horrible outcome when drilling metal tube

[Lanso]

I agree with those who suggested a step drill - I’ve put many 1/2” holes in steel tubes with very little burr.

 

[chip-load]

In addition to that, pretty sure they don't make a 3/8" diameter annular cutter that would make it through that tube in one shot. (edit . . .)

As we all agree the setup and drilling environment is miserable. It is so obvious I didn’t feel it necessary to mention that in my reply. But it is the reason for my recommendation. The rotabroach has a small pilot drill which will locate the peripheral teeth as the teeth engage. Yes, even though it is wobbling; at a low rpm the pilot serves for the tool to track quite well. It’s the only tool that will. We all saw the drill freeze up and the belt slip! Obviously, too much bite (feed rate, or chip load) for the existing, miserable, conditions. Because of the many teeth on the rotabroach the chip-load is drastically less than a 2 flute drill! The feed rate is far less. Most importantly, the “feel” of the cut is magnified and an inexperienced operator can react quicker to a tooth “catching”. The hole breakthrough occurs with a smaller tooth with less chip-load!

Yes, the correct size is available. My post had a link to the Blair Rotabroach and I have added it here again. If you look at the spec it specifies the maximum DOC is ¼”. That is referring to the thickness of the wall (in this case) and not the total travel. The tool will quite easily drill through both sides from one direction. See p/n 11108-3 for a 3/8” hole.

The step-drill suggestion is a good one and usually will save a poor situation. However, I have seen a dull drill leave a burr and it also suffers from having no pilot to guide it (or react to) the wobbling environment.

 

[eKretz]

As we all agree the setup and drilling environment is miserable. It is so obvious I didn’t feel it necessary to mention that in my reply. But it is the reason for my recommendation. The rotabroach has a small pilot drill which will locate the peripheral teeth as the teeth engage. Yes, even though it is wobbling; at a low rpm the pilot serves for the tool to track quite well. It’s the only tool that will. We all saw the drill freeze up and the belt slip! Obviously, too much bite (feed rate, or chip load) for the existing, miserable, conditions. Because of the many teeth on the rotabroach the chip-load is drastically less than a 2 flute drill! The feed rate is far less. Most importantly, the “feel” of the cut is magnified and an inexperienced operator can react quicker to a tooth “catching”. The hole breakthrough occurs with a smaller tooth with less chip-load!

Yes, the correct size is available. My post had a link to the Blair Rotabroach and I have added it here again. If you look at the spec it specifies the maximum DOC is ¼”. That is referring to the thickness of the wall (in this case) and not the total travel. The tool will quite easily drill through both sides from one direction. See p/n 11108-3 for a 3/8” hole.

The step-drill suggestion is a good one and usually will save a poor situation. However, I have seen a dull drill leave a burr and it also suffers from having no pilot to guide it (or react to) the wobbling environment.

Yeah, I'm well aware of all of that fella...At a 3/8" diameter I don't think that a piloted annular cutter will do much if any better than a solid drill. Annular cutters are handy for reducing cutting forces at larger diameters, I honestly don't think it would be of any benefit at all here. I could probably do that hole with a hand drill for crying out loud. And according to your link, the smallest arbor is 3/8" in diameter; if there's any protrusion of the screw holding the pilot drill it won't fit through the hole, and won't make it through from one side anyway. I'd bet the belt slip had nothing to do with the torque required to drill the hole and everything to do with a loose belt.

 

[chip-load]

Thank you for looking up the link.

Yeah, I'm well aware of all of that fella...At a 3/8" diameter I don't think that a piloted annular cutter will do much if any better than a solid drill. Annular cutters are handy for reducing cutting forces at larger diameters

Yes, we agree. They reduce force . . . but it is not only large diameters but all diameters. That is the point. Due to the conditions, less axial force is required.

I honestly don't think it would be of any benefit at all here. I could probably do that hole with a hand drill for crying out loud

Of course, any of us here could do it with our experience . . . and besides, nobody would tolerate such a environment. But we are trying to help someone with less experience.

