RE: Finished arrow weights- How close is enough?
That's why I match the Gold Tips I sell for weight to within 3 grains before fletching or cutting them.
Now for your question, I match my hunting arrows to within 3 grains and my 3D arrows to within 1 grain.
Now I've found that grinding in excess of 5 grains off the tip can cause FOC difference that will affect the accuracy more than the weight difference with some arrows.
An easier way to match them is with set screws that you can add to some point inserts, that way you can add a little weight and shoot the arrow to see if it shoots OK. I've even ran a 8/32 tap through some inserts that weren't tapped clear through to do this.
For target points I've used #8 or #6 buckshot with hot melt to match them.