Drilling holes in Steel

What's the proper way to drill holes in steel?

I'm using a drill press, but am finding that my holes are out of round, and the drill bit is siezing in the hole.

I'm using automotive oil as a lubricant.

What am I doing wrong, or not doing right?

Thanks!

-Noggin

 

This is a long complex subjuect and I was thinking of where to find a written detailed explanation. 1/4th inch holes need aprox 750 rpm and smaller faster and larger slower. Automotive oil isnt the thing, the strand structure of the oil is wrong. I like Rapid Tap or Tap Magic or something like that for small ones and you can use thread cutting oil for larger ones. The grind of the bit is making it go out of round, essentially the point is not centered. There are other minor issues with the relief that cause it to run out. Maybe someone can come up with a site. This is a little like welding sometimes, we been doing it for so long it becomes instinct. I am thinking of getting a drill doctor myself one of these days. Also there is getting the right amount of pressure on the bit. Pressure is good, imagine bits above a 1/4th it is hard to get too much by hand. Not enough makes the bit not cut and creates heat.

 

Obviously this subject is more complex than I'd given credit for.

The steel is 1/8 inch thick, and I'm drilling 3/8 inch holes.

Does that help in creating an answer?

 

Wood Magazine has an excellent chart "Drill Press Speed Chart" at www.woodmagazine.com/compstor/dpsc.html

 

With a common drill bit the hole probably wont be perfectly round. I think there is a different type of bit for thin plates and I am not current enough to be sure what it is.

 

My thoughts, use a proper cutting oil, sharpen the bit, slow down the rpm's. You might try a smaller (1/8) bit first for a pilot hole though this is usually necessary only with heavy stuff. In my opinion many of these smaller drill presses turn a little too fast, even at their slowest speeds, for drilling steel. High rpm's will burn a bit up fast if you aren't careful and make sure this is mild steel that you're drillin on. A 3/8 hole in 1/8 plate should be easy.

 

NogginBoink:

You got some really good solid advice and I hope your problem has gone away.

I'd just like to add that while correct drill speed, proper lubrication, the right bit, it's sharpness, and how fast you are feeding the bit into the workpiece are all potential causes for those out of round holes you are getting there could also be a problem with your drill press - possibly the bearings on the quill. The quill is the part that spins around holding the chuck, and it extends and retracts with a hand lever or wheel.

Check your quill. It's real easy. Turn off and unplug your press and make sure the quill is retracted all the way up. Grab the chuck and move it back and forth and see if there's any slap - or lots of play. Lower the quill and do it again. You'll never get round holes if you have excessive slap. Excess slap means that the quill bearings are badly worn which causes the bit to wander in the workpiece.

While you're at it - check your press for vibration. Vibration is very bad and must be eliminated. It's easy to check.

Check your press set-up for vibration. Put a small cup of water on the work table, set it for an intermediate speed, turn the press on, and look for waves in the water. There really shouldn't be any - but tiny tiny ones are okay. Make sure your press is on a solid workbench or floor. Use a torpedo level and make sure your press is good and level. Next check for vibration in the belt drives, so unplug your press and take the belt off and check for slap on the pulley assemblies; then, with the belt still off, very carefully run the motor and check for vibration. Turn off the motor and unplug it to check for slack in the motor bearings.

 

With all of the good advice you got here let me add one more thing. Many many years ago when i first got started . Had to dill a hole in some steel but they didnt have the right size drill there what they had was to small . I didnt know what to do . A old machinist there ask what i had to do and I told him I need the next bigger drill but they dont have it. He took the drill I had and just sharpen it off center a little bit and said here you go,worked fine. You do have to look out are it can dig in on you. So is your drill dead center when you sharpen it????? ED

 

Your sharpening the drill wrong, the problem is that one of the cutting edges is longer than the other. The angle must be the same (118 degrees for general metal use) and the length of each cutting edge must be the same.

rpm for a 3/8 drill in mild steel is 150 rpm

 

Depending on how many holes you need to drill..

Since it's only 1/8" material, clamp it between two 3/4" boards.
The boards will hold the bit steady and keep it from wandering when it hits the metal.

You might also consider using a metal punch if you have a lot of holes to do.

FWIW, I've never used a lubricant when drilling mild steel, even up to 1/2" holes in 1/4" material, just go slow, let the tool do the work.

 

Here is my 2 cents worth along with all the other good advice above. Drill bit sets are ground in (mostly) 3 different common angles, from aggressive to the less aggressive (flatter) style bit.

