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  • ER collets

    The basic question is; will a 5/8" SAFELY hold a 15mm drill bit.?? That amounts to a collapse of about .035" . First off I've seen these but have only used the set on the mill at the "Makerspace" to hold the drill chuck and "inch" dimension cutters so far. Now have an application that would be convenient if I can use metric drill bits. So what amount of collapse is safe? I've looked and looked and can find no numbers like the usually referred to, ER32, or ER40 anywhere on the set. I'm pretty sure they go to at least 1" (I'm home and won't be down to the machine for a while with this Covid shutdown ) So any helpful hints will be appreciated .
    ...lew...

  • #2
    5/8" seems to be 15.875 mm. you need a 16 mm collet for that. er collets (at least the good ones) have a range of 1 mm down from nominal. usually it will also say "16-15" on a 16 mm collet. (i personnally would not stress a precision collet beyond 0.5 mm.)

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    • #3
      All ER collets are metric.
      If you have fractional ones,
      they are metric.

      --Doozer
      DZER

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      • #4
        So er collets with fractions of an inch on them are just to please metricophobes.

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        • #5
          To hold a 15 mm drill bit, use a 15 mm ER collet.

          If yours are marked in fractions, use the one marked 9/16", actually 15 mm.
          The ER collet marked 5/8" is actually 16 mm. Holding a 15 mm bit will be at its limit.

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          • #6
            Originally posted by Doozer View Post
            All ER collets are metric.
            If you have fractional ones,
            they are metric.

            --Doozer
            And if you have Chinese ones, they are neither.
            I just need one more tool,just one!

            Comment


            • #7
              so you guys figure it i get these collets https://www.amazon.com/Rego-Fix-1132.../dp/B01M9GVS9N they will be metric?

              Comment


              • #8
                Originally posted by Doozer View Post
                All ER collets are metric.
                If you have fractional ones,
                they are metric.

                --Doozer
                Pure and simple BS. Collets are available in both inch and metric dimensions...
                Keith
                __________________________
                Just one project too many--that's what finally got him...

                Comment


                • #9
                  I have a comlpete set of ER collets, all marked in inches.
                  Beaver County Alberta Canada

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                  • #10
                    Originally posted by DrMike View Post
                    ...If yours are marked in fractions, use the one marked 9/16", actually 15 mm...
                    Say what? 15 mm is .5905", 9/16" is .5625", almost .030" difference.

                    In Lew's case using a 15 mm drill in a 5/8" collet results in a .035" collapse. The collet will likely do
                    that but there is a real risk of permanently damaging it. Once overstressed the collet may not grip
                    properly the next time and it may also show some runout--that's my experience anyway...

                    Keith
                    __________________________
                    Just one project too many--that's what finally got him...

                    Comment


                    • #11
                      I found the following quote at Maritool's ER collet sizes page.

                      ER32 series collets have a capacity of .02-.787 inches. Each ER32 collet has a range of .039 inches(1mm). ER32 Collets .094 and smaller have a range of only .015 inches. The size indicated on the collet is the largest size it can hold and can be collapsed smaller within its collapse range mentioned above. For example, ER32-1/4 can grab a round shank from .250 diameter to .211 diameter. Please refer to our ER32 Collet print for general ER32 dimensions.
                      And for ER40....

                      ER40 series collets have a capacity of .094-1.024 inches. Each ER40 collet has a range of .039 inches(1mm). The size indicated on the collet is the largest size it can hold and can be collapsed smaller within its collapse range mentioned above. For example, ER40-1/4 can grab a round shank from .250 diameter to .211 diameter. Please refer to our ER40 Collet print for general ER40 dimensions.
                      So technically your 15mm drill in the 5/8 collet is just barely within the holding range. So TECHNICALLY it should work. And if this was a one time sort of deal I'd say go ahead.

                      But consider this. The inside fit is ground to the nominal 5/8 size. So an item that close to the minimum allowable size is not going to have a great contact area. So it's going to want to slip if you don't tighten the snot out of it. Or you'll need to use great care in how hard you feed the drill. For light duty use I think closing them that far would be OK. But for holding a fairly large size drill bit like this? That's pretty extreme.

                      All in all if this will be a fairly common use for the collets I think I'd want to splurge and buy a metric set to sit along side the others. Or at least fill in the range of collets you have now with the 1/32's sizes. A 19/32 size would only need to squeeze down by about .003 so would be ideal.
                      Chilliwack BC, Canada

                      Comment


                      • #12
                        You say, "Once overstressed the collet may not grip
                        properly the next time and it may also show some runout--that's my experience anyway...".

