Tips for drilling metal

[General Geoff]

Never any need for a pilot drills that go's all the way through the piece of metal.

I would love to have you available to do this black magic of drilling a 1/2" or larger hole through a broken bolt without stepping up from a smaller hole. Every time I've tried it, the large bit just spins on top of the metal, not actually cutting. No matter how much force or how fast or slow I go, even with brand new and sharp cobalt bits. I could be putting 100 lbs of pressure on the drill and it'll just spin on top of the metal.

Chuck up a 1/8" bit and drill a pilot hole? It'll go through no problem, with a moderate amount of force applied. I've found the most effective way is to incrementally drill it out, 1/8" larger at a time.

 

[cherrybomb]

Amen,General Geoff,except I am a believer in lefts for broken bolt removal.

 

[Sugarfryz]

I did convince my snap on Msn to let me trade in my right hand extractor set, for the left hand extractor set. So that'll be nice when i need the drill

 

[6PTsocket]

I would love to have you available to do this black magic of drilling a 1/2" or larger hole through a broken bolt without stepping up from a smaller hole. Every time I've tried it, the large bit just spins on top of the metal, not actually cutting. No matter how much force or how fast or slow I go, even with brand new and sharp cobalt bits. I could be putting 100 lbs of pressure on the drill and it'll just spin on top of the metal.

Chuck up a 1/8" bit and drill a pilot hole? It'll go through no problem, with a moderate amount of force applied. I've found the most effective way is to incrementally drill it out, 1/8" larger at a time.

The little chisel tip on the bit does not really cut so the big bit spins. With a pilot hole. The two cutting edges on the bit have something to bite into so the bit cuts. Just look at the end of a big bit and you will see what I mean. Going in more steps is not always necessary but it does make cutting easier because you are removing less metal at a time so it is less stress on the drill and the bit. The correct lubricant and drill speed also help a lot. Whenever possible, I use the drill press, for better control of the work and the speed.

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[6PTsocket]

Amen,General Geoff,except I am a believer in lefts for broken bolt removal.

The idea behind lefts is not to screw the broken stub in tighter and is helpful if the broken stub is not frozen in there. I find it is usually stuck so badly that it makes no difference. I drill my pilot hole and use the extractor of my choice. I have had good luck with the Alden Grabit bits, that are an extractor on one end and a pilot drill on the other. They only need a very shallow dimple for the extractor end to grab. Both jobe are done with a drill in reverse. I have seen these extractors under other names, too

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[FMC1959]

For drilling lube, I had seen some recommendations for Boelube, and it works great.
https://m.mscdirect.com/mobileweb/product_detail?id=61232534

For drill bits, I have many HSS and a couple of Cobalt sets. With the toughest steels, I use Norseman (HSS/MolyB), they cut when others don't. Here are some cutting tips they have.

http://www.norsemandrill.com/feeds-speeds-drill.php

http://www.norsemandrill.com/drill-troubleshooting.php

 

[Michael_in_DE]

I have a drill doctor I got cheap and it is just TOO EASY to keep bits sharp. It's amazing the difference after they have been properly sharpened. On a tough job it would actually be faster to sharpen it halfway through the job and they try and force a dull bit.

But don't take my word for it:

 

[Sugarfryz]

So I’ve gotten much better at drilling metal since reading this tread. I’ve actually gotten consistent results with drilling. I’m able to get huge chunks of metal coming out and quite often even the huge spirals. Now my boss saw me drilling and when I stepped up to a larger size bit, i messed up a few times and spun the drill when it caught.

He comes up to me saying I’m drilling to slow, I don’t need to put any downforce and let the bit do the work. So he shows me, puts my drill on high speed puts my 7/16 bit in, used no downforce and is just getting like metal dust and it’s making that horrible chirping sound, eventually it drilled through tho.

I mean he’s completely wrong right? Went against everything I heard about drilling. Our master tech came over and confirmed he was doing it right.

 

[Sugarfryz]

So I’ve gotten much better at drilling metal since reading this tread. I’ve actually gotten consistent results with drilling. I’m able to get huge chunks of metal coming out and quite often even the huge spirals. Now my boss saw me drilling and when I stepped up to a larger size bit, i messed up a few times and spun the drill when it caught.

He comes up to me saying I’m drilling to slow, I don’t need to put any downforce and let the bit do the work. So he shows me, puts my drill on high speed puts my 7/16 bit in, used no downforce and is just getting like metal dust and it’s making that horrible chirping sound, eventually it drilled through tho.

I mean he’s completely wrong right? Went against everything I heard about drilling. Our master tech came over and confirmed he was doing it right.

 

[Dingleburry]

Im going to say yes. They are both wrong.
He must of taught your "master tech"
If its not cutting... whats it doing?
You want a smooth uminterrupted cut.
Think of how a lathe cuts.

