Doofus Award

[Pault17]

For the last year or so, since my wife gave me a small 10-inch bench-mount drill press, I have been burning the drill bits up like no ones business. After searching the forums here recently, and having seen various comments made (not on the subject of burning drill bits, but of just drilling holes) I realized that drilling dry is no way to go you don't need oil when drilling wood!

I recently picked up some real "cutting oil" and a little squeeze pump oil can, and WOW!! what a difference. drilling metal is now a whole lot more fun.

Thanks for leaning me a new lesson... Now I just have to pick up some new bits of all sizes..

[John B]

Make sure you are not using too high an rpm when you are drilling, the general rule of thumb is: Smaller the diameter of the drill, higher the rpm

Personally I normally use my drilling machine on its slowest or next to slowest speed unless drilling small diameter holes less than 1/4" diameter and have no need of coolant or cutting compounds unless doing high volume runs.

It also helps if the drill bit is sharp and of good quality, there are some really poor quality drill bits around that work on wood, but not on steel.

Using a drill made from the correct grade of material it is possible and practical to drill through files or springs in their working condition.

You used to be able to get drills to "drill square holes". (Handy if you are making socket sets) Not used one for a long time though.

[Jacob]

Yes, look up the recommended top speed for drilling steel with your desired drill size. The small benchtop drills tend to run very fast. They are usually designed for wood or small holes in light metals.

I have an old 21" drill press, intended for metalworking. It has back gears and must turn down to 20 RPM. It's much less than once per second. It was advertised for up to a 1.5" hole. With that machine, there is oil everywhere, so you might as well put some on the tip of the drill while you're at it.

[Glenn]

Oil on the tip of the drill to cut into the metal. Is that the same oil you put into your car so you do not get metal cutting into metal?

[Thomas Dean]

Motor oil used for drilling holes will harden the material being drilled which in turn will dull the drill bit. Use cutting fluid for best results but if you have nothing else just plain old everyday WATER works good. For cutting stainless you would be amazed at how well Carnation Milk works! Problem with the milk is hot weather....sours! PHEEEW, but it sure works amaizingly well.

[Glenn]

So, let me put this in writing.

If you drill a hole and use motor oil as a lubricant to CUT the metal, this is the same oil you put into your car engine to lubricate and NOT TO CUT on the metal to metal surfaces, bearings etc.

If you drill a hole and for whatever reason (too much speed, dull drill bit, etc) the metal gets hot, the motor oil can act as a quench, hardening the metal you want to cut. The same oil you dip the hot metal into to quench it so it will become REAL HARD.

No wonder the industrial cutting and drilling operations FLOOD the cutting surface with the PROPER coolant for the job, keeping the metal both cool and the cutting tool and the cut well lubricated.

[John N]

glenn, the squirt of oil you place on the drill can not quench the metal (to do this would require taking the metal from above critical temp, to below in a very short space of time).

A cutting oils purpose is to prevent the swarf / cuttings sticking to the cutting tool .

This should not be confused with a flood coolant (water souluable oil) which main purpose is to keep the cutting tool cool. (you can use plain water, but everything rusts!)

The main problem when drilling carbon steels is running the tool too fast, bad quality tools and poor grind geometry (and insufficent feed pressure when drilling, so the tool rubs instread of cuts)

Stainless steels will work harden (one of the metalurgists will know why, I dont

[habu68]

From "the Modern Blacksmith" 1904 Modern Blacksmithing, 1904
DRILLING IRON:

"Every smith knows how to drill, sometimes it gives even an old smith trouble. The drill must be true, the center to be right, if one side of the drill is wider than the other or the drill not in proper shape the hole will not be true. For centuries oil has been used for drilling and millions of dollars have been spent in vain. It is a wonder how people will learn to use the wrong thing. I don't think that I have ever met a man yet who did not know that oil was used in drilling. In drilling hard steel, turpentine or kerosene is used as oil will then prevent cutting entirely. Nothing is better than water, but turpentine or kerosene is not as bad as oil; if you think water is too cheap use turperitine or kerosene. I had occasion once to do a little work for a man eighty years old, and when I drilled a hole, used water. The old man asked if water was as good as oil, and when informed that it was better, said: "I used to be quite a blacksmith myself, I am now eighty years old, too old to do anything, but I am not too old to learn." it ought to suggest itself to every smith that while oil is used in boxes to prevent cutting, it will also prevent cutting in drilling. "

A nice little primer on blacksmithing at the turn of the 20th century

[Thomas Dean]

habu68, Thanks for the quote from that book. I couldn't remember exactly how he said that as it has been a while since I have read the book. A fun read, especially the first couple of chapters! Wish I had a copy, a friend from out church had loaned his copy to me to read.

[habu68]

here it is in pdf for downloading Modern Blacksmithing, Rational Horse ... - Google Book Search