The big box stores sell alot of the aggressive bit sets and the second most aggressive bit sets. If you just grabbed some bits at the store and didn't notice their angle, now would be a good time to check them out a little closer. The more aggressive the bit angle, the more cutting edge you have, and the faster it will want to bind.

Generally speaking the most aggressvise bits are for woodworking, while the least aggressive bits are for steel. I can drill steel as you described with either of the two lesser aggressive bits. I always eyeball the bit to be sure I am not using a bit that is better suited for wood (the aggressive bit). Under ideal conditions, any bit will tend to grab as you break through the hole.

 

The more aggressive the bit angle, the more cutting edge you have, and the faster it will want to bind.

Excellent observation. A small change in the back cut or included angle can make an enormous difference in the cut profile, especially in thin material. I use cobalt bits in the shop and sharpen them on a Darex sharpener, which gives me control of the back cut, through an adjustable cam on the machine, as well as the point angle. I can also split the point, thinning the center a bit to make easier going when hand drilling or starting holes without first center-punching or center-drilling them. Many times I set up bolt patterns on the DRO in the mill and just go from one hole to another, during production operations, without centering. I generally use a mist of water and water-soluble oil, which allows for heavier feeds and slightly faster speeds. When doing heavy machining like boring (in the mill) or shell/side milling, I use flood lubricant of the same type. Automotive oil is great for bearings and sliding things but lousy for cutting.

Lastly, for the original poster, don't scrimp on drill bits; buy good quality American or European high speed steel items, which typically cost 150-200.00 for a complete index of letter, number and fractional sizes to 1/2". Double that (or so) for cobalt (M42 or equivilent). A good set of bits, properly used and routinely sharpened, can last a lifetime. My sets are nearly 20 years old and are still going strong, except for a few which I've broken and replaced over the years.

Have fun!

Pat

 

I leave my drill set at middle speed, for everything, off hand I dont have the rpm, will get it when I go back to my shop. I have found the key to cutting is good cutting oil for SS ETC.and oil as you go.
The bit gets hot and oil cools as it fixes the steel bit.
I also drill, oil, lift the bit out of the hole , oil bit, and hole, drill, and watch that there are coils of shavings happening.
Dont be in a rush to pound out the hole.
For what it's worth I hope it helps ya, Everyone has there own tech this is mine and it works for me and bits keep cutting.

 

Ok The RPM'S / Since I have 4 drill presses I will narrow it down to the one I use in my Mechanic shop. I run it @ about 700 rpm, lots of SS Walter brand CUTTING oil and start with a small bit and work my way up.
When drilling with a hand drill I still use the oil and change bits.
I dont know the speed of the hand drill but its preety quick.
I find a small pilot hole works great as it relieves some of the cutting of the tip of the next larger bit. Time for my break

 

Hey
Here are some things to check.
1 Drill bit is in good shape (go for a cobalt bit)
2 Use lotsa lube (always good idea )
3 Clamp the piece down
4 Most important anything over a 1/4 hole I use pilot drill bits, if i am drilling a 1" hole i would start with a 1/4 bit then a 1/2 then a 1", You will save your bits this way.
5 If the metal is stainless you need good bits like cobalts and go slow with lube.
Hope this helps

 

I've been using a 1/2" bit with 450 RPM's, although it seems to take quite a qhilw. Over ten minutes for 1 holes. I'm using a hand drill and after a little bit of drilling, I take a heavy duty nail and make a hole in the metal. The metal is 1/8". Is it suppose to take this long? The pieces that come off are very small chips, almost like dust.

 

I have read somewhere else to make the chip, the hole will follow. Cutting oil does not actually contact the cutting edge of the bit. A properly made chip will carry waste heat with it away from the bit.

If your chips are too small, then the bit is too dull.

If you take too long to drill the hole, the metal work hardens and it just gets more difficult to cut through.

I found that making holes in 3/8" steel went faster for me without lubricant.

For some holes, an annular cutter may be a better choice than a drill bit.

Have fun.

 

The bit is new so it shouldn't be dull. I had heard that oil wasn't necessary when drilling in 1/8" or less. The bit isn't very hot after drilling for sometime.

 

Kalashnikov: You did not say what you were drilling. It sounds like you are trying to drill your 1/2" hole in one step. Try drilling a 1/8" diameter hole first then a 1/4" and finally your 1/2". The exact hole sizes are not critical. Just start with a small drill and work your way up in steps. There are many different types of drill bits and some are easier to use than others especially when hand drilling. Going up in steps generally will make any sharp drill bit work.

