Ill add my 2 cents (about all its worth)
I like the Brownells screw driver bits. First they carry a large assortment, and the bits are hard, but not so hard that they will snap the blades off, instead if the bit is pushed beyond its limits the blades will twist or bend. Blades that snap off will almost always cause you to make an unsightly gouge somewhere.
I mostly work on Old Colts and Winchesters, the screw slots are pretty standardized for those makers, i.e.. .200 dia head = .030-.032 width screw slot, Ive pretty much gotten all them memorized.
On guns that have not been apart in a while, I always put a drop or two of Penetrant (Kroil Liquid Wrench etc) in the screw slot and on the threaded end if I can get to it; let it sit for a few minutes. Then I take a wooden toothpick and clean out all the grunge in the screw slot.
If you dont know the exact width of the slot, use a set of feeler gauges or pin gauges to measure the slot, that will give you the exact slot width. Think my set of feeler gauges range from .001 - .035, and my smallest pin gauge set goes from .010-.060
Head dia can be measured with calipers.
Something to keep in mind is that on many thin head screws with a tapered backside the screw slot may be cut deep enough that it was cut thru the beveled bottom of the head. Meaning that the head dia on top may be .200, but since the back of the screw has an 82 deg taper, the true dia at the bottom of the slot may only be .180 Using as .200 screwdriver on those screw will result the screwdriver not going all the way to the bottom of the slot increasing chances of slippage and rounding out a screw slot, and making a burr on the female recess that the screw fits in.
V/R
Mike
