Announcement

Collapse
No announcement yet.

Brief Review: ER-40 Collet System

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Brief Review: ER-40 Collet System

    (I evaluated an imported 6-jaw chuck recently. I wasn't happy with the product, it didn't suit my purposes so I returned it to the distributor. But the Chinese are capable of making high quality metalworking equipment, as we know. I'd like to share the following experience as an example of this point. I'll post the other - less favorable - review at another time.)

    After being disappointed by a recent experience, I selected a different distributor this time. I've dealt with the distributor before and would characterize them as follows: the products are fairly typical with a slight advantage in cost, depending on what you are buying. They have a good return policy (that's the common characteristic of these importers, right ? They HAVE to have a good return policy or we'd never buy anything from them, LOL, since the return rate is high).

    This is the workholding device that I required for various needs, in the form of a packaged set:



    The set consists of a NMBT-40 (similar to CAT-40) collet chuck, locking nut and spanner wrench plus a set of ER40 collets from 1/8 inch to 1 inch diameter in 1/16 inch increments. I received the shipment a couple of nights ago and finally got around to removing the individual parts from their sealed-in-oil plastic baggies. The Chinese manufacturers have improved greatly over the past two decades in their manner of packaging and preservation, especially for small parts. (Machinery is a slightly different proposition, the use of a gummy protective coating, applied liberally to near-inaccessible areas is a source of frustration when trying to clean and lubricate a new machine.)

    These parts cleaned up nicely in a plastic bucket of mineral spirits with a soft cloth, and they look great ! Except for the spanner wrench, the external surface of the locking nut and the large driving ring on the NMBT-40 chuck every surface is ground (all of these parts appear to be forgings, black-oxide coated, by the way). The fifteen collets are likewise ground on all surfaces except for the rear and the thin slots on each collet that allow the devices to collapse over a wide range. The number of slots varies, depending on collet size, from sixteen down to twelve on the very smallest collets for obvious reasons.

    It is because of the many slots (and the fact that the collets are slotted from both the face and the rear) that these devices have come to be greatly appreciated for their precision, gripping power and the ability to accommodate a wider range of diameters than any other collet device except for the steel-blade-in-rubber-bushing types like those found in tapping heads. Here is a close-up photo showing front and rear of typical collets:



    Most popular workholding collets (e.g. 5C and R8) have three, sometimes four slots and the useful range is the nominal diameter minus perhaps .001 or .002. The reason is simple: larger workpieces "spring" the collet tapers outward and they no longer fit the spindle taper properly. Smaller workpieces achieve only line contact along the center of each individual "finger" of the collet rather than the desired area contact. The accuracy is slightly degraded by this condition but more importantly, the gripping power is reduced substantially and there is risk of permanent damage to the collet if the drawbar is torqued excessively to provide more grip.

    After looking around for a while, I formed the impression that ER collets seem to be more widely used when spindle horsepower is greater than around 2 HP. The various "ER" series of collets with their many more "fingers" to hold the workpiece, maintain a tighter grip over a wider range of workpiece diameter. Frankly, I'm no expert regarding these collets but I have read that they are capable of accommodating a diametral variation of 1/16 inch (imperial sets), which suggests that 1/16 increments should be able to grip any diameter between the minimum and maximum collet diameters, provided that the workpiece isn't tapered. Here is an intentionally exaggerated sketch of the two types of collet construction:



    The diameter of the workpiece and the diameters of the collet "fingers" are identical in both sketches. Notice how much greater the gripping area of the second collet has become by doubling the number of slots and narrowing the fingers. And because the individual fingers are more flexible, they can accommodate greater deflection and therefore greater variation in workpiece diameters. (The actual ER-40 collets have even more slots thus greater flexibility and gripping power.)

    After cleaning and wiping down the set, I installed the NMBT 40 chuck in my horizontal milling machine, snugged the drawbar and arbitrarily selected a 3/8 collet for my first "qualification" measurement. Placing a four-inch length of ground 3/8 drill rod in the collet, I tightened the locking nut and measured the minimum/maximum runout. I wasn't at all pleased to see runout of .0030 inches when the booklet that came with the set stated that the factory specification is 0.0008 inches. I tried a 1/2 inch collet and saw similar results. My initial thoughts were, "Here we go again !"

