Over the last 6 months, SPS Spindle Parts and Service has ground a number of BIG PLUS spindle tapers in the field with our portable taper grinding system. As a licensed BIG PLUS partner, SPS has the proper gauging and support to verify the accuracy of your tooling interface, and to re-qualify your taper should it need on-site grinding.
While performing our spindle taper grinding over the past several months, we have seen many of the BIG PLUS spindle tapers have been severely bell-mouthed and not making proper taper contact. After talking with the customers and reviewing their usage, we have found that a number of these companies have been using a combination of BIG Kaiser tooling, and standard V-flange tooling. While the BIG Kaiser tooling on a good taper will provide the proper face and taper contact with long life, the standard tooling only making taper contact does not hold up as well resulting in bell-mouthing of the taper. With this bell-mouthing condition, the tooling begins to move further into the spindle taper, and the result is BIG PLUS tooling that does not function properly, locking up only on the spindle and tool face.
Using standard tooling in a spindle equipped with BIG PLUS is acceptable, but it means having to be more attentive to the condition of your BIG PLUS spindle taper. Using standard tooling with higher cutting loads, as well as low drawbar force, are some of the leading contributors to this premature bell-mouthing condition. Once the taper degrades to this condition, the problem should be corrected as soon as possible, as the BIG PLUS interface has been compromised and is no longer working as designed.