How to deepen drilled holes

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manny767

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Aug 27, 2012
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How do you get those nice rounded edges in the holes you drill in your blades to give the holes a finished look? Is that called counter sinking, counter boring? What tool do I need to do it? I'm guessing you use a bit in a drillpress, do they come in different sizes or is it a one size "step" type bit? thanks
 
Yep counter sinking, can get different sized bits like so

counter_sink_set.jpg
 
Chamfer or countersink bit. They are the same thing and can be found at any good hardware store. They cut at an angle, 82 degrees is very common.

A counterbore makes square shouldered holes. They are good for square bottomed screws and are found in sizes corresponding to the screw.
 
The cheater way is to use a larger size drill bit and just knock the corners off the hole.


-Xander
 
Ok this is what I thought. Countersinking for the steel holes and counterboring for things like micarta and handle material holes.
On the countersinking how would you know which size countersink to get?
Does using a larger drill bit work well as fast14riot mentioned or are there downsides to this?
 
The bit has to be able to fit into the hole to work properly, so depends on the hole size but a countersink will cover a range of sizes. It depends on which fastener you use as to whether you counter sink or counter bore. As for a larger drill bit, it works to de-burr a hole, but I would not recommend it if you were using it to countersink or finish a hole, it can look quite rough.
 
manny767 said:
Ok this is what I thought. Countersinking for the steel holes and counterboring for things like micarta and handle material holes.
On the countersinking how would you know which size countersink to get?
Does using a larger drill bit work well as fast14riot mentioned or are there downsides to this?
Click to expand...

I have yet to use a counterbore bit but do have one for a folder I am working on.

Countersink (chamfer) bits are great for chamfering a hole. Every hole you drill in steel should be lightly chamfered to knock the corner off. This helps in avoiding stress cracks during heat treat.

I also use a chamfering bit for my handles. I deeply chamfer them then flare my tube hardware. For solid tube just drilling the hole in the scales is the way to go, no need to chamfer or countersink the scales unless you are flaring tube or want to knock the corner off thong hole tubing for a cleaner look.

Yes a bigger bit will work but I'd prefer a dedicated chamfer bit. For knocking a corner off prior to heat treat just about anything will do.
 
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Yes, a counter sink/chamfer bit is the proper tool for the job, but like I said a larger drill bit is the "cheater way." It often will leave a funky surface on the chamfer and will dull the bit. If in a pinch it works better than nothing.


-Xander
 
I use a tapered diamond stone bit in conjunction wIth chamfer bit to remove any and all chatter marks then a little rubber tipped bit loaded with jewelers rouge to polish it
 
Thanks for the responses. Where would I buy a good countersink bit for average sized holes say 3/16s 7/32s and so on? Usa knife maker only has one countersink i wasnt sure was proper sized or not or how to tell.
 
I do it the cheater way--just use a bigger size drill bit. Haven't made anything where it is really necessary to use a real chamfer bit.
 
I'd recommend countersinking all your holes for three reasons:

1) it reduces possible strain points during heat-treat
2) it makes pin insertion easier both during fitting and when everything's covered in epoxy
3) it leaves a little space for epoxy to pool and grab your pins some more.

I used to use a larger drill bit. This works, but is lousy if you want to leave a hole exposed for some reason. The bits chatter, standard bits are long and have runout, you get eccentric chamfers, etc. A proper countersink bit is inexpensive and is the right tool for the job. I prefer the single-flute bits OR the conical ones with the sharp hole-through cutting edge. Don't know how else to describe them. Those are THE BEST, IMO, and it makes a difference. At home I have only the multi-flute and the single.

-Daizee
 
If you just wont to clean up your drilled holes you can get a countersink with a handle on it, very handy to have....
 
daizee said:
I'd recommend countersinking all your holes for three reasons:

1) it reduces possible strain points during heat-treat
2) it makes pin insertion easier both during fitting and when everything's covered in epoxy
3) it leaves a little space for epoxy to pool and grab your pins some more.

I used to use a larger drill bit. This works, but is lousy if you want to leave a hole exposed for some reason. The bits chatter, standard bits are long and have runout, you get eccentric chamfers, etc. A proper countersink bit is inexpensive and is the right tool for the job. I prefer the single-flute bits OR the conical ones with the sharp hole-through cutting edge. Don't know how else to describe them. Those are THE BEST, IMO, and it makes a difference. At home I have only the multi-flute and the single.

-Daizee
Click to expand...

:thumbup: on all points :thumbup:

The types with a lot of flutes on them are great in production applications where you have a rigid setup, controlled feeds and speeds and lots of holes to make in a hurry, but they are very chatter prone if not used just right. You have to feed them pretty hard to keep all the cutting edges cutting well without hopping around everywhere.

Most folks here are going to have better luck with single flute countersinks. You'll get your best surface finish with these tools with fairly slow RPM and oil, though personally I usually run them fast and dry.

You can get all sorts at www.useenco.com

Lastly, to answer the OP, the rounded holes are made with a round over cutter. These generally are used with CNC and circular interpolation. So, most folks just use a chamfer such as a countersink.
 
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