Acrid Odor Cause

I was making a simple PCB enclosure out of 3/4" MDF to test out my newly installed Bitsetter using 1/8" and 1/4" endmills. The first toolpath made .126" through holes in the corners with the 1/8" cutter. All went well except I detected a faint burning odor. The system paused and asked for a tool bit change.

Good - I turned off the router and shopvac and looked to see what was burning. No smoke but I looked carefully for embers. After several minutes the odor had dissipated so I continued the job to a successful conclusion.

It wasn’t until I was inspecting the enclosure I realized what had happened. The 1/8" endmill has flutes that are 1/2" long. I had made the final 1/4" of the hole by burnishing the MDF with the shank of the endmill. There was no discoloration of the MDF but it was enough to be detected by my olfactory system.

Lesson - compare the depth of cut with the length of the flutes. Adjust accordingly and finish the through holes with a hand drill and bit of the appropriate size.



… or, get a longer bit! :smiley:

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A longer bit is an option and I may add that to my collection.

I was writing to note the importance of working within the limitations of the tools one has and how the job can still be completed.


Just make sure your max stepdown is less than the LOC on the endmill. You probably shouldn’t be cutting 6xD with any endmill in one go anyways :laughing:

Was it a circular interpolation thru hole? That shouldn’t have been rubbing on the shank if so (Unless you had lots of deflection from running too fast).


I think ‘max stepdown’ in your post is equivalent to Depth per Pass in Carbide Create. If so I used the default Depth per Pass for a 1/8" endmill in MDF of .045" If my understanding is correct I was not cutting (6XD = 3/4") in one go. My Max Depth did exceed the length of the flutes on the endmill as stated in my original post.

Not sure what ‘circular interpolation thru hole’ is or how to determine if that is what Carbide Create does.

No excess deflection.

Always fun reading the responses and realize I don’t understand the lexicon for this machine.

Thanks, Bill


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