Technical Shop Class Basics: How to Properly Drill a Hole in Metal

Its very important to clamp your work piece down to avoid injury...

 

Always let the drill bit do it's job, being impatient and putting a lot of pressure on the drill only heats up the bit and dulls it faster, it also can cause the bit to wonder, go as fast as the bit wants to cut and keep it lubed.

 

Was taught by my dad (qualified fitter/turner and machine shop teacher) to use kerosene for lube when drilling aluminum.

 

You can also consider water soluble coolant. You purchase concentrate and mix it with water - ratios of 5 to 1 to 10 to 1 (water to concentrate) in a hand spray bottle. Water is an excellent medium for the transfer of heat - the enemy of cutting tools. You'll note when you spray the coolant on a drill the water vapor (not steam) be created by the heat of the shearing of the metal by the cutting tool. That heat went into separating the water from the concentrate. What little concentrate whirls around in all the cutting action. When you're finished machining you may want to wipe any coolant that didn't get consumed in the machining. Here's an example of a water soluble coolant (concentrate) - not a particular product recommendation.

Anchorlube G-771, 8 oz Bottle Cutting Fluid
- Water Soluble, For Broaching, Counterboring, Drawing, Drilling, Engraving, Fly-Cutting, Hole Extruding, Milling, Piercing, Punching, Sawing, Seat Forming, Spot Facing, Tapping
https://www.mscdirect.com/product/details/00063909
https://www.anchorlube.com/anchorlube.html
"Water soluble fluids blend oil with emulsifiers and additives to create an oil-based coolant to be diluted with water. These fluids provide excellent lubricity and an increased cooling ability over straight oils."

 

Yes. Be sure to wipe everything down every time you use this. A friend bought a horizontal bandsaw several years ago. It was "rated" for water soluble coolant and had the built in pump and coolant storage tank. Unfortunately, after 3-4 years the metal in the coolant troughs rusted through so badly he quit using that bandsaw and bought a new one.

 

We use these in the R&D shop, for sheet metal:


Away from a machine, step bits.

For drilling aluminum, when it cannot be put in a machine, we use undiluted fluid from the CNC mill. For stainless, we use Elmer's white glue. For steel, Tap Magic.

 

We had a local shop, people still talk about this one that happened around 1976, my brother worked down the street in another shop at the time. This was an R&D shop, still is. Someone was turning a large part on a big gap-bed engine lathe. Deep down in back-gears, like 34 RPMs... his shop coat tail got caught in the lead screw. Nobody was around when it happened, safety-101 was not being employed, avoid working alone in machine shops! The lathe didn't even skip a beat. The guy was pulled in and wrapped around the face plate, probably dead in seconds. When someone came in, pieces of the guy & coat were still spinning.

 

We had the best drill sharpener in the world at work, I'll have to see if I can dig up the name, something like Blackhawk.. found it, Black Diamond! That would do 1/8" easy, but tough to get a good sharpen out of anything smaller. When I buy small drills, I always get a package of 12. For work on the Bridgeport, I like screw machine drills. The TiN coated ones hold up well and are only a few cents more per.

This is a good formula that will keep you from smoking up drill bits.
RPM = (CS X 4)/D.
Cutting speed you can look up, mild steel is 100, aluminums are 300 and up. The 4 is a constant, D is the drill or cutter diameter.

 

I keep a few cutting oils around. Water soluble, Hangstefers (sp?) has one with a 50:1 mix ratio, a little goes a long way. Anchor Lube is also good on stainless steel, the green stuff can be thinned with water. Very good on titanium. Mold Dee (made now by Castrol) for tough steels. There is one for aluminum, Alumatap, said to be kerosene (Klansman Cologne..) based. I got a can of Tap Matic fluid, works well with their tapping heads. Plain old WD40 or 3 in 1 oil is good in a pinch, so is MMO.

 

Its really pretty much just common sense what you need to do. When drilling you need to be able to get the cutting edge of the drill to shave a chip rather than just rub and work harden the metal. If drilling large holes, you slow the bit down, and smaller holes you speed up...somewhat. Most drills are dulled because the person doing the drilling runs the hand drill or drill press too fast. Especially hand drills are usually held full throttle when drilling.

Pressure is also important. A lathe/drill press/milling machine will have a mechanical advantage that allows the machinist to exert far more pressure than a hand drill applies. The ease of applying this pressure with the mechanical advantage fools people into thinking they aren't applying much pressure. You usually get notified quickly when too much pressure is applied. On the other hand, too much speed or too little pressure rubs , and doesn't allow the cutting edge to slice a chip. It fools you and you increase speed and make it worse. The drill seems to quit drilling because the workpiece has hardened. Then you try a new drill and it quickly dulls too.