    I removed the NMBT-40 chuck and cleaned the tapers of the spindle and chuck again, then I measured the spindle runout of the machine itself (although I knew it was true). No problem, hardly a flicker on the DTI (I was using a .0005 dial test indicator for these measurements since one was already parked on the mill table in a magnetic holder. (I'm usually reluctant to install the 0.0001 indicator, both from laziness and because I use it only when I must, due to the limited range of .005 travel.)
    Last edited by randyc; 12-07-2010, 11:18 PM.

  • #2
    Repeating the runout measurements, I obtained substantially the same numbers so I got out the camera and started documenting the runout numbers, reluctantly conceding that this set had to be returned. After taking several photos, on a whim I removed the CAT-40 chuck and rotated it in the spindle 180 degrees.

    BINGO ! The following are the minimum/maximum runout measurements (0.0005 inch graduations):



    Maximum runout measurement (0.0005 inch graduations):



    I was pleased with the 0.0006 inch runout, measured 1.6 inches away from the collet face, which corresponded nicely with the factory specification of 0.0008 at the same distance. Now I don't know if the collet chuck actually has to be oriented in this exact manner to obtain these results or if I simply dislodged a particle of dust when I turned the chuck around, LOL. Doesn't make a bit of difference to me … if it has to be mounted a certain way, I have no objection to doing that. After all, that is routine practice to obtain best performance from a 3-jaw chuck in a lathe. What could be simpler than punching a couple of marks on spindle and on chuck ?

    So, that's it - after checking a couple of different collet diameters, I pronounce this experience completely satisfactory. I don't know if I got a particularly good set for my $175 or if the distributor received a particularly good lot - but I am sufficiently happy with the tooling that I promptly ordered both morse taper and R8 collet chucks from the same vendor (to accomodate the set of collets). This will allow the same set of collets to be used in other machinery.



    The two tools on the left are new ones. The small Morse Taper/ER-40 fits the vertical head for my horizontal mill and the other is R8/ER-40 in the event I may want to use the ER collets in the other vertical mill. A further use for this versatile holding system follows from the fact that the Morse Taper in the horizontal mill vertical head is the same as the one in my lathe tailstock. The ER-40 collets in the lathe tailstock are handy for counterboring (with end mills) as well as holding drills, some reamers (if floating reamer isn't required), broaches and other tailstock tooling. (An additional benefit is the ability to hold tooling that is too large to fit in a 1/2 or 5/8 drill chuck.) Here's a photo of a one inch ball end mill with 3/4 inch shank held in the tailstock for making a finishing pass on a ball-socket joint:

    Comment


    • #3
      One reason for tooling the horizontal mill with ER-40 collets was the high cost and limited availability of suitable arbors. For best utilization of the machine, the one-size-fits-all arbor may not work well and probably explains why so many used arbors are bent (from using arbors that are too long for heavy work). Some of the tooling that came with my mill included a shell mill arbor and two full-length arbors (7/8 and one inch diameters).

      Here's a photo of the shell mill with carbide inserts making a finishing cut on some HRS without coolant. The electronic flash did a good job of "freezing" spindle rotation:



      This photo shows the full-length arbor with slitting saws and various spacers installed:



      I wanted the ability to install intermediate length arbors so that the end support could be "choked-up" on any cutter (or combination of cutters) for maximum rigidity. That led me to consider simple ways of making arbors of any particular length and diameter.

      Here's a sketch of a "typical" stub arbor. Although spindle interfaces are standard, the end configuration isn't. The end needs to be threaded for a retaining nut, turned to suit a bronze end-support bearing, center-drilled for a hardened end-support center, combinations of several options and so forth. Unless you're lucky, any arbor - used or new - is going to require some modification.



      The lower part in the sketch depicts a fairly simple arbor that can be made to any arbitrary length that suits a particular set of cutters. The material can be ground drill rod (or a semi-hard alloy of reasonable cost), I think three feet of ground one inch drill rod from Enco costs about $25.

