The blade is not on saw and need to find way to lock so I can get bolt loose

Insert a screwdriver across the blade guard and between two teeth

Unplug the saw. If the blade is moving, wait for it to stop. If the blade arm is locked into its down position, push down slightly on the blade arm to release the tension on the blade arm lock pin. Pull out the lock pin to release the blade arm and allow it to move upward.
2 Rotate the lower blade guard upward and expose the Phillips-head screw that holds the blade bolt cover in place. Loosen the screw and rotate the blade bolt cover up and out of the way to expose the hex-head blade bolt.
3 Push the spindle lock button in and rotate the blade bolt until the spindle lock engages fully, stopping the ability of the blade bolt to rotate.
4 Loosen the blade bolt using a 10-millimeter/12-millimeter combination wrench. The blade bolt is lefthand threaded, which is the reverse of conventional threading. Turn the bolt clockwise to loosen and remove it. Note the placement of the outer washer and remove it as well.
5 Place a drop of machine oil on the inner blade bolt washer. Do not remove the inner washer. If it is missing, replace it before replacing the blade.
6 Slide the replacement saw blade up past the lower blade guard and onto the blade spindle. The blade teeth should point downward at the front of the saw. Saw blades often have rotation arrows that can help you double-check that the saw is installed to rotate the correct direction.
7 Press the spindle lock button in to lock the spindle and reinstall the blade bolt. The blade bolt will tighten in a counterclockwise direction. Replace the blade bolt cover and install the blade bolt cover screw.
8 Position a combination square to check that the blade is square to the saw fence and saw table. If the blade is not square, refer to the procedures in the manual for squaring the blade to the fence and table.
Things You Will Need

• 10-millimeter/12-millimeter combination wrench
• 5-millimeter hex key
• Combination square
• Phillips screwdriver
• Machine oil

Tip

• Overtightening bolts and screws can result in cross-threading. Cross-threading damage compromises the integrity of bolts and screws and can be a difficult error to correct.

Warning

• Do not attempt to install a blade that is too thick in the saw. If the blade washer cannot engage the flats on the spindle, the blade is too thick for the saw.

Best thing to do is to just rest the blade teeth against a peice of scrap wood, and use the allen key/spanner to undo the bolt. As the bolt undoes in the direction of the cut, the blade teeth should dig in and stop it turning. If the blade lock isn't working anymore, it could mean that it has broken inside, so be careful, incase there is a bit of loose metal in the gearbox, it will be quite catastrophic if it gets caught in the gears.

you just have to look for little button close to blade, smash it, hold it while you move the blabe till gets stuck then you're ready to loose the blade! hope this help

Sounds as if the blade is dull. Or perhaps bent. A dull or bent blade blade will 'grab' the wood, rather than cut it, resulting in binding, or kickbacks.

Solution; replace the blade with a fine-toothed, good quality blade. If the blade is new, then check that the blade is bolted tight on the arbor. If the blade is loose, it can result in kickbacks.

Also, check that all the bolts/fasteners/locking mechanisms on the saw are tight, and in good working order. Sometimes a tool new out-of-the-box will have loose screws/nuts/bolts that need to be tightened up.

Also, when cutting, use a smooth, slow, motion, being sure to give the saw the time it needs to make the cut.

try putting the blade against a block of wood and if you have an impact wrench use it and the bolt "will come loose"

There is t shaped scocket type wrench that came wuth the saw that pushes into the saw next to the rear handle it fits the bolt that holds the blade on.There is l shaped metal locking buttom on the front of the motor houseing. The bolt has left handed thread so it loosens in the oppisite deriction as a normal bolt clockwise. push the L shaped button in to lock the blade loosen the bolt remove the washer and blade install new blade in reverise order

Their web site seems to be down at the moment but most circular saw you just need to lock the blade somehow. Sometimes putting the blade up against a piece of wood so it can't turn will get the job done. Unplug the saw so it can't run. Some saws come with a custom wrench to turn a custom bolt, others a regular combination wrench would work. There should be a bolt that goes into the center of the blade. To keep the bolt from coming out while cutting, they are reverse threaded so you loosen it by turning the bolt the reverse direction you on a normal bolt. take the bolt out and be careful you don't loose the washers on each side of the blade. Put in new blade and reverse the process of taking it apart.

First, there is no blade lock button on the Skil model 5150. I called the Skil customer service and they emailed me the exact manual for this circular saw. The method I used to loosen a VERY TIGHT blade stud was: spray with WD-40, imbed the blade in scrap wood, set Skil wrench (usually found in back of foot under handle) on so it could be struck going in counter-clockwise direction. Use hammer to strike handle of wrench a couple of times. To replace blade, finger-tighten blade stud, then use wrench to tighten 1/8 turn or (45°).

You may need to use lock tight on the threads. Also replace the standard washer with a lock washer if possible.