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My Dremel (model 398) has a jammed front bearing probably due to too much dry wall cutting and not enough cleaning. I was shocked happy when I found several of those bearings (used) in my toolbox. I'm wondering how to remove the front shaft (red arrow) and bearing (green arrow). It looks like the bearing is glued to the main shaft of the motor and the front shaft is glued to the main shaft. The red arrow points to a hole in the front shaft. There is no set screw in there, just a hole. The front shaft is where the collet goes with the tools that one might want to use. Any ideas how to remove both the front shaft and bearing? Is brute force the only way to go? Thanks

UPDATE: Added another picture to show the part that holds the bearing removed from the rest of the tool.

tool bearing core

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  • I just remember. The hole in the front shaft is for the push button lock, so it does not turn when changing tools.
    – Rodo
    Jun 26, 2019 at 16:26
  • i too just ran into a seized bearing with my dremel 400 series rotatory tool as well. (from doing sheet rock work no less 😭). i thought i'd be smart and clean my tool with my air compressor and of course that made things worse by pushing the little bits of gypsum into the bearing thus seizing the front bearing. so to work around not removing the bearing. you can remove the bearing sheild with a safety pin then with air compressor and some brake parts cleaner spray in the bearing and slowly work out the jammed pieces (gypsum in my case) from t he race of the bearing. now which lube 🤔
    – ipatch
    Feb 8, 2022 at 22:53
  • Someone at work (back then) told me to just spray the bearing with wd40. I thought it was a caca idea but since I didn't have anything to loose I did it. Over several days I sprayed wd40 and the bearing ... over time I could see the dry wall material coming out of the bearing. I did it enough times and at the end it worked. Now still works. I was wrong about being a bad idea. LOL.
    – Rodo
    Feb 9, 2022 at 2:58

3 Answers 3

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This bearing looks like it was pressed on from the splined end of the rotary shaft. Pull the shaft, tap it gently with a brass rod or a socket which fits around the bearing but won't score the shaft. Do this and the bearing should come off.

Edit to add to my earlier question based on the new image: On a splined shaft as seen on your third image there should be a means to disconnect it safely from the plastic hub (or potentially clutch). Because the inner race of the bearing will be to large to fit around he non-threaded or splined portion of the rotary shaft the only means to replace the bearing is to entirely disconnect the shaft. That said, smaller splined shafts like this often only go back one way so be sure to make exactly how it is in its assembled orientation.

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  • Splined end? Is that where the groves are next to the plastic fan looking thing?
    – Rodo
    Jun 26, 2019 at 20:32
  • Yes, the splined end is the end connecting to the "plastic fan looking thing". Those horizontal grooves are called splines.
    – J Crosby
    Jun 26, 2019 at 20:36
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The real problem is how to remove the threaded nose from the shaft in front of the front bearing. Forget the splines, they only make the shaft O.D. larger. The front & rear bearings are on a one piece shaft. The shaft cannot be removed without total disassembly of the armature including windings and laminations.

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Dremel tool holder piece and front bearing are pressed on the shaft from the front. Stick 4mm nail in tool holder and use any bearing puller to remove bearing and tool holder at the same time or piece by piece. Reinstall new bearing and tool holder in reverse order.

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  • If you have more details that you could edit in to add some additional info to make this more useful, it would be helpful, otherwise this doesn't add anything to the already accepted answer. If you'll take the tour and read through the help center, especially the section on answering, you'll see what's expected here and how this Q&A site differs from other discussion forums.
    – FreeMan
    Aug 4, 2020 at 11:42

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