Help.. Bits Breaking

Why are my bits breaking?!?

I’m cutting 1/4” MDF with a 1/8” 2 flute straight end mill bit. It gets to the area where the tabs are and then goes super deep and my bit breaks. Tonight is my first night setting up my machine and I have broken 4 bits already!! PLEASE HELP!!!

This is what it’s doing… gradually getting deeper as it cuts… (shown is 1/4” Birch) it did the same thing the MDF did

Hard to tell by the picture, but to me it seems, there is a step where the cut is getting deeper and it’s not getting gradually deeper, is it?
Please share your Easel project, I’m sure some of the folks here will have a look at it (I’m not using Easel so unfortunately I can’t be much of a help there :frowning: ).
my best guess right now would be a problem with you toolpath, at least that was my problem in the past when encountering something like this. Do you have that problem with every cut or just with this one project? Maybe try cutting a plain square / circle, just for testing purposes and post the results.

Hi!! It’s every cut I have tried so far. So very frustrating

Okay, does it cut deeper at one mark or is it really gradually going deeper (maybe along one axis)?

It looks like it is gradually getting deeper. Maybe I will just try to cut a horizontal line and then a vertical to see where it may be going wrong

I would think it is either your design or the Z-Axis is loosing steps/something is loose. If you designed it in Easel then the whole “gradual increase in depth” is highly unlikely. My first thing would be to check the set-screw on the Z-Axis pulley if the design is OK.

Feel free to share your Easel design here and people will take a look at it for you.


Brandon Parker

Okay, tried to cut a square. And this happened

It cut fine on the first initial pass and as it was going down the Y cut (i think :thinking:) it gradually started to go deeper and then the next cut (x axis) it was all the way through onto the waste Board and then going back up the bit and the little connector thing came completely out of the spindle!! So IDK… :woman_shrugging:t3:

Are you not tightening the collet well enough? I have broken plenty of bits milling aluminium, but I have never had one come out of the router along with the 1/8" adapter. The bit coming out could also give the same results of cutting at random/ever-increasing depths.

Also, you mentioned that you were cutting 1/4" MDF, but your images appear as if you are cutting plywood.


Brandon Parker

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I press the yellow button on the side to load it and then tighten it until I can’t turn it anymore.

This image is now plywood. I gave up on the MDF but made sure my settings were all correct

Have you checked the set-screw on the Z-Axis Pulley?


Brandon Parker

Is it this one?

Here is what you should check to start with.


Brandon Parker

What do I need to check on this? Like what am I looking for? Sorry if I am being a pain lol but you are being so helpful!!

Check that the set screws are tight…

Here is the part of the instructions where this is.


Brandon Parker

I think Brandon may have been right, I think you’re not tightening the collet or you’re using the wrong size collet. The bit shouldn’t come out.
Where did you get that collet from?
Do you have a 1/4" bit you could try?
Keep us posted