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  • How hot..

    ..should a quill/collet etc. get after about 15 minutes or so of milling?

    I was milling some mild steel before (.375 HSS 4 flute, 1600 rpm, light cuts then a .375 2 flute ball end ) and went to change the bit...hooboy, wouldn't want to try to hang on more than a few seconds!

    Not like "just welded that you dummy!" hot but, ya know.......hot.

    Oh, brand new machine too, an IH mill.
    Len

  • #2
    Hot

    You have perhaps not tightened the collet too well, and the heat is from a friction caused by the mill bit slipping (rotating) in the collet. That would be the first thing I would look at. Actually, contrary to what many people recommend it is not very good practice to use collets for holding the mill bits. They are both hardened and therefore have a tendency to slip.

    A Proper mill holder suitable for your mill e.g. R8 or whatever your machine is equiped with is a much better choice/ for me the only choice, for the standard bit diameters.
    Vic

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    • #3
      Sounds like your spindle bearings may have a problem . I would check them if this is a new mill . I have seen them set up to tight one some of the new imports. NOT UN COMMON TO DAY.
      Every Mans Work Is A Portrait of Him Self
      http://sites.google.com/site/machinistsite/TWO-BUDDIES
      http://s178.photobucket.com/user/lan...?sort=3&page=1

      Comment


      • #4
        200f is not uncommon on a new spindle.If you can touch the spindle and hold your hand there for a few seconds you may only be around 140F which is fine so long as this heating didn't occur in a short duration run.

        That would be my next question,how long did it take to get hot?If it was just a few mintues then yes you have a problem,if it took an hour then not so much.

        Get yourself a cheap digital kitchen thermometer and see what the temp really is.

        It could also be the crappy EP grease they use in some of those machines causing heat.
        I just need one more tool,just one!

        Comment


        • #5
          Diagnose it first, run it at same RPM's and the same amount of time without any bit or collet, if it still gets hot then i think you have a problem, Thier should be a little preload but nothing that will create the type of heat your talking about --- My mill head is new and has preload (i can tell this when i had the belt off and it would coast but not forever, its also a very chatter free head) I can run mine @ 1550 rpms for a half hour and not feel any kind of heat whatsoever...
          you may not even have that much preload but your bearings may be junk,,,


          if you dont see much heat with this test then your cutter is most likly dull.

          Comment


          • #6
            [QUOTE=smagovic]Actually, contrary to what many people recommend it is not very good practice to use collets for holding the mill bits. They are both hardened and therefore have a tendency to slip.[QUOTE=smagovic]

            What would you use a collet for if you weren't holding a milling cutter? While I agree that a dedicated end mill holder is less likely to let the endmill slip, if the endmill is sized properly to fit the collet there shouldn't be a problem there either unless you were doing some really heavy hogging. I mill daily with collets holding the endmill and never have that problem. The reason I don't like the end mill holders is that they start to eat up z axis room especially on the smaller machines. They also move the side load on the endmill farther away from the bearings.

            I would say that you are having a bearing problem also. I can run my machine for a 20 to 30 minutes and still not notice and change in spindle temperature. They may still be a little tight from being new or possible adjusted a little on the tight side causing your heat problem. Good luck and let us know what you find out.
            Jonathan P.

            Comment


            • #7
              Originally posted by smagovic
              You have perhaps not tightened the collet too well, and the heat is from a friction caused by the mill bit slipping (rotating) in the collet. That would be the first thing I would look at. Actually, contrary to what many people recommend it is not very good practice to use collets for holding the mill bits. They are both hardened and therefore have a tendency to slip.

              A Proper mill holder suitable for your mill e.g. R8 or whatever your machine is equiped with is a much better choice/ for me the only choice, for the standard bit diameters.
              Vic

              I know, i know,,, and many of the cnc's use mill holders and the like, if his bit was slipping it would inevitably change its hight position and this would be noted --- esp. if were talking one creating heat,,, To me a high quality collet with a runnout of .0002" is the way to go for a home shop machinist, Iv never had any of mine "walk", they are much more versital because they can also hold stock, Many of your large production cnc's also have thier version of the expandable collet, In my opinion they are also more accurate then sliding a mill bit into a bore and then tightening one side down and pushing the bit over --- close tolerence that they are we all know that they have to have a little clearance to allow install and removal, this amounts to mill bits running slightly eccentric even when used with brand new holders, this situation does nothing but increase, not so with the collets, some can be in service for decades and the wear patterns will remain even, just my two cents but im not a machinist im a mechanic so I will shut my yap after my spanking