And according to your link, the smallest arbor is 3/8" in diameter; if there's any protrusion of the screw holding the pilot drill it won't fit through the hole, and won't make it through from one side anyway.

Who on here would allow such an issue. . . .none of my mandrels have a protruding screw.

I'd bet the belt slip had nothing to do with the torque required to drill the hole and everything to do with a loose belt.

Think about what you wrote. What made the too-loose belt stop?

 

[eKretz]

Thank you for looking up the link.


Yes, we agree. They reduce force . . . but it is not only large diameters but all diameters. That is the point. Due to the conditions, less axial force is required.


Of course, any of us here could do it with our experience . . . and besides, nobody would tolerate such a environment. But we are trying to help someone with less experience.


Who on here would allow such an issue. . . .none of my mandrels have a protruding screw.


Think about what you wrote. What made the too-loose belt stop?

*Sigh* okay then, carry on.

@plastikdreams:

 

[JST]

Ow.... that hurt.......

Lessee....

RPM slow, feed too heavy, chuck not tight, drill press needs some wedges so it sits steady on the floor. Something is "out" with the chuck, maybe, at least the first drill was waving around like wheat in a tornado.

Slow with heavy feed does indeed make for jams. So does drilling in a thin tube, it's the way the drill breaks through the back side of the hole. More RPM and less feed at breakthrough does indeed reduce burrs, and stops jamups

I agree with the suggestion to use a step drill. The are made for thin material, and don't tend to jam up. You cannot drill through tube in one shot, but 8 minutes a hole is just punishment.

There is " surface speed"/ "cutting speed" / "SFM", measured in feet per minute as if the outer diameter of the cutter was rolling along the material. It lets you figure the RPM you need to get best performance of holes per hour, etc.

For mild steel, which I take it that stuff is, 100 SFM is good for a regular drill made of High speed Steel. So you want the cutter, in this case a drill, to be turning at a speed to roll 100 feet in a minute.

100 x 12inches/foot is 1200 inches. the diameter of the drill x pi (3.14) is the circumference, but you can just use 3 and it will be close.

So for a 3/8" drill, 3/8 x 3 is 9/8 or 1 1/8", 1.125 inches circumference. That's the distance per turn. So 1200 divided by 1.125 gives the rpm. It turns out to be a bit over 1000 rpm, so you could go a lot faster as far as RPM than what you are doing, if the drill press can stand it. You don't HAVE TO go that fast, but you can without damage to the drill.

Doing that would let you drill faster, avoid having to bear down on the feed, and may help with the burrs, if you let up on feed when breaking through with regular drills.

Using a step drill you might want to go a bit slower, but it still should be fine at maybe 500 rpm.

You will be drilling from each side with a step drill, but if you have a lot of holes to do you can make a quick jig out of wood and a screw or piece of steel rod to locate the previously drilled hole and let you drill exactly opposite it. Drill all the holes in one side, then use the jig to do all the ones on the reverse.

If you are doing just a few, it won't pay you to do that.

I figure you should have got at least 10 holes drilled in the time it took for that video. I probably would have gotten more like 30 done, but my drill press is heavier than yours, and I would not have done the 3 step process.

Oh, yeah.... Lose the gloves, and get a brush instead of the magnet. Gloves are clumsy, they don't protect against sharp chips, and they get caught in machines.. A brush is a lot faster at getting rid of loose chips, and it still orks on brass and aluminum.

And, if your drill press has the usual tiny base, get a piece of 2' x 2' x 3/4" plywood, or a couple of 2 x 4s, and screw the base to that. If the floor is flat it will be a lot more stable, and if the floor isn't, use wedges. You can get wedges at the hardware store that are used when putting in doors. They work well for stuff like the drill press also.

 

[CarbideBob]

Yeah, I'm well aware of all of that fella...At a 3/8" diameter I don't think that a piloted annular cutter will do much if any better than a solid drill. .

The cutting geometry and push at exit on a Rotabroach is very different than a standard drill bit.

 

[henrya]

The OP seems to have disappeared. Could it be t8me to stop beating this horse?

 

[eKretz]

The cutting geometry and push at exit on a Rotabroach is very different than a standard drill bit.

