I deal with trailer frames almost every day. I'm not sure what they are made of, but some of them are the very toughest doggone steel I have ever busted a bit in!

I no longer use anything less than Cobalt bits to drill steel anymore.

Many so-called Titanium bits only have a "COATING" of Titanium on them, and will go to pieces fairly soon.

"KOBALT" is not a COBALT bit set. It's a brand name - I looked all over the Kobalt bit packages and found no mention of any special composition of the metal.

De WALT HAS A Cobalt bit set they offer. It isn't the same as their other bits, and you should be sure to look specifically for what they are made of before just pulling them off the display and buying them....

Regardless all of that, proper drilling in steel calls for lubrication. Oil your bits with SOMETHING. I use either Marvel Mystery Oil, or transmission fluid most of the time. I also try not to overheat them.

Enough "Dry Drilling" will make a bowling ball out of any bit ever made sooner or later...

Okay people - HAVE AT IT! I know there are machinists with a truckload more experience at this than I have posting here...

SCHOOL ME!

 

Probably hardened steel. The Dewalt and Hitachi cobalt bits are great, I have had good luck with them.
I have found out that with really cheap drill bits, that if you use them in drill press, the flute direction can be reversed.......

 

What size trailers are you talking about? The little private trailers up to the gooseneck variety are probably made of common A36 structural steel. From what I have read in industry journals trailers made for commercial freight hauling are mostly made of high strength alloys for weight savings. Every ounce is important in that application.

 

Anybody that does a lot of drilling should do themselves a favor and learn how to sharpen a drill bit on a plain old grinder.
It is not that hard to do and with practice you can produce edges as good or better than original.
You can adjust the pitch of the cutting edge to cut more or less aggressively depending on the material you are most often working with.
I have never used one of those drill bit sharpeners they sell, so I can't comment on what kind of result they produce.

 

I've used the Drill Doctor and it really does a nice job on the bits and is very easy to use.

As far as drill bits go, the best set I have found are the ones that my dad had. I eventually found the same set at Fleet Farm. Its a 39 piece set or something like that with a black folding case. The bits are made in the USA and hold their edge well. I will only buy those bits and a drill doctor for when they do get dull.

 

Ya I love the Drill Doctor. I can't see how I got along without it! When im drilling through steel and Im not getting anywhere, I work it in the drill doctor for about 30 sec. and it drills like a hot drill bit in butter (sounds dumb, but it is an amazing difference).

But I bought the least expensive one that only cuts buts at 118*(?)...I think thats it.

 

Yeah, I think that is the same on that I have. They work great.

 

When drilling in alloy or any hardened steel you should have 135 to 145deg bit, not the stock 118deg bit. I have not used a drill doctor, so I don't know if they will do a different than 118deg angle. We had one at a shop I worked at, but noone used it, we just did it on a grinder, and use a protractor for the angle.

 

The drill doctor that I have only does the 118 degree tip. I usually drill a variety of different things so I just use the 118 degrees rather than re-grinding or having a second set of bits.

 

Greywolf,

You got this off to a good start. Let me run down all the possibilities.

The first twist drills were a high-carbon steel (often called "tool steel"). This steel is mostly iron with around .8% carbon. This steel can be hardened by heating it above a 1800 degrees F and then quenching by plunging it into water. This process gives a very hard piece, but it will shatter like glass under impact. For most all practical uses the piece is then tempered by being re-heated and held at an intermediate temperature (say 500 degrees F) for a reasonable time (say 1 hour). This process is the "quench & temper" hardening of steel. To make the steel soft again, just heat it for to an intermediate temperature for an appropriate length of time. This softening process is called annealing. These drills will work fine in wood and will do the job in metals (including soft steel). The problem is that everyone is in a hurry, time is $$$, so everyone wants to go fast. The heat generated by the cutting action of the drill bit will anneal the drill bit and it self-destructs.

The answer to this problem, some 75 years ago, is to add alloying elements to steel. These include chromium, molybednum, nickel, manganese, silicon, titanium, cobalt, & other metallic elements. Without getting carried away with the details, these extras in the steel give a lot of benefits, but the most important is the ability to stay hard even up to red-hot temperatures. The most serious family of high-alloy steels are the high speed steels - there are a lot of them. Greywolf's examples are perfect: cobalt is one of the alloys added (in addition to many of the others) in some of the best tools steels. "Kobalt" is just a trade-name trick. Titanium is sometimes IN the alloy mix, but a Titanium Nitride coated drill is not junk. When properly applied this ceramic (metal oxides and nitrides are ceramics) layer is VERY hard and slippery. The chip glides over this surface without generating much heat. THESE ARE VERY GOOD DRILLS. In production, with rigid, power-fed drill presses, they can go as much as ten times longer between sharpenings. They will not be as good in hand-drilling conditions and, when sharpened the coating is lost from the end of the drill, losing some of the benefit.

