40 taper tool length variation.

I have the tree j325. I was having chatter issues with one particular holder and i noticed i could spin it BY HAND without the drive keys installed. I should note that my model of tree has a very unconventional and crappy mrthod of retention.

I tried 3 new different mfg pull studs, all the same..

I decided to check all my holders for gage length to where the stud tightens against. but not having a "gage" I could only check the relative to reach other.

so the all went into my shinty new technara tightening fixture. (this thing has a BEAUTIFULL ground bore that has great contact- i would trust it as a master taper gage for my purpose) and a dial indicator on the bottom.

I measured variance of about .020 across all my holders. avg being 75% within +/-.005

no surprise the chattering holder was the worst, a "flier" about +.010 from avg. so I faced off .015" so now it's one of the tighter holders.

Question is, what variation is "normal"

--- none of the holders look worn out. one of the worst was a brand new nikken.

how do i measure the actual gage length? drop a mic'ed bearing in the gage and measure to it's depth and derive mathiamatically?

Not sure how you would measure, but go to the web sites of the tool holders you have and dl the specs.
Not sure if any handbooks have the std specs but I would look there.
I'd also make sure your retention knobs are correct for your machine. It sounds like you only have a little more than 0.010 of tension travel on your jaws

I just looked and could not find my CAT refference stuff, but IIRC, the length from the gage dia. to the back of the holder is a 2 place decimal and given as a minimum. My guess would be that you have some broken belleville washers in your drawbar. We check all of ours 2 times be year.
http://www.clamprite.com/productinfo.asp

If you need new belleville washers:
http://www.keybellevilles.com/
Replace all of them, not just the broken!
JR

Dan, You had the spindle taper reground in place October 26, 2005. When we started, the tool retention was 440 pounds, when we finished, the tool retention was 420 pounds. Spindle Grinding Service used a Command retention gage to measure the retention. At that time Carl told you the retention was too low. We suspected broken Belleville washers and you said you were going to cut some retention knobs shorter.
I don't care, 440 pounds or 420 pounds of tool retention it is like that car with the motor in the back, it is unsafe at any speed. I would really like to see you get that thing fixed before you get hurt and try to sue me because you did not heed the warning.
If you look back at the posts that you went through after the spindle was reground, the name that told you the 420 pounds was not important maybe he can refer you to someone who
can come to your shop a repair your retention before someone gets hurt.
If you mess up that spindle, you will have to answer to Carl. I'v never seen him mad but you remember, he is a big one.....
Walt.... Spindle Grinding Service..;..

420 pounds!!!
CAT-40 should be around 2,000 pounds or more!
CAT-50 should be around 4,000 pounds or more!

Get the damn thing fixed before you hurt yourself.
JR

Yes!!!! Someone else that understands how important that number is.

I have been through this guys... series 1 spindle Tree j325 has very wacky "drabar". I called a Tree engineer. he told me drawbar gage would not give reliable indication. It is not a DRAW-bar it's a ****ty CAM LOCK bar. no springs at all pullling up. instead they are pushing ramp doward forcing in pins sliding through holes into underside of stud.

anyway, ****ty as it is. I'm running it. the retention # may suck but it is not a design that it inherently dangerous as there is no way the thing can disengage from lack of tension like a typical setup.

no big face mills for me. in fact I keep it under 1" even in aluminum.

P.S. the various spindle service drawings are on the cnc forum along with the whole old sordid story.

Dan Thorsten
262-781-9804
Brookfield WI was the service manager, has engineering background on the machines. ---

-he told me the 440 drawbar # was of no concern on my model.

but thanks for the concern.

Dan

If you remove the keys and can turn the tool, something is bad wrong.
The biggest source of tool chatter is lack of tool retention and or a bad taper. If you keep running that thing, you will have a bad taper.
You have one problem, soon to have the second.
Wish you would have someone look at this machine and determine what is wrond.
The specification on length of tool holder from the gage line to the end of the taper is plus or minus .015 according to the machinerys hand book. It only shows for a NSTS holder V dim minus W dim.
I really am concerned
Walt
PS
Maybe wrong retention knobs to start with, if your machine is so far from knowing it's father, maybe they got the retention knobs mixed up....

What's pushing down? Maybe whatever it is it's not pushing with enough force. The tool may not be able to come out, but if it is not holding with enough pressure, which it isn't, you have a problem. Maybe try bluing a retention knob and see exactly where these cams are hitting. That might tell you something. If the cams are coming in too late, there may be a way to modify the system. I'd still rather see the problem with the machine fixed instead of modifying tool holders that will now only work with this machine. Either way the dynamometer is the way to tell how much pressure is there, and if you can turn a tool by hand you are asking for trouble.

IT WAS ONLY A PROBLEM WITH ONE HOLDER.

I FIXED THAT HOLDER.

I no longer have a loose holder problem since I made my statistical "flier" the same length as my other holders.

that was not the question... I appreciate all the concern but I have:

#1 investigated it, determined the course of action.
#2 taken care of it,
#3 I am taking responsibility for it.


Dan