[tminnig]

I am curious as to the general consensus on what the requirement is for toolholder balancing relative to maximum machine spindle speed capability.

We are buying a new machine with a spindle faster than we have had and are considering a toolholder balancer, but I would like to know if it is truly necessary or not.

Please respond in the poll, and reply with any comments if you have them.

Thanks,
Travis

[Geof]

Below 8000 rpm balancing is not needed for endmill holders but rough balancing is a good idea for face mills and fly cutters.

8000 to 12000rpm is a 'grey' zone where proper balancing starts to be needed; actually I think anything above 10000rpm needs balanced holders.

Obviously anything higher needs correctly balanced holders.

[Dorsal]

Yep!

[PRADEEP R.KHARE]

DEAR SIR/MADAM
UP TO 8000 RPM BALANCING IS NOT REQUIRED BUT IF WE DO IT IT IMPROVES TOOL LIFE & SPINDLE LIFE(TOOLS MUST RUN TRUE WITHIN 0.01 MM THIS IS MOST IMP.
15000 RPM ONWARDS YOU MUST BALANCE THE TOOL HOLDERS ALONG WITH TOOL IS MUST & TOOL MUST RUN TRUE BELOW 0.005 MM MIN.IF THE TOOL OVER ALL LENGTH IS MORE THAN 160 MM FROM GAUGE PLANE OF TOOL HOLDER YOU NEED TWO PLANE BALANCING WITHIN 2.5 G
ABOVE 30000 RPM 1.5 G. GRADE OF BALANCING IS MUST
THANKING YOU
PRADEEP R.KHARE
INDIA
[email protected]

[tminnig]

I just wanted to offer a 'thank you' for the replies so far. Hopefully I can get some more poll results in the near future, but all my research is showing me the same things as you have all discussed thus far.

Kindest regards,
Travis

[Brakeman Bob]

We saw a 30% increase in feed rate when we balanced a Ø32 ISCAR router running at 12,000 rpm.

Above 15,000 rpm even tiny out of balance masses can have a dreadful effect on spindle and draw bar life, never mind the cutting. On our Hermle which has 16,000 rpm all our tools are balanced to G2.5 at 25,000rpm as standard

[bill south]

I have no idea on the requirement for balancing but I do have a question. How does one balance a tool holder?
Bill

[PRADEEP R.KHARE]

We saw a 30% increase in feed rate when we balanced a Ø32 ISCAR router running at 12,000 rpm.

Above 15,000 rpm even tiny out of balance masses can have a dreadful effect on spindle and draw bar life, never mind the cutting. On our Hermle which has 16,000 rpm all our tools are balanced to G2.5 at 25,000rpm as standard

DEAR Brakeman Bob
IF YOU HAVE BALANCING RINGS OR SMALL TAPPED HOLES ON TOOL HOLDER
YOU CAN BALANCE FASTER .
I WAS WITH MPM ERLANGEN GERMANY IN LAST MONTH & I WAS EXPLAINED BY MR.MARK(OWNER OF THE CO.)TO BALANCE THE CNC LATHE CHUCKS ALSO FOR BETTER TOOL RESULTS THAN NORMAL, YOU GET AROUND 15% EXTRA TOOL LIFE,GOOD SURFACE FINISH TOO THAN NORMAL.
PL.CHECK ON THIS WEB PAGE
Startseite - MPM Micro Przision Marx GmbH.
THANKING YOU
PRADEEP R.KHARE

[PRADEEP R.KHARE]

I have no idea on the requirement for balancing but I do have a question. How does one balance a tool holder?
Bill

DEAR SIR/MADAM
PLEASE CHECK WITH Startseite - MPM Micro Przision Marx GmbH. BALANCING MACHINE PRODUCER
IF YOU NEED ANY INFOMATION ON TOOL HOLDER BALANCING I CAN OFFER
MY MAIL ADDRESS IS
[email protected]
thanking you
PRADEEP R.KHARE

[Brakeman Bob]

I have no idea on the requirement for balancing but I do have a question. How does one balance a tool holder?
Bill

I buy balanced (shrinkfit) toolholders directly from the supplier and put balanced cutting tools inthem. For other applications I send tooling to a local balancing company.

