National Electric Code calls for protection of the cable or raceway (conduit).

National Electric Code (NEC)

300.4 Protection Against Physical Damage. Where subject to physical damage, conductors shall be protected.

(A) Cables and Raceways Through Wood Members.

(1) Bored Holes. In both exposed and concealed locations, where a cable or raceway type wiring method is installed through bored holes in joists, rafters, or wood members, holes shall be bored so that the edge of the hole is not less than 32 mm (11⁄4 in.) from the nearest edge of the wood member. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by screws or nails by a steel plate(s) or bushing(s), at least 1.6 mm (1⁄16 in.) thick, and of appropriate length and width installed to cover the area of the wiring.

Exception No. 1: Steel plates shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing.

(2) Notches in Wood. Where there is no objection because of weakening the building structure, in both exposed and concealed locations, cables or raceways shall be permitted to be laid in notches in wood studs, joists, rafters, or other wood members where the cable or raceway at those points is protected against nails or screws by a steel plate at least 1.6 mm (1⁄16 in.) thick, and of appropriate length and width, installed to cover the area of the wiring. The steel plate shall be installed before the building finish is applied.

Exception No. 1: Steel plates shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing.

Building codes dictate how large the holes and notches can be.

International Residential Code (IRC)

Any stud may be bored or drilled, provided that diameter of the resulting hole is no more than 60% of the stud width and the edge of the hole is no more than 5/8” to the edge of the stud, and the hole is not located in the same area as a cut or notch. Studs located in exterior walls or bearing partitions drilled over 40% and up to 60% shall also be doubled with no more than 2 successive doubled studs bored.

Which means for bearing walls with 2x4 studs, the maximum hole diameter is 1 3/8" and maximum notch depth is 7/8". For a non-bearing wall with 2x4 studs, the maximum hole diameter is 2 1/8" and maximum notch depth is 1 3/8". For bearing walls with 2x6 studs, the maximum hole diameter is 2 3/16" maximum notch depth is 1 3/8". For non-bearing walls with 2x6 studs, the maximum hole diameter is 3 5/16" maximum notch depth is 2 3/16".

Check local codes for amendments before proceeding. It might also be a good idea to consult with an engineer, to insure structural integrity is maintained.

In the 2011 version of the National Electrical Code, there was Table 310.15(B)(7). This table was quite handy for determining the service conductor size. In the 2014 version, it looks like they've done away with this table. However, the long code trail that has replaced it, seems to basically say the same thing.

National Electrical Code 2011

Article 310 - Conductors for General Wiring

II. Installation

Typical services (in the US) are 100, 150, or 200 ampere (though 60 is common for older dwellings). Which means you'll be dealing with a possible range from 4 AWG copper to 2/0 copper (2 AWG al to 4/0 al). Which means you'll want a device that can accommodate conductors from about 0.3 in. diameter to about 0.7 in. diameter, if you want to cover the whole spectrum of possibilities.