Introduction: How to Disassemble a Keyless Drill Chuck
I've had this cordless drill for going on 10 years now. It has been a great drill, but recently has been plagued with a sticky chuck, making it hard to open and close the chuck. A few months ago I purchased a newer lithium powered version of this same drill so I figured it would be worth some exploratory surgery to see if I could get this one operating smoothly again.
These same steps/procedures may apply to other brands of drills as well, but this is the first keyless chuck I've had apart. I've labeled the photo with the terms that I'll use for individual components throughout this 'able.
Step 1: Remove Chuck From Drill
First step is to remove the chuck from the drill. Start by fully retracting the jaws into the chuck. Look into the bore of the chuck to see if there's a screw. This could be any type of screw - phillips, allen, flat, star, hex, etc. Remove the screw. Mine was reverse threaded (left hand threaded), and most others will likely be reverse threaded as well. This means that to loosen the screw, you'll turn it to the right. The normal saying "lefty loosey" is wrong when it comes to reverse threaded hardware. This screw may possibly have a thread locker (locktite) on it - mine did.
Once the screw is out, grab the largest allen wrench you have and tighten the short end into the chuck. The chuck will be a "lefty loosey" to remove. Lay the drill down on it's side with the chuck hanging over the edge of a bench as pictured. Hold the drill firmly to the bench and hit the allen wrench downward using sharp blows with a hammer. Hopefully yours comes off much easier than mine did...
If you need to replace the drill chuck, you can stop here and go buy a new chuck. The common threads on the drill are either 1/2-20 for 1/2" capacity chucks or 3/8-24 for 1/4" capacity chucks. Find a suitable replacement to fit your drill.
Step 2: Remove Lower Housing
I searched a while online and couldn't find anything that showed how to get these apart. After some prodding and prying, I determined that this was the easiest way to get it apart. Clamp the lower housing in a vise with the jaws pointed downward. If you are concerned with scratching or marring the outside of the chuck, use suitable protection. Look at the bottom to see what appears to be a shoulder with two flats on it. This is actually a shaft that will slide out. Use a hammer and a suitable "drift" to drive the chuck body from the lower housing.
Step 3: Remove Upper Housing
The upper plastic housing is held to the chuck body with a snap ring. Use a small screwdriver to gently pry and remove the snap ring. CAUTION: if not properly contained, these snap rings can fly off to some unknown place, never to be found again. Cup your hand over the chuck as you're removing the snap ring to keep from losing it, or losing an eye... You are wearing safety glasses, right?
Once the snap ring is removed, you can slide the upper housing off of the chuck body. You'll notice that there are two tabs inside the upper housing that fit inside some slots in the chuck body. These will need to be aligned during reassembly.
Step 4: Mark the Jaws
These photos were actually taken later in the process, but now is a good time to mark the jaws and chuck body. While the jaws don't have to go back in the same holes they were in, they do need to stay in the same order. The easiest way to make sure the order doesn't get mixed up is to mark at least two holes of the chuck and two jaws. I used a spring loaded center punch, but you could use a scratch awl, nail, etc to mark the pieces. I'd avoid using any marking that may wipe off or be removed by cleaners, etc.
Step 5: Final Disassembly & Cleaning
To get the jaws all the way out, there is a bearing race/sleeve that needs to be removed. Unfortunately, the photo I took for this didn't turn out so I'll try to explain. Open the bench vise just wide enough so only the edges of the sleeve rest on the vise. With the jaws pointing downward, drive the chuck body out of the sleeve. NOTE: there are a bunch of little tiny ball bearings inside this sleeve. Use a suitable method of catching all of these tiny bearings. I used a magnetic parts tray under the vise to catch all the bearings that tried to escape.
Once the sleeve is removed and bearings contained, remove the split nut and slide the jaws out of their bores. Clean as necessary. I used a combination of paper towels, pipe cleaners, an old toothbrush for the threads on the jaws, some 400 grit wet/dry sandpaper to remove some surface rust, and a small screwdriver to scrape away some thick grease. Be careful not to scratch, nick, or dent the bores that the jaws slide in or the jaws themselves.
Step 6: Timing the Jaws
Once all is clean, you can start to reassemble. Slide the jaws back in their corresponding bores. Before fitting the split nut, the jaws have to be timed. This is done by putting all jaws at the same height before installing the split nut. If they are not timed correctly, the jaws will not close all the way. Test to see if they are timed correctly by holding both sides of the split nut and rotating the chuck body so the jaws close. If the jaws are all the same height, you have them timed correctly. If one jaw is out of time, it will be lower than the others. To fix this, just remove the half of split nut that is on that jaw and slide the jaw up until it is in time. Put the split nut piece back in place and test again. Once satisfied, proceed to the next step.
Step 7: Prepping the Sleeve
To reassemble, you'll need a way to press things back together. I achieved this by drilling a hole in a piece of wood that was larger than the nose of the chuck body, but smaller than the bearing sleeve. Use a bench vise to press the sleeve over the nose of the chuck and onto the split nut. Stop when the edge of the sleeve is at the bottom edge of the split nut. This is the channel that the bearings ride in.
Step 8: Pressing the Bearings
My chuck had 32 bearings - yours may vary depending on the size of the chuck. Place the chuck, nose down, into the hole in the wood. Place the bearings in the channel. A small dab of light grease will help the bearings "stick" in place. There may be some gaps between some of these bearings, which is fine.
To keep all the bearings in place, you need to keep the chuck upright, so you won't be able to use the vise to press the chuck the rest of the way into the bearing sleeve. An arbor press would be ideal, and you may even be able to use a drill press quill to apply enough pressure. I used a large c-clamp that was held vertically by the vise. Slowly press the chuck all the way into the sleeve, ensuring that all bearings remain in the channel. Fully seat the chuck so that the sleeve is flush with the top edge of the split nut.
Step 9: Finish Reassembly
Finish reassembly by reversing steps 3, 2, and 1.
I did not use any lubrication inside my chuck and it operates very smoothly. You could probably use a light grease, but any type of grease will attract dust and other debris. The clearances for anything to get down into the body of the chuck are very small, so you don't have to worry about larger particles, but eventually enough stuff will get in there to warrant another cleaning. I