Preventing a Tool Holder from Sticking

Some tool holders stick and make a "popping" sound. The solution: frequent cleaning. December 6, 2006

Has anyone experienced issues during tool changes with an ISO 30 holder? I have just recently had a spindle rebuilt and the tool holder sticks and makes a pop when it is trying to be released by the clamping assembly. I have adjusted the sensor on top of the spindle that controls the drawbar, but the problem still occurs.

Forum Responses
(CNC Forum)
From contributor J:
Make sure the retention knob on top of the tool holder is still matched up with the drawbar in the spindle. The drawbar can clamp with balls or fingers. The retention knobs have to match the drawbar style otherwise they can stick resulting in the pop sound or not pull up correctly into the drawbar and then bad things happen.

From contributor A:
We had that same problem after we had a new spindle installed. We tried adjusting the draw bar, new tool holders, and new pull studs. Nothing worked for more than a day or two. About four months ago, (against advice not to) we started giving a little squirt of WD-40 on the pull studs every morning. After we clean the spindle and tool holders in the morning, we protect the rest of the tool holder and tool with a rag being real careful to only lube the stud. We have not had a sticking or pop since we started doing this every morning.

From the original questioner:
I purchased all new tool holders when the spindle was rebuilt and they are both the finger style pull tab. The tools seem to release fine when the machine is completely cool and just after warm-up, but if it makes any cuts the holders begin to stick.

From contributor J:
Is this a fan cooled motor? It may be overheating causing the drawbar to stick. It could be overheating due to the "rebuild" or inadequate cooling. Were the bearings fried causing the rebuild in the first place?

From the original questioner:
Yes it is a fan cooled motor and the bearings were replaced in the rebuild but they were not seized. I have been monitoring the temp of the clamping fingers and the hottest I have been able to get them is 115 F. This temp was taken directly after cutting a sheet of .75”MDF. This temp does not seem excessive to me.

The amount of material that is cut does not seem to affect the issue much. I get the same sticking and popping sound even if I run the machine for 1 minute at a feed rate of 250 IPM.

Does anyone know how far in the clamping fingers should be gripping the pull tab? I used some Dykem to see where the fingers are gripping the pull tab and it appears that the clamping fingers are only gripping about .030” of the pull tab.

From contributor D:
When my main outline tool starts to pop, I know it's time to clean the tool holder and spindle. Even a little bit of a buildup of brown substance around the fat part of the cone seems to be enough to cause the tool holder to stick slightly during tool release. Hence the pop when it releases. What do you guys use to clean the cone and spindle?

From contributor B:
This is a common problem with ISO 30 holders. That is a long taper mating surface and as others have said they are prone to sticking if both they and the router are not kept very clean.

A couple of fixes are to keep a bit of grease on the top of the tangs, clean the tool holders with fine Scotchbrite pads, and clean the internal mating surface of the spindle with fine Scotchbrite (run the spindle on very slow speed and insert the pad wrapped around the end of a small stick). I've also occasionally used anti-seize compound with success, although I don't think that is the best of solutions.

I genuinely think that fighting your way through spindle adjustments is for the most part a waste of effort. Try thorough cleanings and some of the other suggestions listed above and your problem will become intermittent (as is very common) as versus regular.

From contributor R:
You should check the expulsion of the tool when it's ejected. There is a retaining bolt (I think 4mm) inside that you can tighten or loosen to get the desired expulsion up where the tool goes in. You want .6 to .8 expulsion when you eject the tool. Since this is a recently rebuilt spindle, the bolt in mention may be loose. Try tightening it a little and see what happens.