Silly expensive mistake

Hey guys,

I seem to have been put myself in a dire situation. I have been running a few routine jobs these last few days, I noticed a very subtle resistance when removing/installing the collet nut on my spindle while changing tools, but did not think twice about it. That is until, after a simple 3 minute job when I tried to unscrew the collet nut for another tool change, there was suddenly a huge resistance. After a few moves back and forth with the wrenches, situation got worse, I may have been fed up and used excessive force, and by now the nut won’t budge at all either way, regardless of the amount of force I put on the wrenches. The collet itself is not tight anymore, the endmill fell off, and I can wiggle it a bit inside the nut.

So this may well be the most stupid mistake I ever did on my machine, but I conclude that the spindle and/or nut thread got damaged, and with the (silly) attempts at getting it unstuck it is now stuck for good.

I let it soak in oil overnight, to no avail.

I would ask if anyone every successfully found a way out of this, but I’m afraid I know the answer.
My last chance before I ditch the spindle (and then go lie in a corner to cry) would be to try and cut the nut with a dremel and cutting disk, but I suspect it will be absolutely impossible to not damage the spindle shaft in the process (assuming it’s not already damaged beyond repair). Is this a crazy move ?
Any other crazy thoughts to possibly recover from this ?


I assume you tried with the standard length wrenches … if you can extend them of find longer one you would have a lot more leverage and might be able to get the nut out ( longer lever = greater moment of force).
Try with some pipes on the handle of the wrenches.



For what it’s worth, I came across a spindle like this where the machine operator had either cross-threaded the nut, or had an aluminum chip or something get into the threads and still cranked it onto the spindle (HDM). I just brute forced the collet off with basically a breaker bar on the wrenches. I was fully expecting to have to find a die of the correct thread to re-cut the spindle shaft, but other than a weird marred section of thread that posed slight resistance everytime I threaded the nut back on, it’s worked fine since. Dunno if that’s the likely outcome every time, but that’s been my single experience with this kind of problem…


I’d try a quality penetrant like PB Blaster or Kroil and let that soak for a day or two, and then (with a helper) use a couple quality wrenches with black pipe as cheater bars.

If that doesn’t work get a bigger hammer, err, cheater bar.

If that doesn’t work? Go back to step one, but then hit the nut with a MAPP gas torch, then try it again being careful not to brand yourself.

ETA: gently sobbing sometimes makes the gods take pity on you.


I wouldn’t use heat…I think that could damage a bearing in the spindle. More force! Maybe cut the nut with a rotary tool if it gets that far…slowly.


Thank you all, (more) brute force it is then.
Reading that @wmoy once salvaged a spindle this way gives me hope.
And then dremel if the nut won’t give in.
I won’t give up without a fight!

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I hate using stainless steel nuts/bolts for this reason. One small piece of metal and it’s stuck solid. Has anyone ever used anti-seize paste on their collets? Would that be a bad thing to use with the constant vibration?

If gently applying excessive force does not do the trick I might see if an impact driver could encourage the nut to loosen.


Agreed, an impact driver is worth a go.

I was thinking of a socket with a long breaker bar on the nut, the longer the bars the more force you can apply in a controlled way, I have a 1,500mm breaker bar which on those rare occasions I need it, is invaluable. I’d probably use a wall drive socket on the nut too, if you chew the corners of the nut then things will get really difficult.

Might also be worth taking the spindle out of the clamp so that the only force being applied is torque between the spindle shaft and the nut?

Cutting into the nut is a tricky one, you need to cut pretty most of the way through to release the nut threads without damaging the spindle thread, a nut splitter might finish the job for you, but these deep nuts may well need a long cut going top to bottom first.


