I have a Hitachi C12LCH chop saw that won't start.

Check the brush holders and make sure the brush can travel freely all the way down to the commutator.
Look down the brush tube with a light and turn the blade to rotate the armature - look for missing/burnt segments on the commutator.
Also, this has a soft-start module that can go bad - if the brushes and armature are good, switch rings out, and all connections are tight, I would lean toward the module.

It is a matter of terminology. A chop saw is geared more towards cutting bulk things and is heavy duty. A miter saw is precision wood working equipment for cutting angles. It would help to know what make and model you are wondering about

Its conversely sometimes possible if you was asking about a wood saw with a steel saw blade but i cannot advice that in both application its not safe because not only of the difference of power but most it is the much higher RPM by diameter, just beware always on the max rpm you can read on your saw blades!!, it can give strange accidents with objects it can grab and swinging outbroken parts away.

The nut that holds the blade on May gave come loose. Or motor is shot

I'm not sure if you have a chop saw or circular saw. Either way, it sounds like the nut and washer are not tight enough to hold the blade. If you have a circular saw clockwise will tighten the nut and washer onto the blade and hold it in place. Most chop saws are a left hand thread and then you would turn the nut counter clockwise to hold the blade tighter. The blade wobbles because it is not tight.

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.

You likely need to replace the blade i have hitachi 10 inch chop saw with the lazer i love it the best one i have ever had vary well build But any saw is olny as good as its blade if ti were a lesser mechine i would say it could be the baerings but i see how hitachi makes tools so i would say its the blade got over heated at one time now when it gets hot it looses its integreity buy good blades as a rule

Sounds like it but does it have a capacitor (start/run)--what model/type motor is it? and go from there.

This could have many causes...depending on the model of saw, the wood being cut, the blade you're using, etc. etc.
Check that the blade is correctly installed, up to tension, and sharp. Make sure the wheels run smoothly on their on, and under power. Check the horsepower of the motor, and make sure to keep the feed rate down within the motor's capacity. Finally, don't twist the work being cut to a smaller radius than the size blade will handle, or you will bind the blade in the cut.
If you are cutting wood with pitch or grain that is likely to be under tension, perhaps you need to insert a wedge into the cut to prevent the work from pinching the blade as it continues the cut.
I hope that leads to a solution. Sometimes all you can do is feed slowly and be patient...

Use a pencil and straight edge to mark the cutting line on the wood. Place the wood on the saw table and line the mark up with the saw. Place the mark on the right side of the blade to ensure proper cutting. Plug the saw in and put on your safety goggles. Support the wood on the work surface with your left hand, placing it far from the saw blade. Place your right hand on the handle, and push the trigger to start the saw. Move the saw blade down onto the wood. Put constant pressure on the handle to slowly move the blade through the wood. Release the trigger and raise the blade once the cut is complete. Make diagonal cuts in the same manner, by marking the wood and lining the mark up just to the right of the saw blade. Continue as you would for a straight cut. Remove the wood from the saw. Unplug the chop saw and dust the sawdust off. Remove the dust bag from the back and empty it. Vacuum any remaining dust off of the saw.