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horrible outcome when drilling metal tube

iowaguy

Plastic
Joined
Nov 9, 2006
Location
Iowa
I have been trying to figure out how to drill holes through round 1" ERW (11 gauge). Each time I drill, the hole that comes out the far
side of the tube has 'ridges' (I'm not sure of the term) when the bit exits. I've included some photos of the exit hole.

I am using a drill press. I apply a good amount of drilling coolant/oil and clean off the drilling shavings every 15 or 20 seconds of drilling.

I tried to delete the last photo (on the right). That is the inside of the entrance hole and it didn't get 'cleaned' out. I'll save that issue for later...if I can figure out the exit hole problem.

Would you have any suggestions on how can improve this so the outside of the exit hole is smooth?

Thanks.
 

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plastikdreams

Diamond
Joined
May 31, 2011
Location
upstate nj
That's called a burr...hence the term deburring. A file or grinder will take care of it. There are specialty tools made to deal with that too.

Nature of the beast.
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
For the method and tooling you're using, that's not bad. Clean up the burr with a small 1/2 round file, or try a ~120* countersink at the slowest speed your drill press can do.

[Ninja'd by the Dreamer]
 

iowaguy

Plastic
Joined
Nov 9, 2006
Location
Iowa
or try a ~120* countersink at the slowest speed your drill press can do.

[Ninja'd by the Dreamer]

I just looked up 120 degree countersinks at McMaster Carr. They all said they were for rivets. Are those the type of countersinks you were referring to?

I've tried using a file, but I end up marring the tube a bit when I try to file the burr down.
 

Booze Daily

Titanium
Joined
Sep 18, 2015
Location
Ohio
They make drill bits like those spade drill for wood, except they’re for metal.
They have a pointy tip and then are flat. You want that flat to pop a disc out instead of smooshing thru with a traditional drill.
You could try drilling small then swapping to an endmill if it’s not too much pita.
 

J_R_Thiele

Stainless
Joined
Jan 22, 2003
Location
Columbia Missouri
If you have the time...

Clamp a vice so the pipe is centered where you want it,

Drill a smaller hole (say 1/8) through both sides.

Change to larger drill and drill through top hole.

Put a 1/8 in dowel pin in drill.

Rotate pipe so bottom hole is on top and lower dowel pin into hole and clamp pipe in vice.

Replace dowel pin with larger drill and drill out hole.



The faster way: use a step drill for drilling the larger hole, having selected the smaller drill diameter to be a diameter the step drill cuts.
 

iowaguy

Plastic
Joined
Nov 9, 2006
Location
Iowa
You could try drilling small then swapping to an endmill if it’s not too much pita.

I have tried drilling small to larger (1/8" center drill bit into the entrance side, then go to a 1/4" bit through both walls, then a 3/8" bit through both walls). I used an end mill but it bounces all over.

They make drill bits like those spade drill for wood, except they’re for metal.
They have a pointy tip and then are flat. You want that flat to pop a disc out instead of smooshing thru with a traditional drill.


Can you send me a picture or link to the bits that have a pointy tip and then are flat? I am not familiar with those.
 

iowaguy

Plastic
Joined
Nov 9, 2006
Location
Iowa
I have one of those but some of the burs are so thick that I can even bend them off with pliers. The work well with a light ridge around the hole perimeter.

Would these burs be caused by poorly clamped material? I thought I had everything clamped to the hilt.
 

iowaguy

Plastic
Joined
Nov 9, 2006
Location
Iowa
If you have the time...

Clamp a vice so the pipe is centered where you want it,

Drill a smaller hole (say 1/8) through both sides.

Change to larger drill and drill through top hole.

Put a 1/8 in dowel pin in drill.

Rotate pipe so bottom hole is on top and lower dowel pin into hole and clamp pipe in vice.

Replace dowel pin with larger drill and drill out hole.

That flipping over techinque is definitely worth a try. I spend 25 minutes drilling through the tube as it is.



If you have the time...



The faster way: use a step drill for drilling the larger hole, having selected the smaller drill diameter to be a diameter the step drill cuts.

I am not quite comprehending the above suggestion. Are you saying that I could drill 1/8" all the way through then using the step drill to drill to the larger size (3/8") on each side?

