1/4 inch holes - my own personal thorn

T

Travis Fry

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Jun 11, 2010
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I can't drill 1/4" holes. I've tried every bit, feed rate, and drill press speed. I've ruined them on fully spheroidized steel and poorly annealed steel. I've tried fluid and no fluid. I'm not a newbie by anyone's standard, but this is the one thing that continually defeats me. Any advice?
 
aside from some some failed attempt at drilling hardened steel or overheating while drilling I really have not had any issues drilling 1/4" holes. I use medium speed and not too much pressure. cool/lube with soluble oil in a squirt bottle.

all I can say is that the steel should be as close to annealed as possible for best results.

curious to see what others recommend.
 
Have you predrilled? Maybe use 1/8-3/16" first? What kind of steel are you drilling? I have not had any problems drilling annealed steel but thats what I would try. Are you having problems with any other sizes?
 
What kind of problems are you experiencing exactly? Wandering, bad surface finish, excessive heat, bit grabbing and breaking, etc. ?
 
Matt R said:
Have you predrilled? Maybe use 1/8-3/16" first?
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No. As a general rule, if you need to predrill, the pilot hole should be about the size of the drill web. You wouldn't want to chase a 3/16" hole with a 1/4" drill, the point will be unsupported and will wander and there will be a tendency for the drill to auger, overfeed and wipe out the corners.

All that said, drilling a 1/4" hole in unhardened steel shouldn't cause to much trouble. There have been plenty of threads on this subject in the past, no need to dust this off again with a lot of detail but I'll reiterate the fundamentals.

1: Appropriate speeds, between 300-1000 RPM will work on a 1/4" drill in high carbon alloy steel.
2: Feed hard enough to cut a spiral chip or even break a chip. Don't under feed and rub, this causes a lot of problems.
3: let off drilling pressure once the web penetrates the back of the work piece so you don't over do it and wipe out the corners. A backing piece helps prevent this.

Coolant or oil is not required for such a shallow hole, nor is a lot of pecking, but you can use it if floats your goat.


In production I'll run a 1/4" drill in 3V or D2 or Elmax etc at 900 RPM and feed at 4 inch per minute. A knife blade thickness stock is done in one whack, no pecking (under coolant). Done dry you shouldn't stay in the cut more than a couple seconds before pulling out to cool off a moment.

Feed rate is the key. If you're forming a good chip you'll be in and out of the hole in a few seconds without a lot of heat or wear. Feed too hard and you'll break stuff feed too light and you'll wear stuff out. Working properly there isn't a lot of noise or drama, just a quick clean hole. I don't even use fancy drills, just regular old 118 degree HSS made in USA and I'll get hundreds of holes from one in difficult materials.
 
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Maybe it's too obvious but drill presses have an option of limiting how far the drill progresses into the piece. Maybe that happened here?

I got stuck a few times too with new but cheap drill bits. Took another cheapo one and it worked smoothly. But once in a while the bit keeps spinning like on hardened steel. I suspect it got too hot and air hardened.
Is that possible for O1?
What speaks for this is when I drilled under water it went all the way through without any issue.
 
Just when you think you know something a professional comes along and lets you know that what you thought you knew was wrong. Well, you learn something new everyday! Thanks for the clarification but now im going to have to look up the anatomy of a drill bit because I dont know what the web is:D
 
This will seem like a silly question, but do you know how to sharpen a drill bit? I cannot tell you how important that is. Were I to have to throw away drill bits each time one got dull I'd use up all my whiskey money. It's incredibly important, proper sharpening of bits: no matter large or small.
 
Matt R said:
Just when you think you know something a professional comes along and lets you know that what you thought you knew was wrong. Well, you learn something new everyday! Thanks for the clarification but now im going to have to look up the anatomy of a drill bit because I dont know what the web is:D
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It's the thickness of the core at the point. It's the part that doesn't really cut very well and just mushes its way through the steel. If you need a pilot hole, it's to provide clearance for the web on a large drill. But a 1/4" drill shouldn't need a pilot hole unless you're using a very small drill press.
 
I regularly drill 2" deep x Ø5/16" holes in annealed O1 or W1. I also regularly drill Ø1/4" holes through two knives at once (total depth = 0.41"). I'm working with a home depot (Rigid) drill press - nothing fancy.

The 5/16" holes I do in one shot at 700 RPM - no pilot whatsoever, although I do have a locating fixture with a drill bushing.

The 1/4" holes I do at 1100 RPM (the next speed up) - again, in one shot with no pilot.

If I am drilling a single knife, I will start it with a spotting drill or a center drill (the kind meant for lathe work). I prefer the center drills because I get less chatter.

I have drilled thousands of these holes and NEVER broken a bit. I use water-soluble oil coolant in a wash bottle. Left hand squirts the coolant, right hand works the downfeed. I use cobalt drill bits.

As Nathan has said before, a common mistake is underestimating the amount of downfeed force that you need to apply. I did a lot of woodwork before I got into metal work and it was a big adjustment. On wood, the bit pulls itself into the work. On metal, you need to use some muscle.
 
In both blade steel and titanium I have drilled with a C drill bit (norseman brand I think) and chased with a four flute carbide reamer, never had an issue.
 
If you don't know how you should learn to sharpen your drill bits..but you may already know that.
 
The only 1/4" holes in steel I have done are pin holes in the tang. Center punch and a step bit with some oil. Using a drill press vice and a cheap HF press. Never had an issue.
 
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