How do I get my slider tighter and sharper?
The same way you get to Carnegie Hall.
what you said and I’m not sure if this is good advice or not but I’m going to copy and paste my response to a very similar question:
Check your grip and release out. If you are throwing slurves than your release and grip are too much like a curve ball. Try adding a tiny bit more space between the fingers and moving your release/spin of the wrist angle down just a tiny bit.
If you are essentially are going for a fastball slider with late break modify your fastball a tiny bit until you get what you want. Throw a 2sm fastball grip but use your wrist and fingers to get that spin then slowly move your index closer to your ring if you need more break, keep this up until you are happy. By accident you may come up with an entirely different pitch in between what you are looking for.
If you want it to be closer to a fastball than a curve than start with the fastball. I know this isn’t technically a slider by grip but I throw mine with a 2sm grip and they go hard, however the negative is they aren’t going to cause batters to buckle their knees chasing out of the zone.
It’s all just what you want the pitch to do.
Throw harder and start learning about spin. Spin axis affects movement. The better the spin is the better the movement. However, it’s impossible to really know what you need to work on to get a better slider without seeing you pitch. There’s a lot of mechanical factors that play into slider movement besides just grip unfortunately.
Any article references?
Also, I know the slider is supposed to come off of your index finger , would adding finger pressure to my index finger increase spin?
Here’s a pretty good video: https://www.instagram.com/p/BEj3TZ_B4gP/ I’m not as big on finger pressure, I think I lose arm speed and things slow down when I overly grip them. I like to hold everything like an egg as the old saying goes and throw it with the intent to generate fastball arm speed. I personally relied more on proper wrist positioning and finger placement to get the ball to roll off the fingers properly instead of trying to force it with finger pressure. However, I have played with guys who swear by pressure so to each their own I suppose.