# What type of drill bit



## Mike8623 (Apr 25, 2021)

I'm looking to drill a hole thru a tube I've made. The hole will be off center and I'd like the hole on the other side to be as close as possible to the one on the starting side as possible. I could use a center drill to start but it's doesn't have enough length to do the other side.

Is there a type of drill bit that is rigid like a center drill but same diameter to length.  The tube diam. is 1/2"


----------



## matthewsx (Apr 25, 2021)

Carbide will be stiffer. If you're drilling across tubing and want the hole to be accurate start smaller than you need and step up.

John


----------



## projectnut (Apr 25, 2021)

They do make extra long center drills.  I'm not sure what size you need, but KEO makes several between 4" and 6" long.  If you use a center drill you're going to need to peck drill the hole.  A typical center drill only has a flute one spiral long.  If you don't retract and clean the swarf out regularly it will pack in, break the drill, and possibly ruin the hole.


----------



## Mike8623 (Apr 25, 2021)

#2


----------



## mikey (Apr 25, 2021)

A D-bit or gun drill might work but you have to remember that once you get beyond about 4:1 depth to diameter, deflection will become a real issue and a carbide drill might be necessary.


----------



## Mike8623 (Apr 25, 2021)

The shoulders on the tube are 1/16" . What speed would you use on the carbide drill


----------



## Aukai (Apr 25, 2021)

This is my over thinking, but do you have the right diameter center cutting end mill? Any drill bit to drill a hole in 1/2" tubing off center will want to walk I would think.


----------



## Mike8623 (Apr 25, 2021)

Yah the walking is my problem


----------



## Aukai (Apr 25, 2021)

That's why I was thinking end mill. If you can locate the hole from both outsides, make a flat with the end mill first, then drill. If you have the correct size of end mill for the hole, can it go all the way through?


----------



## Mitch Alsup (Apr 25, 2021)

Joe Pieczynski has a video on drilling a long hole through a part.

It starts out drilling about 4 hole diameters deep with an undersized drill
then you chase it to size with a reamer
then you drill another 4-6 hole diameters with a properly sized drill,
chase it with a reamer,
and on, and on and on.

He drilled a 4" long hunk of aluminum with 1/4" (±) hole and the far end ended up without wander.
The reamer allows the flutes of the drill to have something supporting them that they will not cut preventing wander.


----------



## mikey (Apr 25, 2021)

Mike, I'm having trouble visualizing what you're trying to do here. You mentioned that you made a tube with an off center hole. So, you have something solid chucked up in a 4-jaw that is offset to bring the center of the proposed hole onto the spindle centerline, is that right? Now you need to drill a hole to turn that solid thing into a tube?


----------



## extropic (Apr 25, 2021)

How to ask a comprehensive question:

I want to machine a hole completely through a (SPECIFY MATERIAL) tube with 1/2" OD and 1/16" wall.
The finished hole diameter is to be (SPECIFY DIAMETER AND TOLERANCE).
The hole center is perpendicular to the tube axis and located (SPECIFY DIMENSION) from the edge of the tube (or from center of the tube).
My problem is that the hole enters the workpiece on a sloped surface.
What cutting tool should I use to create this hole?


----------



## Mike8623 (Apr 25, 2021)

What I did was turn down a piece of round bar stock to 1/2 inch in my lathe. The piece is 5 inches long. I drilled it out thru and thru so I have a 1/16 shoulder. I then indicated a centerline on the work using the tip of my cutting tool.

I then put it in my mill vise and centered the work piece. I need to drill a hole thru the entire piece just above center of the "now tube".


----------



## Mike8623 (Apr 25, 2021)

Come on guys, I dont ask questions the best way  they could be asked and I dont do well on this danged phone anyway....I thought this was the friendly forum, not " Practical Ma......" forum.


----------



## extropic (Apr 25, 2021)

Mike8623 said:


> What I did was turn down a piece of round bar stock to 1/2 inch in my lathe. The piece is 5 inches long. I drilled it out thru and thru so I have a 1/16 shoulder. I then indicated a centerline on the work using the tip of my cutting tool.
> 
> I then put it in my mill vise and centered the work piece. I need to drill a hole thru the entire piece just above center of the "now tube".


WHAT?

Please see reply #12.


----------



## Mike8623 (Apr 25, 2021)

extropic said:


> WHAT?
> 
> Please see reply #12.


Sorry guys, forget I asked the question in the first place


----------



## extropic (Apr 25, 2021)

Mike8623 said:


> Come on guys, I dont ask questions the best way  they could be asked and I dont do well on this danged phone anyway....I thought this was the friendly forum, not " Practical Ma......" forum.



Friendly is our goal.

Clairvoyance . . . not so much.

Help us out by providing an unambiguous description of the situation.


----------



## Flyinfool (Apr 25, 2021)

I dont think anyone here is trying to tell you to go away or that you have a stupid question like you get on some other forums. We are just trying to understand the question so that we can give a good answer.

You described the tube that you have adequately, we need more info on the hole that you want to make as that will change the recommended method of making the hole.