One company I know around here went to the expense of buying their own balancing machine (they have also bought their own CNC grinder so they can make their own solid carbide cutters too).

[Astonlee]

You cannot just select a rpm and anything above that would need balancing, because there is a big difference between a the weight/mass HSK40 shank compared to a 50 shank toolholder, so there a very big difference in the rpm range as to when the need to be balanced.
The shanks feature also have a major influence to amount of balancing that needed to be carried, like the Din 69871 (CAT) which has unequal drive slots, with a drilled dimple, and vee notch in the side of the shank, compared to BT shank which as equal drive slots and no notches or dimples on the shank. Also the basic manufacturing quality of the holder will also have an effect, the more ground feature the better. Like really good quality HSK shanks have the inside of the ground, whereas the cheaper version are just turned.

[Rockyr49]

You also need to take into consideration the condition of the spindle taper. ALL spindle tapers wear over time. They become bell mouthed. The big end gets bigger. When this happens creates less contact between the tool holder and the taper. It can cause all kind of problems including finish issues, vibration. excessive tool wear and others. The most perfect holder in the world is only as good as the taper it goes into. If you have these problems you may need to have the taper reground.

Rocky
Spindle Grinding Service Inc

[underthetire]

I agree with rocky. A little story from last Friday. I work on my days off at my real job to help an independent service guy in this area. He is actually my best friend. We were balancing a horizontal spindle for 12k rpm. Got the balance very close, .1 gram. Everything looked good, but we left the transducer for the balancer on. Customer put a different holder in and we ran it up. Sounded different. Ran a balance test again, now we were out .5 grams. Both holders were "factory balanced to 20k". Both looked ok, both had the same brand end mill. Put the other holder in and back to .1. Went up to another shop, put a gauge pin in a balanced holder, used there balancer, balanced the tool, and now holding at .2 gram. So as you can see, there was big a big difference even with the same brand tooling . None of the results were terrible, but there is a difference. This was a standard cat 40 btw.

[BKGUY]

Are you talking about buying balanced holders or balancing each tool assembly individually in a tool balancing machine? You need to be careful when buying balanced holders. Some holders you buy, come with a balancing certificate where they were, supposedly, balanced at the factory. Also remember that the "G" tolerancing scale for balance, is very old. It was developed back in the '40s. Most of the balancing that is discussed for tooling, when it comes to G2.5@20,000 RPM, or G1.0@xxxRPM, is mostly smoke and mirrors. A balancing tolerance of G2.5 is for machine spindles. Really, anything within G6.3 is fine for a tool assembly. I do agree though that the better the balance, the better a tool will run.
When tool holders are balanced at the factory, they are balanced without the nut installed (in the case of a collet chuck). So when you install a tool and put the nut on, the balance has changed dramatically. The real way to check balance is by measuring the gram/millimeters of imbalance that is present. Which a good tool balancing machine will allow you to do. You can buy holders with balancing screws that allow you to balance an entire tool assembly on a balancing machine. See link below for an example of holders with balancing screws.

http://www.bigkaiser.com/pdfs/mega-er-grip.pdf

[Brakeman Bob]

I used to believe that G6.3 was good enough, then I caused over 8,000 GBP worth of damage running a HSK heat-shrink holder certified as G6.3 @ 25,000 rpm up at 21,000 rpm. It pulled so hard on the drawbar it broke the expanding collet that pulls the tool holder back into the taper. Didn't take long either; I was warmng the spindle up and put the empty holder in the spindle and was going up in 2,000 rpm increments, 3 min a time (starting at 1,000 rpm) - I wrote a program just for the purpose. At 19,000 everything was fine, then the machine upped the rev's and BANG! It scared the life out of me....

The spindle had to go back to Switzerland for repair and the report said plainly that unbalanced tooling had been the cause. A very uncomfortable time for me. After that I have all my tools balanced to G2.5 at full rev's plus one third (i.e on a 16,000 rpm machine the tools are balanced at 24,000).

BKGUY is right about about grams force per millimetre being the only true measure of out of balance forces but I find up to about 40,000 rpm G2.5 works OK. I tried having tools balanced to G1.0 but it meant rebalancing the tool assembly every time a cutter was changed, even ones sold as "fully balanced".