Tips for drilling steel

[Paticus]

I will be drilling about 40 1/2" holes through 3/8" steel. Any suggestions for drilling that size?

I must be doing something wrong, the other day I was drilling through some 3/8" plate and after 2 holes my bit stopped cutting, just spinning half way through the hole not making any progress... Titanium 1/2" deWalt Bit w/ some 3-in-One for lube.

Should I expect to burn through bits like that?

I will be using a Delta drill press that can drop down to around 300 RPM.

 

[toomanytoyzz]

I will be drilling about 40 1/2" holes through 3/8" steel. Any suggestions for drilling that size?

I must be doing something wrong, the other day I was drilling through some 3/8" plate and after 2 holes my bit stopped cutting, just spinning half way through the hole not making any progress... Titanium 1/2" deWalt Bit w/ some 3-in-One for lube.

Should I expect to burn through bits like that?

I will be using a Delta drill press that can drop down to around 300 RPM.

Are you making sure to oil the bit? Once you overheat the bit it's done. Also drill a pilot hole first than step up to 1/2". What size DP are you using?

 

[Paticus]

What size DP are you using?

16.5" Delta 17-900. I didn't lube the bit, just the metal

 

[gtermini]

Get yourself a screw machine length twist drill. They are way more rigid and less prone to chatter dulling.
Get some Rapid Tap cutting oil.
Speed should be between 600 and 800 RPM.
Clamp the work if practical.
Center punch your drill spot.
Make sure to keep constant feed pressure on the drill to prevent dulling. If the drill isn't cutting, it is dulling it.

Greyson

 

[fatfillup]

Plus slower is better!! Pilot holes then working up to the size is the way to go. I tend to use 1/8 inch for the first pilot hole. Then depending on how big I am going will determine how many steps. Plus how good are your bits? More cutting oil the bigger you get also.

Slow speed and oil and at least 3 steps to get to where you want to be.

 

[kts]

Might want to look into cobalt bits. I needed to drill through some stainless and cast iron recently and my HSS/black oxide bits were taking forever. Picked up some cobalt bits and they went through the stainless and iron like butter.

Go slow, use oil, and keep them from getting hot. I killed a bit pretty quickly by going too fast and too much pressure, tip was glowing red. Lesson learned.

 

[HMCFab9]

If you are using the DeWalt Pilot point drill bits, you should be able to drill that without a pilot hole, but a 1/8" hole to start it would be better.
If you are not using the pilot point bits, you will need to drill a pilot hole, maybe one size between that & 1/2 & then the 1/2" hole.
Make sure the drillpress is running slow enough for the bit size & oil the spot before drilling.
Do Not just start out with a 1/2" regular bit & expect it to work.

 

[Dave455]

You mention a 'titanium' drill - assume that's titanium nitride coated (TiN)! They are o.k. provided you get good ones, but once they blunt, that's it, you chuck 'em away! For that reason I prefer Cobalt drills for anything above 1/4 inch!

Start with a good centre spot, then pilot drill with maybe a 1/8 drill! Then go up to maybe 1/4, then 3/8, then finally the 1/2 inch! (do the most work with the smallest drills)

Keep your drills really sharp, and if you have coolant available, use it! If not, some proper cutting fluid!

300 r.p.m. should be fine for the final drill, and maybe even a bit faster, but best to go slow till you see how the material is cutting!

 

[toomanytoyzz]

I remember a few years back the guys who live next to my dad's bodyshop were working on some project and needed to drill ten 3/4" holes in 1/2" plate. Well, the one knucklehead had a Hilti hammer drill and thought that would get the job done with ease. I told him he was crazy, but he didn't listen. About an hour later he had gone through three bits and about a 1/4" of the metal if that in hole #1. I told him to go to the tool rental place and ask for a magnetic drill. The guy looked at me like I was crazy, until he got back with it and poked them holes through the plate like a hot knife through warm butter.

 

[0.511MeV]

Here is a good primer on feeds and speeds for HSS twist drills:
http://vikingdrill.com/Feed_Speed_Face.html

I consider most of the twist drills available at big box home stores to be trash when it comes to actual metal work. There are any number of brands that are good, and can be found relatively easy, including on sites like amazon.

You don't say what kind of steel... make sure you know what it is and if it has been hardened. If you look at the chart I linked, steel speeds range from 20 to 110 sfm. That is a huge range.

