My machine caught fire today

So as the title says, I started a fire today with my Shapeoko XXL. Luckily we caught it pretty early and no extensive damage was done, and nobody was hurt. After cleaning everything up and some damage control, I’ve identified what happened, but I’m looking for reasons WHY it happened.

About a week ago I had an incident where the end mill started slipping out of the router and cutting all the way through my material and into the waste board. I quickly stopped the machine and figured I forgot to tighten down the collet. However, today I was sure I double checked everything prior to starting the job. About 1.5 hours into the operation, I heard violent grinding sounds and smoke coming from the shop. I quickly shut down power and put out the fire that was quickly growing both on the waste-board and inside my dust collection system. After cleaning everything up, I discovered the same issue had happened as before. The end mill had slipped out over 1" from where I installed it. The cutter was plowing through all of my material, through my waste-board, and even into the stock waste-board underneath. A spark was ignited from one of the threaded inserts, and sucked into the shop-vac. So far, I can tell the dewalt router is trashed, but I haven’t checked any of the Shapeoko electronics.

My question is this: how could my 1/4" end mill have slipped out of the collet even after tightening it down? Is this a common issue with the dewalt router? Was this user error, or do I have a defective router?
Any help here would be much appreciated. I’ll attach some images of the router and my stock after this all happened.

Thank you.

Sorry to hear that. How did you stop the fire in the dust collection system?

One of the first times I used my S3 with the Carbide Compact Router (with the C3D precision 1/4" collet BTW), I had the same thing happen, but I stopped it before there was any smoke or fire. There is a deep gouge in my stock MDF base from when it happened.

The CCR has a different style collet than the DeWalt, so in my case I think it was just that I didn’t tighten it enough. Up-cut bits also tend to pull the cutter out of the collet as opposed to the down-cut bits I have been using lately. Now that I make sure it’s tightened “monkey-tight” (not “gorilla-tight”) I haven’t had a problem since. I also make sure there is no sawdust in the gripping areas when I change cutters.

Your comment about a spark from the threaded inserts starting the fire makes me think that maybe brass inserts would be a better choice. Brass doesn’t spark.

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I just emptied an entire fire extinguisher and 2 gallons of water into the shop vac. Its trash now. Come to think of it, I think the threaded inserts are brass. But I’m not totally sure. I’ll double check that next time I install them.


Collets wear, especially the cheap ones, you need to buy a new one that will hold the endmill corectly. I guess that the first time was a warning and you should have made an order at that time.


Measure the bit to ensure it’s not a 6mm bit


Sorry to hear of this happening, but glad you got it under control before losing your house or injuring anyone. I only have one thing to add that could be a culprit.

Measure your endmill diameter. Make sure if using the standard 1/4” collet you have 1/4” endmill, not 6mm. 1/4” is 6.35mm and even though a metric 6mm “looks” the same it isn’t. It’ll tighten down, it will probably even work for a little while, but will eventually slip. If it’s not that then maybe one of the other suggestions above?

I suspect your “spark” had nothing to do with the metal inserts, probably just the friction buildup from the endmill rubbing (like a Boy Scout with a fire bow, but at 20,000rpm). You’ve got crazy rubbing plus a great source of fuel (sawdust) coupled with a great source of oxygen (router blowing, plus dust collector sucking).

Thank you for sharing this topic, maybe it’ll remind folks (like me) to never leave these machines running unattended. Glad you’re ok!



Very sorry to hear about this, but glad no one was hurt.

Please note that we specifically ask that folks not leave the machines running unattended:

Please remember to be safe, no matter how boring and tedious it is.


It’s a great lesson on why we don’t leave them running alone! I’m glad the problem wasn’t worse, and you were watching.

I’ve had issues where I’ve run the collet into the wasteboard and put some good burn marks into things, but thankfully never more than that. I’ve never had an end mill slip out of the collet - I’ve had them push into it, but never pull out.

Winston has a nice video on shapeoko fire safety, and collects some of the video from other incidents.


Thanks for the tip. I just measured the bit, and it seems to be the proper 1/4" bit. total diameter is .246. This is the one I purchased direct from Carbide3D

I’m baffled to how the bit could have slipped so far. You can see in the image how far the bit has moved. I tightened it down with only .875" sticking out.

I use the ones from these guys and have never had a problem. I have split the shaft of one Dewalt with the one that came with the router. Which caused the precise bits 1/8" the get stuck on and lost the collet, nut, and the router.

