Recommended drills for metal?

lastcowboy32

Well-known Member
Every time that I go to drill metal, I go to Home Depot, or Lowes, or Tractor Supply...and I buy the best bits that they have for drilling metal.

Aaaaaaaaaand I might be lucky enough to get one hole drilled, before it turns to a blunt instrument.

I am running cool/slow. I am even using drilling oil (OK...sometimes)

Even so, I've watched videos of an engine rebuilder fixing cracks in cast iron by drilling something like ten or twelve holes in the crack and then peening these special rivets into the holes. OK...what kind of bit is he using? He just drilled ten or twelve holes in cast iron...with no fluid or oil...one after another...with the same bit.

And every hole drilled as easily as if he was drilling into a maple board.

What kind of bit is that?

I have a tormek sharpening system in my shop at home; so I don't care if they are really expensive bits...but able to be sharpened.
 
It could be the drill/tool, it could be the machine, or it could be the material, or it could a combination of all three. Most bargain house tools are just plain cheap HSS/COBALT drill bits with or without Titanium coating. They should be sufficient for drilling wood, plastic, and soft metals. When you get into cast iron and especially hardened steel, you are going to need carbide cutting tools. The hand held drill devices available, including battery operated ones, are of a low Horsepower and don't have the torque to really push the tool. Try this: take a 1/3 hp electric drill motor and a piece of cold rolled 1018 steel and try to drill a hole. It isn't easy. Now take the steel sample to a Bridgeport and using the same drill bit and try again. It goes much easier because the Bridgeport has the torque with a better/higher horsepower rated motor. The workholding too will affect tooling. If not secured properly, you are wasting efforts and if you are using a carbide tool and the workpiece moves, you will break or chip the carbide -not good. Th e drill tip features come into play as well. A standard HSS drill will have a 118? point. We used 135? tips in Parabolic style carbide drills for cast iron and steel hole making. A spotting tool or center drill always helps first by making a pilot hole for the drill. Trying to do all that with a hand held device is not recommended. Technical drilling like on an engine head or block will require a magnetic base drill unit so it is clamped securely to the workpiece and will not move when in use. If you are dulling drill bits fast, chances are you are using the wrong tool for whatever material you are drilling into. A standard HSS drill will not cut into hardened steel. You need carbide. What are you trying to do?

Tim *PloughNman* Daley(MI)
 

Right now, I'm making a bracket for holding the jack on my rake.

I cut pieces out of a scrap, 1/4" thick, plough tip; and I fabricated (welded them) to make the bracket. Now I need to put two holes through each side of the bracket and two mating holes on each side of the rake frame. That's a total of eight holes. I'd like to use 3/8" bolts.

If I don't have the right bit, I'll be there forever.

I have a fully functioning wood shop at home...and I have all sorts of bits (forstner, twist, spurred augur, brad, etc) for making nnice holes in wood. For metal, I usually just buy a bit for the task at hand and toss it out when I'm done.

I was just wondering if there was a better way than burning through HSS and/or cheap cobalt/titanium "metal" drilling bits from big box stores.

As a side note...OK...It's overkill...my jack bracket is heavier than the rake frame :) But the old plough tip was just the perfect size piece of scrap for this job.
 
Also, I'm using high quality drills. I have a craftsman drill press and/or a high power, variable speed, 1/2" chuck electric hand drill that I would use for this task.

There's no way that I'm getting the rake frame on a drill press, but I can drill pilot holes and hold good, steady pressure and positioning with the hand drill. It has the T attachment for both handed operation.
 
I also have an "acetylene drill", but the holes would look sloppy, and I don't really want to heat the rake frame. I bought it used a couple of years ago, and someone has already torched, welded, broken, patched and broken this frame many times in its lifetime.
 
There is a couple of trick to drilling metal.
#1 low RPM and good down pressure.
#2 a good coating oil.

I have bits that are decades old that I use all the time. Yes I have sharpen them many times over the years and do so on my bench grinder with no special tools other then simple know how. My largest bit is 1 inch. Also for big holes start small and slowly work you way up
 
What is plough tip? If it is a wear point on a plow it is hardened steel that will be very hard to drill. Most bits are for mild steel. Cast iron is soft & easy to drill.
 
Depending on the rake some of those have some pretty hard steel in them that can be very hard to drill a hole in even with the high $$ drill bit. One example of a real hard piece of steel to drill a hole is is a T-post
 
It sounds more like the bits are sharpened at the wrong angle. The only time I have issues drilling metal is drilling stainless steel. I always buy the cheapest bits I can find.
 
if its a plow point, like the other guys said, its a tough alloy. i have a few drill bits here at the shop for boron steel, some body panels on cars are made from it and its next to impossible to drill without a specialty bit. these are a tungsten alloy, they are real spendy. very slow speed, lots of cutting oil and they go right thru. i have 8 and 10 mm bits.
poke here
 
Use a torch to blow hole smaller than what you need, take a heavy punch and stretch the hole to the desired size while it is red hot, clean up with a small grinder and it will look like a drilled hole.

Pete
 
Go down to Sears and get the best set they have. Don't know what they are made of but they are very hard and very sharp. Only problem I have had with them is breaking them when I get them in a bind.(My Fault). There has been nothing that I have not been able to drill through and the edge stays sharp.
 
Buy a good grade of drills and use them properly with a good lubricant. Most variable speed drills are too fast for drilling hard steel. Then learn to sharpen your own drills. It only takes a little practice.
 
(quoted from post at 12:11:21 07/05/17) Use a torch to blow hole smaller than what you need, take a heavy punch and stretch the hole to the desired size while it is red hot, clean up with a small grinder and it will look like a drilled hole.

Pete

That's an idea that I didn't think of to get a clean hole with the torch!
 

Yes, what I was calling a "plough tip" is the replaceable "wear point" that you mention.

I'm also a little baffled about another comment...not yours...about cast iron being soft and easy to drill.

The rockwell hardness on cast iron is something like 86. It's similar to stainless steel in that respect. I've never had any luck at all with drilling cast iron.

Although, probably the absolute worst metal that I've ever tried to drill is the big hunk of spring steel under a ford 640 seat. I put a little divot in it after a couple of minutes and just decided that I didn't need to move the seat bucket that badly.
 
If you have a steel supplier go buy their store as they usually sell tools, ie drill bits. Bought a set a few years ago and they are still going strong. Best I ever had, including all best ones at Lowes or Home Depot. My theory is, they sell steel, they know steel and they want to make their steel customers happy so they sell good tools.
 

That makes sense to me Glen. I'll check the welding supply shop the next time I'm there to get tanks filled. I don't have a regular steel supplier. I'm always working with old equipment and scrap pieces. If I need exact little pieces, I (don't judge me) just grab pieces of metal at TSC or one of the big box construction stores.
 
Next time you buy drill bits buy a flat file too. Cast iron, cast gray iron, and ductile or nodular iron
drill pretty easy. DUCTILE was sometimes referred to as "Semi-steel" and drills a little tougher. But
gray iron has lots of carbon strings or flakes in the metal, drills fine dry, no oil. Chips should be
small and short, almost like wood chips. Ductile iron can have slightly longer chips, almost like steel.
Sharp bit and medium rpm you should be able to push a hole through cast iron very easily. Now Chilled iron
is harder than the hubs of hades. Don't even try drilling it. White iron is another name for chilled iron.
If a good sharp file will not bite into a piece of steel or cast iron you will not be able to drill it,
don't even try, you will just burn up the bit.
 

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