I don't bother with pilot holes in something like mild steel. I center punch, use a center drill to get a good starting point, and then drill straight to size. Ream if necessary.

 

[Hammer1963]

A few tips from a machinist. One, do NOT use a lubricating oil. You must use cutting oil or a coolant for cutting steel. Next, use a center drill, followed by a drill a little larger than the web (tip) of the 1/2" drill bit. Use a good quality HSS bit that you can sharpen. Lastly, you will get a good chip or curled chip with a properly sharpened HSS bit, so make sure you relieve the pressure of the bit every few seconds to break the chip. NO need for Cobalt bits if you use good quality HSS bits to start with

 

[jakemac]

I used a HF step drill to go through 1/4" plate with no problems. If the steel isn't hardened, it should work for 3/8" plate as well. Go slow and use plenty of cutting oil.

 

[Jswain]

Do you own a bench grinder/know how to sharpen drill bits on one? If not it will be cheaper to buy one in the long run then buying a new bit everytime one overheats.

Put the drill on the slowest speed, centrepunch, predrill with a 1/4" bit, use plain water in a spray bottle to cool the bit/metal, there should be chips flying if it's drilling...if not your getting too hot/dulling the bit and will need to resharpen. Save your money on drill bits unless your a professional drilling all day everyday a cheap set(doesn't matter if it's TI coated once you have to resharpen that's gone) and a bench grinder will last a LOOOONG time.

 

[OccupantRJ]

When drilling, press the bit into the metal as you count for about three seconds, then stop. Repeat this over and over. This will break the stringers into chips that will eject from the hole, and gives the bit short cooling cycles. These chips are also removing some heat as they leave. On a drill press, clamp the work or the vice the work is in. If not, the tremor will dull bits quickly. I machine daily, and against most opinions, I do most of my drilling dry, or with just a few drops of rapid tap to break the surface tension. For deep hole drilling, the stop start cycle becomes even more important, and the drill has to also be retracted from the hole to clear the flutes of chips. Try this sometime. When drilling the end of a round rod, spot drill the end of the rod, then invert the rod and chuck it into the drill chuck. Invert the drill and clamp it using a V block or vertical notch in the vise jaws. Start drilling and see the resulting difference. I make spotwelding tips at work and use this method for deep hole drilling of water cooling holes into the tips, often drilling three inches or more deep into copper. I rarely use the lathe for this type drilling any more.

 

[gonefirefighting]

slow and easy with lots of lube............


this method works great for drilling steel as well

 

[toomanytoyzz]

When drilling, press the bit into the metal as you count for about three seconds, then stop. Repeat this over and over. This will break the stringers into chips that will eject from the hole, and gives the bit short cooling cycles. These chips are also removing some heat as they leave. On a drill press, clamp the work or the vice the work is in. If not, the tremor will dull bits quickly. I machine daily, and against most opinions, I do most of my drilling dry, or with just a few drops of rapid tap to break the surface tension. For deep hole drilling, the stop start cycle becomes even more important, and the drill has to also be retracted from the hole to clear the flutes of chips. Try this sometime. When drilling the end of a round rod, spot drill the end of the rod, then invert the rod and chuck it into the drill chuck. Invert the drill and clamp it using a V block or vertical notch in the vise jaws. Start drilling and see the resulting difference. I make spotwelding tips at work and use this method for deep hole drilling of water cooling holes into the tips, often drilling three inches or more deep into copper. I rarely use the lathe for this type drilling any more.

Show some pics of this if you could. I would love to be able to make my own spot weld cutters.

 

[Paticus]

Awesome advice so far!

It turns out I was doing a few things wrong. I will pick up up 3 different sized carbide bits this weekend and step up as most of you advised. Also, I guess I need to pick up some real cutting fluid. The momentary drilling every 3-4 seconds also makes sense.

 

[OccupantRJ]

Learn to sharpen cutting tools. With the proliference of inserts in the machining trade, it is fast becoming a lost art. At work, I take worn out double angle milling cutters, machine gullets, then silver solder in carbide triangular inserts to produce special angle long life milling cutters for the horizontal mills. I then sharpen these cutters to custom angles on a K.O. Lee tool and cutter grinder. This all started from learning how to sharpen a drill bit when I was in my teens. With tool sharpening skills, you can make most anything you want.

 

[OccupantRJ]

Awesome advice so far!

