Drilling Holes in Frames and other 3/16"-1/4" metal

[geocrasher]

Hey all, I'm terrible at drilling. I don't know what it is, but I tend to just kill drill bits. I see fab shops on youtube just chuck in a bit, hit the drill at full speed and go through 1/4" mild steel like it's nothing. Nope, not me. I end up with a smoldering hot divot and a dull bit.

What am I doing wrong? And which drill bits should I be buying for this? I have an old grill guard for my Suburban that I'm going to turn into a winch mount, but the holes on the frame don't line up (different year) so I will have to drill out new holes in the frame. I'm guessing those are 5/8" bolts. Plus, I want to be able to do this reliably without screwing things up every time!

Thanks for any help. Also, hello again IH8MUD. Been a long time since I posted

 

[e9999]

2 things come to mind first: using the right pressure and using sharp enough bits. You need to exert enough pressure that it digs in evenly rather than "rubs" its way through the hole, so to speak. I think that people often don't put enough pressure on the bit. If you use a sharp bit and push on it just right, you should be able to get long corkscrew-like chips, I would think. Of course, if the bit is not very sharp to start with, that is unlikely to happen. You may want to learn how to sharpen the bits yourself, it's not that difficult and you may enjoy using your very own very sharp bits after that. Probably best to practice with a drill press, you get much better control that way.
As to drilling holes in the frame, I'm skittish about that, especially biggish holes, and also especially for a winch which is gonna pull big time on those bolts; some of those frames are not very thick. Can you reinforce the frame where you'll attach the mount for peace of mind?

 

[geocrasher]

Honestly I hadn't given it much thought. The frame is 3/16" and from what I understood that was enough. I don't think a stiffening plate would be a big deal. Thanks for the advice. I think I probably don't push hard enough on it, or the drill bit is dull.

Is there any kind of drill bit that I should be looking for specifically? Thanks again.

 

[Waorani]

Quality bits (think not Harbor Freight/etc) and start w/ smaller bit (1/8) and work up.

 

[PIP]

Drilling is a shearing operation at the microscopic level. It takes immense pressure to operate a drill bit in steel correctly.

In industry, drills are fed into metal in Inches Per Revolution (IPR) a starting feedrate for a 1/4" drillbit in steel would be .006" per rev. What that means is for a 1/4" drill bit to break through the other side of a .188" frame rail by .100" it needs to do it in 48 revolutions. If your hand drill is spinning 500 RPM you should be through the frame rail in less than 6 seconds. If you aren't, the drill bit is rubbing and you're not applying enough force.

If you're burning up drill bits you need to slow down the RPM. It is very easy to calculate the Surface Feet per Minute (SFM) that you need. Just google SFM for drilling or there's even charts that lay it out crystal clear. When in doubt, go slow.

Other tips-

Your pilot drill size should be the same diameter as the web thickness of the drill bit you are following up with when drilling in 2 steps. If you're going big enough you need 3 or more steps and don't want to use an annular cutter or holesaw then use your best judgement. A large drill bit taking a small DOC puts a lot of stress on the corners of the drill and is hard to control. That's why it's a good idea to leave a bit more meat than less at a time.

Think of the purpose of pilot drilling/step drilling in terms of matching the width of the cut to the feed force you have available. If you know you can push a 1/4" split point bit through 3/16" steel in 6 seconds then you know that you have enough force to push 1/8" width of cut per flute plus the pressure to force the zero SFM center of the bit through the material. You can assume that you have enough force available to cut more than 1/8" per flute if you didn't have the zero SFM center to push through the steel. Therefore go a little wider, like 3/16" width of cut per flute.

Buy some real cutting oil. Apply it with a small acid brush. You should see a little bit of smoke. A lot of smoke means you're doing it wrong.

The shape and color of the chips tells you if you're doing it right. With HSS drill bits you want silver or slightly tan chips. When you see blue you are running too fast or not removing enough heat (if you have coolant available). If you were using carbide you want to see blue chips.

Good drill bits are so cheap. Throw out dull ones and buy new ones in sizes under 1/2".

