If this is a new saw, return it to the store for an exchange, but if it's an older than a few months:
These contractor saws often acquire this problem. It's usually dust, specifically pine dust (it has sap thus making it stickier), on the screw or the sliding mechanism. What I do is:
- Unplug the saw
- Remove the blade
- Dismount the saw from its stand
- Lower the mechanism all the way
- Flip the saw over onto its table
- Access the screw and the lift mechanism
- Use a brush to remove the accumulated wood dust from the screw and the mechanism.
- If you have a leaf blower or access to one; blow the interior of the saw (wear eye protection always!)
- Do NOT oil the mechanism, this will only serve to gum everything up faster - use a dry lubricant (graphite or silicone) or none at all.
To avoid this in the future;
- Avoid resinous woods (not a likely solution).
- Blow the dust from the saw interior when finished using it (this works well) - use an air hose or a leaf blower, the leaf blower actually works best.
- After cutting and before stowing the saw; run the blade to its highest position and then down below the table. This pushes any dust off the mechanism and screw.
If you find little or no dust accumulation, it's possible the saw has a bent screw or binding mechanism and will require service.
Always be safe; unplug the saw and remove the blade when working on it, and always retract the blade below the table when not in use to prevent damage to the blade - or being cut by an exposed blade; they're sharp!