Trying to avoid future VFD issues

CNC Machines
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I have had some issues with my 65 VFD collet nut and spindle threads. I can’t express how careful I am with making sure everything is aligned and trying to make sure I am not over tightening but all that didn’t avoid me wrecking the threads to the point the nut wouldn’t come back off. This is after running my 5 pro allot of hours and creating some firewood and some great items. Carbide support has been amazing throughout this and helping me out. I have a new spindle but I am noticing even with just going to hand tight and maybe 1/8 to 1/4 of a turn after that which doesn’t seem tight at all I am getting what I can only describe as resistance (I can hear was can only be described as a metal scraping noise) the threads when taking the nut back off. The resistance is not right away either, it is after about two turns of the nut. Stumpy nubs talks about that resistance possibly being a self releasing collect but not sure if that is the case here. If I shake the bit loose inside the collet the resistance is gone and all is smooth again. This lead me to think I was putting the bit in to far but not going in as far didn’t seem make much difference.

This is what happened before the threads went bad last time after about 100 hours of spindle run time and who knows how many bit changes.

I want to make sure this is not repeated so looking more into the process for installing and removing the collet. I have been following the YouTube carbide and IDC video guides for the process but that doesn’t really say much about how tight to make the bit just don’t over tighten. I found several “guides” saying to tighten with both wrenches in one hand. I found a video from cutting it close and he mentions a torque wrench to avoid over tightening. Do any of you do this and if so what wrench do you recommend?

He also mentioned the bit needs to be 3mm from the top of the collet and if I honor the rule of cutting the flutes and 1/8 or so from the collect face that seems to be fine for collet spacing at the top.

I would very grateful for any advice on what is working for you all so I can avoid this issue.

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The first turn is just loosening the nut. Then the resistance is the collet being pulled away from the tapered face inside the shaft. Wiggling your tool, or tapping on the collet nut usually frees the collet so you don’t feel that resistance. :wink: Clean the collets & inside of shaft every time you change collets. But this is generally normal. :wink:

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Sounds good, I am very OCD about cleaning but I will add the bit shake to my process from now on.

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Cleaning is a big part of it, we ran some tests - no dust boot - and the amount of dust that enters the collet is quite impressive. This can really build up.

Some dust will shake loose, some will need to be brushed out. I’d check the threads between changes.

Also make sure you press the collet into the collet nut first.

Once a month I ultrasonic clean all my collets and nuts.

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I have also found hygiene to help a ton. I tend to get a good amount of aluminum chips in my collets and nuts while running. So I make sure to clean those out at every tool change. Usually air works, but I still have a brush handy. I also have an ultrasonic cleaner that I run the nuts and collets thru frequently. I also use some anti-seize on the threads.

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Thank you for the information. I used a small brush on the threads, air inside the spindle taper, collet, and on the collect nut. I had not considered using my ultra sonic cleaner. I will add that to my process.

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Thank you for the information, I got so focused on cleaning everything I hadn’t considered anti seize on the threads.

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I clean my collets with brake cleaner. I spray brake cleaner on a qtip and clean the inside of the router shaft as well. If you put something on your treads be careful it does not get transferred to the collet itself. The collet and router shaft must be oil free and dry. If you use anti seize on the threads just use very little. A little goes a long way. After applying lightly wipe the outside threads so remove excess. The part in the inner threads is enough.

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Thank you for the information, really appreciate it. I used brake clean to get all the shipping oil off but only cleaned with air after that. Souths like I need to do more on depth cleaning more often.i hadn’t considered my ultra sonic to help with the cleaning as was suggested so adding that as well.

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If you use an ultrasonic cleaner make sure the parts are thoroughly dry before putting them back in the VFD. Brake cleaner dries very quickly so maybe follow the ultrasonic with brake cleaner. If you have a way to spray air use that as well. The collet has places for ultrasonic liquid to hide.

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Collet seating and bit seating can be tough to some people. Make sure that the collet is clicked into the nut before anything else. A properly seated collet nut will stay in the nut without falling out if the nut is turned upside down and let hung freely. The bit seating is important to make sure the bit is thru the front and back of the collet. That is the proper seating. Now you have to take that with a grain of salt, because the further out the bit is sticking the higher chances of bit chatter or deflection.

Best rule of thumb is to insert the bit into the collet after the collet is seated properly into the nut, and then twisting on the nut until it is just hand tight. Then back off a hair, slide the bit all the way up to the stop inside the spindle, and then pulling it back down at least a 1/16 of a inch, a little further wouldnt hurt, but usually 1/16 is enough. Then tighten the nut with both wrenches. Now, as far as the amount of torque to apply is sometimes tough depending on the person. If you are heavy handed, then it woild be easy to tighten the nut down too tight. And if you are soft handed, mean no disrespect to anyone here, then the nut will not be tight enough and when cutting begins to vibrate the bit too much, or the cut is more on the heavier cut, then the bit will tend to move up or down inside the collet.

Do some experimenting with your collet to know its proper torque, but a good rule of thumb would be to seat the collet by wrench tightening until it is not easy to turn, then it is ready for the final torque, and this could be as much as 1/8 of a turn to 1/4 of a turn. As for removal, the nut will break free and then turn until there is resistance. This is the collet being removed from its seat while still holding the bit. Once this happens, you should be able to remove the bit from the collet, if you so desire. Once the collet and nut have been removed, using compressed air to blow out the collet of fine dust is desirable. If you dont have compressed air, ergo, air compressor, then remove the collet and use an old tooth brush to brush the collet clean between the little slits in the collet.

When putting back on the nut to the spindle, it should always go on easily by hand only. This should allow you to hand thread on the nut all the way to almost full seat, many turns onto the spindle, before you feel resistance. At no time should the nut feel crunchy, tough to turn on the treads at the beginning of threading, or bumpy. If you feel this, at any point, remove the nut and collet from the spindle and clean throughly. Do not use any pliers of vise grips on the spindle threads at any time. This will ruin/destroy the threads and you will not be able to fix then without complications further down the road.

I know this is a lot that I wrote, but in all of my years working in metal machine shops, I have seen things that others have done to tools, tool holders, and collets, that made my blood boil with frustration because I usually am the one that has to come fix their mistakes, and they would lie to me about what they did when the evidence speaks for itself.

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I find that there are issues with ER type collets when dust or debris in the collet nut and collet as well as in the spindle taper inside). I have the 80mm spindle , ER25. And ER40 on a Mill and Lathe. Compressed air works very well to insure all these items are free of debris . An old toothbrush works very well for cleaning the collet nut as it has some recesses that are hard to reach. After wiping out the spindle bore , use my finger to swab the taper to ensure its clean. Tightening the Nut can only go so far. As the collet will collapse (squeeze closed) . Good luck

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