If your drill bit is making "dust" that is not good. The bit is probably dull. Starting with a small hole and going up in sizes will help. A cheap/imported bit can dull almost instantly so your new bit could be dull already.

 

pilot dane, you are spot on about pilot drilling, it is far quicker, when drilling using hand held power tools or when useing small pillar drills. If anyone takes a look at say a 3/8" drill bit and an 1/8" drill, the area that is ground to a point (not so much of a point as a ridge) is far broader on a large drill than a smaller drill, its this point that provides most of the resistance to drilling, so a small bit has a narrow point and has less resistance and drill easy. once you have an existing hole its then becomes easy to drill a large hole because either the point of the drill fits in the hole or has less contact with it, meaning less resistance.
of course you could resharpen/grind the drill so that it is point relieved (difficult to explain how to do, and even harder to do it), basically you use a grinding wheel, reshaping the back edge of the drill (the non cutting edge) so as to narrow in size the point of the drill. then you can stuff a 5/8" drill through 1/2" plate with relative ease

 

Well what I had been doing was dilling for a little bit, then make a hole, maybe 1/4", and continue drilling. It is a Blu-Mol 1/2" Black Oxide bit.

Could the reason the chips that come off being so small be because I'm not putting enough pressure on the drill?

Thanks for the help

 

I tried using more pressure, and it cut through the metal like nothing. I guess that was my problem.

 

Old thread I see, however, I will try and address what the problem was the fellow was experiencing and correct some misunderstandings.

The fellow was drilling 3/8" diameter holes in 1/8" thick steel. Even with a brand new drill bit the problem with walking and out of round holes is caused by the simple geometry of the drill point. By the time you reach the full diameter of the bit you have already penetrated the steel and now have nothing to support/guide the bit. Even if you use a smaller bit to pilot you will encounter the same problem so you need to have something underneath the material to "catch" the drill point and provide support for the bit so that when the body of the bit gets to the parent material you have the support you need for a round hole.

ALWAYS use lubricant when drilling steel. You may feel like it is doing fine but you are dulling your bit rapidly without lubricant. Please remember that WD-40 is NOT a lubricant. A cheap oil can filled with 90wt gear oil works just fine. There is nothing wrong with TapMagic, just harder to find usually. With regards to how fast to drill, speeds and feeds have been established for years and are readily available on the internet. A good investment if you are doing much of this is the Machinery Handbook, it is the bible for working metal.

Another viable option for drilling in thin metal is the use of a piloted counterbore. This will give you a very round hole. Also it is possible to use a four fluted core drill, these have a more shallow drill point angle. Of course if it is critical you use a reamer. Consult McMaster-Carr Supply Co. and you can research and find every kind of drill bit, counterbore, reamer, hole saw you can imagine and at very reasonable prices, reasonable shipping costs and rapid delivery and they will sell to the individual just as well as a company. I've been using them for years, you get the better stuff at a better price than the big box stores which tend to only care one line of products.

 

I just drilled 72 five/sixteenth inch holes in a 1/8th inch steel plate bar, the 2 titanium bits are as good as new. what I did, 1-- clamp both ends on a workbench with a good board underneath to catch bit as it breaks through, 2 -- pre punch each hole twice with a center punch, 3 -- drill ist pilot holes with a 5/32 bit. 4 -- place drops of tap magic in bit up to I inch (I now believe in this stuff, get the 4 oz can, more than enough), 5-- drill SLOW!, really really SLOW, often as slow as 5-10 rps, stop frequently, fill the growing holes with more cutting fluid (if you think this is tedious try stopping to go buy new bits), 6 -- cut 2nd round with the 5/16th bit. the torgue on the bigger bit will cause your variable speed hand drill to come on too fast, so try popping the trigger for a series of short bursts. 7 -- take a 6 inch piece of 1 inch thick board, ream out 2 holes almost through with a flat wood bit, set a couple soda bottle caps in these holes and you got a little cutting oil dipping station for your bits. re dip your titanium bit evrery few second, 8 -- drill in short bursts, then pause and re dip. 2 or 3 pops at a time is fine. I STILL GOT MY DRILL BITS, LIKE NEW !!

 

Thanks for your help.

This thread is over ten years old and hopefully the original poster has already found a solution to his problem.