I know I already bored most of you to tears, but the bottom line is that one has to be careful. The marketing people will play their games - you need to read the fine print. You usually do get what you pay for. Most American-made drills are very good, although expensive. There are still some old time companies like Cleveland, Precision, and Chicago-Latrobe, but they are expensive. If you buy one size for a special job, it will be worth it. You can probably call or e-mail the factory to get a recommendation.

For most of us wailing away with a hand-held drill, an "import" drill bought through a US distributor will give more value. I agree with all the sharpening comments. I just bought an attachment to use with a bench grinder, which costs a lot less than one of the machines. When I get it set up, I'll do a new thread on how good (or bad) it is.

The reason I spent time on the theory at the beginning is to underline how important heat is. Heat comes from speed. The larger the drill, the less rpm. The smaller the drill, the more rpm. (If you do a lot of drilling, get a little chart of recommended speeds.) The rpms of hand-held drills are such that they are not too fast for the largest size the chuck will hold when cutting soft steel. A lot of structural steel has hard "inclusions" that can really tear up a drill bit. In a drill press, you should slow down, and perhaps use a larger amount of thrust. This is hard to do with a hand drill unless it is variable speed and you are 300 pounds of muscle. If not, then drill a pilot hole 1/4 the diameter of the final hole and keep the pressure on as much as you can.

I will be happy to entertain anyone who wants more detail.

 

Thats very interesting information.

How does one know how fast to drill?

 

I drill tool steel all day. The best steel bit is a Guhring GTX-100. They have parabolic flutes (whatever that means) a 135 deg. angle and a split point. They are really too fragile (and WAY too expensive) for hand drilling. I'm in the hand sharpening camp, since I can control a number of factors, but, then, I've been doing it for 35 years. Things to look for: Both cutting edges need to be the same angle, the same length, and the cutting edge needs to be the highest point, with the heel sloping away. I'm always amazed when someone brings me a bit that they " keep sharpening but it still won't cut", and the heel is higher than the cutting edge. Look at the drill sideways to see this clearance. You also need to slightly rotate the drill as you bring it up so that the clearance goes in a slight circle, otherwise you will wind up with a hump behind the center point. If you have a real steady hand, and a very sharp corner on your grinding wheel, you can split the point almost to the center, resulting in much less pressure being required, but this is an advanced skill. It pays to look very closely at a new, well-made bit to study what it looks like. You can buy a cheap little gage for sharpening bits. It has the proper angle, and little markings to make sure each side is the same length. If you want a drill to drill a little oversize, intentionally grind one edge more than the other. To echo what Acheda said, look up and learn the proper RPM for the drill you are using. Better too slow than too fast. If the chips are blue (and so is the bit) you are running too fast!

 

MisterCMK, There is a simple formula:

RPM = (cutting-speed x 4) / diameter

In a sentence (because it is hard to type in formulas clearly):

(drill-revolutions-per-minute) equals (cutting-speed times 4) divided-by (drill-diameter)

For soft steel, cutting speed = 100 feet-per-minute
For aluminum, brass, & bronze = 200 feet-per-minute
For miserable materials = 50 feet-per-minute or less

These are very gross figures, but far better than guessing. Machinists who cannot do math in their heads and would be embarrassed to get caught opening a book will go up in rpm until the chips are blue and then back off. (This does work, but you have to back off the "right" amount.) Note that both too fast and too slow are bad. Most people run small drills much too slowly.

If you use spread-sheets, it is easy to generate a table for your drill set. These sorts of tables are available from the people who make drill bits on a plastic card that you can put in your pocket or keep in your drill index.

One more thing: do not be afraid to work the drill. In most cases "getting 'er dun" will result in less wear, so long as you do not overheat the drill. Taking twice as long results in twice as much material sliding over the drill bits cutting edges and HALF the drill life.

P.S.: For you mathematicians: the constant 4 comes from combining 12-inches/foot and the ratio of a circle's circumference to its diameter (pi)

 

I see and deal with everything from 5 X 10 utility haulers to ALFA Fifth wheels over forty feet long.

Travel trailers are not so bad, but any fifth wheel frame is going to be tuff, especially at the front end where stress can be expected.

 

Those trailers are still probably standard A36 steel. Try stainless and work hardening tool steels... Jay probably knows ALL about those!!! -hehe

When I was young and could see what I was doing, and do it without shaking, I used a regular grinder and even sharpened the special bits for the guys on the radial arm drills, -but that is no more. I have a huge assortment of dull bits waiting for a drill doctor...