Can someone let me know if I am picking good parts to build my first machine with.

1 LMC16 x 650mm rail bearing shaft XYZ table CNC router (Y Axis)
1 LMC16 x 4 pc linear ball bearing XYZ table CNC router (Y Axis)
2 24" 1/2-10 ACME Lead Screw w/ Delrin Nut for CNC Router(Y and X Axis)
1 12" 1/2-10 ACME Lead Screw w/ Delrin Nut for CNC Router(Z Axis)
2 3/4" Round Precision Ground Rod 24" (X Axis)
1 1/2" Round Precision Ground Rod 24" (2 x 12") (Z Axis)
2 SC20UU x 4 pc linear ball bearing (X and Z Axis)
1 3/4" 4'x8' MDF
1 G540 4 axis controller (when it comes out)
3 282oz-in stepper motor 2 phase

I am looking for opinions

Thanks
Haku

Use 1/2-8 2 start or 1/2-10 5 start acme.

What is the difference??

Thanks
Haku

You'll get 3-5 times more speed than with single start 1/2-10.

I mean what is the physical difference, a different pitch??

Thanks
Haku

I'm still learning this stuff as well so you might want to wait for someone to confirm but this is my take on it.

You can think of each start as a separate spiral running the length of the rod. A 1 start has a single spiral groove like a normal screw. A 2 start has 2 spirals, like a double helix, so you you would get an effective 4 tpi out of a 1/2-8 2 start or .25 inches per revolution. A 1/2-10 5 start would give an effective 2 tpi so for every turn of the screw you would move .5 inches.

Yes, 1/2-8 2 start is 4 turns per inch. 1/2-10 5 start is 2 turns per inch.

Plus higher efficiency. Multi-start screws are usually higher efficiency than single. Some of the motion screw manufacturers publish information about there screws.
Look here.
http://nookindustries.com/acme/AcmeAvailability.cfm