      But the ER-40 system has a lot more going for it than this single reason; that's why I decided to go ahead and buy collet chucks for several other machines. I hope that my experience with this system might be helpful to others who are considering it.

      Cheers,
      Randy C

      Comment


      • #4
        I have run ER's TG100, R8, B&S, Rubberflex, and MT collets, and they all work to some extent. I prefer TG for tough work.

        Using a collet to drive a 3 inch or larger keyed cutter on an arbor, is a poor choice.

        The cutter will at some least wanted time, get hung/overloaded/clogged.

        The arbor will then spin in your ER WUNDER collet, taking the collets precision with it. While spinning the feed is still moving, bending arbor or taking off more teeth/breaking cutter. Also possibly bending collet out of shape...

        Collets are one form of toolholding, not the ONLY form.

        A under $50, NMTB 40 1in or 3/4in endmill holder, would allow you to also use a flat (weldon style) on your arbor stub. And 1 in end mills, boring head shanks, etc. The end mill holder will also give you a lot more vise clearance without the clunky collet nut in the way.

        The amount of runout on a typical milling machine saw cutter mounted on an typical arbor is a bit amazing..
        Last edited by Bguns; 12-08-2010, 12:55 AM.

        Comment


        • #5
          Originally posted by Bguns
          I have run ER's TG100, R8, B&S, Rubberflex, and MT collets, and they all work to some extent. I prefer TG for tough work.

          Using a collet to drive a 3 inch or larger cutter on an arbor, is a poor choice.

          The cutter will at some least wanted time, get hung/overloaded/clogged.

          The arbor will then spin in your ER WUNDER collet, taking the collets precision with it. While spinning the feed is still moving, bending arbor or taking off more teeth/breaking cutter. Also possibly bending collet out of shape...

          Collets are one form of toolholding, not the ONLY form.

          A NMTB 40 1 or 3/4in endmill holder, would allow you to also use a flat (weldon style) on your arbor stub. And 1 in end mills, boring head shanks, etc.

          The amount of runout on a typical milling machine saw cutter mounted on an typical arbor is a bit amazing..
          Thank you for your comments, Bgun.

          I don't recall suggesting that collets were the ONLY form of toolholding. I do have some NMBT-40 tooling and I'd love to have a full set of NMBT-40 stub arbors, shell mill holders, end mill holders, and so on. That's NOT going to happen - I don't support a family with this machine.

          The machine (and the workholders) are not required for heavy work since I am a home shop machinist, as the forum title suggests. This post (and ALL of my posts) was intended for those who share my interests and do not own multi-horsepower machinery OR the budget for an extensive tooling inventory. I don't doubt that, for your needs, ER-40 may be a "poor choice" but CAT-40/ER-40 collet tooling systems seem to be very common in 2 - 3 horsepower production machinery - just a personal observation.

          The tooling that you recommend is exactly what I didn't want - that was the point of the last couple of paragraphs of my post. Collet-held tooling is easy to make and completely adequate for my needs and probably for those of us for whom this is a "hobby". Industrial tooling is expensive and I do not have the option of deducting it from my self-employment tax.

          Cheers,
          Randy C

          Comment


          • #6
            I have an honest question, and I'm not being facetious here. Why do people use collets? Is it because of increased accuracy i.e. runout over that of a 3 or 4 jaw chuck?
            Brian Rupnow

            Comment


            • #7
              Originally posted by brian Rupnow
              I have an honest question, and I'm not being facetious here. Why do people use collets? Is it because of increased accuracy i.e. runout over that of a 3 or 4 jaw chuck?
              In a lathe as I understand it... yes. You can easily beat a 3 jaw for runout and it's a lot faster than dialing in a 4 jaw. On the mill, since I have a by 1/16's set of ER25's I can hold most any drill bit in the collet and get much better runout than in the drill chuck.

              If I start planning to chew out significant amounts per pass I generally go back to end mill holders or normal R8 collets.