Also, I am using 135 degree bits. Should I be using something different?
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
I just looked up 120 degree countersinks at McMaster Carr. They all said they were for rivets. Are those the type of countersinks you were referring to?

I've tried using a file, but I end up marring the tube a bit when I try to file the burr down.

The listing by McM is valid for use with shallow angle rivets, but they're also used when you want a wide angle countersunk. The wide angle means you don't have to press down as far on a surface to remove all the burr.

Be aware that as the countersink "rides" the edge of the hole it will move up and down as it follows the "saddle" of hole/tube OD. Ideally the spindle speed is very slow to make this easier, like 100rpm or so.

If the drill press won't go that slow sometimes you're better off using a battery powered hand drill at low speed for the task.
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
One other drilling method you can try is to go through the tube completely with a drill about 12% smaller than your final size, then drill with the final size through each side independently. This will push both burrs to the inside of the tube, where you can "ream" them out with a drill to match the tube ID.

The second/third drilling operation can sometime lead to grabbing, you can mitigate this by "dubbing" the edges of the drill bit with a grinding wheel. Search Youtube for examples of drill dubbing to see how it's done.

135 degree split point cobalt drills are a good choice for this work, just don't let the bit grab and shatter from the torque spike. Cobalt drills are usually more brittle than regular HSS drills.
 

L Vanice

Diamond
Joined
Feb 8, 2006
Location
Fort Wayne, IN
I have one of those but some of the burs are so thick that I can even bend them off with pliers. The work well with a light ridge around the hole perimeter.

Would these burs be caused by poorly clamped material? I thought I had everything clamped to the hilt.

First, you are trying to machine a type of steel that is meant for forming and has a low machinability rating. In other words, it is difficult to machine. It can be punched cleanly with the proper, but expensive, equipment.

Second, you are trying to drill through cylindrical surfaces with a tool that wants to drill through perpendicular flat surfaces.

Lastly, I suspect you have not selected a drill bit that has a chance of doing what you want, as evidenced by the pictured results.

So I will point you to a readily available drill bit that has at least a chance of making relatively clean 3/8" holes through 1" round steel tubing. They are called DeWalt Pilot Point. These bits have a split point for easy starting on curved surfaces and a very sharp shoulder at the outer diameter that will leave a minimal bur if the speed and feed is optimized. Think of it as drilling first with a small bit and then with the size you want, but only using one bit. Cutting oil will help slow down dulling of the bit. They make these bits in cobalt alloy at a higher cost and longer life. You can buy the 3/8" bits by themselves, but the sets are a better buy.

DEWALT Titanium Drill Bit Set, Pilot Point, 21-Piece (DW1361) - Jobber Drill Bits - Amazon.com
DEWALT Cobalt Drill Bit Set with Pilot Point, 14-Piece (DWA1240) - - Amazon.com
Amazon.com: DEWALT Drill Bit, Pilot Point, Industrial Cobalt, 3/8-Inch (DWA1224) : Everything Else

Of course, a bit that leaves less burr on the outside of the tubing will also leave less burr on the inside.

Larry

41flaRMcTBL._AC_SL1050_.jpg


Larry
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
If you're getting burrs that you can't bend with pliers you probably need to sharpen your drill. What speed are you running the drill? If you're going way too fast you will be dulling even a new one almost instantly. If you took 25 minutes to do one hole, something is very very wrong. Drilling that hole should take no more than a minute.
 

dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
One other method that would reduce primary burr formation would be to bore a hole in steel bar (round or rectangular) matching the OD of the tube. Drill a cross hole matching the one you want in the tube through the bar and split it. (If splitting it would be difficult for your setup, clamp or tack weld two flat bars together and bore down the center split line) Clamp the tube in your fixture and now you have a guided entry which is a plus and the exit hole will have very little burr. If you intend to do a large number of holes, a drill bushing in the entry hole will be a good idea.

A round file will make a neater job of deburring the exit hole than will a countersink since the countersink will want to elongate the hole.

Denis
 

GregSY

Diamond
Joined
Jan 1, 2005
Location
Houston
I've actually been drilling tube this week, and have similar burrs. Only, it didn't bother me....just knocked them off with a belt sander.

If I didn't want the burrs for some reason...I'd mill the holes. But that's a lot of work as compared to the drill bit/belt sander.
 








 
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