How do I drill holes straight across a length of pipe?

[sixdogs]

Good stuff here and ideas I never thought of. How about I clamp the angle iron to the pipe and draw a line. Then I leave the angle iron in place and center punch where I want to drill holes. Then I clamp the pipe into a vise on my drill press table and drill the holes. It doesn't seem I would need the flat spot ground off if I did it this way? Sound OK?

 

[Sodo]

Lower the drill bit (motor off) until it touches the scale and if the drill bit is off center, the scale will tilt to one side. Keep trying until when you sandwich the scale between the drill and the pipe, it stays horizontal. And yeah, don't grind a flat on the apparent TDC first. It only works on a curved surface.

The scale would still work, scale being much wider than the flat spot.

The 'flat' that you 'grind' is a tiny ding, about half the size of the drill bit, just enough to keep the bit from sliding off before it bites in. Good stuff here. The scale method sounds like a good way to level things out, for example if you have to drill on thru the opposite side.

 

[chim]

I showed a guy how to do this a couple weeks ago in the shop at work. We have drill presses and drill press vises and that helps.

Mark the locations of the holes with lines across the pipe. Don't bother making X's, just distances from the end of the pipe.

Clamp a piece of angle iron in the vise with the angle in a "V" position.

Put a bit in the chuck and place the clamped angle under it. Lower the bit and move the vise till the bit drops right into the bottom of the V.

Clamp the vise down.

Clamp a piece of scrap steel to the pipe and set a magnetic level on it.

Move the marks under the bit and drill away while keeping the scrap piece level. The holes will be centered and aligned. When my guy did it this way he didn't need to use a center punch.

 

[k0ua]

A lot of these descriptions I sure didn't understand, and I am a pretty handy guy.. But someone please tell me, why once you have a straight line scribed on a pipe and you align that line directly under a drill bit, why when you drill won't all of the holes drilled thru that line, be in a line and be directly thru the center of the pipe. I say they will be as long as you are careful to make sure that the center point of the drill bit is directly on the line.

 

[CalG]

I've used a clamped on a "pendulum" to aligne all the holes on a pipe drilling application. Longer is better, have the pendulum just clear the floor, and hang about a pound on the end to make things easy. A lathe drive dog is ideal , along with a piece of strapping and a vice grip clamp.

Once you have the drill vice set to center the pipe under the drill, the pendulum helps keep everything in a row. A little tough for the first hole if it's near the end of the work, but it's easy enough to shift from position to position.

 

[CalG]

A lot of these descriptions I sure didn't understand, and I am a pretty handy guy.. But someone please tell me, why once you have a straight line scribed on a pipe and you align that line directly under a drill bit, why when you drill won't all of the holes drilled thru that line, be in a line and be directly thru the center of the pipe. I say they will be as long as you are careful to make sure that the center point of the drill bit is directly on the line.

The holes will be aligned if done as you describe. Directly under the drill bit might be the variable. It can be tough to get a drill bit point to "bite" accurately on a round surface.

 

[k0ua]

The holes will be aligned if done as you describe. Directly under the drill bit might be the variable. It can be tough to get a drill bit point to "bite" accurately on a round surface.

I often use an automatic center punch set to a light setting to dimple my line at the measured mark, and then use a very small drill bit to make the initial hole.

 

[Sodo]

... then use a very small drill bit to make the initial hole.

I do that too sometimes :laughing: I break the 3/32 first, then 5/64, then the 7/64 then the 1/16, then after all the small bits are all used up I have to resort to methods without pilot holes.

 

[CalG]

I often use an automatic center punch set to a light setting to dimple my line at the measured mark, and then use a very small drill bit to make the initial hole.

If the work is center punched, but then aligned poorly, the drilling process assures that the exit hole will NOT align with the entrance hole due to the flex in the drill bit.
And if the drill bit is stiff, the hole will be off center.

Alignment under the drill press quill is paramount!

 

[jwmorris]

How precise? You can drill with precision on pipe without a center drill but your setup will be a bit more involved. Also, the angle or your tubing are likely not straight enough for extream accuracy down the length, if using that method.