Hand tool for countersinking screws

[SuperCracker]

What kind of tool would have been used originally for countersinking screws? I can never seem to get satisfactory results with store bought countersinks and, like so many tools, I've resigned myself to just making something myself.

Any pictures of original tools would be great.

[Mark Elliott]

They had countersink bits for their braces.    I have a bunch of them.   I also have a bunch of modern ones, different angles and number of cutters.   As long as you keep them perpendicular to the plane of the hole, they all work well for me.  They are best used in a drill press, but obviously that won't work with every application.   I also have a modern countersink in a file handle for hand use.   I probably use that one the most.

[Jim Kibler]

One interesting point regarding hand cut countersinks is that the flute spacing is not likely to be exactly equal.  This is of advantage in that they are less likely to chatter as compared to some modern ones.

[Habu]

I've always harbored a suspicion that the reason my re-sharpened countersinks perform so well is that when I'm done, the flutes are no longer evenly spaced. 

[Ryan McNabb]

The uneven flutes are important to prevent a harmonic setting up and making "rippled" sinks.

The mistake is to use a countersink with a larger included angle than your screw heads.  This can take time, playing around with different screw suppliers and different countersinks until you find a good match. 

I know Track sells a lot of screws but another good source I've found is www.blacksmithbolt.com   They specialize in unplated screws and will do custom orders.

Screws and screw slots are a constant source of frustration - one of the small things that's a really big thing.

[SuperCracker]

interesting.

The chatter is what gave me headaches, I think I will go give one of my sinks a good sharpening and see if it makes a difference.

Thanks

[Acer Saccharum]

As Ryan sez, the uneven flutes will make the 'sink run smoothly. There are also single flute countersinks, and 'chatterless' styles.

The six flute hardware store countersinks are the worst tool ever invented. They chatter in metal and wood.

The below work really well.

[T*O*F]

So, why doesn't anyone use these?  I use them almost exclusively and only use countersinks by hand to clock my screws.  No chatter problems to worry about.

[Acer Saccharum]

I use those, too, TOF, in my Bridgeport milling machine. But by hand drill or drill press, they will chatter the teeth right out of your head. You need a rigid set up for those tools.

[T*O*F]

I use those, too, TOF, in my Bridgeport milling machine. But by hand drill or drill press, they will chatter the teeth right out of your head. You need a rigid set up for those tools.

Interesting how different people have different results.  I don't have a mill but have never had a chattering problem with them.  I wonder why that is.  Most of my drill press drilling is done with the part resting on a block of wood.  I don't even use a vise.

[Acer Saccharum]

Dave, experience may vary. 

Most of the trouble I've had with that style tool is on thinner metal. Once the point stops guiding the tool, as in just the countersink part is contacting the metal, all $#*! breaks loose.

On thicker metal, the straight point section supports the countersink, keeps it centered. Chatter less likely.


I hate the idea of holding stuff by hand while drilling. I've seen awful things when the drill grabs, and the part swings 'round...and 'round, bashing and cutting any flesh within reach.

[Bob Roller]

I use the center drill as shown for all light countersinking jobs.
I always counetrsink the the depth of one thread on both sides
of an thru hole such as found in a lock plate.To me,it is the
difference between PROfessional work and PERfessional work and it makes the job easier too.

Bob Roller

[Acer Saccharum]

Bob, it's the details that make the real difference in the quality of a job. Countersinking that little bit first gives the thread a place to start without having a burr stick up above the plate. To countersink after threading messes up the thread start, and doesn't look as good.

[Jim Kibler]

Who doesn't hold parts by hand at times when using a drill press  For me, it's sort of a judgment call.  How big is the drill, how big is the part, how well I can hold it and how accurate do I need to drill.  Sometimes a vise is called for, sometimes the mill is best.  As to using a center drill, I believe the included angle is typically 60 degrees, while a wood screw is most often 82 degrees.  I've certainly had mixed luck with countersinks, especially when not used in a rigid set-up.  I have a six flute one that I probably got from MSC.  Not sure who manufactured it, but I love it.  Has little tendency to chatter, and cuts fast and true.

Jim

[T*O*F]

As to using a center drill, I believe the included angle is typically 60 degrees, while a wood screw is most often 82 degrees.

Jim,
They come in all common angles.  I know, I had to buy another complete set.  Whilst building a gun with English screws, I kept getting a ring around the screw head instead of a seamless fit.  Come to find out, they were a different angle than American screws.

[James Wilson Everett]

Guys,

The question was what kind of tool would have been used originally for countersinking screws.  So, lets try to back off away from the Bridgeport and get back into the 18th c.

There are three styles of countersinks; for a brace, for a bow drill, and for a hand held tool.  These are scans from the mid 18th c Wyke tool catalog.  None of these chatter when used by hand, they probably all chatter when attached to an electric motor.

The countersink for use with the brace, for use in wood only


The countersink for use with the brace, for use in metal, like a very large drill bit


The countersink for use with the bow drill, for use in metal



The countersink for use hand held, for use in metal and only for very tiny screws - probably not used by a gunsmith


I do have some original examples if you guys would like to see them

Jim

[Eric Smith]

Thats a nice illustration. Thanks James.

[FL-Flintlock]

The spade type (#371 as shown in Jim's reply) work great and won't chatter or grab in thin/soft metals if only one side cuts and the other rounded off.  The O-flute style like Acer pictured are also good for thin/soft materials.  The spotting-drill style that T*O*F pictured also come in single-flute as do non-piloted countersinks but most have face/relief angles that are too aggressive making for the tendency to grab & chatter.  Another benefit unique to the spade style is they allow one to easily adjust the lay the lay of the screw ... not that anyone would ever find the countersink plane not being copasetic with the work.  If you're partial to piloted countersinks, get yourself a good set of three-flute carbide aviation countersinks - the better sets with the accompanying shell guides & micrometer depth stops will spoil ya right quick like.

[James Wilson Everett]

Guys,

Here is a spade type like #371 in the flesh.



Countersinks that are absolutely guaranteed not to chatter are the ones sharpened to a bow drill cutting edge, like a knife edge.  You use these leftie - rightie - leftie - rightie with the brace or bow drill.  They scrape rather than cut, but really do form the countersink quickly and smoothly.


If more of us would actually try the traditional methods!!!

Jim

[Acer Saccharum]

Great stuff, Jim. Thanks!