BT30 spindle drawbar grippers in pieces

Hello there again,

I think I got all the possible unluck with this Kitamura machine.

I am not sure if this happened to someone before m I personally never heard of it...

After running the machine 10 hours yesterday, and fixing another issue thanks to the help of this forum, today I have run 1st part, fine second part then I heard one of those noises you don't want to hear, run to the machine, stopped it, and then realize spindle was spinning but the tool wasn't clamped properly.

I haven't really noticed any dent on either vise/spindle nose, the 6mm end mill snapped, I am "glad" this happened with this tool, as the tool before that one, on the program is a 3" shell mill, I have used the same tool holders before many times, even on more "heavy-duty" work, never had any problems.

I think there is only 1 drawbar gripper left.

I think I am getting all the possible unluck with this machine as it has been 1 year of nonstop problems.

It seems there are no scratches on the spindle taper either, I checked with the tenth clock spindle taper, and run out seems to be less than 1 micron, however, if I push the spindle nose from the side there is a 0.002mm play, not sure about this.

I will have to call the engineer in again, do you know what could have caused the drawbar grippers to snap? Drawbar tension?

Spindle has been refurbished and refit 2 weeks ago

I managed to find the drawbar grippers the machine dropped ,

Would I just need a new coil spring?

poxino said:

I managed to find the drawbar grippers the machine dropped ,

Would I just need a new coil spring?

Click to expand...

here the picture

You need to contact your spindle rebuilder and get the spindle checked again - even if you can't feel it, the bearings may be damaged, and the spindle bore could be scarred from the tool holder coming loose. This should be checked before further use.

As they're checking those aspects, they should also go over the drawbar components with you present (presuming they're not too far from you), so you can get an explanation of what failed and why. Having a tool come loose is a really bad thing, and you need to keep the risk as low as possible.

It's even conceivable that the pneumatic issues you're having are tied to the spindle drawbar failure - you definately want to make sure that air control is not part of the reason for the holder drop.

Unfortunately, this is the downside of machine tool ownership - maintenance and repairs. Have to budget for them, painful as it is...

Milland said:

You need to contact your spindle rebuilder and get the spindle checked again - even if you can't feel it, the bearings may be damaged, and the spindle bore could be scarred from the tool holder coming loose. This should be checked before further use.

As they're checking those aspects, they should also go over the drawbar components with you present (presuming they're not too far from you), so you can get an explanation of what failed and why. Having a tool come loose is a really bad thing, and you need to keep the risk as low as possible.

It's even conceivable that the pneumatic issues you're having are tied to the spindle drawbar failure - you definately want to make sure that air control is not part of the reason for the holder drop.

Unfortunately, this is the downside of machine tool ownership - maintenance and repairs. Have to budget for them, painful as it is...

Click to expand...

This is really painful as the amount of repair costed me so far 20000 usd , it went a little bit more than what I budgeted for it

Did the bolt come out or loosen that holds the finger in? Did it harm the grippers? I would really try to find the spring, but I am sure you are.

IF the bolt wasn't loctited in place you can remove it from the spindle nose. The problem is the barrel that the bolt threads into is threaded onto the drawbar so it may start unscrewing from there when trying to remove the grippers. How you know is it will unscrew a few turns then tighten up as the barrel bottoms out in the spindle shaft.

The grippers are not made by Kitamura, they are an off the shelf item. I will see if I have photos already and if not hunt down my old ones and take some photos and get the part #.

Here is what I have. The gripper is made up of 4 fingers, one bolt, and the spring. I think they are around $1200-$1400 depending on where you get them. They screw into the barrel on the right-hand side of the drawbar in the photo.

If you can't remove them without pulling the drawbar out then you have to pull the spindle motor off. It's not too hard but there are quite a few steps involved. Here is a thread I did when I rebuilt my spindle. I have the photos to finish the thread but haven't taken the time to do it. Just pulling the motor to get the drawbar out will not mess with the alignment when installing it IF you don't pull the motor off the steel plate between it and the head. When installing use a torque wrench to tighten the bolts as they are not as tight as I expected, or others who have done this procedure on my mill. The aligning parts are no longer as round as they are supposed to be.

If your spindle rebuilder installed the drawbar then you need to discuss this failure with them. It should be considered a warranty repair. If you installed it then you should be pretty familiar with the parts and should not be too hard to figure out what came apart.

Vancbiker said:

If your spindle rebuilder installed the drawbar then you need to discuss this failure with them. It should be considered a warranty repair. If you installed it then you should be pretty familiar with the parts and should not be too hard to figure out what came apart.

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Hi thanks for many replies as usual , it gives me a sort of "mental" support too

Spindle has been rebuilt by a company then a service engineer installed it for me.

I will try to discuss this with them , but I believe I will have to wait until the 4th of Jan

If it's a warranty repair and they want it back find out if they will accept just the drawbar as it is way less work to pull and install it vs the whole spindle. But if the fingers were loose in there while tools were being changed it could have screwed up your spindle shaft. I am curious if the spring broke letting the fingers fall out or if the bolt backed out causing the problems. It is good to inform yourself as much as possible in case the rebuilder starts talking jive.

One of the grippers are still in the spindle

Here the pictures I wanted to attach earlier by the way

DavidScott said:

If it's a warranty repair and they want it back find out if they will accept just the drawbar as it is way less work to pull and install it vs the whole spindle. But if the fingers were loose in there while tools were being changed it could have screwed up your spindle shaft. I am curious if the spring broke letting the fingers fall out or if the bolt backed out causing the problems. It is good to inform yourself as much as possible in case the rebuilder starts talking jive.

