Problem drilling mild steel flat bar

[Oscar]

Well... guess there's one way to find out! You go ahead and buy me a set of them, I'll use them till they're dull, then try and sharpen em.

I prolly could touch one up if I was in a pinch. I've turned regular drills into split points with a sharp corner on a bench grinder and a set if diamond files.

Look up "hyper step" drills. It's a twist drill, but the point is ground in steps (like a normal step drill). They're supposed to be pretty great.

Actually, here's a link to some. Apparently "hyper step" is just a sorts generic term for them.
https://www.amazon.com/Norseman-2290...77678630&psc=1

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Pretty interesting, I didn't know they existed!

[Oldiron2]

You do realize that these kind of bits, with the 3 flutes, were originally designed to widen holes. It's very hard to find them anymore. I'd like to have a decent set of the diameters I work with the most.

And..........."cobalt" is just a sales gimick to sell HSS. Sorta like Titanium, or other coatings/additives. In the end, it's the sharpened HSS cutting edge that does the work.

Regular HSS, off the shelf, is plenty hard to drill anything but steel that's harder than HSS. Provided it's kept sharp.

The relief angle is key to the deal. The sharper the angle, the better it cuts. It will actually suck its way down into the steel. Kind of like a plow. On the flip side, the cutting edge will decay much faster. But if you have a bench grinder, it's not an issue. Takes about 3 minutes to sharpen a bit. I came to this the hard way. I got tired of throwing out bits when they got dull. Found that the drill bit sharpening machines are mostly junk.....................bought a General Hardware drill bit gauge, and never looked back. You can virtually get a lifetime out of most any drill bit, if you learn to sharpen it freehand.

Sammmm, it's not that simple. The "tool steel" category has a good variety of formulations, each having different properties and thus different uses, particularly in production where changing tooling slows the whole process. Wear can be the very gradual removal of the metal (atoms), or fine but slow chipping, or catastrophic breakage. Besides price (not shown), the table below demonstrates these different properties.

[Flyer58]

But can you sharpen a 3-flute cobalt drill bit with all the relief angles?!?

Only three?
I have no idea what this is for. It came in a box of bits and fittings I bought at an auction. Countersinking? I paid $4 for the collection and it included a small box with $5 in coins.

[psacustomcreations]

Yes, that is a countersink. Depending upon what it is made from, it may do well on wood and aluminum, but not so well on steel

[Oscar]

Only three?
I have no idea what this is for. It came in a box of bits and fittings I bought at an auction. Countersinking? I paid $4 for the collection and it included a small box with $5 in coins.

Yea, that's not a drill bit, it's a counter-sink bit

[Roert42]

Cheap counter sinks work well for deburring holes. Pop them in the cordless drill and give them a couple rotations to clean the edges up.

The hardened ones for cutting steel and stainless chip too easily when using them to quickly deburr holes.

[Sberry]

I like a step drill for cleaning.

[CAVEMANN]

Titanium Nitride coatings are an anti-wear coating and certainly are not a gimmick, and when it comes to cobalt, Cobalt is a very hard, brittle tool and will hold up well if handled and used properly, they won't take flexing because they''l break. Our shop ordered all of our end mills and carbide insert tools with the TIN coating, it allows faster cutting speeds and last longer.

[tapwelder]

When you you sharpen bits with coating what happens to the coating?

[52 Ford]

Titanium Nitride coatings are an anti-wear coating and certainly are not a gimmick, and when it comes to cobalt, Cobalt is a very hard, brittle tool and will hold up well if handled and used properly, they won't take flexing because they''l break. Our shop ordered all of our end mills and carbide insert tools with the TIN coating, it allows faster cutting speeds and last longer.

AlTiN is supposed to be even better than TiN. I have no experience with it. You can't use it on Aluminum, though.

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[52 Ford]

When you you sharpen bits with coating what happens to the coating?

It goes away. BUT, it's still on the flutes. Keep in mind, you're only removing material on the RELIEF side if the cutting edge. So, the areas that are actually having swarf rub on them are still coated.

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[BigAl22]

Just finished a 60 hour welding course. Instructor was 30 year welding veteran. Same thing happened with our A36 steel. He said we’re only getting cheap Chinese steel, which contain recycled steel. He said they may melt-down a crankshaft or other hardened steel in the mix, which you are hitting.

[CAVEMANN]

Just finished a 60 hour welding course. Instructor was 30 year welding veteran. Same thing happened with our A36 steel. He said we’re only getting cheap Chinese steel, which contain recycled steel. He said they may melt-down a crankshaft or other hardened steel in the mix, which you are hitting.

Alloys should be added in measured quantities and the changes tested to see the resulting product, screw-ups can be reformulated to get the proper carbon ratio, if it's not getting that quality control then the end user is getting screwed. I don't know about modern steels, but Chinese QC has improved on most things, if it hasn't improved on steel, then they're producing bed-rail crap.
Going back to the original problem, I've had success turning the piece over and tackling it from the back side, but have never had it happen with mild steel, only stainless which is horrible for work hardening if you ever let a bit dwell in the hole without cutting. I also wonder if the OP had a very dull bit that got so hot that it transferred alloy into the hole.

