Using a Drill Press like a Lathe to make a Center HolePosted on December 30th, 2010 4 comments
My friend was building a Stirling engine and when he found out that I owned a small lathe, he asked if I’d machine a piston and cylinder for him. Having some materials on hand like copper tubing for the cylinder and some solid aluminum rod for the piston, I agreed to make the parts. Another one of the parts he needed was a 7/16″ bolt with a hole drilled down the center of it. He had tried to make the hole with his drill press, but ran into a problem where the hole he drilled was not centered. This became apparent only after the hole was finished, of course, as it exited the far end of the bolt off center.
I had an idea about a procedure for drilling an accurate center hole in a cylindrical part with a drill press by first aligning a drill vice to hold a drill bit stationary while using the drill chuck to grip and spin the work piece. My drill’s chuck can hold a drill up to 1/2″ in diameter, which would be more than sufficient to grip a 7/16 bolt on its shank. I thought I’d run a quick experiment and document the procedure for anyone else who may want to try using a drill as a lathe for making a center hole in a cylindrical part.
A lathe is most often used to turn a part using a cutter that can either remove material from the diameter or from the part’s face. But it also has a very nice feature when a drill chuck is inserted in the tailstock, and that is to accurately drill a hole precisely down the center of the part. An example of that is shown below.
Normally, you would use something called a center drill to start the hole and then swap it out for the drill of the proper diameter. If the hole is large, you may have to drill with several drill sizes to get it up to the finished diameter. In this case, the hole I wanted to make was just .125″ in diameter so it was possible to do with just a single drill in one step. The procedure I describe below would need to be modified by resetting the alignment for each drill if you need to open the hole up in several steps.
If you didn’t own a lathe but had a drill press and a drill vice, here is a procedure for drilling a center hole in a cylindrical part.
First, you put a drill of the desired diameter in the drill chuck and tighten it. Then gently raise the drill table, clamp the table to set its height, and then and move the drill vise to the bit and clamp the drill vice down on the bit. The drill vice must have a ‘V’ groove one its jaws to align it vertically on the drill bit. This is important for a subsequent step. After everything is aligned, then use a pair of ‘C’ clamps to hold the drill vice to the table so it cannot slide from side-to-side. Then un-clamp the drill bit from the chuck and the drill vice and turn the bit upside down and clamp it in the vice’s V-groove again so that its tip is facing upward. Then clamp the workpiece in the drill chuck. In this case, I’m using a .5″ diameter section of aluminum rod as the workpiece.
Here the drill is clamped in the vice pointing upward and the workpiece is just partly visible and clamped into the drill’s chuck.
Then turn the drill on. Just like on the lathe, the drill bit will be stationary and you can lower the spindle with workpiece and it will drill the hole accurately through the center of the part. Remember to lift up on the spindle periodically to clear out the metal chips. If you got everything aligned correctly, the drill will make the hole directly in the part’s center. In my case, the hole was within .002″ of being concentric with the outside diameter of the part on both ends of the part. That’s about as accurate as you would get with a lathe so the technique works well.
It may not be apparent but the part is spinning, the drill bit is stationary.
Here’s the finished part with the hole perfectly centered.
4 responses to “Using a Drill Press like a Lathe to make a Center Hole”
This is a good idea. But I have a question. As I understand it, you clamp the drill bit in the chuck, and you essentially use that to “pull” the vise around underneat the chuck so that it ends up perfectly centered under the chuck. Then you put the bit in the vise, and put the stock to be center-drilled into the chuck.
But doesn’t this depend on that drill bit being rigid enough to actually pull the vise around and get it straight under the chuck? Drill bits all have bend and deflection. Maybe with a 1/8″ bit or larger, you can get away with this. But I imagine that if you were trying to do this with anything smaller than that, the bit could not get the vise to align under the chuck without the bit itself possibly being deflected a little. Those vises are heavy.
Am I missing something? Should this work even for a very small bit, say, 1/64″ ?
The drill vice is free to slide around the drill’s platform initially, so the bit doesn’t need to pull the vice into position, you can slide the vice into position without having to put any strain on the drill bit. Then you clamp down on the bit with the vice which will align it with the chuck. Then when it’s aligned, you clamp the vice with ‘C’ clamps. At this point, the drill bit is clamped on both ends.
Then you unclamp it from the chuck and the vice and lift the chuck, and put it back in the vice with the cutting end pointing upward toward the chuck. Now you have a stationary drill bit positioned directly in alignment with the jaw’s center.
I agree a very fine drill bit may be too delicate to make this work. Drilling a center hole with a thin drill bit is always problematic because it can wander on its own due to having low rigidity. This technique may therefore be limited to center holes that are 1/8″ or larger. The ‘v’ groove’s size will also be limitation. Too large a groove and the vice will be unable to clamp on to it and keep it vertical, which is critical to achieving a straight hole.
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Thanks for the reply!
I think we are in agreement here. The key point is this one:
“Then you clamp down on the bit with the vice which will align it with the chuck. ”
At that moment, as you clamp down on the bit with the vise, the vise moves that last little bit to become centered directly under the bit. And yes, the vise is free to slide around, but it isn’t “zero friction”. It’s a big heavy steel vise, so a thin drill bit will probably bend a little rather than the vise moving.
I wanted to clarify this because I am in the same boat – wanting to center drill some round stock, but not having a lathe, and I’ve tried your approach (in a vertical mill), and I run into this issue with very thin bits.
Thank you very much for the tutorial. I think it is a good one and very helpful.
I found this at the perfect time. Just ordered some .25″ diameter aluminum rod that I need to drill a 3.3mm hole in the center so I can tap it to an M4, .7 pitch.
Can’t wait to try it, thanks for posting.
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