I took a night course on the Care and Restoration of Metal Artifacts at the Canadian Conservation Institute in Ottawa in the fall of 1997.
One of the instructors, Mr. George Prytulak, emphasized the importance of using slotted screwdrivers that fit the slots on screw/bolt heads perfectly. Standard screwdrivers are simply tapered like a wedge and only engage the screw/bolt head at the very top of the slot even though the tip has bottomed out.
The solution is to have the edges of the blade parallel to the slot edges (i.e. hollow ground bits).
The one profession that is very particular about nicks and marred screw/bolt heads is the firearm repair profession. The instructor showed us a beautiful set of bits/handles with varying shank diameters and blade thicknesses.
The Brownells catalog shows their standard set (shank diameter 0.12 to 0.36, blade
thickness 0.030 to 0.070) and their thin-bit set (shank diameter 0.12 to 0.36, blade thickness 0.020 to
0.025). These are listed as their Magna-Tip Screwdriver Sets with following prices:
22 Bit Starter Super Set $55.73 US
44 Bit Professional Super Set $93.03 US
58 Bit Master Super Set $102.46 US
18 Bit Thin Bit Set $40.46 US
The Master Super Set also includes Allen head, Phillips head and square head (Robertson in Canada) bits.
I have found that these bits/handles are indispensable for work on military radios and keys. You may notice that some slots on screw/bolt heads have nicks even though the last screwdriver to touch these heads was at the factory.
My conclusion is that hollow ground screwdrivers were not widely available and not required at the time of manufacture due to the expediency of wartime manufacture. Careful selection of a hollow ground bit to give a snug fit should prevent further nicks during disassembly/assembly.
After two years of use I dont know how I got along without them.
I have found Brownells to be very professional in their business and their catalog is something to behold about ½ thick of gunsmithing supplies. According to their catalog Brownells will ship to other countries.
The address of the company is: Brownells Inc., 200 South Front Street, Montezuma, IA, 50171, USA. Tel (515) 623-5401, Fax (515) 623-3896 or check out their web site.