Reported to be the only system that provides simultaneous taper and flange contact in a 7/24 cone interface, the Big-Plus dual-contact connection between the machine and tool is robust, reliable and accurate. Despite the fact that Big-Plus was developed over 25 years ago in Japan by Big Kaiser’s parent company, Big Daishowa, the adoption of the spindles is still seeing solid growth across industry.

Christian Spicher, head of sales and marketing at Big Kaiser, says: "Many manufacturers will already have Big-Plus compatible machines, and many of their spindles may actually be Big-Plus compliant, but they may not be aware of this fact. As a result, machine tool users are missing out on the benefits provided by this rigid dual-contact interface.”

For customers unsure of whether they have a Big-Plus spindle, the easiest way to check compliance is to place a standard tool into the spindle and see how large the gap is between the flange face of the tool holder and the spindle face. On machines without the Big-Plus system, the standard gap for DV50 should be clearly visible at approximately 3.2 mm. With a Big-Plus DV50 spindle, the gap is approximately half that size. Naturally, gap sizes vary accordingly for DV40 and DV30 configurations, but nevertheless, with Big-Plus the gap is always visibly smaller compared to alternative spindle interfaces. As another option, manufacturers can ask their local ITC representative to confirm compatibility.

While competitors offer dual-contact tool holders that claim to provide a similar flange and taper contact solution to Big-Plus, these holders are not typically made to sufficiently tight tolerances and may not provide a sufficiently rigid contact interface, says Big Kaiser. Using unlicensed tool holders risks a less robust connection and expensive spindle damage, potentially voiding the machine’s warranty.

To help its customers, Big Kaiser has developed a simple test. If a Big-Plus spindle is used with standard V-flange tools, over time this will result in wear on the spindle and alter its geometry. Since a rigid, simultaneous taper and face contact is required, geometry is a critical factor, and even minor deviations will impair the Big-Plus spindle’s ability to deliver its full potential. To address this issue, ITC can now offer special spindle and tool-taper cleaners, as well as arm-alignment tools. However, to restore a Big-Plus spindle to its proper specifications, the most effective option is a certified regrind.