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Countersinking: which tool is best?

dcmartin

dcmartin

Joined
Oct 25, 2010
Messages
1,233
So lately i've been making scales for some of my folders.... I've been using a standard "V" shaped countersink bit and it has served me well. My real question is, which bit would you recommend for a "flat" not a "V" shaped countersink?

Usually the countersink at the pivot is flat not a V

Any help would be appreciated.

-Thanks
 
Hint for 'ya: That is a "counterbore" when it has a flat bottom, and a "countersink" when it has an angle. :D (Sorry, I'm an engineer, can't help it!)

Best way I've found to do them, if you do not have a mill to use an endmill, is a step drill. Those can be had either from some knifemaking shops, or from a supply house like McMaster.

EDIT: McMaster's supply of them can be found HERE.
 
Last edited:
Excellent! McMaster and Granger both make them, or you can make your own if you're careful and have a lathe or a precision grinder. :)
 
So a Counterbore is the "proper" tool for pivots and hardware?
Is this so you only drill the hole one time?
 
I'm not a knifemaker, just an engineer who works in the machining and manufacturing field, so I can only partially answer that question, honestly. The counterbore / step drill is the common tool for getting two perfectly-aligned diameters to meet at a square corner. It's by no means the ONLY way to do so. If you have a suitably rigid setup, you can also use a chucked endmill or plunge-rated carbide router bit to do the counterbore, or an actual boring head if you have a bridgeport or other suitable mill.

For the average person with a drill press, though, the counterbore is hard to beat. It guarantees that your step will match up perfectly with the through hole, and the screw head will be nice and concentric inside the recess.
 
A step drill would be a versatile tool for the home shop.

What is normally used is a counterbore tool. The pilot on the end is the size of the clearance hole and the cutting edge is the size of the counterbore so you need a tool for each screw size.

An end mill would be used on a machine tool to minimize tooling.

tool.jpg
 
Is a step drill more price friendly than a counterbore?
I was looking at the McMaster website that Komitadjie posted and those prices would add up!
 
Well, typically you'll only need ONE for the job, and they last a long time. I would get a drill of the correct size, then a counterbore if I was doing it myself. Buy once, cry once.
 
What size and type of screws are you using for pivots and hardware? With that answer someone can pin point what your looking for.
 
Robert Carter said:
What size and type of screws are you using for pivots and hardware? With that answer someone can pin point what your looking for.
Click to expand...


Also, what "machinery" are you using? If you are using a hand drill or just a drill press you better have something with a pilot or that cuts both hole and counterbore at once.

If you have a machine tool, or if you can rig up a set-up which holds the part rigidly in the same spot in a drill press then possibilities to fudge it open.

If you can clamp the part in a vise, then clamp the vise to the drill press table lined up right over the spot you need the co'bore you could...

1. Drill the hole
2. Drill the co'bore with a drill, taking the tip of said drill very slightly less deep than where you want the flat bottom of the co'bore
3. Take a drill of the same size which you have ground flat on the cutting end and use it to make the bottom of your co'bore flat.

You can clamp the part up in any way to where it will not move at all and you are just changing tools.

A flat bottom drill will not cut well and will walk all over the place if you use just it. It will cut well enough to cut the drill point out of the bottom of your co'bore and the existing hole will pilot it. If you want to get fancy, rough the co'bore with a drill about .01" less than the diameter of the flat bottom drill rather than one the same size.

("flat bottom drills they make the rockin' world go 'round"...nemind)
 
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