Review on Dremel 4000-4/34 Variable Speed Rotary Tool by Adam Gechem

There are a few reviews here discussing issues customers have had with the collet on this Dremel. I just bought this model and I think I can understand the problem that at least some users are having. First, a few words about terms. The solid shaft on which the cutting or grinding tool is mounted is a mandrel (or Dremel also calls it an auxiliary shaft). When you attach a router bit to your Dremel, this rod slides into a silver-colored hollow tube called a collet. The dark metal nut that covers the collet and screws onto the device is called the collet nut. All of the accessories that come with this Dremel model use 1/8 inch diameter mandrels/rods. Most other accessories that Dremel sells are also this size. although some use 3/32", 1/16" or 1/32" shanks. When my Dremel 4000 arrived I noticed that none of the 1/8" shanks fit in the collet. I think some other buyers who have had this problem have concluded that their Dremel came with the wrong collet. However, when I took it apart a bit, I found that the collet simply stuck tight in the collet nut, compressing its diameter so the shanks didn't match. I unscrewed the collet nut from the Dremel and used a small screwdriver to push the collet out of the back end of the collet nut. This allowed the collet to open to its full diameter; all supplied shafts now fit. So if you buy one of these and don't think the shanks will fit the collet, try this before you conclude it's the wrong size. Dremel could probably do a little quality control to make sure everything is running smoothly. If you really need a different collet size for other mandrels/bars not sold with this kit, Dremel sells the 4485 Collet Nut Kit (about $6-7 in 2015 at hardware stores) which includes the four collet sizes listed above.