                        In my understanding, ER collets ARE designed to handle a range of sizes and that range is 1mm or 0.0393". So using them in that range is not over-stressing them.

                        Also it is hard to see how even an over-stressed ER collet could have it's runout changed. Each segment is still the same size or thickness so there would be the exact same distance between the collet holder and the work or tool that it is holding all around it's circumference. I have seen collets (not ERs) that had one of their segments bent inward more than the rest, but that was probably from some kind of accident, probably with nothing being held in the collet. The guidance for the segments of a collet comes from the collet holder and the nut if that is used with that type of collet. Over-stressing may change the rest position of a collet's segment, but it can not change the runout. Only wear or physical damage to the guiding/closing surfaces would do that.

                        It is also hard to see how a collet, ER or otherwise, could not grip properly just due to a past experience where it was over-stressed. I would think that any loss of grip would have more to do with physical damage to the gripping surfaces and the surfaces involved with closing it.

                        Frankly, in my experience, RE collets can be closed all the way down to the point where their slots close completely and they spring back to their original size when that pressure is released. I see no reason not to use them for their full rated range (1mm).

                        As for true inch sizes of ERs, while most are made in metric sizes, I do believe that they do exist. The ones I have are all in metric sizes. But there are various sets advertised where the sizes are given in inches. It is difficult to know if a set that is advertised as inch sizes are really made to actual inch increments. One set that I have was advertised as inch sizes, but upon inspection I found that it was really metric. It may not be infallible, but if you see a set that is advertised with oddly spaced inch sizes, it is probably a metric set. And if you see a set with evenly spaced inch sizes, there is a good chance that it is actually made to inch sizes. But the only real ways to tell would be to either ask or to measure them after receiving the set.

                        Another indicator that a set that is advertised as inch sizes may actually be metric is if the number of collets in the set does not match the range needed, from smallest to largest, using inch sized increments. So an ER23 set that is advertised to cover a range of 3/32" to 3/4" has the 22 collets that would be necessary to cover that range in 1/32" steps, then it is probably inch sizes. But if an ER32 set is advertised with that same description but has only 18 collets in it (2mm to 19mm), then it is probably using 1mm steps and is actually a metric sized set.

                        You say, "...that's my experience anyway..." but I have to wonder just what that experience actually was.



                        Originally posted by LKeithR View Post

                        Say what? 15 mm is .5905", 9/16" is .5625", almost .030" difference.

                        In Lew's case using a 15 mm drill in a 5/8" collet results in a .035" collapse. The collet will likely do
                        that but there is a real risk of permanently damaging it. Once overstressed the collet may not grip
                        properly the next time and it may also show some runout--that's my experience anyway...
                        Paul A.
                        SE Texas

                        Make it fit.
                        You can't win and there IS a penalty for trying!

                        Comment


                        • #13
                          I think you forget one of the primary tenets of machine shop work: "Everything is made of rubber."

                          Those jaws or segments of the ER collet will deform under pressure and there will be a broad area of contact, not just a single line as Euclidean geometry suggests. Jacobs chucks, with only three jaws that have narrow tips, routinely hold large drill bits. My smallest ER collet has four segments and they are much wider than the jaws of a Jacobs chuck.

                          And yes, if I were trying to hold a large drill bit in an ER collet, I would tighten the snot out of it.



                          Originally posted by BCRider View Post
                          I found the following quote at Maritool's ER collet sizes page.



                          And for ER40....



                          So technically your 15mm drill in the 5/8 collet is just barely within the holding range. So TECHNICALLY it should work. And if this was a one time sort of deal I'd say go ahead.

                          But consider this. The inside fit is ground to the nominal 5/8 size. So an item that close to the minimum allowable size is not going to have a great contact area. So it's going to want to slip if you don't tighten the snot out of it. Or you'll need to use great care in how hard you feed the drill. For light duty use I think closing them that far would be OK. But for holding a fairly large size drill bit like this? That's pretty extreme.

                          All in all if this will be a fairly common use for the collets I think I'd want to splurge and buy a metric set to sit along side the others. Or at least fill in the range of collets you have now with the 1/32's sizes. A 19/32 size would only need to squeeze down by about .003 so would be ideal.
                          Paul A.
                          SE Texas

                          Make it fit.
                          You can't win and there IS a penalty for trying!

                          Comment


                          • #14
                            I know that er32 collets have a 1mm range, i.e a 14mm collet should be able to hold anything between 13mm and 14mm. In your case, you should be able to hold a 15mm drill in a 5/8" collet

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                            • #15
                              https://www.lyndexnikken.com/images/...ER.collets.pdf

                              Says it all.
                              Beaver County Alberta Canada

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