How big is the hole you are making?
How far off center are you making the hole?
What is the material of the tube?


----------



## Mike8623 (Apr 25, 2021)

Thanks to all that replied


----------



## Weldingrod1 (Apr 25, 2021)

Many suggestions:
Start with an end mill to get a flat spot.
Center drill that flat spot.
Do it with an end mill from both sides.
Make an external and internal jig with holes to guide the drill at all four transitions.
Press a plug in the bore and clamp a square sleeve on the od (same material as the tube). Drill through the whole works and Bob's your uncle ;-)

Carbide is much stiffer, but will shatter on the non-uniform cut on the angled surface. HSS is what you want for the drilling tool.

Sent from my SM-G892A using Tapatalk


----------



## Mitch Alsup (Apr 25, 2021)

Mitch Alsup said:


> Joe Pieczynski has a video on drilling a long hole through a part.
> 
> It starts out drilling about 4 hole diameters deep with an undersized drill
> then you chase it to size with a reamer
> ...



Found the video::


----------



## Nutfarmer (Apr 25, 2021)

if you have any number to do I would make a simple fixture. Start with a square piece of stock larger than tube dia. Then drill your cross hole all the way through. Next bore out the hole for the tube and slit one side. If enough material is left on the slit side a simple bolt can be used to clamp the tube in place. The square stock will support the drill so it won't bend and slide all over. Drill one side then flip it over and drill the other side.


----------



## mmcmdl (Apr 25, 2021)

Just send it in to my guys in at work , garrentee the hole would be off center !


----------



## silverhawk (Apr 26, 2021)

Nutfarmer said:


> if you have any number to do I would make a simple fixture. Start with a square piece of stock larger than tube dia. Then drill your cross hole all the way through. Next bore out the hole for the tube and slit one side. If enough material is left on the slit side a simple bolt can be used to clamp the tube in place. The square stock will support the drill so it won't bend and slide all over. Drill one side then flip it over and drill the other side.


If you have a close tolerance on hole placement in cross drilling a bar or tube, I believe this is the easiest way (if you don't have an end mill the right diameter or even a mill, even if only making one part).

Sent from my SM-T500 using Tapatalk


----------



## Mike8623 (Apr 26, 2021)

That tube is what I have been working on. A cutter head for rifling s barrel. That is my 3rd tube. I'm just not satisfied with it.


----------



## Flyinfool (Apr 26, 2021)

If you can get a spotting drill, possibly a center drill, the right size, you may be able to just SLOWLY drill thru. Even that far off center. The other option is to SLOWLY plunge a center cutting end mill of the correct size all the way thru both walls. If the hole must be a precision fit that is not available in a spotting or center drill, then your only option is a fixture that makes the drill think it is going thru solid metal the whole way.

Of course the option above with making a fixture will also work well. But you will need a fixture for both the inside and outside of the tube or the drill will walk.
.


----------



## Aukai (Apr 26, 2021)

You bored/drilled out this tube correct? Spot the holes drill them first, then drill/bore the tube, then no deflection on the inside.


----------



## Mike8623 (Apr 26, 2021)

All of you have been very helpful. I want to thank all of you for helping me out.


----------



## Mike8623 (Apr 26, 2021)

Aukai, I was there 69-70....1st battalion 7th marine regt.


----------



## Flyinfool (Apr 26, 2021)

See, we are not so terrible once we figure out what you are trying to do. Sometimes what is very clear in the questioners head is not so clear to the rest of us, so we ask a lot of questions to get caught up. Sometimes peoples attempts at humor do not translate well thru a keyboard.


----------



## Aukai (Apr 26, 2021)

I was in high school in 69-70, my avatar is in remembrance of my Uncle, USMC.


----------



## Mike8623 (Apr 26, 2021)

Semper-fi


----------



## silverhawk (Apr 26, 2021)

Mike8623 said:


> That tube is what I have been working on. A cutter head for rifling s barrel. That is my 3rd tube. I'm just not satisfied with it.


So, my brain is running amok, and that's probably not a good thing. I am curious to know if you are using plans to make this rifling head (or cutter), or if this is a home design. I would like to know more about your project.

Sent from my SM-T500 using Tapatalk


----------



## Mike8623 (Apr 26, 2021)

About 4 months ago I bought a well made rifling and boring machine. It has been in my garage on a trailer waiting for the snow to melt enough to get it in my shop.

I intend to make a few rifle barrels. I will buy a gun drill, but will make the reamer and cut rifling head as laid out in Charles Moore book, "Steel Helix". The rifling head/cutter is coming along and I will start the reamer shortly. Moore gives you enough info to figure it all out as it relates to each specific caliber.

I went to gunsmithing school for 4 straight years back in the early 90s after retiring from my 1st job. But then life got in the way and I started my second career until medical problems put a stop to it. My wife and I bought some land in Montana moved and built a house. I now do gunsmithing in a very small town of about 400 people. I dont charge because most of these folks are working 2-3 jobs and barely making it.


----------

