Tool Holder Falls from the Spindle!

[cngbrick]

Remove the impact wrench assembly from the mill head. See if you can take off the drawbar socket from the impact wrench and use a 1/2 inch drive ratchet handle to manually tighten the drawbar. Release the spindle brake, put the spindle in neutral and rotate manually to feel for any binding. If all is well, run the mill without the impact wrench and see how it goes.

 

[CarbideBob]

Something is wrong here.
I remove the key (the screw) on this type.
I know many think this bad. I'd be chasing the drawbar and why.
The washers or shims up top have to do with how deep it goes or if it not right.
Bluing here is on those threads, not in the spindle taper.

 

[AndrewZ]

Remove the impact wrench assembly from the mill head. See if you can take off the drawbar socket from the impact wrench and use a 1/2 inch drive ratchet handle to manually tighten the drawbar. Release the spindle brake, put the spindle in neutral and rotate manually to feel for any binding. If all is well, run the mill without the impact wrench and see how it goes.

Got it.... I may have to find a other way of tightening the draw bar, but it should be no problem.

 

[cngbrick]

Something is wrong here.
I remove the key (the screw) on this type.
I know many think this bad. I'd be chasing the drawbar and why.
The washers or shims up top have to do with how deep it goes or if it not right.
Bluing here is on those threads, not in the spindle taper.

I proposed blueing the taper to see if the alignment pin was interfering with pulling in the collet or somehow pushing it off axis. I agree with you that the pin is not needed. If the drawbar is not tight enough to prevent the collet from slipping in the taper there is nothing that pin will do to help.

 

[CarbideBob]

Are there washers in this setup at all? I have not seen one, but the spindle has not been removed so...

In case you did not yet see post #40. Quite possibly the holder falling down was caused by the alignment screw not being tight enough, and now there are precarious noises.

And yet it should work with no screw???? As I said I remove such and run 8 inch milling cutters on a R-8.

 

[AndrewZ]

And yet it should work with no screw???? As I said I remove such and run 8 inch milling cutters.

Yes sorry, I deleted the post. I was not sure if you were referring to the alignment pin or the other pin. The other pin hole has been tampered with in case that may have something to do with the issue.

Tightening it without the impact now to see if improved.

 

[AndrewZ]

Remove the impact wrench assembly from the mill head. See if you can take off the drawbar socket from the impact wrench and use a 1/2 inch drive ratchet handle to manually tighten the drawbar. Release the spindle brake, put the spindle in neutral and rotate manually to feel for any binding. If all is well, run the mill without the impact wrench and see how it goes.

The impact wrench is possibly not working properly. Any straight forward ways to diagnose it?

First, when the impact was removed the grinding noise was gone. Also, turns out the ringing has been a problem with the machine all along and was stated to be because of some bearing, but it's not from the motor as I understand. The sound seems to come from lower.

Second, when the impact was unseated after tightening the draw bar on a collet with the impact, the draw bar was not tight. Worse, each time spindle was turned on the draw bar moved upwards by a short amount (never moving back down), visible although hard to see in the video below. The toolholder remained in place.

Draw Bar Top

Watch "Draw Bar Top" on Streamable.

streamable.com

Is the shaking of the draw bar seen on the video normal?

 

[cngbrick]

Can you tighten the drawbar with a wrench so that the collet is properly pulled in?

The runout ("shake") appears excessive, the causes could be numerous: drawbar bent, bad bearings in the Varispeed unit, drawbar not the right size for the spindle (measure spindle bore at top and compare to drawbar shaft). You'll have to observe and see if you can identify the issue. It may be time to call in a machinery repair person.

With respect to your impact motor: can you identify the brand? You may be able to get a rebuild kit from the manufacturer if it's someone like CP or a well known company.

 

[Booze Daily]

I had a power drawbar on mine and the socket cracked. I don’t remember what symptoms I had, but you might want to check that.

I replaced it with a Kurt.

 

[AndrewZ]

Can you tighten the drawbar with a wrench so that the collet is properly pulled in?

The runout ("shake") appears excessive, the causes could be numerous: drawbar bent, bad bearings in the Varispeed unit, drawbar not the right size for the spindle (measure spindle bore at top and compare to drawbar shaft). You'll have to observe and see if you can identify the issue. It may be time to call in a machinery repair person.

With respect to your impact motor: can you identify the brand? You may be able to get a rebuild kit from the manufacturer if it's someone like CP or a well known company.

The collet is properly pulled in by the impact (for most collets). But yes, I tightened the draw bar at least enough with a wrench that each time the spindle was started the draw bar would not move upwards. The runout may have been mitigated, but still noticeable.

Strange about the impact wrench. It seems to function fine on inspection... I will tighten one more time with it and not touch anything, just to be sure the draw bar didn't become loose for some other reason.

Repair person has been called in, but appears very busy. Not the best area for repairs...

