DRAWBARS
As the force behind the toolholder and the stability of the spindle, you can’t underestimate the importance of the right drawbar. Not only do we manufacture our own drawbars for an improved design, but we also provide only quality materials in our thicker drawbar shaft for better balancing and longer lifespan.
How We Counteract the Natural Breakdown of a Drawbar
By applying what we know of a Bellville spring’s lifespan, we have created a superior drawbar that will keep an effective clamping force longer. As the Bellville springs flatten inside the drawbar, providing the clamping force needed to keep the spindle steady and in place, they naturally begin to wear down due to tension and corrosion.
They naturally lose clamping power and become susceptible to breaking due to fatigue and corrosion according to Dr. Scott Smith. Smith estimates that average life of a drawbar is only two and a half years if a typical CNC machine is run for two shifts every day. Besides this natural break down, one broken spring increases the pressure placed on the other springs, lowering their lifespan even further.
How do we counteract this natural corrosion? Our Belleville springs are coated with a special non-corrosive coating to keep rust and dissimilar metal corrosion from becoming an issue within the center of your spindle shaft. These materials contaminate your spindle taper and tooling, eventually ruining the inside of the spindle shaft and prohibiting cost-effective future spindle rebuilding.
Why Drawbar Health is So Important
Peter Zilinski wrote a lengthy article on how drawbar corrosion can affect how your entire machine functions. Here are three problems he lists that can come from an aging or breaking drawbar:
- Chatter from a previously stable and precise tool
- Spindle grinding
- A machine crash resulting from a tool pulling out of the spindle.
While the first two are seemingly small, the last one is very serious and one reason that you should regularly schedule check-ups and maintenance for your drawbar.
Our specially-coated springs and in-shop manufactured drawbars will last longer with more protection from corrosion and breakage. With proper checks and maintenance, you can easily make repairs and keep your drawbar in top shape.
