20 Most Recent Dremel 400 Series Xpr Rotary Tool Kit with Xpr Multisaw and Xpr Planer Attachment 400 - 6/90 Questions & Answers

This can happen if you accidentally depress the spindle locking button while the tool is running -- a common problem since Dremel did not include any type of interlock to prevent it, and the button is right where you'd hold the tool for best control. If that happens, you probably will need to replace the tool or send it to Dremel for repair.

Rotary tools can be divided into two types— Cut Out Tools and Basic Rotary Tools. The biggest difference between the two is the size of their motors. Cut out tools usually have larger motors.

Dremel Service and repair:http://www.dremel.com/en-us/customerservice/productsupport/ServiceAndRepair/Pages/default.aspx

Those digital dremel's are touchy when the get hard use. learn to use it without the display or try to return it regardless if it spins, it's fine.

Go to Dremel ->LINK. Just be sure to set the parts right.

it is possible that you stripped lock mechanism on the collet, for the beginning, never, ever, use wrench to tighten the collet! just hand tied, if it slips, tight it bit more, but with hands only.

i never used wrench on the collet and never have any trouble with any of my dremels.

to close, just hold firmly in one hand pressing locket button, tighten up with other hand, to undo, reverse procedure.

if you find bit is too lose, then you have collet inserts, find that one which hold bit firmly and use it on this particular bit. standard collet is 1/8" (3.175mm), but in the set there are collets from 0.0394'' (1mm) to 0.177" (4.5mm). do not use wrench...

just inspect now if thread is not stripped, on spindle and on collar, if locket still hold, if these are damaged, you need to change damaged part. and follow the advice :-)

if you find this advice useful, pleasae do not hesitate leave your remark and vote4 for me, thanx!

Sorry, but I seem to have ( essentially ) the same problem... no positive lock. holding the button down while rotating the shaft to find the "best hold" then applying extra pressure sometimes helps. I had no problem with an older model. 400 XPR also seems to overhheat badly.
My ultimate solution: purchasing the model 4000.

Could be the brushes burned out. Don't panic, they are user replaceable. If you have the user guide it should explain exactly how to do it. If you don't have the guide you'll first need to get a set of replacment brushes from a larger hardware store. Make sure to get brushes for your model. On the side of the tool are black slotted caps that can be unscrewed BE CAREFUL THE SPRINGS UNDER THE SCREW CAP CAN GO FLYING. With the cap removed the old brush will fall out and can be replaced with the new one. 2 brushes, one on each side are needed. The 400XPR is a newer model so if this doen't repair it, there may be a defect in the tool.

The attachment is 'keyed to the motor assembly so it will only go on in one direction. If it was mistakingly forced on in a different manner it can get jammed. Try twisting it from left to right while pulling straight out.

absolutely astounding! Had my Dremmel for 10 years and abuse it and use it it has been wet and its out in the shed. Never had a days trouble.

Now when it was in the case was the case shut? My thoughts are mice piddle which if it gets inside will corrode everything. I say this because a bigger drill of mine got damaged in that way. No external signs of damage but when opened the damage was there and it could also be then smelled.

My only other thoughts on this is to get you to check the plug to see a wire has not pulled off, after that I would suspect the dremmel switch has a fault.

all shots in the dark! but have to start somewhere when you are riding blind.

Thanks for using FIXYA

which manual you are talking about

check and see if you have the right collet insert in the chuck if it is too big it wont lock the shaft. does the chuck turn? if so your collet is not locking the flex shaft

blow out the ducts on the side and if that is not it replace the brushes.

I would go direct to Dremel.com or call them at 1-800-437-3635 and get the schematic and parts you need, I just checked and they have a parts diagram online that you can view. go to the section about manuals/literature and type in your model number. Good luck