 

[cngbrick]

Have a look at the Kurt pneumatic drawbar owner's manual: https://www.kurtworkholding.com/wp-content/uploads/2021/09/Automatic-Drawbar-Manual.pdf

These drawbars are all very similar in operation. Read through the manual for installation and alignment procedures as well as drawbar sizing.

 

[AndrewZ]

Have a look at the Kurt pneumatic drawbar owner's manual: https://www.kurtworkholding.com/wp-content/uploads/2021/09/Automatic-Drawbar-Manual.pdf

These drawbars are all very similar in operation. Read through the manual for installation and alignment procedures as well as drawbar sizing.

The dimensions may not reach all the tolerances (for example attempting to retract Z all the way results in an error on the machine), but importantly what immediately caught the eye...

The picture is not very clear, but is that the thrust bushing/hard washer in the spindle? There is no way of fitting it in the spindle here. The bushing is as large as the shaft.

I doubt that's the issue, but interesting. Inspecting the impact wrench more closely tomorrow to see for sure if it tightens the bar or not.

 

[CarbideBob]

The washer just goes on the drawbar when you stick it in.
With the drawbar removed the collet should go in by hand to full seat. (When aligned with the key).
It is just a long bolt and nut assembly. When tight there should be no up/down going on if the quill is not moving.
The washer serves to not chew up the back end of the spindle when you tighten it.
While the same looking there are different length bolts (drawbars) used for different machines. Sometimes you cut to fit.
When I said blue I meant remove the drawbar and blue it then stick in and tighten. (you can use grease).
Make sure it has clear threads past the tight point and screw your collet onto it by hand past this point looking for bind.

Again, just think bolt and nut holding something together. The bolt is the bar, the nut is the collet.
Some runout up top is normal but yours is maybe a bit high. That is a bent bar but these still usually hold just fine and the socket has a ton of sideways play.

I have never had one of your machines but have had a lot of B-ports and power drawbars.
Most common failure is the vanes in the impact go bad and it does not make enough power.
Lack of air pressure to it being right behind as number two. (bad fittings, bad regulators, etc)
These show up as spun tools or endmill pull out, not a drop out of the collet so I am so very confused.

The impact up there also has a up/down air cylinder and slide which may get sticky. It has to go up and be free in space.
Make sure this part works.
If it touches the bar during running that will be bad. If you are in forward and the socket up top holds the bar a bit what happens?
Whine noise up top?
Bob
(sorry for long post, curious and still learning)

 

[AndrewZ]

Can you tighten the drawbar with a wrench so that the collet is properly pulled in?

The runout ("shake") appears excessive, the causes could be numerous: drawbar bent, bad bearings in the Varispeed unit, drawbar not the right size for the spindle (measure spindle bore at top and compare to drawbar shaft). You'll have to observe and see if you can identify the issue. It may be time to call in a machinery repair person.

With respect to your impact motor: can you identify the brand? You may be able to get a rebuild kit from the manufacturer if it's someone like CP or a well known company.

Ok, I believe the issue is finally discovered. The problem is that indeed, the draw bar is not tightened properly, and when this happens, each time the spindle is turned on the draw bar jumps up a bit (normal?). Even so, it is possible to tighten the bar with the impact wrench enough that the problem does not occur, with enough care.

Three considerations:
1. Something is wrong with the thread after all? Is it normal to suddenly come to halt when tightening by hand (after approximately 10 turns)... in this case the draw bar still jumps up when spindle turned on... and then be able to go further with a regular wrench, maybe quarter turns or more in which case the draw bar stays in place when the spindle is powered up.

2. There is an issue with the wrench? This said, on inspection it seemingly works fine. The wrench for sure is much less aggressive than the impact wrenches on videos I have seen. Sounds like a stationary car vs. a speeding one at 100 MPH. The psi reading is fine, above 90.

3. Partial user error... Since the machine gives an error before Z is fully retracted, the Z axis may not always have been retracted enough and/or the "IN" button not pressed in fully with proper time taken. This said, even after my best attempt with the impact wrench, while the bar at least did not come up when the spindle was powered, it was still easy to tighten more with a regular wrench.

 

[AndrewZ]

The washer just goes on the drawbar when you stick it in.
With the drawbar removed the collet should go in by hand to full seat. (When aligned with the key).
It is just a long bolt and nut assembly. When tight there should be no up/down going on if the quill is not moving.
The washer serves to not chew up the back end of the spindle when you tighten it.
While the same looking there are different length bolts (drawbars) used for different machines. Sometimes you cut to fit.
When I said blue I meant remove the drawbar and blue it then stick in and tighten. (you can use grease).
Make sure it has clear threads past the tight point and screw your collet onto it by hand past this point looking for bind.

Again, just think bolt and nut holding something together. The bolt is the bar, the nut is the collet.
Some runout up top is normal but yours is maybe a bit high. That is a bent bar but these still usually hold just fine and the socket has a ton of sideways play.