              Comment


              • #8
                collets

                The collets were designed for holding round material (there are also square hole collets though they are less common))(hardened/==collet/soft=material) to be worked on, on the devices, such as a lathe. They were and are used prominently on the watchmakers lathes for example. Collets improve accuracy when there is a need for remounting of the material for some reasons. This is in comparison with the say 3 jaw chuck, where you can practically never guarantee the same mounting conditions when you removed the piece you are working on. They were designed long time before anyone heard about any CNC.
                Take care. Vic

                Comment


                • #9
                  "This is in comparison with the say 3 jaw chuck, where you can practically never guarantee the same mounting conditions when you removed the piece you are working on."


                  It took me almost a year of indicating, testing and goofing around to finally come to the conclusion that it wasn't me that had the problem but the three jaw chuck...

                  When i first picked up machining i couldnt figure out why everytime i remounted a piece i couldnt ever get it to spin perfectly true even though it was reading perfect when i took it out - i marked stuff, indicated stuff, tested stuff...nothing worked. I could get darn close but not perfect. Slowly i found out that this is a failing of three jaw chucks...

                  Comment


                  • #10
                    you should contact the hardinge company and let them know they are going about it all wrong, making R8 collets for mills clamping power isn't about hard or soft material, from mills to grinders there are many instances of hardened items correctly being held in a collet. Successful holding of a collet or any clamping for that matter is a function of the coefficient of friction x the clamping force being greater than the applied force, ie cutting force.

                    I understand the argument for end mill holders, but frankly have never found the need. Collets don't slip for me on a full size mill unless i forget to tighten them and they have advantages.
                    .

                    Comment


                    • #11
                      One moment please, Vic. Have you ever seen a lathe that came from the factory with an R8 taper? Me neither. And how often do you see a mill set up with the stock in the spindle and the table holding the tooling? And all those R8 collets around the world are for holding stock? Something is not adding up for me.
                      .
                      "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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                      • #12
                        I would not be too concerned about the collet. The heat transfer from the tool is most likely to blame. If the end of the spindle is that hot I might start getting concerned. I have gotten a Bridgeport spindle nose hot from heat transfer in the past but not hot enough to be uncomfortable. I would feel the spindle in the area where the bearings are located. If it is more than warm you may want to try running without tool and monitor the change in temp to verify you have a spindle problem. Preload may be to blame.

                        Comment


                        • #13
                          Originally posted by TGTool
                          One moment please, Vic. Have you ever seen a lathe that came from the factory with an R8 taper? Me neither. And how often do you see a mill set up with the stock in the spindle and the table holding the tooling? And all those R8 collets around the world are for holding stock? Something is not adding up for me.
                          Well first,I use collets all the time for the above mentioned reasons(rigidity,daylight savings etc)

                          However they are intended to hold things with soft shanks,i.e. drills,reamers etc.Me I don't care,they hold endmills just fine.

                          Endmill holders offer one advantage,tool location repeatability.Weldon shanks hold tolerance from the weldon flat to the endmill's end.You can drop a dull endmill out and replace it with a new one and the location stays the same within a thou or less.If you were running production with unskilled operators instead of machinists you would want that system since it means repeatability without extra setup by your skilled labor.
                          I just need one more tool,just one!

                          Comment


                          • #14
                            As far as the heat issue... It is also possible that some of the heat is conducted up from teh cutter. Cutting material creates heat of friction, depending on material and coolant etc. That, added to the normal bearing heat could be noticeable.

                            Judging heat by someone's words is pretty impossible...

                            There are to me just four basic temperatures detectable and describable.....

                            1) Not hot.... my pet cat/dog is that warm

                            2) About as hot as I'd ever want to take a bath/shower in

                            3) too hot to hold onto for long

                            4) I got a little spit on my finger and it went "psst" when I touched the part"


                            Sounds like #3, which is probably not that awful hot in the grand scheme of things, but may be hotter than bearings should be running, althouugh probably not damaging to them.
                            1601

                            Keep eye on ball.
                            Hashim Khan

                            Comment


                            • #15
                              Harbor freight sometimes has laser no touch thermometers on sale. Mine was $39.95. Works great, checks engine temp on thermostat housing, heater hoses etc. Would tell exactly how hot your mill was running at any point (bearing housing ,end mill etc.} JIM
                              jim

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