While spindle failures can result from a variety of issues, the majority of premature spindle failures can be traced back to preventable maintenance and tooling problems rather than the spindle itself. The most common root causes include contamination, insufficient drawbar force, damaged toolholders, poor spindle taper contact, crashes, and improper operating practices. Over time, these issues create vibration, heat, and excessive bearing loads that lead to expensive spindle repairs.

At SPS Spindle Parts & Service, we frequently find that low drawbar force is one of the leading causes of spindle taper damage. When the drawbar cannot properly clamp the toolholder, microscopic movement occurs between the toolholder and the spindle taper. This movement, known as fretting, damages the taper, increases runout, reduces machining accuracy, and places additional stress on the spindle bearings.

The recommended drawbar force for your spindle depends on the machine manufacturer, spindle design, and toolholder style. The best place to find the correct specification is in your machine’s operator or maintenance manual.

If you no longer have the manual or the specification isn’t available, refer to the drawbar force chart below for typical values by machine and spindle type. If you’re still unsure, the SPS Spindle Parts & Service team can help you determine the correct drawbar force for your equipment.

Maintaining the proper drawbar force is critical to spindle performance. Too little clamping force can allow the toolholder to move within the spindle taper, causing fretting, taper damage, increased runout, chatter, poor surface finish, premature tool wear, and even tool pullout during machining.

In fact, low drawbar force is one of the leading causes of spindle taper damage. Regular drawbar force testing is one of the simplest and most cost-effective preventive maintenance practices you can perform to extend spindle life, improve machining accuracy, and avoid expensive spindle repairs.

Capellini spindles are designed and manufactured in Piacenza, Emilia-Romagna, Italy, a region internationally recognized for its precision engineering and advanced manufacturing. Located about an hour south of Milan, the Capellini facility combines decades of machining expertise with modern spindle manufacturing technology.

Capellini remains a family-owned company. The founders are still actively involved in the business, while the next generation leads the company—one son serving as CEO and the other overseeing engineering and product development. This hands-on leadership helps maintain the company’s commitment to quality and precision.

Unlike many spindle manufacturers that outsource critical components, Capellini produces most spindle parts in-house. The company began as a precision component manufacturer before expanding into the design and production of high-performance grinding and milling spindles. Manufacturing key components under one roof allows Capellini to maintain strict quality control, achieve exceptional machining accuracy, and ensure consistent performance throughout every spindle they build.

As the exclusive North American representative for Capellini Electrospindles, SPS Spindle Parts & Service provides sales, engineering support, service, and repair for these precision-built Italian spindles.

No. SPS Spindle Parts & Service is the authorized North American repair center for Capellini Electrospindles, so your spindle can be repaired here in North America without the added cost, shipping time, and downtime of sending it back to Italy.

As an authorized Capellini service provider, SPS has direct access to factory specifications, genuine replacement parts, and the technical support needed to restore your spindle to original performance standards. Every repair follows Capellini’s engineering requirements, ensuring the spindle meets the precision, accuracy, and reliability expected from the manufacturer.

By having your Capellini spindle repaired at SPS, you benefit from faster turnaround times, lower transportation costs, and expert service from technicians who specialize in precision spindle repair. Our goal is to return your spindle performing like new while minimizing machine downtime and helping you get back into production as quickly as possible.

A kiss grind removes only a very small amount of material from the spindle taper—just enough to restore proper toolholder contact without unnecessarily reducing the taper’s life. In many cases, the imperfections are not deep wear but raised material caused by toolholder fretting, minor damage, or debris transferred to the spindle taper.

During the spindle taper grinding process, SPS uses precision equipment to remove only the high spots while continuously monitoring material removal. Once the taper achieves approximately 70% or greater contact, we verify spindle runout to ensure the taper is performing within acceptable tolerances. If additional grinding could further improve contact, we discuss the options with the customer before removing any more material.

Our goal is always to restore spindle accuracy and maximize spindle life while removing the least amount of material possible.

In most cases, no. A properly performed spindle taper grind does not significantly affect drawbar force. Before any grinding begins, SPS measures the drawbar force to establish a baseline. After the spindle taper has been restored, we measure it again to verify that it remains within specification.

If we find that the spindle taper damage was caused by insufficient drawbar force, simply grinding the taper will not solve the underlying problem. A weak or worn drawbar can prevent the toolholder from seating correctly, leading to poor taper contact, fretting, chatter, increased runout, and premature spindle wear.

When low drawbar force is identified, we recommend repairing or replacing the drawbar before returning the machine to production. This helps protect your newly restored spindle taper, ensures proper tool retention, and maximizes machining accuracy and spindle life.

At SPS, our goal is not just to restore the spindle taper, but to identify and address the root cause of the damage so the problem does not return.