On a large one, sure. Not a whole lot different when there's a pilot drill and not much room between the pilot drill and the annular cutter because it's barely bigger than the pilot... Very minor reduction. With his shaky setup, odds are he'd shatter it without a pilot.

And after looking at that arbor again, it doesn't appear that it will actually go through a 3/8" hole anyway. It says 3/8" shank diameter. After the shank that mounts in the chuck, there's a portion that's larger than the shank. So no way to do this from one side all the way through with a 3/8" hole.

 

[CarbideBob]

On a large one, sure. Not a whole lot different when there's a pilot drill and not much room between the pilot drill and the annular cutter because it's barely bigger than the pilot... Very minor reduction.

It acts more like a step drill or plunging endmill at the exit.
Since there is no angle this helps shear the exit without folding over at the edge.
And yes this is a very shaky setup for using such.

There are two exits here. The one on the outside not so hard to deburr.......the one on the inside?
Bob

 

[EmGo]

The one on the outside not so hard to deburr.......the one on the inside?

If it's not too far from the end, three-sided scraper. Plus you can't see all the gouge marks on the inside

If you're crazy, run a dingleberry hone down the tube afterwards, those are cheap and fast.

 

[CarbideBob]

....If you're crazy, run a dingleberry hone down the tube afterwards, those are cheap and fast.

Seen that tried and it seems like a good idea. However often it just folds some of the burr back inside the hole.
Different drill point angles and point grind types act in all sorts of ways on exit burrs.
It is a rabbit hole.
Bob

 

[EmGo]

Seen that tried and it seems like a good idea. However often it just folds some of the burr back inside the hole.

I meant run the dingleberry thru after you deburred with the three-sided scraper but ja, tubing is often made out of some really nasty stuff to deburr.

How about thermal ? Put it in an explosive atmosphere and light it off. Even if it didn't work well, that would be fun

 

[eKretz]

I meant run the dingleberry thru after you deburred with the three-sided scraper but ja, tubing is often made out of some really nasty stuff to deburr.

How about thermal ? Put it in an explosive atmosphere and light it off. Even if it didn't work well, that would be fun

Actually, I have torch deburred a few times, works pretty well. Guessing OP doesn't have one though. Not sure I'd want him trying it either way... Though I bet you'd watch.

 

[fciron]

Can we change the title to “Horrible outcome when asking question on forum”?

 

[EmGo]

Can we change the title to “Horrible outcome when asking question on forum”?

Why ? He got a whole bunch of different approaches to try, some of them will probably work for him.

How is that a horrible outcome ?

 

[CarbideBob]

Why ? He got a whole bunch of different approaches to try, some of them will probably work for him.
How is that a horrible outcome ?

The OP got a whole lot of "use a better machine, it wobbles too much, fixture not rigid" .
These 100 percent wrong and clueless on drill exit burr formation.
Sad to see this here.
Bob

 

[eKretz]

The OP got a whole lot of "use a better machine, it wobbles too much, fixture not rigid" .
These 100 percent wrong and clueless on drill exit burr formation.
Sad to see this here.
Bob

He got plenty of good advice in addition to that. Nor was pointing that out wrong. He doesn't seem to know any better; should everyone just ignore that shaky mess and not let him know so he can't improve his setup in the future? That's constructive criticism in my book. Besides that it's a public forum, not a babysitting club... One ought to expect that on the Internet. Just the way it is.

Not sure what you are meaning about drill exit burr formation... Yes it's normal to get a burr, but not like he's describing - a burr that's basically cold-formed and thick as hell where he can't even bend them with pliers. That is a dull tooling problem in my experience.

 

[fciron]

Why ? He got a whole bunch of different approaches to try, some of them will probably work for him.

How is that a horrible outcome ?

He also got two pages of a people arguing over stuff unrelated to his question.

I just can’t help myself. I have this crazy dream where people on the internet act right for a change.

 

[EmGo]

He also got two pages of a people arguing over stuff unrelated to his question.

Oh, the poor baby. Let's start a gofundme for people who have to put up with unrelated arguments when they ask for free info on how to solve a problem.