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replace toolholders after new spindle install?

R

RFD

Aluminum
Joined
Oct 28, 2005
Location
Boston, MA
I have a new spindle installed on one of my machines and am curious to know if I really should replace toolholders that show fretting from the old spindle. This is not a high RPM machine, 6000RPM CAT40. Any guidance is appreciated.

Thanks

Richard
 
Unless the fretting is really serious, I wouldn't worry about it. If there's signs of metal transfer/adhesions, I'd carefully stone them off with a very fine stone. If you're running any very small tools (which would suck with only 6K), buy a few new high-quality holders for them alone.
 
And if you decide to "polish" the holder tapers, I'd not use anything courser than 1200 WoD paper, and be sure to use it uniformly along the taper. Don't stay down at the major diameter fretted area alone, you don't want to reduce this area too much or you'll just damage the new spindle with fresh fretting. Make sure the smaller parts of the taper also are touched up, then clean carefully before use.
 
That doesn't look bad at all. If you run a fingernail over the surfaces do you feel any "catching" at all? Subsurface can be ignored, but if anything is proud I'd try to work it down.
 
I'd go along with Milland's plans, however just to be sure - run a blue check on each and every toolholder you have - the subject's been covered many times on PM.

It doesn't take long, and as my old mentor used to say ''only blue is true Sami lad''
 
Depends on how picky you are but.... I would stone them with an ultra fine ceramic hone to make sure nothing is proud and try to only drill or light mill with the worst ones, no heavy milling. Cleaning the "rust" out of the fretted areas with some fine scotchbrite and oil does help with it not returning. Be gentle with the scotchbrite. Agree that what you show in the picture is not bad at all.
 
My older spindle taper is not perfect, and I've not had any issues using it. I'd be surprised if heavy milling with a 40 taper would not introduce some fretting in a so called perfect fit. There goes perfection. But hell, less than perfect will still make good parts. I put a new endmill in my less than perfect spindle, and cut a new feature exactly to width without doing any fudging whatsoever with tool radius comp. That's good enough for me.
 
I noticed a RAPID degradation in tool life after this incident. Started popping 3/16" ZCarb tools on a 6Al4V Ti job I've run for years. I know that cutter life down to the minute it seems.
 
RFD said:
I noticed a RAPID degradation in tool life after this incident. Started popping 3/16" ZCarb tools on a 6Al4V Ti job I've run for years. I know that cutter life down to the minute it seems.
Click to expand...

Same lot of tools and Ti? If not, if you have any tools and Ti from previous lots for which you have empirical data try some of those to reduce variables.
 
RFD said:
I noticed a RAPID degradation in tool life after this incident. Started popping 3/16" ZCarb tools on a 6Al4V Ti job I've run for years. I know that cutter life down to the minute it seems.
Click to expand...

Have you put a test indicator into the spindle bore and checked it for runout? Make sure to check the major diameter and at least midway up the taper. A new spindle's no guarantee that the taper is concentric. Next put the working toolholder in without a collet, and check its taper too. Concentricity errors will kill endmills, especially smaller ones, in tough materials.

I've used plenty of ZCarbs in Ti and 17-4ss with great results, doubt its the cutters.
 
RFD said:
I noticed a RAPID degradation in tool life after this incident. Started popping 3/16" ZCarb tools on a 6Al4V Ti job I've run for years. I know that cutter life down to the minute it seems.
Click to expand...

Bad tool life on small tools is why I Had to replace my spindle.
Get those indicators out as mentioned.Something is amiss.
 
Milland said:
A new spindle's no guarantee that the taper is concentric.
Click to expand...

I'm very curious about why this might be a common view. I would think that a new spindle assembly would be THE answer to a non-concentric/worn spindle taper issue, if one makes the assumption that a new spindle assembly should essentially be a factory-spec replacement. Just wondering.
 
It's not a common thing, but when you're breaking small tools running a similar program and the only thing different is the spindle, it's time to check it for concentricity (and blue up a good toolholder and check for mating). New isn't always perfect...
 
Always do your own inspection after getting your spindle rebuilt. I had one tight at the top of the tool holder when blued off. It was the same tool holder that I supplied with the spindle for them to test their work when grinding the taper. Out she comes and back to the spindle shop for them to grind it while I wait. It's only right after it passes your inspection, which includes some cutting.

On edit- I do understand that the bad tool life is why he replaced the spindle. Nonetheless everything new should be validated.
 
If it is a new spindle would check for runout and while you are there stick a tool in it and yank on the thing and see if you can measure the axial play. Should be .0002-.0003 or less. If there was an error in the rebuilding process or the preload is just too light you can sometimes see a lot of movement...

Most spindle rebuilders will grind the taper while it is running in the new bearings so you really should not have much run out. Using the right setup it is not hard to grind it to get good contact in the taper and less than .0002 tir at the end of a standard sticking out 12 inches from the spindle. That should translate in to less than .00005 runout at the length of an average tool.
 
Absolutely check a new spindle. Use bluing to check the taper, an indicator to measure runout and if you have access to a dynamometer check tool retention. Any one or a combination can cause short tool life. I've ground more "new" spindles than I care to count.

Rocky Russell
Spindle Grinding Service Inc.
 
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