End mills in lathe chuck

Advert

End mills in lathe chuck

Home Forums Beginners questions End mills in lathe chuck

Viewing 24 posts - 1 through 24 (of 24 total)
  • Author
    Posts
  • #57067
    Derrick Watson
    Participant
      @derrickwatson66926
      Hi,
       
      I’ve read a previous post on here in which most people thought that you should not use an end mill in a drill chuck. But, it is OK to use an end mill in a lathe, using a 3 jaw lathe chuck ?
       
      cheers, d.
      Advert
      #5235
      Derrick Watson
      Participant
        @derrickwatson66926
        #57070
        Anonymous
          It has been done, but personally I wouldn’t do so, for the following reasons:
           
          1) The TIR of a 3 jaw chuck probably isn’t that good, and if it is, you shouldn’t be using it for milling!
           
          2) The milling cutter will be much harder than the chuck jaws, so the grip will not be particularly good
           
          3) The jaws will only grip over a small area, compared to a proper milling chuck – see above
           
          4) A largish chuck holding a small endmill increases your chances of getting a bonk on the nose or hand when getting close to see what is going on
           
          No doubt there are many other reasons too. Use an ER style collet chuck, preferably mounted directly on the lathe spindle nose.
           
          Regards,
           
          Andrew
           
          Edit: Of course there’s no reason not to use an end mill in a lathe, just not in a 3 jaw chuck

          Edited By Andrew Johnston on 18/10/2010 16:57:34

          #57072
          mick
          Participant
            @mick65121
            Just use the auto lock chuck held in the spindle taper, for light work there shouldn’t be any need for a draw bar. 
            #57073
            Tony Pratt 1
            Participant
              @tonypratt1
              I agree with using a milling chuck in the internal taper but please use a draw bar
              Tony
              #57074
              JasonB
              Moderator
                @jasonb
                Or if you don’t want the cost of an ER or Milling chuck then a MT collet with drawbar will do nicely. Just make sure you can get the cross slide close enough to the spindle.
                 
                Jason
                #57078
                Derrick Watson
                Participant
                  @derrickwatson66926
                  thanks all, looks like I should probably think about getting a collet. A couple of follow up questions tho:
                   
                  1) what is TIR (showing my newness to the hobby here).
                   
                  2) a drawbar is? – from a quick google search I’m guessing it’s something that holds the taper into the head stock (from the gear side).
                   
                  3) how would you get a taper out of the headstock spindle – it wouldn’t be like a tailstock mechanism
                   
                  4) what’s the difference between an ER and a milling chuck?
                   
                  5) I’ve got a Sieg C2, it looks like the following ER32 attaches to the backplate having removed the chuck rather than being spindle mounted
                   
                   
                  would this be better than a spindle taper type of setup?
                   
                  Sorry for all the questions, cheers, d.
                  #57079
                  Anonymous
                    Hi Derrick,
                     
                    TIR = total indicated runout
                     
                    In simple terms, how wobbly the tool is compared to the spindle axis with which it should be concentric.
                     
                    Regards,
                     
                    Andrew
                    #57081
                    James fortin
                    Participant
                      @jamesfortin46829
                      ive used a 3 jaw for light milling using no bigger than 1/4 inch endmills and this is ‘ok.’
                       
                      i think i saw a article by harold hall telling you that if you didnt have a collet chuck then bore out a hole in some bar stock the size of your endmill ,and put a grub screw in the side to hold the endmill in.
                      #57082
                      JasonB
                      Moderator
                        @jasonb
                        1. Total Indicated Runout. if you hold a bar in te chuck and then measure the runout with a dial gauge this will show the TIR, 3 jaw chucks are not the most accurate and usually have a few thou TIR particularly the cheaper end of the market. This runout will cause a milling cutter to cut oversize
                         
                        2. Its basically a bolt that screws into a thread in the end of teh tapered tooling and draws it into the socket and prevents it from comming out.
                         
                        3. Loosen the drawbar slightly and give the end a tap with a lead or copper hammer, this will break the tapers grip.
                         
                        4. A milling chuck is made to hold screwed shank milling cutters and prevents them being pulled out by heavy loads, often called a Posi-loc or auto-loc chuck. Er collets can hold a larger range of sizes than milling chucks which just cover the common shank sizes, Metric ER collets can also be used on imperial stock but its best to have the correct sizes.
                         
                        5 Provided the backplate is perfectly concentric with the lateh spindle nose then it will be fine but bear in mind that if you later get a milling machine you will need a taper mounted one although the actual collets can be used in both.
                         
                        A MT collet like these will be a cheaper option if you just want to hold a couple of milling cutters.
                         
