I agree with bushveld about all "spring steels" not being equal. I feel you would be better off modifying a good quality screwdriver bit by slowly grinding it to the required shape without over-heating it and drawing the temper. If you temper too soft, the bit may twist and deform and damage the screw slot. If you temper it too hard and brittle, it may suddenly break, and cause you to gouge or scratch the surface surrounding your screw. A thin screw slot requires a thin well fitted blade which is more easily broken, and increases the chances of bad things happening. So start with good penetrating oil to help things get moving.
You might also check if Brownell's or Wheeler has magnetic tip individual bits that are close to your needs. My own set of Wheeler bits seem to be a little on the brittle side, and I have had some break on stubborn screws.
Those Crown Cabinet screwdrivers from Amazon do not appear to be hollow ground, and if so, would be unsuitable for most gun work without modification.
You are correct that these Crown cabinet makers screwdrivers are not hollow ground. However, they have such outstanding build quality, handle form and alloy steel that they can be made into outstanding screwdrivers for a gunsmith, and this is the reason that you will see them on the benches of gunmakers here in the USA, UK and Europe.
Firstly, you will notice how long the steel shaft is on the screwdrivers-- which allows for heat treating the tips without damaging the handles from heat after the tips are shaped according to how the gunsmith/gunmaker wants them. Secondly, and very important the handle as Mark has stated is oval shaped which allows the hand to grip the handle with great leverage in removing tight screws. Thirdly, you will see that the top of the steel shaft where it meets the wooden handle has a flat, this flat is just perfect for placing an adjustable "Crescent" type wrench to assist in removing those impossible to remove screws by turning the screw drive blade with both its handle and the adjustable wrench at the the same time.
I have two sets of these Crown cabinet makers screwdrivers. One set that I have ground and re-heat treated in the traditional gunmakers shapes; and a second set that I left unchanged. The heat treating of the steel on these screwdrivers is simple and the tempering I have found should be drawn to a light brown colour. For those of you who have somewhat limited experience of how to judge the correct colour of "cherry red" (a term that is anything but correct in telling someone at what colour to quench steel) just heat about 1 inch of the bottom (don't overheat and do not hurry the heating as you do not want to "burn" the steel) of the screwdriver shaft to where a magnet will not longer adhere to the tip and then quench it in oil---I use 5W20 Mobil synthetic oil or peanut oil heated to about 100 degrees F as a quenching liquid. (Peanut oil is wonderful medium for spring making due to its high flash temp) Then polish the tip (400 -600 grit emery cloth is good) that you have just hardened and apply heat with a low flame from a propane torch about 1 inch back from the tip of the screwdriver and and watch the tip color change as the heat progress from the flame to the end tip. When the tip changes colour from dark straw to light brown, quench in the oil.
While we are in this discussion about screwdrivers you should note that our ideas here in North America of how a gunmakers turnscrew or screwdriver's tip should be shaped is not universal. I noticed this decades ago while I was working in England and visited gunmakers shops and looked at their screwdrivers. I had also noticed that Jack Rowe made his turnscrew tips in a shape not hollow ground. For those of you who have a copy of the video "iNSIDE HOLLAND & HOLLAND" look at the shape of the turnscrews that the gunmakers are using in that video. I have not ever visited an Italian gunmakers shop, but I suspect their turnscrews are shaped peculiar to us since they use such narrow screw slots. Bottom line is I have some turnscrews/screwdrivers shaped as Jack Rowe did his and some shaped hollow ground.
Further to the "hollow ground" of the tip. If one thinks of the perfect way to hollow ground a turnscrew or screwdriver tip (according to good engineering and machine shop principles, it seems to my way of thinking that the perfect hollow ground shape should be wider by about .003" to .004" at the very tip for a length of about .010" to .012". If ground this shape when one exerts rotation of the screwdriver in the slot of the screw, then the wider bottom of the tip does not allow the screw slot top to be "buggered" as long as you do not allow the screwdriver to slip. I have seen few people pay close attention to grinding screwdriver tips and correctly heat treating them.
Stephen Howell
