Spindle Drawbar Force Gages

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Truly the best, most economical tool for spindle drawbar force testing!

CNC Machines using pull-studs for tool retention experience a slow but progressive loss of tool holding force from the time the machine is new. This little known fact has a major impact on surface finishes, cutting tool life, and eventually on your productivity.

Testing a drawbar requires a force gage which simulates a tool being held in the spindle. Those spindle force gages were extremely accurate electronic gages costing $4,000 or more. But now, the Clamprite Gage performs this measurement at a fraction of that price.

The Clamprite Gage was designed for accurate spindle tension testing right on the machine. The actual force exerted by the spindle drawbar mechanism is read directly on the dial, so there is no need for any calculations or conversions. Drawbar force checking is made easy using the Clamprite drawbar force gage.

Drawbar testing takes less than one minute, so production time is barely affected. Its simple and rugged design requires no batteries, electrical cords, or delicate electronic components to pre-set, calibrate, or burn out.

The Clamprite Gage works on any machine using the pull-stud method of tool retention. And with the Clamprite HSK Spindle Adapter, you can now test HSK spindle drawbar force for a fraction of the cost of other methods. HSK type spindles must be tested often. HSK drawbars have considerably higher drawbar force than other taper types of similar size, and must retain at least 75% of new spec. pressure in order to seat the arbor properly.

And now CAPTO spindles can also be tested with the Clamprite Gage using the CAPTO Spindle Adapter.

Finding just one drawbar problem before major damage occurs or before productivity is affected will return the price of this tool many times. The Clamprite Gage costs about what you would pay for just a few cutting tools. Begin testing your machine drawbars on a regularly scheduled basis. Let the Clamprite Gage work for you.

Machining with low drawbar force is like machining with a loose cutter!

Drawbar mechanisms are located inside of the machine's spindle. Since these mechanisms are hidden from view, very few people have ever seen one. So when chatter, poor surface finishes, low cutter life, tool holder corrosion and fretting, and sporadic problems begin affecting cycle times; the programs, tools and fixtures, feeds and speeds and cutters are frequently examined. Although the drawbar may be the problem, it is seldom suspected until after much time has been spent exploring more conventional solutions.

Low drawbar pressure will create some very elusive and challenging machining problems.





Spring-pressure holds tools and cutters in the spindle against the cutting forces.

When the springs wear out, a tool can be pulled from the spindle during a cut.


Drawbar springs do not wear slowly and evenly. Regular testing is important because the springs do not slowly wear out. Drawbar springs fail by breaking. Drawbar force drops suddenly and dramatically once one or two springs fail.

Drawbars operate under heat, humidity, tension, compression, and severe vibrations. It's not surprising they wear out faster than the rest of the machine. Actually, it is amazing that they last as long as they do under such harsh circumstances.

Everyone has heard about a machine losing a spindle, but you seldom hear of a machine losing a drawbar. That is because when a weak drawbar "drops" a tool it is usually during a cut with an endmill or face mill. When that happens, you will likely lose the spindle, the cutter, the part and the fixture. Worn drawbars are the number one cause of spindle damage. The drawbar gets repaired along with the rest of the mess but seldom gets the blame it deserves.

A drawbar may only cost $600 to $1,200 to repair, but losing the spindle may easily cost over $10,000 - particularly when lost productivity is added to the bill. Avoid all these troubles. Test your machine's drawbar condition with the Clamprite Gage.

See our article in Modern Machine Shop magazine: Don't Forget the Drawbar

All Clamprite Gage Kits come with a Certificate of Accuracy traceable to NIST for ISO 9000 shops



Find out if your drawbars Clamprite.

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