[Flyer58]

Alloys should be added in measured quantities and the changes tested to see the resulting product, screw-ups can be reformulated to get the proper carbon ratio, if it's not getting that quality control then the end user is getting screwed. I don't know about modern steels, but Chinese QC has improved on most things, if it hasn't improved on steel, then they're producing bed-rail crap.
Going back to the original problem, I've had success turning the piece over and tackling it from the back side, but have never had it happen with mild steel, only stainless which is horrible for work hardening if you ever let a bit dwell in the hole without cutting. I also wonder if the OP had a very dull bit that got so hot that it transferred alloy into the hole.

I did the OP and the first bit was used and might have been slightly dull but had just cut through 4 holes without any problem. When I got to hole #5 it just stopped and spun. I wore out a second sharp bit in the same hole and then a third bit went through after I flipped over the metal and drilled through a small crack where the others had stopped short. The second and third bits were sharp when I started. The first bit was totally rounded off.

The remaining 3 holes were easily drilled out. I think they were 1/4 in holes and bits #2 and #3 were slightly smaller. I did hit a starting dimple to mark each hole location before drilling and to center the bit.

It's seemed like that one spot had a harder metal mixed in yet looked the same after removing the mill scale.

[smithdoor]

Technically it not A36 steel . But I can see Chinese giving bad steel.
Recycled steel has been around for over 100 years but mill would bring back to sepc.

In my line work if I purchased A36 it had to meet A36 specifications and have paperwork from mill showing it does.

Dave

Just finished a 60 hour welding course. Instructor was 30 year welding veteran. Same thing happened with our A36 steel. He said we’re only getting cheap Chinese steel, which contain recycled steel. He said they may melt-down a crankshaft or other hardened steel in the mix, which you are hitting.

[StandarDyne]

Regular HSS, off the shelf, is plenty hard to drill anything but steel that's harder than HSS. Provided it's kept sharp.

Yep, I've had better results using regular plain old vanilla HSS bits than anything else...

[Toolmaker51]

Let's assume I'm a talented old hand at drilling. Drill RPM is absolutely tied to cutting efficiency, but not more so than feed rate. Skimming through the posts hints that most are working mild steel. 'Mild' denotes insufficient carbon and alloys for responding to heat treatment, among other qualities. HSS will drill if properly sharp.
I'm betting the lack of penetration is due to High Carbon drill bits, not in the class of industrial grade.
HC will drill but reduce speed to lowest that will produce chips, which indicates feed pressure in some proportion of speed.
The usual sequence of hand drilling is not observed, a proper punch mark, one or more pilot holes to reduce engagement of next size.
Drills operate in solid material in the following order, starting with punch mark. The drill point (chisel) does not actually cut, it extrudes metal outward for cutting edges to engage and shear away from parent material, following the flutes to exit. The sides do not cut, there is no relief behind that cylindrical form creating a cutting edge. The purpose closes gap between the hole and bit so more chips eject; instead of jamming between.

[Uniballer]

I had to drill 128 13/32" holes in 5/8" cold rolled steel greenhouse rafters milled in the mid 1920s. While I have hand sharpened drill bits for years I found that a Drill Doctor DD500X gave me a better, longer wearing surface, especially on the 1/4" bits I started the holes with. I totally agree that for most purposes HSS bits are the best value, and that efficient drilling requires a slow speed, and proper pressure, and appropriate lube where possible.

[N2 Welding]

Not uncommon. If dead set on entering that spot, I have had success spot annealing plate. Casting can be a real pain, I have had multiple boxes, where 50 from one lot drill fine, then none from another lot will drill.

What is your prefered meathond of spot annealing?

[CAVEMANN]

What is your prefered meathond of spot annealing?

N2, you can heat to red with a neutral flame and cool slowly in lime to maximize cooling time. Uniballer, I'd suggest you find a drill speed/feed chart, you'll find your theory on drill speed is not totally true, proper speed & feed will maximize bit life. You talked about drilling 128 holes in some bars, we had a job that came in to our machine shop 1-2 times a year that consisted of nearly 1200 1/16 inch holes spaced 1 inch apart over the entire diameter of a 1/4" thick 316L stainless steel plate nearly 6 feet in diameter. Stainless steels are a different animal, let a cutting tool dwell in the cut and it will work harden the steel, no ifs, ands or buts. Another of our jobs involved 1 1/2 inch holes in a steel that was nearly as hard as the drill bit, we had to use high speed steel bits, cobalt wouldn't handle the shocks, it took a hell off a lot of feed pressure on a very slow speed, the bit would wrap up and twist making noises like it was going to shatter. Most everyone seems to think that super slow rpms when drilling small holes in mild steel is the proper thing to do, if your bit is sharp the the drill speed chart is your friend.