Tool Holder Handedness and Safety

For peace of mind, use tool holders that are tighened, not loosened, by the direction of rotation of the tool. April 17, 2009

I need to know if a right hand threaded collet chuck is tightened correctly, will the nut be affected (loosened) by a left hand rotation of the spindle?

Forum Responses
(CNC Forum)
From contributor T:
As far as your question, Iím not sure. I do it all the time and have not had any come loose yet.

From contributor J:
I use left hand bits, but never in a right hand tool holder. It doesn't sound safe to me.

From contributor W:
I use right hand tools in right hand toolholders and left hand bits in left hand toolholders, it only makes sense.

From contributor J:
The potential to loosen in this configuration is when the spindle stops/starts. Especially if the machine has a DC brake that stops the spindle quickly. From a liability standpoint if something bad were to happen resulting in injury you will be in an indefensible position.

From contributor M:
If LH tool holders weren't deemed necessary, they wouldn't be made. It's a cheap insurance policy towards safety. Yeah, you might get away with a right hander 99 times out of a hundred, but that one time when it sends your tool, nut and collet flying in who knows what direction, you just have to hope none of your body parts are in their path! Think about it this way, the nut on a saw arbor always tightens against the rotation. The same principles are at works here too.

From contributor K:
Why not simply use a left/right hand HSK tool holder?

From contributor T:
I would only like to add, along with placing yourself or your company in an indefensible position, you are also placing someone's health and life in jeopardy! In my opinion, this never warrants the risk!

From contributor H:
I have seen RH holders used for LH but, there is always that chance. I don't think anyone would tell you itís safe, but it is done. I guess it depends on how much liability insurance you have and if you want to test it out. We do have the LH holders if you need them.