It turns out I was doing a few things wrong. I will pick up up 3 different sized carbide bits this weekend and step up as most of you advised. Also, I guess I need to pick up some real cutting fluid. The momentary drilling every 3-4 seconds also makes sense.

I made a 36" bellhanger's drill yesterday by extending a bit and then drilling a hole through the flutes with a 1/8" carbide drill, but unless you are doing this type of specialized machining work, carbide is not the end all, be all, that beginners seem to think it is. Carbide is more of a "save your ***" application drill. I use import polished flute drills from MSC for most of my work drilling. Nothing special in that, and they are inexpensive. A superduper drill will not make a person a superduper machinist. Attention to detail does, along with experience gained over time.

 

[OccupantRJ]

Show some pics of this if you could. I would love to be able to make my own spot weld cutters.

Although I have made a few spotweld cutters, you may have misunderstood. In this instance, I am not making spotweld cutters, I am making the copper tips to spotweld with in the spotwelding machines.

 

[Hammer1963]

WARNING ....................... Carbide bits made for cutting metal, are not the answer here. They are extremely expensive and break very, very easily if you have experience using them.

 

[Paticus]

WARNING ....................... Carbide bits made for cutting metal, are not the answer here. They are extremely expensive and break very, very easily if you have experience using them.

What is the answer then? These titanium bits are tired and cannot be sharpened, apparently.

 

[OccupantRJ]

What is the answer then? These titanium bits are tired and cannot be sharpened, apparently.

They can be sharpened, they just wont be Coated any more.

 

[ol'Red]

A few tips from a machinist. One, do NOT use a lubricating oil. You must use cutting oil or a coolant for cutting steel. Next, use a center drill, followed by a drill a little larger than the web (tip) of the 1/2" drill bit. Use a good quality HSS bit that you can sharpen. Lastly, you will get a good chip or curled chip with a properly sharpened HSS bit, so make sure you relieve the pressure of the bit every few seconds to break the chip. NO need for Cobalt bits if you use good quality HSS bits to start with

Listen to hammer.

 

[LG63]

I usually drill my pilot hole 1/4 to 1/3 of the finish diameter and drill away. I see no advantage to stepping up beyond the initial pilot hole. In fact if your last step diameter is too close to the finish diameter it makes the bit want to self feed into the material which never ends well.

 

[Outlawmws]

A few tips from a machinist. One, do NOT use a lubricating oil. You must use cutting oil or a coolant for cutting steel. Next, use a center drill, followed by a drill a little larger than the web (tip) of the 1/2" drill bit. Use a good quality HSS bit that you can sharpen. Lastly, you will get a good chip or curled chip with a properly sharpened HSS bit, so make sure you relieve the pressure of the bit every few seconds to break the chip. NO need for Cobalt bits if you use good quality HSS bits to start with

Listen to hammer.

One other thing: "Steel Plate" doesn't mean much: what kind? Hot rolled cold rolled, SS?

For drilling its all about speeds and feed, and the technique Hammer described.

Google "drilling speed feed" and print yourself a chart...

Lastly HHS will drill most anything unless it is real exotic. You should not need cobalt, titanium, or carbide at all... (we won WWII on HSS for Pete's sake...)

 

[andywander]

You should be spinning the drill at somewhere between 300-450RPM, and advance it at about 3" per minute-so the 3/8" should take about 8 seconds or so.

Make sure you use a quality drill-I am not so confident in DeWalt drills.

 

[alwaysFlOoReD]

This bears mentioning again; you only need to drill one pilot hole just slightly larger than the web of the 1/2" drill bit. This will be about 1/8" to 3/16". The cutting edge of the drill bit should be cutting all across the face of the edge...so from the inside all the way to the outside. This will prevent breakage of the outside tips of the face and promote an even wear pattern.

Richard

 

[t100]

the ideal drill speed for 1018 with 1/2" drill bit is 560rpm.

get an oiler, squirt a drop or 2 on the fresh metal while the drill bit cutting down. you need to get the oil on the tip of the bit, where the most of the heat is.

I wouldn't mind drilling at 300rpm without pilot hole.

 

[sasquatch12]

Just my opinion, but Hammer is correct, and forget the coated drill bits, buy good USA made HSS. All the hype about these coated bits is mostly sales BS.
(Doubt if you'll find a good HSS bit at big box stores.) Go to an industrial supplier, and as posted "Learn" to resharpen the bit.

 

[t100]

forgot to mention, clamp down your work piece firmly on to the table, vibration eats drill bits for lunch.

