Clamprite - The most economical tool for checking spindle drawbar pressure

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About Clamprite

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 pressure 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. Until recently, 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. Also, the Clamprite Gage can be used with common tool holders as the interface between the gage and machine spindle.

However, the Clamprite Spindle Adapters are less expensive than standard tool holders, and shop owners tell us the cost of the Clamprite Spindle Adapters is returned by the second or third time the gage kit is used. This is partly because finding the particular holder that was used at first can be time consuming, because it is usually back in use on a machine by the time it is needed again.

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.

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.

The Standard Clamprite Gage Kit is Only $769

Have you ever wondered what holds the tools in the spindle while machining?

Click Here to See a Typical Drawbar Assembly

- - 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.

Testing a machine drawbar requires a special instrument. So even if a drawbar is suspected as the problem, very few shops have a way to determine a drawbar’s condition.

Low drawbar pressure will create some very elusive and challenging machining problems. Avoid these problems by using the Clamprite Gage. See if your spindles can still Clamprite!

Shown at right is a typical drawbar assembly. Most drawbars are constructed similar to this, with some machines having over 140 Belleville springs.

Drawbar tension is commonly 1800 to 2500 Pounds of Force for #40 taper spindles, 3800 to 4800 for most #50 taper spindles, and higher for heavy duty machines or larger spindle tapers. Drawbar force varies considerably from machine to machine. Check the owner's manual for your machine.

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 conditions!

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 the trouble. Test your machine’s drawbar condition with the Clamprite Gage!

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.