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ER collet system

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  • ER collet system

    Please forgive me for asking a probably really dumb question, but being really new to collets I figured I would check with the people that actually know what they are doing lol.

    I am going to have my buddy make me a new mill shaft and want to set it up for a collet system. After a lot of reading it seems that the ER style is the best way to go, so I started reading about them. While I haven't found any info yet as to what the actual numbers mean (like ER16, ER-32) it seems the larger the number the bigger the dia the collet will hold.

    So question is, with all the collet sets I see advertised (the ones that come with the chuck and screw on cap) that are for example R8 .... are ALL the chucks the same outside dimension (would assume R8 is R8, but im dumb on this) with only the inner dimension being different, based on the ER number. So, could I swap a ER-16 and ER-40 in the same shaft ?

    I want to be able to get a new shaft (or spindle, not sure on the proper terminology lol) made that will give me the most flexibility I can get

    Sorry to bug you for what is probably such a dumb question, but after 3 hours surfing for any data on collets I still am not clear (maybe my brain is too old and I need an updated memory card lol)

  • #2
    An R8 spindle will take ER collet chucks from ER16 to ER40, although the ER nut that holds the collet in place differs in size considerably from ER16 to ER 40. Look a under collets
    for pix of the their R8 ER chucks for an idea of the variance. Spindle is the word your are looking for I believe when you refer to mill shaft. The answer to your other question, yes any R8 tooling will fit
    the R8 spindle. Unless you have a high speed spindle however there is not much point in more than one ER collet chuck. Tooling in ER16 size generally implies spindle speeds in the 2000 to 10,000 rpm range.
    Last edited by sch; 03-25-2013, 12:02 PM.


    • #3
      thanks very much for the explanation and the link, it sure helps to see actual pics of things in use. Well currently my spindle range (via pulleys) is between about 150 RPM and 6000 RPM. Most of the work I do isnt tiny, so using 1/2 or 3/4 shank stuff is common (why I figured maybe a ER-32 or ER-40)

      I guess the other question I have is with the spindle itself. I can have a buddy make me on for what ever I chose (MT, but probably R8), since he has more than a dozen lathes from 3 ft ones to ones to do huge crankshafts. Once the spindle is done, do I need to heat treat it ? If it is a good idea I can ask him to assist me with that too (read about it but have yet to try doing it).

      Again, thank you and to everyone else that takes the time to answer my questions, which are pretty lame sometimes. I love this forum as I have learned more in the few weeks I have been here than years reading stuff on line and watching machinist work. You guys are the best Thank you


      • #4
        For the mill you want to use R8 spindle. That will give you the most flexibility and tons of cheap tooling choices. Then you can use any ER (extended range) collet chucks with an R8 shank.
        For making the spindle, the ideal situation would be to make it out of a high carbon air hardening steel, harden, draw it back to about 45 - 50 Rc. You want to leave the bearing journals about .015 oversize and the R8 part about .015 undersize until heat treat is done, then grind the bearing journals to size on centers and grind the R8 part turning on the spindle bearings or the journals.
        Last edited by Toolguy; 03-25-2013, 12:56 PM.


        • #5
          Thanks for advise on the materials, going to see what diameter I can make it out of and give it a shot. Will probably look for a place that can harden it for me as Im not sure I could get it right myself lol. Hopefully I can tackle this, being the newb that I am and with limited tools. Will have to read up on grinding as thats something else I know squat about lol.


          • #6
            If the spindle is big enough then consider an NMTB taper in 40 size or bigger.
            Paul Compton


            • #7
              Well, I kind of have free play with the spindle, as the one currently in was made for a chuck (which sheared at the threaded end, plus I think collets are the way to go) and is 1" dia (using pillow bearings blocks). If I have to go to a bigger dia (1 1/4" or 1 1/2") I can change out the bearings with something else, like press fit ones into steel plates if need be. Since its a home made machine I have a lot of leaway, just not a ton of cash to buy a premade spindle. So far it looks like I will need to spend about $150.00-$250.00 for a ER collet set for R8, which means I need to make this spindle myself or Im better off buying a used mill (which wont ever happen as the wife would shoot me lol).
              I figure since its a home made affair all I can do is get it as close to perfect as possible, but doubt I can get 0.002" resolution with the tools I have. I know its not ideal but chances are I wont even be able to afford someone heat treating it, let alone grinding it I know many here can turn out super stuff, but as I am a machinist-wanna-bee with no real life skills, I get pretty excited if the thing even works LMAO. I may not succeed (another reason to keep cash outlay as low as possible) but at least I enjoy trying, as thats why I got the lathe in the first play, to at least try to make things

              Either way, I have learned a ton of stuff here, and thats really all that matters in the end, learning and "playing"


              • #8
                Well, after contemplating the work involved making an R8 spindle, Im wondering if its better to bite the bullet and buy one I can modify. I guess I could find a way of lengthening the read made unit to the size I need (which is about 18" long). I found this one courtesy of one of you


                One question I had was all the R8 drawings I have seen have a "key-way" marked on them, but this one doesn't show it ?? Am I missing something ?

                If I can figure out a way to add an extension to this then it may make life so much easier


                • #9
                  The R8 key way is a sore point.... Because some spindles with the internal key have been found/manufactured with the internal key improperly positioned so the R8 tool will not fit. These are
                  generally of far eastern extraction. General opinion is that the internal key in the spindle does NOT contribute in any way to the functioning of the spindle/tool interface, which relies on friction
                  alone to work. Dinna fash yourself over this. You might check with Griz or Smithy over available spindles in R8 for their mill drills which would be longer, though not likely 18"
                  Last edited by sch; 03-25-2013, 06:45 PM.


                  • #10
                    You can probably find a used Bridgeport R8 spindle on eBay cheap. They are about 23" long.


                    • #11
                      Well, have looked for a used BP one, average price $550.00 on Ebay I did a bit more digging on LMS and found a longers one


                      Its about 12" long which I can live with Since the key-way isnt a sticking point now I will probably get this one. One thing for anyone that knows, should I grab 2 bearings from them or just source ones myself. Not sure if these bearings would be ok or if I should look for another more robust type. Probably going to have to build some form of housing to hold both bearings and be able to true it up on my head.

                      What do you all think, will this spindle hold up OK (assuming they are already ground and hardened).


                      • #12
                        Contact plaza machinery.

                        He might have a used spindle. You can also get the spindle in quik-switch 200 which allows faster changes and dedicated tool holders with a fixed offset.


                        • #13
                          Oh, if you are looking for a generic mill spindle I have a couple r-8 spindle shafts lying around.


                          • #14
                            Yes, basically all I need is some form of R8 Spindle, as long as the total length is at least 12". With the set up I have I need around 12" from the face (where the collet goes in) to the end for it to work with my set up (currently the spindle in there which is a 1" shaft has the lower 8" for "bearing area" and the upper section for belt pulleys. So any R8 spindle that's at least 12" long (16 would be better) will work for me. The BP ones I have seen are more than long enough, but even the used ones carry a hefty price tag.
                            If you have one you can part with just let me know what you want for it. While the LMS one could be made to work, its pushing the limits of being short.