Okay, since I have so damn many of these Bosch drivers and impactors, here's a side-by-side comparison with each one chucking a 1" Milwaukee Phillips #2 bit, fully seated in the tool.
PS20 vs. PS21
PS40 vs. PS41
25618 (18V Li Impactor) vs. 26618 (18V Li combo 2-speed drill/driver and Impactor)
PS10 vs. 26618
Note that all of these tools lock the bit in place with various success. All but the PS21 keep the bit in place mainly with the friction of the locking ball in the chuck. If the bit sticks in the screw, it will pull out of the chuck fairly easily. The PS21 has a similar mechanism, but with a slightly smaller ball and a tighter locking action against the slight groove in the bit. With the bit locked in the PS21 chuck, it won't come out with pliers. Releasing the chuck on the PS 21 lets the bit come out with fingertip grip. On all the rest, the bit is too far back, you need pliers to withdraw the bit, or if the chuck is not too dirty, shaking and tapping the tool with the chuck pointing down will let the bit drop out.
As Stuey shows, all of these tools have at least some wobble in the chuck. This will eventually get worse over time as the inside of the chuck wears, bit even with the mileage on some of these tools of mine, I haven't noticed any increase. The reason why the PS21 seems to have more wobble is because the chuck itself is shallower, for one, simple geometry will show this is inevitable. Depending on the type of bit, if the locking groove is too wide or cut too far forward, part of the groove will extend outside the chuck, leaving only the heel end to maintain radial integrity. Most often this isn't a problem, except for long bits. Even the best fitting drill bits will wobble in a 1/4 hex chuck. The best solution I have come up with is a conversion chuck, particularly this one made by DeWalt:
This particular chuck has an unusual hand tightening method in the collar actually "impacts" to loosen or tighten. Insert the bit, tighten the chuck by hand, then hold the black outer collar while pulling the trigger. The collar strikes internal ramped anvils to tighten the chuck, much the same way a typical impactor functions. The same process works in reverse. If you pull the collar toward the tool, you make the hits harder. The hidden beauty is that if you push the collar toward the bit, the impacting stops and the collar lets the rest of the chuck free-spin smoothly in hand. Holding the chuck in this way stops all wobble, and it's very easy to precisely place the spinning bit. I keep this with the 26618 combo driver since this is my go-to tool to carry when I want only one tool to handle impacting, drilling and driving, and I don't need to use hex-shanked bits. I have yet to find some really good hex drill bits, most I have come across have pot metal shanks molded onto (at best fair quality) drill bits, and the runout on some of those things is atrocious.
And, yes, I do have way too many power tools of all kinds. This is a mere fraction. I should do some reviews.