Is it possible that the collet itself made contact with something? In theory because of the thread direction versus the direction the router spins this shouldn’t happen (it’s constantly tightening). There’s other things like a dirty collet(I blow mine out with shop air between jobs). Or is it possible your stock came loose (no telling what all could happen). Or just an out of spec or worn collet? This may go down like the disappearance of Jimmy Hoffa, you may never know, haha! I would toss all of the above (router, collet, endmill), and just keep CNCing. The only thing you may glean from this experience is to never walk away from a running machine. I work (for my day job) with companies that run multiple CNC machines “lights out”, meaning they run with very little human interaction, but these are machines that cost 100’s of thousands of $$$. A ShapeOKO isn’t, and will never be at the hobbyists price point, a machine you can walk away from. I’ll admit I’m guilty of running inside to use the bathroom or to pour a cup of coffee with my machines running, so I’m not trying to beat on anyone, this is just a good reminder for me that “stuff happens”.


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Lucky you are. I would bet that the collet had dust and chips in it and you really didn’t tighten up bit well enough. Chips got hot, shrank and then bit is loose. And guys, please don’t walk away from these things for more than a quick bathroom break. I see a lot of folks with these in the house and a lot of those in an enclosure, which leads to not observing them closely.
Careful you must be.


i am so glad you are safe and things are ok!
agree with those that said it probably wasn’t a spark from the threaded insert, but rather friction from the tool and wasteboard. i’ve also had an endmill drop out of a collet and it started smoking in the two seconds it took me to get off my stool and lunge for the power. it does not take long at all for things to go very bad once they go bad. scary stuff.

Looking at the burns on the board, there are some pretty wide marks that look like the ones I’ve gotten when I’ve plunged the collet into the work.


I had a similar situation a few months ago. I was in the shop doing something else and heard the Shapeoko making a terrible racket. I turned it off and the oak I was cutting was smoking a little. What had happened is when cutting the tabs on the last pass the tabs turned loose and the oak was jammed up and the router was still trying to move and spin. I caught in in time. The dust collector sometimes worries me when cutting cherry on my table saw. Cherry is very susceptible to burning on the edge when cutting. I always check the bottom of the saw table cavity and watch the bag for any smoke.

This was a good warning about the dangers of working in a workshop. I keep 3 fire extinguishers inside the shop in various places next to the exit doors. I have an additional two fire extinguishers outside on my covered patio. I do a lot of work outside under the over hang. I have a volunteer fire department that usually gets to a fire just in time to spray the ashes. So I take fire safety very seriously. I use a lot of oil based finishes and have a metal covered bucket with water in it I put all the rags used for cleaning and finishing in the water and close the lid. In the summer alcohol and oil based finishes can spontaneously combust when wadded up and put in the trash.

Hopefully all who read this will take the precautions necessary to avert the near disaster this was.

I hear on the radio talking about fire safety often. They recommend drilling the family about what do to when the smoke alarm goes off. Most people that have a fire panic and if you do not have a designated muster area for the family you are worried one of your children are still in a burning house. So talk to your family about what to do if there is an alarm and what to do and where to go. Make them actually leave the house. They may need to open a window and escape or go out doors they do not usually do not use. Thankfully no one was hurt and only pride and replaceable things were damaged.


Anyone installed one of this,, to prevent such accidents?


@HDRyder posted about the fire extinguisher balls he is using, and if I had room above my Shapeoko I would probably choose that option.

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Those look cool. For my setup the tube format fits better since I can stick them on the ceiling of my enclosure.

The balls are cheaper though, but i wonder how they’ll work in that open air environment since they need the fire to be right under them to activate them. By that time the whole room will be on fire, and way too big for the two balls to extinguish it.

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For what it’s worth, I had a fire start because I was using a carbide bit that was too dull. It caused a lot of rubbing instead of cutting, and caused embers in the sawdust in the enclosure. I was watching it when it happened, and it took only seconds for a fire to start. I was able to put it out before it spread, but it was scary as hell. Lesson learned. Always watch the machine, and don’t be a cheap bastard by using a dull bit… especially in phenolic.


I agree with a lot of the comments here and will add a bit. if things are slipping the first thing I would do is inspect all the parts and make sure there is nothing stopping them from operation. dust can build up and create rocks that will hold parts open or give the impression things are tight when they really are not.

Next I would clean and oil any part that has to tighten just to make sure threads are not sticking and I am getting full range of motion with no effort.


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