Tapered Slots on Lock and Tang Screws

[Elnathan]

Do you guys taper the slots on your lock and tang screws? With the top jaw screw it makes sense, since it is a deep slot to begin with, but with shallower slots I am wondering if it might make the screwdriver prone to torquing out. Thanks.

Elnathan

[keweenaw]

File the slots to fit the screw driver you use.

[Elnathan]

File the slots to fit the screw driver you use.

Ah, well, as it so happens I am making the screwdriver right now and wanted to know what kind of fit I should be aiming for. I made a hunting-pouch screwdriver for the top-jaw screw once, tapered the screw slot some time later, and then discovered that after I tapered that the screwdriver no longer fitted well. I figured that I should resolve the question of whether or not to taper the slots before I finished filing down the tip of the new screwdriver.

[keweenaw]

If you case harden your screws the slots will stay the shape you cut them and be much less likely to get messed up over the years.  I just use a little taper on mine.  The large headed screws - top jaw and cock - simply look a lot better with tapered slots than parallel slots. 

[Jim Kibler]

I re-file all screw slots with a knife file.  I have a screw driver filed to fit this shape and it is therefore a good fit on all the gun screws.  A slot with a slight taper is traditional and works quite well in my experience.

[D. Taylor Sapergia]

I agree with you Jim.  I have two or three knife files in various sizes so that I can easily recut the slot.  With screw drivers that are ground to fit, they are more positive, and less likely to slip that when cut with a hack-saw, or factory milling machine. Case hardening the screw makes them last in perfect shape a lot longer than not doing so.

[B Shipman]

Case hardening working bolts is so easy everyone should do it. All that's required is to heat the head of the screw to dancng red heat, dip it in Kasenite. The stuff should stick in a blob to the head. Then heat it again with a torch until it melts. The longer you hold it, the deeper the case. Drop it in water and it should result in a "pop". Rock hard suface with a soft shank.
Clean it up and leave the grey mottled surface as I do even on fancy guns, or polish it. Fire bluing will reduce the hardness but still be tougher than nothing done at all.

[Curt Larsen]

This is a variation on this thread.  I don't know if any of you have tried one of those Pickering tools that TOW and others sell.  They are designed for tapered slots.  I picked one up at  a show a while  back and had one problem with it.  The screwdriver head fit tapered slots well, but bent after one or two uses.  Anyone else tried one of these and had better luck, or are they just junk?

[smallpatch]

I've been using a Pickering for a couple of years now.  They work great.  Just got to be careful that the pick doesn't scratch the finish when using the large screwdriver.  Mine seems hard as nails, what were you using it for "Head bolts"??  Just kidding.

[Robert Wolfe]

What kind of file do you buy for cutting slots in screws - what size is good for typical rifle work? I bought one via the internet and was surprised when it arrived that it was good for watch sized screws and not much else!

[keweenaw]

Screw slotting files tend to be very expensive.  What Jim and Taylor are suggesting is to buy some knife form needle files.  These come in different sizes and cuts an can either be used to cut a slot or to taper out the slot that is already present on factory screws.  Good ones are also not cheap.http://www.toolsavings.com/products/Hand%20Tools/Files/Swiss%20Precision%20Needle%20Files/Knife%20Swiss%20Prec@@2e%20Needle%20File.aspx

[Acer Saccharum]

When forming the screw head, you can cut a narrow slot with a jeweler's saw(they make heavy blades). Then make a swedge to punch the taper into the slot cut by the saw. Grind your swedge the same contour angle as your screwdriver.

[Dr. Tim-Boone]

Unless there is some very compelling reason historically to make tapered slots it seems to me that square cut hardeened slots with a screwdriver hollow ground to fit and hardened is mechanically more sound and less likely to slip and bugger up the screw head.   When I was an apprentice cash register mechanic at NCR I spent my first six months sitting in front of a grinder hollow grinding and hardening screwdrivers to fit NCR Screws,,,,,and making spring hooks... and sweeping floors....  I have a small flat warding file with one safe edge for squaring up slots to fit my screwdrivers

[keweenaw]

Tim,

The problem is not with square slots in the screws, it's with the screw drivers.  Unless you buy very good screw driver bits, the parallel tipped ones tend to twist off in very tight screws which does terrible things to the screw heads.  On my modern work I use square slots, often very narrow and have appropriate interchangeable bits for my Brownell's screw driver.  On my longrifle work I taper the slots.

Tom

[Jim Kibler]

One other thing to consider is that by it's nature, a slightly tapered screwdriver will solidly bear on the slot, provided it doesn't bottom out.  A parallel sided slot and screwdriver must be sized very carefully to have good contact.  The tapered slots are traditional and work well.  I've not experienced any significant tendency for screwdriver sliping with this set-up.

[Acer Saccharum]

The problem comes in when the gun owner uses a crappy ten cent screwdriver that's all worn and rounded from years of using as a prybar, nit pick and turnscrew. The end is round, the blade is twisted, and the alloy is low. Under stress, it skitters out of the slot, but not before bugging up the top edges of the screw, then scoots rapidly across the woodwork.

I highly esteem a well made turnscrew.

Tom

[Dr. Tim-Boone]

Yep... Make em to fit ...whether straight or tapered.  The right tool for the right job...........