              Comment


              • #8
                Collet

                Also, on the lathe, with a lever collet closer and collet stop if needed, you can change parts with the lathe running. On a production run this saves a huge amount of time and effort over stopping the lathe, twirling the chuck key 2 times and restarting for each part. I use the lever collet closer a lot of times anyway just for the convenience factor. It is THE easy way to open and close a collet. For production on the mill I use a lever indexing head or an air powered collet closer. This is for 5C collets. I have a full set in 1/ 64 increments plus numerous specials. I also made a 5C to R8 adapter that comes in handy on occasion.
                Last edited by Toolguy; 12-08-2010, 01:34 PM.

                Comment


                • #9
                  Personally, I'd always prefer using the lever-closed 5C collet setup on dad's lathe for fractional inch size parts or raw stock 1" and under. I use the 3 jaw for most other things because it's a 10" Pratt Burnerd Super Precision and runout is less than .001" everywhere. Failing those two options, we've got a 12" 4-jaw Pratt Burnerd chuck that's been mounted only once or twice so far. That's only because the other two options work as well as they do.

                  I have used ER collets in the smaller sizes (ER16, ER11, & ER8) for years. I think they're best used for toolholding rather than workholding, but whatever works best for you is the right choice.

                  Comment


                  • #10
                    I recently bought a very similar set of collets with an MT3 arbor. They were cheap and I initially had real difficulty getting them to hold anything worth a damn. Figured I got my money's worth until I realized that the clamping nut had it's taper ground off center. After chucking it into the lathe and cutting a new taper on center they work like a charm. Now I find them near indispensable for many tasks.

                    Comment


                    • #11
                      Originally posted by randyc
                      ...The lower part in the sketch depicts a fairly simple arbor that can be made to any arbitrary length that suits a particular set of cutters.
                      One possible pitfall with this is that it has no shoulder against which to tighten the cutters and relies on the ER nut to provide both this resistance and a true-running surface to keep the cutters true. Also tends to pull the arbor out of the collet as you tighten the cutter-retaining nut and as it self-tightens during use. Also, also means you have to run the spindle in the direction such that the ER nut is not loosened by the cutting forces (a lot of arbors have LH threads).

                      Easily solved with an integral shoulder on the arbor.

                      Comment


                      • #12
                        I response to Brian Rupnow, I like collets because they are easier to work with (5C collets), don't leave that many marks on the parts, and they are safer. You can hold your file or tool right up near the collet without nearly as much fear as when using a chuck.

                        As I have stated here before, I got sucked into the ER collet scheme for holding parts in a lathe and I think it is a sham if you want to hold short parts. You can make discs to put int he back of the collet to support it, but if I have to go through all that I might as well have used a chuck! Basically on a large collet like a ER40 you have to have maybe 3/8" to 1/2" into the collet to engage enough into the taper to lock down. On large parts or bar stock going through your spindle its not so much a problem though. On a 5C collet you don't have this problem at all.

                        KEJR

                        Comment


                        • #13
                          Originally posted by randyc
                          Thank you for your comments, Bgun.

                          I don't recall suggesting that collets were the ONLY form of toolholding. I do have some NMBT-40 tooling and I'd love to have a full set of NMBT-40 stub arbors, shell mill holders, end mill holders, and so on. That's NOT going to happen - I don't support a family with this machine.

                          The machine (and the workholders) are not required for heavy work since I am a home shop machinist, as the forum title suggests. This post (and ALL of my posts) was intended for those who share my interests and do not own multi-horsepower machinery OR the budget for an extensive tooling inventory. I don't doubt that, for your needs, ER-40 may be a "poor choice" but CAT-40/ER-40 collet tooling systems seem to be very common in 2 - 3 horsepower production machinery - just a personal observation.

                          The tooling that you recommend is exactly what I didn't want - that was the point of the last couple of paragraphs of my post. Collet-held tooling is easy to make and completely adequate for my needs and probably for those of us for whom this is a "hobby". Industrial tooling is expensive and I do not have the option of deducting it from my self-employment tax.

                          Cheers,
                          Randy C
                          Hi,

                          I think you missed his point. You don't need a full set of NMBT40 holders. Just one. Get either a 3/4" or 1" end mill holder. the set screw that holds the Weldon flat secure will provide better grip than an ER collet. Particularly on large cutters. Then you just need matching straight shank arbours with a flat for your face mills and boring heads or what ever other tooling you want to use. You can use the straight shanks you already have, just mill or grind a flat into them. Nor will it hurt their continued use in your ER collets either. Or make some new arbours yourself.