                         
                         
                        Jason
                        #57083
                        KWIL
                        Participant
                          @kwil

                          OK to use a collet in the headstock spindle with A FULL length shear, but do not try it with a gap bed machine because the carriage will not get close enough because of it.

                          #57086
                          Dinosaur Engineer
                          Participant
                            @dinosaurengineer
                            Derrick,
                            TIR or the more correct abbreviation T.I.R. is the total swing of an indicator . If for example a dial test indicator (D.T.I.)  is adjusted to read Zero on a perfect spindle which has no run-out then the T.I.R. will be zero.   If say the D.T.I. is set to read zero at one particular point on a piece of silver steel ( smooth round piece of steel) in the 3 jaw chuck , then the indcator may for example go to minus 0.003″ at it’s lowest point to say plus 0.002″ at it’s highest point for one full revolution . Thus the T.I.R. would be 0.005″ which is the total indicator “swing”. You may hear of eccentrics or eccentricity. Eccentricity is the amount the actual centre of say the piece of silver steel in the chuck, is from the true centre of  the spindle revolution. Thus the chuck at the gripping point of the silver steel diameter is said to be eccentric by an amount of 0.0025″ . This is half the T.I.R.
                            Hope this helps

                            Edited By Dinosaur Engineer on 18/10/2010 19:40:36

                            #57101
                            The Merry Miller
                            Participant
                              @themerrymiller
                              What are the chances of  an endmill walking out of a Myford ER25 collet without additional restraining devices?
                              I am asking  the question before I try it out.
                              At present I use the three jaw chuck and wrap a piece of paper around the endmill before I clamp up. (not for precision milling I might add)
                               
                              Len P.
                              #57104
                              Anonymous
                                Unlikely, if it is done up properly. ER collets need to be done up ‘pretty damn tight’, to at least two grunts worth.
                                 
                                For ER25 collets above about 8mm, a quick search on the internet shows tightening torques between 70 and 90 foot-pounds. Unless you’re the proverbial gorilla you’re not likely to achieve that with normal spanners!
                                 
                                Regards,
                                 
                                Andrew
                                #57105
                                Tony Pratt 1
                                Participant
                                  @tonypratt1
                                  Very little chance of it moving if you are sensible ie don’t take massive cuts and extremely fast feeds, you have got nearly total clamping area with the ER series collets so don’t worry too much. I used them on industrial CNC machines and had no problem that I can recall, you will find them a lot more secure than a 3 jaw chuck.
                                  Tony
                                  #57109
                                  MICHAEL WILLIAMS
                                  Participant
                                    @michaelwilliams41215
                                    A three jaw scroll action chuck really is the most awful contraption ever devised  for gripping anything . Apart from problems mentioned above there is a fundamental flaw in the design of these chucks in that even with the workpiece gripped tightly by the jaws the whole package of work ,jaws and and scroll is not actually bedded against anything in the chuck body (except by chance sometimes) and can float around to the extent of any clearances between jaws and body and scroll and body . In posh chucks this is no great difficulty since clearances are small but in some cheaper chucks it is a serious source of problems . What actually happens in practice is that the jaws and work tend to bump over to a random location and stay there under lighter cutting loads but under heavier or intermittent loads they can randomly change position causing chatter and loss of accuracy . You can spot the symptoms of this if an otherwise ok lathe is producing work which is not quite round – often the infamous 3 or 5 lobe cam shape as found on some ground silver steel rods .
                                     
                                    The situation with a four jaw independent chuck is quite different – when its locked down the whole thing is solid .
                                     
                                    As for holding endmills in any kind of chuck the fundamental problem is that all modern type spiral tooth end mills will screw themselves out of the chuck given the least oportunity and this problem can only be overcome by gripping the endmill very hard or by providing mechanical retraint via the holding thread on the shank . Endmills also have to run very true not only for clean cutting action but also because any eccentricity will make the screwing out tendency even worse .

                                     
                                     
                                    #57110
                                    John Olsen
                                    Participant
                                      @johnolsen79199
                                      The cheapest way of holding endmills securely that I can think off  is a taper fitting for the lathe mandrel with a hole bored in the end to fit the milling cutter. The cutter is then secured by a set screw, or preferably two at right angles. The hole does need to be a good close fit on the shank of the cutter. These are made commercially, but would be not too hard to make at home, assumming you are able to turn a taper. The far end should be tapped for a drawbar. You do of course need one for each shank size. There is the objection that if the hole is slightly oversize, the cutter will be eccentric, while if the hole is exact it will be hard to get the cutter out.
                                       
                                      I have a commercal one acquired somewhere along the way with a no 4 Morse taper that fits my mill drill, however it has hardly been used since I have two Posilock chucks and one Clarkson, as well as a set of ER16 colletts which is handy for  the smaller plain shank cutters.
                                       
