See how the sleeve and jaws hold the bit
Front views show counterclockwise opening and clockwise closing. A cutaway shows the jaws gripping the straight shank, with cutting flutes outside and the Milwaukee-specific 1/16-inch back-off at the inner end.
Open and close: view from the bit toward the drill
1: Turn the sleeve counterclockwise to open the jaws. 2: Turn clockwise to close them. Check jaw movement with power disconnected; this is sleeve movement, not the motor direction switch.
Grip the shank, leave the flutes outside
1 is the smooth round shank; 2 is the cutting flute. For Milwaukee 3403-20 and 3404-20 drill bits, touch the bottom, center the bit, then back it out about 1/16 inch (1.6 mm) before tightening. The dimension marks the internal end gap. Enlarged schematic, not to scale; the flute is outside the jaws.
Keep the bit centered before the final tightening
The straight example is centered between the jaws; the crossed-out angled example is not. Hold the bit centered as you tighten by hand. For these Milwaukee models, completion requires the ratcheting sound AND the sleeve reaching its hand-tight endpoint.
Original explanatory views for the Milwaukee 3403-20/3404-20 example, not a dimensioned product drawing. Remove the battery first. The 1/16-inch back-off applies to drill bits in this manual, not every chuck or screwdriver bit.
Know which part to turn
These steps cover the US Milwaukee M12 FUEL 3403-20 drill/driver and 3404-20 hammer drill/driver. Both have a spindle lock, so you tighten the chuck sleeve by hand. The sleeve surrounds the jaws at the front of the tool. The torque-adjustment collar behind it is a different control.
On a typical round-shank twist drill, the jaws grip the smooth shank, not the fluted cutting section. All three jaws should surround that same gripping section, with the bit centered between them. Do not leave a bit barely inserted just to gain extra reach.
Check the bit before fitting it
Choose an undamaged drill bit or screwdriver bit suited to the tool and the job. Check the shank for bending, damage or heavy wear, and make sure its size falls within the drill and chuck’s permitted range. Fitting through the opening is not enough. You do not need a chuck key or pliers to tighten this chuck.
If an old bit has been slipping, inspect its shank before using it again. More tightening will not repair a damaged bit. If a sound bit goes in crookedly, release it and start again rather than forcing it straight as the jaws close.
Fit the bit in four steps
Clockwise and counterclockwise below are viewed from the front of the chuck, looking toward the tool body. Watch the jaws too: they move apart as the chuck opens and toward the center as it closes.
- Release the trigger, wait for the bit to stop, and remove the battery. Let a hot bit cool before handling it. Leave the battery out throughout the change.
- Hold the tool steady and turn the sleeve counterclockwise by hand until the jaws open far enough to admit the accessory straight.
- Use the method that matches your accessory:
- Drill bit: insert its shank until it reaches the bottom of the chuck, center it, then withdraw it about 1/16 inch, or 1.6 mm. This is measured from the internal bottom, not from the chuck mouth to the flutes. If the jaws would still grip the flutes, check that the bit is suitable before tightening.
- Screwdriver bit: insert it far enough for the jaws to grip the hexagonal shank. Do not use the drill-bit bottom-and-withdraw method, or grip only the working tip.
- Keep the accessory centered and turn the sleeve clockwise by hand. You should hear ratcheting and continue until the sleeve will turn no farther by hand. Hearing a single click is not enough; there is no extra reverse turn after locking.
The 1.6 mm withdrawal and this locking method apply to these two models. Do not assume every keyless chuck works the same way.
Taking the bit out
Stop the tool and remove the battery first. Turn the sleeve counterclockwise until the jaws release the bit. Ratcheting while opening or closing is not itself a fault. Never hold the sleeve and pull the trigger to let the motor do the tightening.
Check before putting the battery back
Look for three things: all jaws grip the same part of the shank, the bit does not lean to one side, and the sleeve is fully tightened. If you cannot see how the bit is seated, release it and fit it again. This is an installation check, not a measurement of chuck accuracy or spindle runout.
Then secure the workpiece and prepare the settings and protection for the job. Do not hold a powered bit to check its grip, or deliberately make it slip under load as a test.
If the bit will not stay put
- Jaws on the flutes or a visibly crooked bit: leave the battery out, open the jaws fully and refit using step 3. Correct the position before adding any tightening force.
- Sleeve tight but bit still loose: check the shank’s shape, size and condition. If the chuck still cannot retain a confirmed compatible, undamaged bit, stop using it and arrange service.
- Repeated loosening or slipping during use: stop and remove the battery. Do not carry on by retightening after every hole. Note the model, bit size and circumstances for the repair technician.
Slipping alone does not tell you whether a jaw, bearing or spindle has failed. If correct refitting does not solve the problem, do not start dismantling the chuck to find out.