How to Check Spindle Drawbar Force with a Clamprite Gage


We offer the Clamprite Spindle Drawbar Force Gage and spindle taper adapters for measuring the drawbar force of CNC milling spindles.

How to Use the Clamprite Spindle Drawbar Force Gage

By placing the Clamprite Gage (with an appropriate taper adapter) into the spindle taper, and causing the drawbar to pull on the pullstud (or retention knob) that you have threaded into the internal transfer screw coupling, it takes less than one minute to check the drawbar pull force against the machine manufacturer’s recommended level. The force gauge is simply hydraulic, with no batteries, no cables and no delicate electronics to go wrong. Since the piston surface area is 1 square inch, a pressure gauge converts directly to pounds of force. Many shops use the Clamprite Gage and most say it paid for itself the first time they used it … because they caught a drawbar exerting low force and they corrected it, before that caused a crash and cost a spindle taper regrind (see Spindle Taper Grinding) or a full spindle repair (see Spindle Repair). Keep a running record of each spindle’s measured drawbar pull, and be alerted to drawbar force loss and trends over time. The more frequently you check spindle drawbar pull, the sooner a spindle drawbar force loss will be detected.

Benefits of Measuring Spindle Drawbar Force

The Clamprite Spindle Drawbar Force Gage is the best selling tool for testing the spindle drawbar pull force of CNC Machining Centers. The use of this economical spindle drawbar force checking tool will maximize machine up time and minimize spindle down time costs associated with wear and damage of drawbars, clamping collets, pull studs, toolholders and tool tapers. By measuring the tool clamping force with this gage, spindle repair costs and repair time can be minimized.

Why Measure Spindle Drawbar Force, Why Check for Spindle Drawbar Force Loss?

Drawbar force is often the first thing to weaken or fail on a CNC Machining Center!

A stack of 100 to 150 Belleville springs provide the retention force that pulls the toolholder into the spindle taper. Belleville springs wear grooves into the drawbar and the friction between these springs and the drawbar can result in drawbar force loss, which can permit chatter, bad finish, reduced cutter life, and scrapped parts. Belleville springs can and do fatigue and break, resulting in extreme loss of drawbar force. Programmers will often compensate for this, unaware that one spring after another is failing.

The toolholder can eventually pull out of the spindle taper during a cut, causing damage to the spindle taper, bearings, toolholder and pullstud, cutter, and fixture. A routine force check with a spindle drawbar force gage would have revealed drawbar force loss, which would be the cue to initiate corrective action.

How to order the Clamprite Spindle Drawbar Force Gage

Check our full webpage for gagehead sizes, spindle taper adapters – Spindle Drawbar Force Gage – or

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