Most people buy Jobber length drill bits. I don't know why. But they do. Do you need to drill through 4" of steel with your hand drill? If you are buying drill bits from a real supply company buy screw machine drill bits. They are much shorter, cheaper and easier to control. Shorter drill bit is more rigid.

Another thing, pay close attention to how the bit is cutting. When you barely perceive it is not cutting as good, stop, replace or sharpen the drill and repeat.

Here's a common scenario- You need to drill a 5/8-3/4" hole in your pickup's frame rail. You have a silver and demming drill bit in your 1/2" hand drill. Your hand drill runs around 600 RPM, but it's variable speed. 600 RPM is way too fast for a 5/8" bit without coolant so you try to slow it down, but at slower speeds the drill stalls so the speed is all over and the drill bit dulls quickly. Stop drilling as soon as you sense it's not cutting as well and go touch it up on a belt sander. Even if this cycle is drill for only 5 seconds and sharpen for 30 seconds it's still way more effective and easier on your body than trying to push a dull drill.

Oh, and learn how to sharpen drill bits quickly by hand. It's a one banana skill too many never bother to figure out. Throw that drill doctor thing in the recycle bin and ask an old timer to show you how to do it.

 

[ceylonfj40nut]

Quality bits (think not Harbor Freight/etc) and start w/ smaller bit (1/8) and work up.

I have great success with the Bauer titanium brand of drill bits from HB. Equal to some machine carbide bits. Was blown away. Like said above. Pressure, slower, good cutting oil. Need to see metal chips or screws. Not shavings. Very little smoke.

 

[AirheadNut]

Drilling is a shearing operation at the microscopic level. It takes immense pressure to operate a drill bit in steel correctly.

In industry, drills are fed into metal in Inches Per Revolution (IPR) a starting feedrate for a 1/4" drillbit in steel would be .006" per rev. What that means is for a 1/4" drill bit to break through the other side of a .188" frame rail by .100" it needs to do it in 48 revolutions. If your hand drill is spinning 500 RPM you should be through the frame rail in less than 6 seconds. If you aren't, the drill bit is rubbing and you're not applying enough force.

If you're burning up drill bits you need to slow down the RPM. It is very easy to calculate the Surface Feet per Minute (SFM) that you need. Just google SFM for drilling or there's even charts that lay it out crystal clear. When in doubt, go slow.

Other tips-

Your pilot drill size should be the same diameter as the web thickness of the drill bit you are following up with when drilling in 2 steps. If you're going big enough you need 3 or more steps and don't want to use an annular cutter or holesaw then use your best judgement. A large drill bit taking a small DOC puts a lot of stress on the corners of the drill and is hard to control. That's why it's a good idea to leave a bit more meat than less at a time.

Think of the purpose of pilot drilling/step drilling in terms of matching the width of the cut to the feed force you have available. If you know you can push a 1/4" split point bit through 3/16" steel in 6 seconds then you know that you have enough force to push 1/8" width of cut per flute plus the pressure to force the zero SFM center of the bit through the material. You can assume that you have enough force available to cut more than 1/8" per flute if you didn't have the zero SFM center to push through the steel. Therefore go a little wider, like 3/16" width of cut per flute.

Buy some real cutting oil. Apply it with a small acid brush. You should see a little bit of smoke. A lot of smoke means you're doing it wrong.

The shape and color of the chips tells you if you're doing it right. With HSS drill bits you want silver or slightly tan chips. When you see blue you are running too fast or not removing enough heat (if you have coolant available). If you were using carbide you want to see blue chips.

Good drill bits are so cheap. Throw out dull ones and buy new ones in sizes under 1/2".

Most people buy Jobber length drill bits. I don't know why. But they do. Do you need to drill through 4" of steel with your hand drill? If you are buying drill bits from a real supply company buy screw machine drill bits. They are much shorter, cheaper and easier to control. Shorter drill bit is more rigid.

Another thing, pay close attention to how the bit is cutting. When you barely perceive it is not cutting as good, stop, replace or sharpen the drill and repeat.

