Radial hole in bar technique

[mattg]

Hello all
I need to drill a number of holes radially into bar and tube.
What is the best way to accurately mark the centre of the bar? Any tips for making sure two radial holes are perpendicular?
Maybe Im missing something obvious, but my holes always seem to come out off centre, and trying to measure it out with callipers just seems the wrong method!
Thanks
Matt

 

[Shox Dr]

Are these to be drilled Freehand or drill press etc

 

[Welderpaul]

You need a pipe square. Like a standard engineers square, but it gives a 45 degree angle. Put in on the end of the bar, scribe the line, then turn it approx 90 degrees to the first line and scribe again.
Where the two scribe lines intersect is the centre.

A lathe is the way, no need to mark the centres, just chuck it up and drill.

 

[astro_al]

Paul, i think his holes are to be radial, you are describing axial holes. I think? Al

 

[knoba]

If you mean down the length of the bar here is the method I use (if you have a drill press and some v blocks);

* Place V block on drill table
* Lower quill on to V block until the chuck centres it
* Clamp V block to table
* Put drill bit in chuck and set depth stop
* Material in v block and drill away. Centred every-time!



(if using pilot drills or under 4mm in dia. keep the drill bits lead real short.)

Cheap home made v blocks here

 

[Delgado]

If I'm understanding you right? It'll be hard to do freehand, one way with a drill press is to mark a centre line up the outside of the tube/bar with a bit of angle, mark where you want the holes, put it in a machine vise and measure from the jaws to the centreline untill it is perfectly inbetween the two(centred). Then clamp both the tube/bar nice and tight, and the machine vise to the drill bed, and drill right through.

 

[mattg]

Yes, its by drill press.
V block idea sounds like a plan, and the marking with a bit of angle sounds good.
What about getting a second hole in perpendicular to the first?
Thanks!

 

[Welderpaul]

Oops. Only just got up, still half asleep

As above, sitting the round in the right sized piece on angle, then scribing along the edge of the angle is quick and fairly accurate.

 

[Hitch]

If the holes are through both walls of the tube, put a close fitting pin through, drop into the vee blocks, then use a couple of matching thickness shims between the machine table and pin.

 

[Delgado]

Yes, its by drill press.
V block idea sounds like a plan, and the marking with a bit of angle sounds good.
What about getting a second hole in perpendicular to the first?
Thanks!

Depending on the size of the bar/tube, if it's a small OD i'd just drill straight through, if not measure the circumference with a soft tape, half it, measure from first scribed line and mark again with angle.

 

[mattg]

Thanks chaps, v. helpful!

 

[knoba]

I love this forum! I might go out and do some perpendicular axially centred holes just for the shear hell of it...

 

[Highpower]

These work pretty well to find the center quickly. http://www.amazon.com/Center-Finder-Gage-Quality-Import/dp/B000U7R5II/ref=sr_1_20?ie=UTF8&qid=1295327462&sr=8-20

Put the gauge in your drill chuck and lower the quill over your round stock. Align the marks on the gauge then clamp your work down. Replace the gauge with your drill bit and go to work. I like Hitch's idea for locating a perpendicular hole.

 

[Shox Dr]

Do you have a lathe. If so there is is tool you place in the tailstock with a V perpendicular to the axis. Enabling the bar to be held while a drill bit is spun in the chuck

TGD Tools sell them

 

[Pete.]

That's called a crotch center.

If you have a drill press and nothing else then measure the OD of the tube, then put a 10mm bar in the chuck and set a stop away from the bar the radius of the tube less 5mm. The stop must be at least as tall as the radius of the tube.

 

[fluxcored]

If I'm understanding you right? It'll be hard to do freehand, one way with a drill press is to mark a centre line up the outside of the tube/bar with a bit of angle, mark where you want the holes, put it in a machine vise and measure from the jaws to the centreline untill it is perfectly inbetween the two(centred). Then clamp both the tube/bar nice and tight, and the machine vise to the drill bed, and drill right through.

I mostly use Delgado's method but I only drill straight through the other side with drills 5mm and above for a perpendicular hole.

For interest, Popular Science has a very nice article in the public domain for indexing round tube or rod without expensive dividing heads or rotary tables. It is titled "Family Secrets from an old-time machine shop" in the January 1967 issue. Enjoy!

 

[Shox Dr]

It's called a Plain of bend, (POB) they are used in Tube Bending

 

[RedOrZed]

I mostly use Delgado's method but I only drill straight through the other side with drills 5mm and above for a perpendicular hole.

For interest, Popular Science has a very nice article in the public domain for indexing round tube or rod without expensive dividing heads or rotary tables. It is titled "Family Secrets from an old-time machine shop" in the January 1967 issue. Enjoy!

Cheers!