 

[Paticus]

So it sounds like quality hss bits may be a better option than carbide, and I need to learn how to sharpen them. And only need to do it in 2 steps, a pilot then the main hole with cutting fluid and the proper speed/pressure.

This is just what I was looking for.

Btw it's brand new A36 flat stock

 

[sasquatch12]

Yes, and i forgot, get yourself at the same time a drill point gauge , this will let you see if you have both lip angles the same length. Take your'e time, it will take a bit of practice, but once you learn to sharpen your'e own bits , you will enjoy walking over to the grinder, and zip-zip, in a few seconds have a nice sharp bit again.
(Watch garage and yard sales for quality USA made drill bits, often you can find them dull, but dirt cheap.)

 

[e-tek]

Carbide drills are EXPENSIVE. Has anyone ever tried using masonry bits with the flares ground off? I've heard they work VERY well, even in hardened steel.

 

[Bo Heck]

A 1/8" pilot hole will allow your bit to break through the other side without building up too much heat as larger bits tend to do before they break through the work piece. Less heat means your drill will last longer. Cutting oil will also help, don't need a ton just a squirt at the beginning and one during. Run the drill press as slow as possible, at 300 RPM and exert enough pressure on the drill to get a proper chip. Too much pressure and you will likely generate too much heat, have blue chips and cause your drill to slip. Too little and it will squeal and dull your drill, don't baby it. Most people do not feed with enough force and high RPM + low feedrate will kill a large drill. Aim for your chips to not change any color, straw colored means you're on the edge. You will probably need to peck drill.

Please don't use carbide, there is no cause for that and a drill press will eat it. A single decent HSS drill from Cleveland, Precision, Triumph, etc should be plenty good and not need sharpening if you treat it right.

I drill steel up to 40 rockwell (C) nearly every day with cheap Precision brand drills. This should be a cakewalk for a HSS drill.

Don't forget to clamp your work securely.

 

[pipsters]

Cobalt 1/2" bit thru 3/16" steel using a 1/2" hand drill

Just a dab of some wheel bearing grease which is probably the wrong thing to use but I drilled 8 of them and the bit was still going thru nicely. I did start with a 1/8" pilot hole after the first one to keep the 1/2" bit from wandering around (I was using a hand drill after all).

 

[markw365]

I have used my rotabroaches to cut 9/16" holes in 1/4" steel plate. They advertise for up to 1/2" plate. They work much better than twist drills for drilling holes.

 

[lilscorpion]

:

For drilling its all about speeds and feed, and the technique Hammer described.

Google "drilling speed feed" and print yourself a chart...

Lastly HHS will drill most anything unless it is real exotic. You should not need cobalt, titanium, or carbide at all... (we won WWII on HSS for Pete's sake...)

...and maybe managing the heat. I've drilled through 1-inch plate with a 1 1/2-inch bit pre-drilled with an 1/8-inch hole. Feed was silly slow, RPM barely moving, and a drop or two of cutting oil every so often. The chips would turn blue shortly after they broke. Nothing fancy, HSS bit. Cut a dozen holes or so, touched the bit up on the grinder wheel, and did it again.

Getting the speed and feed right is easy on a knee mill and it's much harder to do on a drill press (especially if your min RPM can't get low enough) but patience goes a long ways.

 

[cyato]

I have used my rotabroaches to cut 9/16" holes in 1/4" steel plate. They advertise for up to 1/2" plate. They work much better than twist drills for drilling holes.

A 1/2" Rotabroach cutter would also be my first choice in the OP's situation. I got my first Rotabroach set about 6 months ago and can't believe I didn't pony up sooner. All of the advice with the twist drill bits are great too (and probably cheaper), the annular cutter is just faster. One thing I learned using the annular cutters with a hand drill is to start the hole at high speed (like the video), then slow down to reduce heat and keep from burning up the bits. Starting a hole with a Rotabroach at slow speed can cause the cutter to catch and wander off. Drilling a small pilot hole, rather than just making a center punch can help guarantee that the cutter won't wander. The cutters are super sharp, but can also break pretty easily. Clamp your work piece securely! The speed of cut, and the cleanliness of the hole with the Rotabroach is very hard to beat.

 

[RivennHewn]

Carbide drills are EXPENSIVE. Has anyone ever tried using masonry bits with the flares ground off? I've heard they work VERY well, even in hardened steel.

Everybody who has hit re-bar while drilling concrete.