Here's a common scenario- You need to drill a 5/8-3/4" hole in your pickup's frame rail. You have a silver and demming drill bit in your 1/2" hand drill. Your hand drill runs around 600 RPM, but it's variable speed. 600 RPM is way too fast for a 5/8" bit without coolant so you try to slow it down, but at slower speeds the drill stalls so the speed is all over and the drill bit dulls quickly. Stop drilling as soon as you sense it's not cutting as well and go touch it up on a belt sander. Even if this cycle is drill for only 5 seconds and sharpen for 30 seconds it's still way more effective and easier on your body than trying to push a dull drill.

Oh, and learn how to sharpen drill bits quickly by hand. It's a one banana skill too many never bother to figure out. Throw that drill doctor thing in the recycle bin and ask an old timer to show you how to do it.

Fantastic information! I have mixed results drilling holes with a hand held drill, usually due to chatter where the bit tries to drill a triangular hole. Because of that I try to use a drill press wherever possible, but sometimes that just isn't an option.

There is a lot of good info about hand sharpening drill bits online. Unfortunately I don't have a bench grinder or belt sander available, but just knowing the basic concepts about how a bit cuts has enabled me to sharpen a couple of drill bits in the field with either an angle grinder or dremel tool. It was by no means a perfect job but both times it enabled me to finish the holes necessary.

 

[PIP]

Fantastic information! I have mixed results drilling holes with a hand held drill, usually due to chatter where the bit tries to drill a triangular hole. Because of that I try to use a drill press wherever possible, but sometimes that just isn't an option.

There is a lot of good info about hand sharpening drill bits online. Unfortunately I don't have a bench grinder or belt sander available, but just knowing the basic concepts about how a bit cuts has enabled me to sharpen a couple of drill bits in the field with either an angle grinder or dremel tool. It was by no means a perfect job but both times it enabled me to finish the holes necessary.

People often get too caught up in the "perfect" sharpening job. In my experience it's not that big of a deal if you're off a little bit as long as nothing is dragging in the cut.

In fact, it's common practice to grind HSS drill bits with the point off center. When you don't have quite the right size drill, especially for larger bits, you can grind the point offset and the bit will drill a hole equal to twice the diameter of the longest cutting edge.

Bottom line it's better to have a sharp bit, even if it's sharpened a bit funky than to keep drilling with a dull bit.

 

[e9999]

^ that's true but inaccurate points can also be a problem if you need a hole of given size so it's not a sloppy fit, and I want that most of the time. I do have a fancy bit sharpener affair, but I also bought a used General bit holder rig that you mount next to a bench grinder and gives very accurate sharpening, it was all of $10 at the flea market for a pristine example (maybe $20 new) and gives good result and is fun to use. Sure you need a bench grinder but most DIYers have one already. Now, of course, none of that beats the satisfaction of doing it entirely by hand on a hand grinder just by eyeing things out, but I'm not there yet...

 

[geocrasher]

There is just so much epic info in this thread-THANK YOU! I sincerely appreciate you all. I have some ideas now. I definitely am not pushing hard enough and I'm also going way too fast I'm sure. So, push hard, slow down, use sharp bits. Love it.

Take care and if I run into issues, I know where to go. I've been on IH8MUD for almost 20 years on and off and remember Woody's post on the LCML announcing the forum, and it's really cool to see how far it's come over the years. At one point, I even built/ran the servers he had!

 

[PIP]

^ that's true but inaccurate points can also be a problem if you need a hole of given size so it's not a sloppy fit, and I want that most of the time. I do have a fancy bit sharpener affair, but I also bought a used General bit holder rig that you mount next to a bench grinder and gives very accurate sharpening, it was all of $10 at the flea market for a pristine example (maybe $20 new) and gives good result and is fun to use. Sure you need a bench grinder but most DIYers have one already. Now, of course, none of that beats the satisfaction of doing it entirely by hand on a hand grinder just by eyeing things out, but I'm not there yet...

The purpose of drilling is not to make a hole of a given size. It is to make a hole within the tolerance range for the next operation or a clearance hole for a fastener.

Drills do not make on size holes well. Drills do amazingly well at following the center of rotation. The proper drill can drill infinitely long holes with incredible location accuracy, but size is usually secondary.

Accurate size holes are made by subsequent operations such as boring, reaming, honing, burnishing, forming.

It is incredibly easy to sharpen a HSS twist drill by hand and get something that works well enough.

