What size screw do I need?

[OM2]

I bought some 30mm wood screws from Toolstation: 'Single Thread Countersunk Pozi Screw 3.0 x 30mm'

The head is tooo small. I need to use the small screw bit.
What do I need to get to use the bigger size bit?
Should I buy these screws instead: Single Thread Countersunk Pozi Screw 4.0 x 30mm?

They also have Single Thread Countersunk Pozi Screw 3.5 x 30mm.

Thanks.

 

[CBW]

Sorry, this doesn’t make much sense to me. What exactly are you trying to screw together?

 

[Deleted member 174758]

From the foregoing I presume that your 3.0mm screws use a PZD#1 bit. Next size up is PZD#2 which is generally used on sizes from 3.5 to 5.0mm, with a few manufacturers opting for PZD#3 on 5.0mm screws. 6.0 screws use PZD#3 bits and are about as large as most people ever use