Not saying you can't apply too much pressure, but usually the culprit starts with too much drill speed. Try drilling holes at about half the speed you normally do and see if results are not more satisfactory.

You can write a book on cutting oils and coolant. In production shops, high speed feeds and continuous cuts generate heat. The water based coolant helps keep the heat down in the part and the tool. It is seldom needed in a home builders shop. Oil of any kind usually helps, but you seldom find a place to use it when drilling on your car. It is handy for tapping holes and reaming and drilling something restrained in a machine.Use of virtually any non-flammable liquid usually helps. I wouldn't get caught up in any one type of oil being particularly better than another in any situation other than production machining. When I tap threads, I usually squirt a little WD-40 on the hole and tap.
Not because its the best, but it does what I need, its easy to wipe up, doesn't create a big mess, and I'm lazy.

Edit Note: The rpm range you use for drilling will be faster when drilling aluminum than the rpm range you use for drilling steel. Stainless usully mimics regular steel but generally requires more pressure to cut a chip.

Look at some of your drill bits. See if they all have the same tip angle ground on them. The web in the middle of large drills often creates a problem because it pushes against the surface rather than cuts and resists your attempt to drill. Thats one reason you drill pilot holes before using the larger drill sizes.

 

We used to have to watch training videos showing us not to wear loose clothing, especially a tie when operating any machine, but especially lathes. Then when the oil/gas shortage hit, they turned the heat down in the manufacturing buildings and everyone had to wear coats and gloves. Then summer came and they cut the ends off the water cooler cords......but kept the A/C working in their offices. Never saw a machinist that wore a tie to work...only engineers.

 

Not saying some engineers aren't capable of doing machine work but we had an unspoken rule about our engineers using equipment, don't let them.

 

I'm an engineer.

 

I do know that, and I'm pretty sure I understand your broad range of capabilities.
You were the first person to come to mind here, precisely why I worded my post so diplomatically.
To be clear, we had some very capable engineers, we had some that had to hire out having their shoes tied too.
We even had one where it was common knowledge that we check any work he did after lunch as his lunch did not consist of "food", if you catch my drift.

 

You are correct, though, and, very sadly, everyone is called an engineer these days.

I have to deal, daily, with engineers that design things that cannot be built, and would accidentally kill themselves in a machine shop.

Worse than that, I have to deal with self-important "software engineers".

The way that I was raised is that engineers are responsible for designing things. Software is not a thing. It is the basic difference between a product, and a service. If you can drop it on your foot, it is a product (aka: thing). If you can't, it's a service.

Without software, hardware is manual. Without hardware, software is fantasy.

 

As a shop foreman I had to deal with many types of engineers. The worst type were those fresh out of school. they thought their book training was sufficient to direct us how to do things. I used to tell them you went to school, now you are in the real world, and this is how it is really done. When I got my first job as an apprentice, the old timer toolmaker showed me how to sharpen drills. It wasn't that easy, but I eventually got to know how to do it. He also showed me how to sharpen drills for different materials. Later when I was employed as a set up man I learned how to sharpen drills to be used on some exotic metals. This was a great education that I am still able to use.

 

1961: This is Mr. Schrianka, the Long Beach Poly HS Metal Shop teacher.

Hello,

One of the most memorable teachers from our old high school between 1957-62 was our classic, metal shop teacher, Mr. Paul Schrianka. He was an ex-Navy military man and let us know it, daily. Overall, he was a nice guy and an excellent teacher. He was the one to give our small group, lessons on using the large drill press for “proper drilling” techniques. We all knew how to drill a hole, but he opened our eyes to the shop techniques to make things easier and more precise.

“Who needs a table top vise, we can hold it…ha. Oil? What oil, just power drill it through…and the last great one, who needs a starter drill first?” He was a stickler for doing the proper way in all things metal working. The safety facts always came first in his shop, the proper lathe protection and tools, the tube bender, the milling machine, the sheet metal bender, etc. We all got the week’s worth of instruction. Our class had the best safety record in all things metal, including gas welding and arc welding.

Jnaki

We were all anxious teenagers, but those "nit picky" lessons taught us stuff we still carry on today. I am sure he is gone, now, but thank you Mr. Schrianka for those valuable lessons. In our long time history, how can I remember his name? My brother was in his class several years earlier, so comparisons were always made. "Hey, aren't you that quiet guy's brother?"

The teacher allowed me to do extra projects in class (hot rod related) and liked my car. (he saw the Impala during my brother’s time in class…) The Impala was able to be driven right up to the rolling door in the back. But, one story still rings around in my mind since those teenage years.



MR. SCHRIANKA METAL SHOP 1961:

He was a gruff old guy that ran his metal shop class like the military. He always challenged his students to do better in projects and made the class fun. He told me that my skills were good enough to do special projects and not do the simple class projects. He taught me to weld and arc weld, run the lathe, spin metal, and form parts boxes out of a metal bending machine. I completed a stick shift bracket and shifting mechanism for my friend's manual transmission car.