Keep in mind here if you are drilling through steel by hand the first drill you start with should be a split point drill. You aren't going to sharpen one of those by hand. When that gets dull you throw it away and grab another.

The following drills you use to step out the hole have no reason to be split point. The center isn't cutting and if you sharpen it off center it doesn't matter one bit because the center point has no bearing on the drilling operation.

RE: Drill sharpeners-

When I went into the manufacturing business I bought a huge 30"x60" cabinet at auction filled with about 900 lbs of freshly sharpened HSS drill bits in every size under 1/2"- Letter, number and fraction. I quickly found the reason why they were sold was because the employee that sharpened them all did every one of them wrong in some kind of sharpening machine. Tens of thousands of drill bits and not one will make a chip. Any drill sharpening jig or machine is subject to human error. Before a person uses a machine to do it they should be forced to do it by hand so they get what they are trying to accomplish.

I remember I was taught how to sharpen drill bits in High School metalshop class. I didn't retain that info, but years later I was faced with my deadlines and livelihood depending on drills being sharp. I stared at the melted end of a twist drill for a minute and concluded there was really only one way you could grind a new cutting edge on there, spent a few minutes standing in front of a belt grinder with a cup of cooling water and I had a drill bit that cut like new. I think that really is a great way to learn how to do it- Logic your way through, visualize what the drill tip is doing when cutting and follow that up with visualizing the motion you would have to move the drill bit in to create the proper cutting edge and clearances.

 

[e9999]

for anybody trying to sharpen bits by hand, I would suggest to get one of those little drill point gauges to check angles and point centering, at least in the beginning. They're not that expensive and it will help learn how to center the point properly. Although I've used a protractor from a combination square set in a pinch instead. Kind of hard to use all those for very small bits, though.

 

[ntsqd]

When I need to buy, I buy 135° Split-Point Stub Length drill bits from places like MSC-Direct, Travers, Use-Enco, and occasionally McMaster. I don't even try to sharpen those. Use until dull and then toss them. Buy them by the package, not onesy-twosy, so that you're not stuck when one is dull.

For the little that I need to use I buy good drilling and tapping fluids rather than trying to concoct something that might work as well. About the only non-traditional fluid that I'll use in drilling or tapping is when I'm working with aluminum and out of the good stuff. Then I'll use WD-40.

I don't use a lot of steps in drilling bigger holes. I'll at most drill a pilot hole, and then maybe a hole slightly bigger than the web of the on-size drill bit. The reasoning behind this is that each successive hole that you drill is that much more opportunity for the hole to wonder away from where it is supposed to be. You'd think that the next bigger bit would follow the existing hole, and that's only mostly true. If the drill motor operator introduces any bias, intentional or not, the hole will wonder.

FWIW, this comes with the sharpening gauge in a pocket at the rear and has a LOT of handy useful info in it:
Engineer's Blackbook

 

[LINUS]

1. Use lube, clinging oil on vert surface

2. Pilot bit a 3/16” where you metal punch to locate hole & work up hole diameter.

3. Slow speed & heavy pressure - by the time your lube smokes, that bit is junk.




I’m betting the long posts were informative, but I been lucky to run all sorts of portable drills to stationary presses we set auto-depth / RPM & you just keep lubing while watching long corkscrews of drilled material whip around the bit (razor sharp bastids!) — but you know esp on SS if your speed & dive is set right when that machine sends out those long “corkscrews” instead of powder crap & smoke the bit.

If you do alot of vertical holes in sheet steel, Milwalkee makes a magnetic based 1/2” chuck we use if we’re adding to existing structure - saves you leaning into the drill & perfectly perpendicular holes.

 

[ntsqd]

BTW, with a little ingenuity you can use one of the hole-saw type tube notching tools as a poor man's mag base drill.

 

[e9999]

the speed is really critical too of course. There are tables for rpms by bit size and material. The one surprising thing with that for me is how low the speeds need to be for steel and common size bits. In fact, I would bet that a large number of DIYer with a drill press routinely exceed the recommended speeds. One of those drill presses with only 2 pulley wheels will likely not go much under 500 rpm I think, and that's about the limit on steel for 1/2 or 5/8 IIRC. So anything bigger than that is probably not good for the bit.