 

[WittHay]

We always used 1/2" drills when drilling truck frames or the outside rails of flatbed trailers. they run at around 550 rpm. You apply moderate pressure. If you use a high speed 3/8 drill with no pressure, its not gonna work

Recently mounted a large vise to a 3/4" thick metal table. Used a Milwaukee 1/2 cordless set at the slowest speed which is around 550 rpm. Drilled through it no problem

 

[hangfirew8]

So I’ve gotten much better at drilling metal since reading this tread. I’ve actually gotten consistent results with drilling. I’m able to get huge chunks of metal coming out and quite often even the huge spirals. Now my boss saw me drilling and when I stepped up to a larger size bit, i messed up a few times and spun the drill when it caught.

He comes up to me saying I’m drilling to slow, I don’t need to put any downforce and let the bit do the work. So he shows me, puts my drill on high speed puts my 7/16 bit in, used no downforce and is just getting like metal dust and it’s making that horrible chirping sound, eventually it drilled through tho.

I mean he’s completely wrong right? Went against everything I heard about drilling. Our master tech came over and confirmed he was doing it right.

Small bits are spun fast. Large bits are spun slow. Every combination of size, drill bit type, and material have an ideal speed/pressure (feed rate). Experienced guys will find that ideal rate by feel. You'll know you have it when the two long continuous spirals of swarf coming spinning out. Then stay on it at the speed/pressure.

Keep all those broken bits if they have the least amount of fluting on them. Sharpen them, or have them sharpened, and then you'll have short bits for those tight spots. I combine them with an angle air drill and if I can get to it, I can drill it.

Another tip, if you're drilling out a broken bolt with a jagged head, keep some mounted stones and use the air die grinder to make a place to drill. Use a cylinder stone to make a trough. Then a small round stone to make a dent in the middle. Then drill away.

 

[seber]

Drilling holes is part of my steady paycheck! You must not be using good bits!

Also motor oil is not a good lube for drilling. You are suppose to have metal on metal contact. The motor oil gets in the way.

Here is what a manufacturer actually has to say.
http://www.vikingdrill.com/viking-Drill-Troubleshooting.php
I believe CoyoteKyle is just trolling. Funny stuff.

 

[jonesg]

Originally Posted by ez-duzit View Post
Use a center drill, first, to drill a pilot hole.


Of course you center punch.

The advantage of the center drill for creating the pilot hole is that it is extremely rigid, for the size of the pilot hole, unlike an equivalent diameter drill bit, and so is highly unlikely to snap under pressure.

The very tip of a centering bit can snap off.
If it's allowed to drill beyond the shoulder.
The shank is thick to prevent wandering.
The flutes are designed to steer the bit toward the centerline of the spindle or chuck.

 

[pstemari]

The very tip of a centering bit can snap off.
If it's allowed to drill beyond the shoulder.
The shank is thick to prevent wandering.
The flutes are designed to steer the bit toward the centerline of the spindle or chuck.

The flutes on a center drill are designed to match the angle of a lathe center. The little pilot is there to ensure clearance for the tip of the center—without it, you would have problems if the center was pointier than the hole.

Actual spotting drills don't have a pilot, but you don't want to sink them in past the edge because that would leave the main drill bearing on a narrow edge, not the conical face.



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[BFHtime]

Default Re: cobalt high speed drill bits
I have found that drilling hard items works better with slow speeds, and plenty of cooling. Cooling with cutting oil or just about any spray lube, or even used oil. Thicker oils have a tendency to pull the chips away, assembly lube for example. Fast enough not to stall is, is fast enough, anything more with increase friction. Keep steady pressure, while applying plenty of cooling cutting oil.

This thread made me look up a previous post.

I have a pretty good amount of experience breaking bolts, as I used to He-Man everything so tight I would often break stuff, until I got some nice torque wrenches. Now I have a better feel when tightening.

With my many broken bolts, I have found the best extractors to be left hand drill bits, for getting the bolt out. I have many types of extractors, each requires skill will each particular tool type. Some are good for certain situations, but left hand drills are best imo.

Slow speed and enough pressure to slow down the speed of the drill. It does require feel. I put pressure while turning the bit slowly, to just not stall the drill. When using a hand drill, slow steady will get you there, and make your bits last. The best lube I have used is engine assembly lube, it keeps the chips from accumulating on the tip, which causes more friction. The engine assembly pull the chips up the flutes. I do start with a small bit and work my way up. Not using every size bit. If you have many sizes, this would be waste of time, wear on the bit, unless what you are drilling is very hard, especially if someone already heat hardened it by drilling. I start with the smallest bit that will support the weight of the drill I am using without flexing like it would break. You learn this after you break enough bits. I try to keep making a steady flow of chips. I wipe and clean the chips away when needed. I also never give up on trying to get the bolt to back out, with left hand drills, if I think there is a reasonable chance it will back out which it usually does. If corroded bad I save the left drills and just use cobalt righties. I drill a through hole to give a place for chips to go.