@Julien You are turning it the correct direction, aren’t you? :smiley: Just asking to cover that possibility. :smiley:


Try a little heat just to make it warm but not hot enough to damage the end bearing. Once it is warm put some pipe thread cutting oil on the top exposed threads. The cutting oil will work down fast. Then tighten and loosen the nut in small amounts. Cutting oil works great it is made for high friction cutting and should lube the nit and threads enough to get it off. I’m sure the threads on one or both will be damaged but you can salvage the collet.


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This may sound crazy but what about putting it in the freezer, then warm, then freezer etc. The expansion/contraction cycle may help. Also if you could clamp a couple of wrenches on it so that there was constant unscrew pressure as it went through that cycle.

Other than that I wondered whether you dip the nut into liquid nitro and then hit it with a ball hammer to see if it would shatter.

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6 point socket or box end wrench on the nut, longest handle wrench you have on the spindle. Move the spindle to close to end of x axis. Brace wrench on spindle on machine upright and apply constant pressure on the socket. You can try LIGHTLY tapping the nut while applying pressure. Don’t hit it hard.

Don’t listen to the people saying to split the nut. The spindle is way harder then the nut and you will damage it.

I second the nut splitter, If the Dremel doesn’t work. More likely the collet is damaged then then shaft. It might be easier to remove the spindle and work on it on a bench.

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Holy words I can’t say on TV.

The Dremel might be your only way to remove it without damaging the shaft. Fine cuts relieve the pressure giving it a place to flex or break the nut off.

In regards to heat, YES you have to be careful. Please don’t get it too hot. Heat on the nut will expand the metal. I am sure you have it on the bench so heat will be less likely to travel up.

Good Luck

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I just received my new Carbide 3D VFD Spindle kit and I notice when I unscrew the collet nut that right near the end when it’s about to come off it stops and I have to use the wrench to re-loosen it and it comes off. Not sure if this is normal but has had me worried and I’ve only taken the collet nut off maybe 5 times so far. Now I’m thinking and wondering if mine might start to do what yours is doing here. It’s definitely each time had me feeling like oh crap.

Not sure if I should just reach out to Carbide 3D and possibly get a new spindle or possibly just a new nut is all that’s needed. I definitely don’t wanna be down the road and it becomes worse.

Hope you find a way to get this resolved. It does make wonder if when balancing these nuts if they are just being slapped on the same spindle but so quick that they get a small slight cross thread.

My 2 Cents
If heating, IMHO, keep the 13 mm wrench on to absorb some of the spindle heat and protect the bearing. Be quick, you want to expand the nut but not the spindle
After trying all the cutting oil and heat tricks.

Many times I have had to use a Dremel or likes there of. I cut both sides of the nut but not into the threads. Stop short of the thread. Sometimes this weakens the nut enough that you can go back to the wrenches, the cuts can allow the nut to expand. If not, then split the nut, sometimes just a big flat screw drive can be put in “one” of the cuts. A twisting motion is better then driving it in. The spindle is hollow so we want to avoid crushing forces. Twist and or Pry
The nut is partially over the collet so if you need to weaken it more, cut deeper into this area and across the bottom, if you happen to hit the collet, oh well. When you try to split the nut you can come from the bottom end instead of the sides, it allows greater leverage / force on the deeper cuts in this area. You can get two wedges in. And the shaft can take greater forces in this direction.
This should save the spindle,

It really comes down to a judgement and feel.
I hope this gave you some ideas.
Good Luck


Thank you all again, lots of food for thought on how to approach this. As usual my wife was right when she literally forced me to seat and post on the forum instead of cursing.

The two spindles (from different origins) I have been using both do this, I would not worry. My problem is most likely “just” some metal debris that got stuck between the nut and shaft, so just be mindful of how clean the shaft thread/collet nut are when you screw it on. As long as the movement of the nut is smooth when putting it it, I would not worry at all.

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If its an ER style collet, it should do this (or at least all mine do). Its part of the collet that helps eject the bit. The old Porter Cable hand routers collets do the same. The PreciseBit collets I have for my DeWalt 611 router on one of my CNCs does the same.

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