How do I drill a hole across the diameter of a rod?

[JPMacG]

I need to drill a hole exactly through the diameter of a 1-1/4 inch round brass rod. I have a drill press and a drill press vise, which will hold the rod parallel to the drill press table. How do I accurately locate the hole?

On my first attempt I missed the diameter by about .030 inch. That is, the center line of the hole missed the axis of the cylinder by about .030.

If I had a milling machine or an xy table for the drill press this would be easy, but I don't. I do have a lathe, but I don't see how it would be useful for the task.

 

[Flammable_Solid]

You need to find the highest point of the round bar. Put the bar in the vise. Use some marking fluid, or permanent marker, to help you see what is going on. Put a center drill in your drill press chuck and lightly lower the center drill to make contact at the highest point. Lightly swing the vise side to side to verify that you have found the highest point (it will scrape through the marking on the outside of the OD). Secure the vise to the drill press table. Use the center drill to start your hole and look at the markings to see that you didn't drift off center when securing the vise to the table.

Drill in a bit deeper than you normal would with a center drill so that you can open the hole up to the correct diameter. Don't force the drill into the round bar, as the drill bit can flex and head off course.

Or you could throw the bar in the 4 jaw chuck on your lathe and do almost the same process.

 

[NightWing]

You need a crotch center. Years back I had one. Can't remember if I made it or bought it. Today, nobody has them listed.

Here is a video showing an application. The guy isn't too safety conscious, but that's another story.

http://www.youtube.com/watch?v=Kz6Tfohv7IE

 

[NightWing]

I don't know how large a hole you need but one of these might do the trick. I forgot I have these for both drilling and tapping in both fractions and metric sizes. Contact Gator tools to see the product line. The photos don't show it but the bottom has a ground V the length of the jig so it sits square and on center to the bar being drilled.

http://www.amazon.com/Gator-V-DrillGuide-Standard-Portable-Drilling/dp/B0061FY004/ref=pd_bxgy_hi_text_y

 

[mikey]

I need to drill a hole exactly through the diameter of a 1-1/4 inch round brass rod. I have a drill press and a drill press vise, which will hold the rod parallel to the drill press table. How do I accurately locate the hole?

You can use a center finder if you don't need to be precisely on center but very close. Search for "center finder for round bar" and you'll see that it is a simple Y-shaped tail that pivots on a rivet at the end of a bar held in the chuck. When the indexing lines line up you're pretty close to being on center. I've used mine a lot for jobs that don't have to be precise fits.

If you need to get closer than that you can use an edge finder and get within a thou or two of dead center.

 

[Marco Bernardini]

Assuming the drill bit is perpendicular to the table (not always the case with a Chinese drill press :biggrin, a V block is a fast way to find the diameter of the rod.
The lower point of a V block is easier to be found than the higher point of a rod, and they are on the same line.
Center the V block, then put the rod into it.
Just be careful not to drill the V block: eventually you can drill the most of the hole on the block and finish it keeping the rod in the vise.
If you file a bit the starting point you get a better result.

 

[Mac1]

Take a short piece(1") of the same diameter rod you want to drill. Chuck it in the 3 jaw on your lathe and drill thru the center the correct diameter hole. This is your drill bushing. Put the rod you want drilled in a drill press vise and set this drill bushing you just made over the location you want drilled. Put vise on drill press table and drill thru the bushing. Hole will be centered. Save the bushing for the next job.

 

[JPMacG]

Wow, what great responses. Thank you all!!! )

 

[chips&more]

Mac1 and I are thinking alike. That would also have been my suggestion. The locating disc could be almost any material but needs to have the same OD and same whole diameter as your drill bit. Also, the vise jaws should be standing proud of your part so you have something to locate off of. Hope all this makes sense? I know just one picture is way better than a thousand words!...Good Luck.

 

[markknx]

If all of those do not work. You could always drill it in the lathe by mounting it to the cross slide using a angle plate or V-block. use the cross slide mic to center it as you would in a mill. if it is to long to mount vertical you could do it horizontal by milling a v on center of the angle plate using the lathe before mounting the shaft. this would put the shaft on center with the head stock. these will get you a very accurate hole. Mark