    • #11
                      Part of what would make me do it is to get a larger swing. Sometime in the future I'm sure I'll be in for a larger lathe, but 'money is no object' doesn't apply at this time, if it ever will.

                      I think about all the talk regarding 3-in-1 machines, and how they are significantly compromised as either. If you started with a 'real' milling machine, you don't lose anything in that regard. If you then add a headstock, carriage assembly, and tailstock, you would get the lathe part also. Whether the lathe is sub-par or not would largely depend on what you would do with it. Threading capability certainly does complicate things, and you'd be in for quite a bit of careful fabricating to get the lathe part together.

                      Yes, it would be a chore to demount and remount the lathe 'accessory' all the time, but it may not be needed to do this all the time. Any 3-in-1 machine doesn't allow you to do this, so this would be some improvement in that regard.

                      One thing that I'm trying to get a handle on mentally is the rigidity issue. Would the mill table compare favorably to a lathe bed of similar size in that regard- considering that mill tables are usually pretty solid, plus the fact that it's intimately connected to another solid base, the Y axis, it should be pretty good.

                      As far as the carriage goes, you might be able to adapt one of those XY tables for the job. In the meantime, the mill spindle can hold tooling, whether it's rotating or not. Cutting from the back side with tooling mounted on the non-rotating spindle would be pretty easy- no carriage needed at all. You could also cut from the top- there's enough length to the mill column to allow a full 16 inch diameter turning capacity. The tailstock- well it really depends on what you need it to do. If the primary function is as a steady, it can be pretty straightforward. It's all a project, and you can make it do whatever you need it to.

                      In my case, the diameter turning capacity could be as large as 15 inches. If I kept the length of the headstock to within about 6 inches, I'd still have about 12 inches of length capacity. If my mill table was longer, this would go up, but I don't see this as a limitation- when I've needed a larger diameter capacity, there was never a need for length as well.
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                      • #12
                        Tormach has an accessory lathe that sits on the bed of their CNC mill. The lathe is CNC too and can be used as a 4th mill axis or a CNC lathe. It might be worth looking at that to get ideas for your situation. Just trying to help look at this from different angles.

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                        • #13
                          Too bad you don't live in the Seattle area. I have a lathe and no mill and my buddies with mills are getting burned out doing my stupid little projects. :-)

                          metalmagpie

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                          • #14
                            I thought about this situation- the common thing is to have a lathe, then buy or make a milling attachment for it. I've never heard of going the other way around, but in many ways it does seem more appropriate. You don't get much of a mill by using an attachment on a lathe, but a mill table offers a better support for an accessory lathe. As pointed out however, threading capability would be very involved to fabricate, and length would be limited. Threading is not something I do a lot of, and I can't recall any time I've been limited by the length of my lathe bed-

                            You might also consider that the x axis has a lead screw, and it's set up parallel to what the accessory headstock spindle would be- I can see that a 100 tooth collar could double as a lead screw dial and a sprocket for a belt drive. Without a major brain cramp you could see how to arrange a sprocket on the spindle, plus a belt tensioner to give some common sizes of threads. A 1 to 1 drive would give you 10 tpi, for instance.

                            I'm not a gunsmith, nor do I turn axles- most often I use screws and bolts for fasteners. I guess you just weigh the compromises you have to make either way, and go from there.

                            By the way, for threading in the way I've just described, the tooling would be held in the mill spindle. You would have to lock the spindle, and you would have to make up a suitable toolbit holder. The holder can be as simple as a boring bar. The only accessory that you would really need then is a powered headstock.

                            If you built a carriage to carry the cutting tool, then you couldn't use this simple threading method.

                            The main thing I don't like about carrying the cutting tool in the spindle is that the bearings take the pressures, and are not rotating- but I don't think cutting pressures would be nearly high enough to be a problem anyway. There is one bonus of this method- you can angle the threading tool very easily to conform to the helix angle! And if you wanted to make very coarse threads, say 4 tpi, then you just use an end mill and mill them. Square threads made easy-

                            I have an idea or two for the headstock- very simply, it would be a housing with bearings and a spindle, etc, but the spindle would have a relatively large flange heat shrunk on as a faceplate. An arrangement would be made on that for chuck mountings, etc. The flange would be toothed, and the main drive belt would surround that, plus the sprocket on a jackshaft below the spindle. A shield would cover this whole mess. The motor would go within the housing, with the shaft coming out the left side. The motor shaft and the jackshaft are now parallel and on the same side, so some stepped pulleys and an idler gives you speed changes. If your main jackshaft sprocket is say 1/2 to 1/3 the size of the spindle flange, you already have some step-down there. To overcome this and have your highest spindle speed, the motor would either have to overdrive the jackshaft, or spin faster than normal. Faster than normal is the norm with treadmill motor adaptations already, since they are designed for 5000 or more rpm to begin with. I think it would be easy enough to get a good range of spindle speeds, including a 'low range' which would make 'back gear' unnecessary.

                            Of late I have been considering the use of 'third member' tapered roller bearings for the spindle. These are apparently common on differentials- the ones I was looking at have an ID of 2.25, or was that 2.125- plenty large enough for a meaty spindle and still a good size of through-hole.

                            I better quit now- I don't need another project- yet.
                            Last edited by darryl; 02-20-2013, 12:26 AM.
                            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                            • #15
                              I owned a bridgeport before I bought a lathe, and for the most part when I needed to turn something I just needed something small trued up or cut to a specific OD. I had a 4" chuck mounted on an R8, would mount a lathe tool in my kurt style vise and lower the quill to move whatever I was cutting past the cutter, instead of moving the cutter relative to whatever I was turning. It worked really well for that kind of work, and since I have a DRO on the mill and I don't on the lathe, I could get it really close to the correct size faster there than I sometimes can on the lathe (but the setup might take longer).

                              Huh, maybe I should put a DRO and a VFD on the lathe... there are times now that I'll go to the mill first just because I know that I can do it faster on the mill, even though it might be more appropriate on the lathe.

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