                          And as Bguns also suggested, those Weldon style end mill holders are often a lot more convenient to use in a horizontal mill. They reach over the solid vice jaw easier than a holder with a big nut on it.

                          I understand about the money part. But that one NMTB40 holder would have cost you less than half of that ER collet set and holder.

                          dalee
                          If you think you understand what is going on, you haven't been paying attention.

                          Comment


                          • #14
                            Originally posted by djc
                            One possible pitfall with this is that it has no shoulder against which to tighten the cutters and relies on the ER nut to provide both this resistance and a true-running surface to keep the cutters true. Also tends to pull the arbor out of the collet as you tighten the cutter-retaining nut and as it self-tightens during use. Also, also means you have to run the spindle in the direction such that the ER nut is not loosened by the cutting forces (a lot of arbors have LH threads).

                            Easily solved with an integral shoulder on the arbor.
                            First - the post evaluated the ER-40 system, rather than the afterthought of being able to quickly and inexpensively make an arbor for a special purpose.

                            However, since the arbor is now part of the topic, the sketch depicts a shoulder on the arbor that prevents the arbor from being forced into the collet (should the arbor not be bottomed against the drawbar). Spacers are always installed between the collet face (or any other toolholder) before a cutter is installed - otherwise the table can't be cranked close enough to the column for effective work. The spacer provides the shoulder function that prevents movement of the cutter.

                            I'm not getting the "pull the arbor out of the collet" thing. The ER-40 system offers a major improvement over other systems: dual tapers, front and rear. But perhaps that's not what you refer to - insofar as any other mechanism that would produce that effect, maybe I didn't emphasize adequately the point about being able to support the arbor by "choking up" ?

                            That was the entire idea of making short arbors. The overarm not only supports the free end of the arbor but also applies adequate axial pressure to prevent movement of the cutters (note the thrust washer in the sketch). Perhaps all horizontal milling machines don't include the features of my small machine.

                            I also don't get the "loosening" of the ER nut during operation - the only effect that could do so is the inertia of the nut - IF the spindle was reversed at some very high speed which is definitely not within the capability of any machinery that I own, LOL. (Check out the recommended tightening torque for ER-40 systems, as a matter of interest.)

                            Thanks for your comments.
                            Randy C

                            Comment


                            • #15
                              Originally posted by dalee100
                              Hi,

                              I think you missed his point. You don't need a full set of NMBT40 holders. Just one. Get either a 3/4" or 1" end mill holder. the set screw that holds the Weldon flat secure will provide better grip than an ER collet. Particularly on large cutters. Then you just need matching straight shank arbours with a flat for your face mills and boring heads or what ever other tooling you want to use. You can use the straight shanks you already have, just mill or grind a flat into them. Nor will it hurt their continued use in your ER collets either. Or make some new arbours yourself.

                              And as Bguns also suggested, those Weldon style end mill holders are often a lot more convenient to use in a horizontal mill. They reach over the solid vice jaw easier than a holder with a big nut on it.

                              I understand about the money part. But that one NMTB40 holder would have cost you less than half of that ER collet set and holder.

                              dalee
                              Thanks, for explaining and that is a good point. NMBT-40 end mill holders are great toolholders and it would be fairly simple to make 3/4 or 1 inch toolholders to fit a single holder ... but the ER-40 set works on THREE different machines, provides good performance and is very cost-effective.

                              The system covers 90% of the range that I normally require with LOTS of holding power. I can grip any particular piece of scrap (or the two or three diameters of OH drill rod that I keep around) used to make a temporary boring bar, reamer, angle cutter or whatever ... don't have to turn something to a specific diameter to accomodate the single NMBT-40 end mill holder that I own.

                              Cheers,
                              Randy C

                              edited to add: regarding Bguns comment, that little milling vise isn't a normal feature on the horizontal - there are a pair of substantial moveable jaws normally mounted on the table that don't have the drawback of the small vise (regarding the overhang).
                              Last edited by randyc; 12-09-2010, 01:18 AM.

                              Comment

                              Working...
                              X