I have never had one of your machines but have had a lot of B-ports and power drawbars.
Most common failure is the vanes in the impact go bad and it does not make enough power.
Lack of air pressure to it being right behind as number two. (bad fittings, bad regulators, etc)
These show up as spun tools or endmill pull out, not a drop out of the collet so I am so very confused.

The impact up there also has a up/down air cylinder and slide which may get sticky. It has to go up and be free in space.
Make sure this part works.
If it touches the bar during running that will be bad. If you are in forward and the socket up top holds the bar a bit what happens?
Whine noise up top?
Bob
(sorry for long post, curious and still learning)

So it is correct that the draw bar has a tight point past which it takes a wrench to tighten it properly? Is it normal that the draw bar shoots up a bit if not tightened past the tight point, when spindle powered?

I believe you may be to something with the common failure of the impact. It sounds much tamer compared to videos I have seen, but I never recall it sounding so powerful though. Can this problem be verified somehow, repair is a new impact?

Thanks for taking the time!

 

[cngbrick]

The threads on the drawbar should always screw in freely by hand in the collet without any binding or stiff spots. If you have stiff spots the thread in the collet or drawbar is bad or dirty. An elongated thread may not look bad by eye but when the thread elongates the pitch changes and makes it incompatible with the mating thread.

We can't evaluate what you mean by hand wrench tightening more than the impact wrench. The drawbar will not remain tight if only screwed in by hand. You need to put enough torque on it to draw in the collet into the taper and clamp on the tool. You can use a torque wrench to evaluate how much torque is on the drawbar.

At this point if the Kurt manual and the advice from the contributors to this thread have not provided you with everything you need to evaluate and correct the problem with your drawbar system I recommend you find a competent technician to continue the work. A competent repair will save you potential damage to your spindle (very expensive) or ruined parts in the future.

 

[AndrewZ]

The threads on the drawbar should always screw in freely by hand in the collet without any binding or stiff spots. If you have stiff spots the thread in the collet or drawbar is bad or dirty. An elongated thread may not look bad by eye but when the thread elongates the pitch changes and makes it incompatible with the mating thread.

We can't evaluate what you mean by hand wrench tightening more than the impact wrench. The drawbar will not remain tight if only screwed in by hand. You need to put enough torque on it to draw in the collet into the taper and clamp on the tool. You can use a torque wrench to evaluate how much torque is on the drawbar.

At this point if the Kurt manual and the advice from the contributors to this thread have not provided you with everything you need to evaluate and correct the problem with your drawbar system I recommend you find a competent technician to continue the work. A competent repair will save you potential damage to your spindle (very expensive) or ruined parts in the future.

The draw bar screws in freely by hand up to a point, past which it has to be tightened by wrench about quarter turn, or it moves upwards when the spindle is turned on. I am mostly wondering about whether the impact wrench performs up to spec or not, which has not been covered yet.

If you do not wish to help, that is fine... it has been a quite lengthy thread with some newbie mishaps indeed. Thanks for the help so far, has been helpful!

 

[cngbrick]

It's not that I don't wish to help, I just feel that based on your level of understanding of machinery that we may miss some obvious issues that may lead to more costly damage (or injury) in the future. I feel you would be best served by hiring a competent technician. You can watch the work being done and learn from that for the next time you need to service your drawbar.

Consider that a mistake in ajustment may damage your spindle in which case you would be looking at several thousand dollars to fix.

 

[cngbrick]

If you take the drawbar out and screw it into a collet you should not need a wrench at any point. The drawbar should screw in freely until it runs out of thread or bottoms out in the collet. If there is any stiffness between cleaned and lubricated threads then there is damage.

With the drawbar in the spindle you should only feel resistance when the drawbar pulls the collet into contact with the spindle taper and the tool in the collet. Then add the torque that is required is to tighten the tool into the collet, possibly 15 to 25 ft-lb (some pneumatic drawbar manufacturers claim up to 50 ft-lb).

 

[CarbideBob]

So it is correct that the draw bar has a tight point past which it takes a wrench to tighten it properly? Is it normal that the draw bar shoots up a bit if not tightened past the tight point, when spindle powered?

I believe you may be to something with the common failure of the impact. It sounds much tamer compared to videos I have seen, but I never recall it sounding so powerful though. Can this problem be verified somehow, repair is a new impact?

Thanks for taking the time!

Open up the top.
Tell the impact top to do it's thing.
Take a wrench, vise-grips whatever and while holding the brake can you tighten it more?
At 90 psi you should not unless you use a 3 foot bar on the wrench. Even then just barley as the bolt now becomes a real stiff spring.
The other common is a bad or leaky air hose connection so while inputting 90psi it never gets to the wrench.
Failure is normally at the fittings in/out but sometimes a split hose. I should have mention that. Normally you hear the air leak.
Bolt and nut, no up/down after tighty acceptable.

Other testing options need big dead blow hammer and whacking.
Bob