We brought a similar transmission into class and I made a paper model and then made the exact pattern in metal, with moving rods and pins. It actually worked and later we installed it on my friend's old hot rod. Then I made a similar one for another friend for his automatic transmission. That worked even better. I was on a roll. I seriously thought of doing this for a living, building hot rods and racing.

But, one time, the teacher challenged me to a contest. There was a problem in class and one of my friends was going to get in trouble. Mr. Schrianka asked the whole class for details of what happened in this incident. I forgot the actual incident, but I will never forget what came later. He was really pissed that no one would step up and state the facts. So, since I was one of the leaders (star athlete and big club guy) in the class, he told me that I had the responsibility to speak up.

I told him that I would not say anything about my friend. He told me that if I did not, I would be suspended from the football team for the playoffs. (He actually said that, but I knew he could not do that, since I had nothing to do with the incident) So, I became the scapegoat and he started to say stuff about being the star athlete, big club guy, the guy who always walked the girls to class and was usually late to metal shop. He started to rip me in front of the class. I could not say anything because I would give him some reason to send me to the office.

Finally, it came to a point of calling me "weak." (in character) Now, my friends took it the wrong way (weak) and yelled at me to challenge the teacher to the "sledgehammer" contest. OMG the teacher had a smile all the way across his face.

The "sledgehammer" contest was his favorite. In all of the years at LB Poly, he never lost this contest. Everyone in school knew of the "sledgehammer" contest. So I said ok, thinking I would immediately lose and the incident would be over.

The contest involved raising a 20 lbs. wooden handled sledgehammer straight out, extending the arm out to the side.

I had never lifted any weights, but I was fairly strong. The first time I tried lifting the sledgehammer, I could barely hold it out for less than 15 seconds, before I dropped it to the floor. The teacher did not lift the sledgehammer before the contest. He was very confident. After practicing lifting the hammer all period, I was ready. So at the last 15 minutes of the class, we had the contest.

Word spread fast and there were lots of kids looking in the windows of the classroom. The teacher lifted the sledgehammer for one minute. Everyone "booed" him. Then it was my turn. I held it up for 30 seconds and I was shaking. So, the confident teacher said two out of three.

So, the next time, I lifted it up for 40 seconds. My adrenaline was pumping fast. Everyone cheered ! Then the teacher lifted it up for 35 seconds. I won! But, he had a smile on his face and we all later thought he lost on purpose, just to make me weak and tired. Now, the chips were down. It was the last time in front of all these friends and students. So, he lifted first and lasted 55 seconds. He was shaking the whole time as he was getting tired. Now, it was my turn and I was pumped.

Everyone was yelling…go for it! I picked up the sledgehammer and it felt like a ton of rocks. I held my breathe and lifted it up even with my shoulders. It seemed like forever and I was shaking the whole time. I thought I dropped it after about 35 seconds, but everyone was cheering. I couldn't understand why they were cheering. Then everyone started to pat me on the back. I had actually kept the sledgehammer up for 57 seconds and WON! I was so exhausted, but very happy.

Then, Mr. Schrianka came over and shook my hands. He had never in his 20 years of teaching metal shop, lost the "sledgehammer" contest. I had his respect and admiration. Word spread fast and I was the "hit" of the campus for the rest of the day. Whew! We never got in trouble for the actual incident and I got to play in the football playoffs that Friday night.

 

To quote my father "There are people with B.A.s in engineering who are a long way from being engineers."
Note- My father was accepted to G.M.I. and attended Clarkson College however it was in the height of the muscle car wars, he figured why engineer automobiles when I can get paid to work them.

@jnaki your story of Mr. Schrianka remains me of a story.

A couple year ago one of the new young welder/fabricators in the shop asked if I help me put an axle under his trailer.

He wouldn't follow instructions he was ramming, jamming, beating, and banging. I sternly said "Rodriguez listen to me I have done this before!"
At that point it hit me-
I have become my father and that's why he used to say all that stupid shit.

 

When I was going to Galileo High School in San Francisco, in 1956-1957 I took auto shop, machine shop, and wood shop classes. Our teacher for the machine shop, and auto shop was Mr. Presoto, yes, he drove a 1939 De Soto. In auto shop on the first day of the first semester he would ask the class, "who knows about working on cars". Naturally, a bunch of us raised our hands. He then would ask the class, 'when re-packing the front wheel bearings, which would you use, fine, or coarse, valve grinding compound, and why.". After getting several answers, and the reasoning, he would ask a second year student, which would you use. The answer was, "I would use wheel bearing grease". Thus, he let us know that we didn't know what we thought we knew. He was a great teacher, and I learned a lot in his classes.