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Balancing Over 20K - Reality


The balancing machines are accurate from < 1gmm to <0.5gmm depending on the model (expressed as +/-0.5 & +/-0.25grmm).

BT30-ER11H-060 body weighs in at .95 lbs
BT30-ER16H-070 body weighs in at 1.05 lbs

To balance BT30-ER11H-060 body to G2.5 @ 25,000 RPM requires a maximum allowance of 0.4115gmm.
To balance BT30-ER16H-070 body to G2.5 @ 25,000 RPM requires a maximum allowance of 0.4548gmm.

With the balancing machines @ <1.0gmm and <0.5gmm how can you pre-balance the above for G2.5 @ 25,000 RPM's? 

To get real serious ask about the calibration requirements to hold 1gmm or better and how much time on the machine is required to achieve 1gmm, you will be shocked.  Unfortunately most manufacturer's of tool holders are not truthful about balance because less than 3% of the customers actual own a balancing machine.  If you own a machine then you are balancing the tools assembled and the pre-balance accuracy doesn't seem to matter as much.

To improve the customer's odds you need to add weight, the cutting tool can usually bring up the total weight so the balancing machine can sense the part properly and give an accurate response.  Pre-balanced tools are there to help eliminate the imbalance from production, any more is a waste of money for both the manufacturer and the customer.   A customer that is truly running high speed must buy a balancing machine to maintain machine warranty and achieve tool life.

Some suppliers advertise BT30-ER11 and ER16 @ G2.5 @ 25,000 RPM's, it is impossible to guarantee.  Some manufacturer's advertise "symmetry" designs, this is a nice way of saying "designed for balance but not actually balanced".  These designs have no G rating and there are up charges for actual dynamic balance.  No tool holder manufacturer can pre-balance the assembly and guarantee it will work in your application.  Consider the variable, retention knob weight and tightening torque, cutting tool weight, material, length and preset position.  When you are trying to run at or above 20K these variables take the tool in and out of balance and there is no way to compensate with just the holder, you need a balancing machine.
There is a few companies out there and the largest catalog house who say "balanced to 30,000 RPM" with no grade.  That is like saying "I am driving 100" but is it MPH or KPH?  To determine displacement you need both RPM and Grade or it means nothing. 
Now add the fact that cutting load, interrupted cuts, over tightening knobs, gremlins, all are going to force a re-balance of the tools.  
Now consider that 99% of all cutting tools are not balanced... 

I have lost count of phone calls from end users who want must balance for 20K or higher for the machine warranty, then they want to be able to change tools without re-balancing.  If you change the tires on your car without re-balancing it can damage your wheel, bearings, drive shafts, etc... the same is true with machine tools.

We here at HPI-PIONEER use the same standard that is used in Germany, G6.3 @ 20,000 for 40 tapers and smaller, G6.3 @ 15,000 for 50 tapers.  G6.3 removes all of the imbalance in production while providing a solid consistency between tool changes.  If you require a finer balance the tool must be balanced assembled so there is no value in pre-balancing the holder any finer.
   We do have a balancing machine in Chicago with the ability to pre-balance the holder to your specification or balance an assembly for you.

To win the war, have the customer request the facts and do the math themselves (or with our help) and take a realistic approach to balance.  Yes balancing is a 20-30K investment in equipment but if you are truly running high speed you will pay for the machine in tool life, reduced wear and faster production times.

Any questions please contact sales@gohpi.com

For more information on how to calculate balance see Balanced Tool Holders
Above body, BT30-ER16H-070 is how every tool holder manufacturer balances, body only.  Weight is 1.05 lbs.


Above assembly with sample cutter weight is 1.35 lbs. (sample cutter weight
is 0.1 lbs in this example)
The cutter weight is extended from the nose causing additional imbalance that must be corrected.

Above is all the parts required in every assembly.
The preset screw, collet, retention knob are not dynamically balanced.  The collet nut is balanced by HPI-PIONEER but not by all manufacturer's.
Clearance in the thread of the preset screw, retention knob and nut can cause imbalance.
Cutting tools are not dynamically balanced, even if they were uneven cutter wear causes enough imbalance to force a re-balance of the assembly at G2.5 @ 25,000 RPM's.  It is that fine of a balance!