doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com European screw slots

Don't the very narrow English gun screw (pin) slots have a taper to them, in other words, wider at the top and very narrow at the bottom? I once read this, and read that it was because if you have a "V" shaped slot and a correspondingly ground screwdriver blade, when sufficient down pressure is applied as the screw is torqued there can be no movement of the blade in the slot. It would always be a perfect fit, so long as the width was right.

One of you Englishmen please tell me if this is so, or if the slots have parallel sides.

SRH

Hi Stan.

As the slots in the screw heads are cut with a slitting saw when manufactured in quantity the slot sides are parallel the same would also be true if the slot is cut using a hand piercing saw (jewellers saw). The V shape you are thinking of possibly comes from the way armours screw drivers are hollow ground to give a very close fit at the top of the screw head slot to prevent damage to the slot by the screw driver caming out when you turn it. There is also a way to make the screw driver dig its self into the walls of the slot this is accomplished by giving the screw driver a couple of sharp hammer taps on the blade which produces a small bur at the end.

damascus,

I had more in mind that the screws I remembered reading about were not made in quantity with slitting saws, but were hand made, on the older guns. Wish I could remember where I read that.

Thanks, SRH

They sell them by # size and I can never remember which is which.

I use a chart like this one that gives the .000" blade thickness so I know what I'm ordering.
I use #8 size the most and it cuts about a .020" slot with a hand saw.
You can see there are some mighty fine slots to be cut with these.
Lots of broken blades if you're not careful!

The whole number sizes (8 down to 1) hold up well doing slots in screws. That'll cover .020 down to .012 though they can cut a little wide if you're not careful. Sometimes you can use it to advantage on an odd size w/a double or multiple cut.
#8 and #4 sizes will just about satisfy any custom work.

Getting much finer, they get chewed up in the thick steel pretty easily and the screwdrivers needed to work them are getting silly thin especially for larger screws that are torqued down.

http://www.anvilfire.com/FAQs/jewelers_saw_blades.htm


FWIW,,those V shaped screw slots being discussed are often found on early American muzzle loading arms. The hand made iron screws were commonly made with distinctly V shaped slots. I don't know if was as a result of the hand tools used in their making or a style of the time. Perhaps both. The screwdrivers were shaped as such to fit the V slot. The top of the slot in the screw head can be very wide at times narrowing quickly to a bottom.

Kutter, thanks. That's really helpful.

V shaped slots were cut with a file of the same shape. Gunsmiths that did this did not buy their files, they made them, and made them to fit.
Mike

Kutter and mike,

Thanks for the "vindication" of my memory. I just had the time frame, type of gun, and country wrong.

Thanks for the explanation on how they were cut, too.

SRH

Having somewhat a working knowledge of early American methods I believe (but am not positive) that "V" slots were forged in screw heads using chisels. Very simple and quick and fitting to a small shop with limited tooling. It is amazing how good they were with forging metal!

European screw slots is most often tight...not lik dem nalens gals...

Damascus: Your idea that the slots were cut to prevent amateur work is the best explanation I have heard thus far...concerning the tapered slots, they will by nature rotate the screwdriver blade up and out--not for me! Steve