Countersink drill bit issue

T

toobit

Joined
Apr 13, 2020
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First time I used a countersink drill bit on my 1/4 inch steel knife and it worked for one hole but the others it wouldnt catch and I damaged the bit. I also used oil on the bit while I was drilling.

Any advice as to what I am doing wrong? The countersink says it was made for metal.

0zjB7ND.jpg

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You may have overheated the cutting edge on the first hole. Hard to tell from the picture, but it looks like the cutting edge changed color where it cut into the steel, indicating that it got too hot. Since you used oil, you should have seen some smoke if you overheated it. How fast was the drill? Maybe you need to slow it down a bit.

Did you use a drill press or a hand drill? Using a hand drill can help if you have problems with wobble on the drill press. Your arm automatically compensates for the wobble, I guess. Clamping the blade down to the drill press table makes things worse in my experience.
 
Hubert S. said:
You may have overheated the cutting edge on the first hole. Hard to tell from the picture, but it looks like the cutting edge changed color where it cut into the steel, indicating that it got too hot. Since you used oil, you should have seen some smoke if you overheated it. How fast was the drill? Maybe you need to slow it down a bit.

Did you use a drill press or a hand drill? Using a hand drill can help if you have problems with wobble on the drill press. Your arm automatically compensates for the wobble, I guess. Clamping the blade down to the drill press table makes things worse in my experience.
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I used the drill Press so I couldn’t really change the speed. I was lightly drilling into it. I did see smoke but I thought a lot of that was due to the oil. I’m wondering if there’s a better countersink bit that I can get.
 
A hss countersink that size works best at 100 rpms or less. Most home drill presses are just about worthless for drilling holes over 1/2" in diameter. A counterstrike makes things worse because it has more cutting edges. A "zero flute" and single flute c-sink doesn't help unless you drill and countersink in the same setup with the item bolted down.
 
mike-E said:
A hss countersink that size works best at 100 rpms or less. Most home drill presses are just about worthless for drilling holes over 1/2" in diameter. A counterstrike makes things worse because it has more cutting edges. A "zero flute" and single flute c-sink doesn't help unless you drill and countersink in the same setup with the item bolted down.
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Interesting. So should I use a hand drill?
 
I watch some videos it looks like some people use the drill press and drift the power on and off in order to get a nice counter sink.
 
toobit said:
Interesting. So should I use a hand drill?
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If you cannot lower the speed on your drill press, use a hand drill at low speed. You can probably still use the bit you have to practice on smaller holes, it looks like the edge is only burned in a small area. Buying a better counter sink won't help if you cannot slow it down.
 
If you just want to deburr the holes, you could use a larger drill bit instead of the countersink.
 
This is why I buy carbide countersinks.

Most HSS countersinks marked "for metal" are only good on mild steel. Knife steel and any hardened steel will destroy them fast. Just drilling the holes will harden many knife steels ... which means the countersink is trying to cut hardened steel.
 
toobit said:
First time I used a countersink drill bit on my 1/4 inch steel knife and it worked for one hole but the others it wouldnt catch and I damaged the bit. I also used oil on the bit while I was drilling.

Any advice as to what I am doing wrong? The countersink says it was made for metal.

0zjB7ND.jpg

tFXncsZ.jpg
Click to expand...
Wait a minute ..................what are you trying to do here ..to enlarge holes or what ? Seems to me that you push countersink to deep ? Why ? All you need is one-two millimeters taper .........?
b6HEQgW.jpg
 
Was that steel hardened already? If so, it's probably not as hard as the knife blank you have. As was mentioned already, it's just to dress the edge of a hole, it isn't a "drill bit" to make a hole. A drill bit is for making the hole, a counter sink is for a slight taper & to clean the burr off of the edge.
 
I have I believe that same cheap ryobi countersink and have done many holes with it with no issue always on unhardened steels and like mentioned above just enough to deburr and knock down the sharp 90 only takes a couple seconds.
 
Those holes look a bit large for that size/angle countersink. Step bits fro Harbor Freight do a decent job for countersinking larger holes. I have a cheap HF 8" drill press, and that in addition to their step bits have worked fine for chamfering larger holes.

https://www.harborfreight.com/3-pie...oated-high-speed-steel-step-drills-91616.html

Put it on the lowest speed and take a couple little "bites" to get the size chamfer you want.

I've never had good luck with those 4 flute countersink bits from Home Depot etc., at least not with my drill press on blade steel, they're get chewed up pretty fast like yours.

~Paul
My Youtube Channel
... (Some older vids of some of the older knives I made)
 
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