Makita LS1013 Sliding Compound Mitre saw will not lock at chosen positions/angles on the turnplate other than the standard stop points. Turning the handle will not lock the turnplate anymore it used to it just moves freely now until it hits the nearest stop point. Does anyone know how to fix this ? Machine is 3 years old.

My saw had this exact same problem, here's how i fixed mine.

okay so here's a schematic of the saw
http://www.toolpartspro.com/image/LS...-Makita-PB.pdf

whether you have the exact same issue as my saw, in order to further investigate you need to get to the mechanism that locks the saw. To do this you need to take the turn base (140) off the foot base (156) . its really not too hard, just a little awkward setting the saw in different positions to remove the various parts.

Specifically on mine I had issues with the threaded rod (118) not screwing into the stopper holder (135). You'll see this part when you flip the saw upside down.

So to remove the turn base(140) from the foot base (156)....

Remove the kerf board (108) and under you will see a big bolt, go ahead and remove this. Then there are 4 more bolts which take off the guide rule (117), this what your piece of wood is put against when making the cut. Once these 5 bolts are out, the turn base can now be separated from the feet. Now you'll have a better view of the mechanics and see what is or isn't happening when you screw the handle to lock the miter position.

Part 136 (turn stopper) is what actually wedges to a pocket in the foot base which makes the saw lock. when you screw in the handle it actuates this part. make sure that is happening. I had to take out the threaded rod (118) and tighten it on a vice and work the stopper holder (135) deeper onto the threaded rod. use WD 40 to help it a long. You'll need to take off some other various parts to to get the rod out. this will be obvious once you have everything turned over.

Now that everything is apart you can blast it with some WD40 or what you think is best here. I used lithium grease. You'll see its especially important to lube up the pivot post that the 2 bases center on, (where the big bolt under the kerf board goes). also the slide plates (153) may be rusty, they'll fall out when you separate the 2 base plates. clean those up and spray them and anything else which will help with smooth movement.

the only important item to check once everything is put back together is the guide rule. this can be adjusted slightly in or out of square. Get a nice framing square and make sure your locked in at 90 (or actually 0 degrees on the saw) Sliding the saw the full distance of the cut on the square is ideal and maybe this was a good time to recalibrate that movement anyway.

hope this works.
Ben.