                                      I would note that although the lobing seen on the silver steel may be similar, it actually has a different cause, it is a problem with the centreless grinder that they have used.
                                       
                                      The action of the forces on a milling cutter, or on a job in the lathe for that matter, is very like what you do to get a post out of the ground, grab it at the top and wiggle it in a circular motion.
                                       
                                      regards
                                      John
                                      #57121
                                      MICHAEL WILLIAMS
                                      Participant
                                        @michaelwilliams41215
                                        I said ground .
                                         
                                        Actually it is quite astonishing how many round things encountered in engineering are not round at all . Just for example :
                                         
                                        Bright drawn bar , ordinary grade precision ground bar , silver steel , any slender turned work , anything with a hole in it that has been gripped in an ordinary chuck for turning , anything that has been turned between chuck and centre and most drilled or reamed holes !
                                         
                                        Some of the problems people have with getting good fits between a rod end and a hole are made worse by out of roundness – the percieved or measured sizes do

                                        not give a true value for the amount of metal actually interacting where the two surfaces meet .
                                        #57127
                                        Gordon W
                                        Participant
                                          @gordonw
                                          Blank, soft ended Morse tapers are easily bought, with draw bar hole. Just put one in the mandrel and drill the needed hole. Tap for grub screw. Ample for the very light milling you will do on a lathe.
                                          #57129
                                          Peter G. Shaw
                                          Participant
                                            @peterg-shaw75338
                                            I’d just like to add my two pennorth, not that I’m any sort of expert, but through experience on my lathe.
                                             
                                            I have tried to use the 3 jaw chuck to hold a milling cutter. It wasn’t particularly good with much vibration. It did do it though – eventually. I think I also experienced the dreaded walk out of the cutter, ie where due to the vibration, the cutter slowly works it’s way out of the chuck.
                                             
                                            Using a direct MT3 collet and drawbar, cutting was much better and smoother.
                                             
                                            The drawbar is inserted into the lathe mandrel from the opposite end to the collet, and is used to force (by pulling) the collet further into the taper in the mandrel. This in turn causes the slightly flexible parts of the collet to clamp down even tighter onto the cutter thus hopefully preventing any further movement. I think as well, by using the collet, I reduced the overhang away from the mandrel bearings thus stiffening up everything. Finally, the collet is likely to be more accurate than the 3 jaw chuck, thus reducing out of balance forces.
                                             
                                            Now, I use a milling machine!
                                             
                                            Regards,
                                             
                                            Peter G. Shaw
                                            #57136
                                            John Wood1
                                            Participant
                                              @johnwood1
                                              Thanks Derrick for starting this thread, it’s been a real eye opener for me who naively thought that 3-jaw chucks were pretty good and that milling in the lathe was easy and accurate.  In the light of all the valuable gen which has come to light from those learned scribes above, I am now going off to review my turning and milling techniques with the view to improving accuracy across the board.  Thanks guys.
                                               
                                              All the best
                                              John  
                                              #57140
                                              Derrick Watson
                                              Participant
                                                @derrickwatson66926
                                                Thanks, I’m glad it’s been of use to others.
                                                 
                                                On a related note, I’m now wondering whether a collet could also be used to hold a work piece. I’m thinking about small (e.g., 3 to 8 diameter mm) rods – obviously the collet would need to be an appropriate size. Would the stability etc advantages of the collet over the 3-jaw chuck also transfer to this use?, or is there a reason not to do this?
                                                 
                                                Again thanks for all the help, d.
                                                #57141
                                                JasonB
                                                Moderator
                                                  @jasonb
                                                  Provided the collet chuck is accurate then its an ideal way to hold small items, often the main method of workholding on watchmakers lathes etc.
                                                   
                                                  Jason
                                                  #57143
                                                  MICHAEL WILLIAMS
                                                  Participant
                                                    @michaelwilliams41215
                                                    Collets can be used to hold any type of round tool or workpiece and in some cases square and hexagon . After exploring all the problems of ordinary self centering three jaw chucks you would find using collets instead a treat from the Gods !

                                                     
                                                    Unfortunately you may have to start another thread now since there are many different collet systems …..
                                                  Viewing 24 posts - 1 through 24 (of 24 total)
                                                  • Please log in to reply to this topic. Registering is free and easy using the links on the menu at the top of this page.

                                                  Advert

                                                  Latest Replies

                                                  Home Forums Beginners questions Topics

                                                  Viewing 25 topics - 1 through 25 (of 25 total)
                                                  Viewing 25 topics - 1 through 25 (of 25 total)

                                                  View full reply list.

                                                  Advert

                                                  Newsletter Sign-up