Click to expand...

I attached some pictures

Vancbiker said:

If your spindle rebuilder installed the drawbar then you need to discuss this failure with them. It should be considered a warranty repair. If you installed it then you should be pretty familiar with the parts and should not be too hard to figure out what came apart.

Click to expand...

If the spring on the grippers broke do you think that is a warranty item?


Interesting photos, it looks like your grippers are different. I don't see the bolt in the end of the drawbar but it looks like something is left on the end of it.

poxino, if you have to pull the spindle make sure the holes in the clamp ring for the screws that hold the steel pin in place go all the way through so the screws bottom out on the pin and not counterbores in the clamp ring. It was found out that having the screws bottom out in counterbores would eventually break them from the clamp/unclamping stressing them. This would allow the pin to drift out while the spindle was spinning causing all kinds of damage.

DavidScott said:

If the spring on the grippers broke do you think that is a warranty item?......

Click to expand...

IMO, it depends on what they did. If the old parts were re-used then it gets very gray. Did the spring just happen to reach the end of life coincidentally within a very short time since the assembly was rebuilt? Likely no way to tell.

If all new parts were installed by the rebuilder (or supposed to be) then IMO, it is absolutely a warranty issue.

I have never worked on a 30 taper Kitamura so the following may be totally off base.... I suspect that there was an assembly error. Typically the retention fingers are not able to come out when the drawbar stroke is correctly adjusted. The garter spring in not intended to retain the fingers, just to cause them to open when the drawbar is unclamped. If the unclamp stroke is excessive then the fingers could disengage from the drawbar shaft, but when the stroke is correctly adjusted the upper sections of the fingers should not enter into the larger diameter bore of the spindle where they could slip off the groove in the drawbar shaft.

Hello guys , after waiting several weeks , I have the machine running again.

I had to order the new gripper, then slindle had to come out to install the part then re assembled everything.....

I have run the machine today, and it seems like toolholders sticks to the spindle taper, particularly the "low weight" ones , some others seem ok as before.
If I toolchange manually, the sticky ones , once they come out seems to have some oil on the taper as well.Some of them I have to gently tap with the dead blow nylon hammer , which I suppose isn't too good....

Any suggestions?

Tools sticking in the taper is often a sign of an improperly assembled drawbar or incorrectly adjusted stroke length or knockout distance.

Will it call for other damage , what do you suggest me to do?

Repair it as needed to operate properly. Using the toolchanger to yank stuck tools out of the spindle will cause damage or excess wear and tear on the mechanism.

All my machines have a procedure in the manuals to adjust the drawbar and knockout. I would assume Kit to have a similar procedure. That is what I would look at first

It sounds to me like you don't have the knockout distance set right, as in not enough. As Vancbiker said, do not run it this way, you can tear stuff up. I have looked and can't find where mine is written down but from memory I think it was .018"-.021", I know I set it .019"-.02". The first order of business is to measure yours. How much does your tool holder travel between clamped and released? Even if you are going to have the work done it is good to know this now, and after they leave.

What can limit drawbar travel is:
1 - Incorrect travel set by the air cylinder, this is just a normal adjustment.
2 - The spindle coupling is incorrectly positioned so the collar pin bottoms out in the slots limiting drawbar travel, this is why I drop the air pressure to test when adjusting travel. I screwed this up when I put my machine back together so understand how easy it is to do.
3 - The springs on the drawbar are adjusted too tight to give enough travel. The rebuilder may do this to increase drawbar tension, like mine did.

I am assuming the grippers and pull studs are correct.

Since you had the work done I would think you should call them to have them fix this as they either did something wrong or didn't finish the job by setting the knockout distance.

If you want to do it yourself then you need to know what your correct knockout distance is. It is probably the same as my machine but don't assume, you have to get this right. Once you know then remove all of the sheet metal from the head so you can get to the drawbar air cylinder. Loosen the nut where it attaches to the yoke and turn the cylinder shaft to adjust, you want to unscrew it to get more travel. I would test the drawbar knockout travel with minimal air pressure, around 35ish psi, in case you have other issues, like the spindle coupling is not in the exact right position. Once you have the knockout travel right then return the air pressure to normal for final inspection. The hardest part is getting access to the nut and shaft as it is tight in there. Adjusting the knockout travel is a normal thing whenever you do much work to your spindle, like you have had done.

Our machines are very close but not identical so keep that in mind when listening to my advice.

Hello guys,

thanks for the many replies as usual!

So, I have been setting the machine today, I have probably done 40ish tool changes (because of the job I am doing), then decided to leave it anyway as it might cause other damage(as you said as well), hopefully, is not damaged already.

I believe the main reason is what you stated earlier on this thread.... but here other machine symptoms I noticed today when manually clamping and unclamping tools...

This is happening since replacing the pull stud gripper, machine was clamping/unclamping tools as it should after the spindle rebuilt, but on the other hand I did not have much chance to run the machine after that as it failed within 10 hours...

I tried to manually tool change tools when the machine was "cold", and I managed to do that on all of them without any issue, once the machine warmed up, I then started to have the issues, particularly when running the tools at high speed, but still some of the tools were still unclamping perfectly as it should ( 2 out of 7 tools ) regardless the weight of them, where some others they seemed completely clamped even with the unclamp button pressed...

I will certainly speak with the engineer, it's the 3rd visit since the rebuilt...

But God knows when I will have this done, I would like to repair it by myself, but it does not sound like the easiest job to do.

I am getting to a stage with this machine that I am scared to run it as there is something going wrong every week...
luckily I have this forum