Introduction: Make Center Drilling of a Rod Easy

Picture of Make Center Drilling of a Rod Easy

I often use a short piece of 3/8 inch rod as a collar to make a stop end for a 3/16 inch axle in my projects. I have too much difficulty drilling a centered hole in the 3/8 inch rod. I made an accessory for keeping a hole centered without difficulty.

Materials

  • 3/4 inch rod

Tools

  • Vise
  • Drill press
  • Drills
  • Drill press vise
  • Grinder with cutting wheel
  • Grinder a stone wheel

Step 1: Cut Stock

Picture of Cut Stock

I cut a piece of 3/4 inch rod about an inch long. It came from a piece of exercise equipment I found on the curb waiting for garbage pickup. I tried to cut it as squarely as possible. I ground rough edges away after cutting.

Step 2: Drill

Picture of Drill

I put the 3/4 inch rod into a drill press vise and centered a pilot hole as best I could. Although it appeared my hole would be centered, it drifted a little. I drilled a 3/8 inch hole half the length of the 3/4 inch rod.

Step 3: Drill Again

Picture of Drill Again

The beveled center at the bottom of the 3/8 inch hole automatically centers a 3/16 inch drill. I drilled through the rest of the length of the 3/4 inch rod with the 3/16 inch drill.

Step 4: Use

Picture of Use

Place the accessory on the end of a 3/8 inch rod.

Step 5: Drill

Picture of Drill

Put a 3/16 inch drill into an electric drill. Put a few drops of oil into the 3/16 inch hole and begin drilling. All that is necessary is to get a good start on a hole, the remainder of the hole can be drilled by hand without the accessory.

Step 6: Ready to Use

Picture of Ready to Use

Saw a short section from the end of the 3/8 inch rod. Slip it onto the end of a piece of 3/16 inch rod and weld the collar in place.

Comments

Bill WW (author)2016-02-26

Looks like another great method, Phil. We could also use it with wood dowels, probably best to use brad pointed bits.

See other methods of drilling concentric holes in metal rods in my Instructable:

https://www.instructables.com/id/Find-exact-center-and-drill-concentric-holes-in-me/

Hashem_Mehyar (author)2016-01-14

I was excited when I saw this, but all the imperial measurement is making my head spin :(

Bill WW (author)Hashem_Mehyar2016-02-26

Yes you are correct, Hashhem. See my Instructable (link in previous comment above) where I apologized for not including SI units. I write for a woodturning journal where all units are given in both Imperial and SI.

Phil B (author)Hashem_Mehyar2016-01-14

Only two sizes were mentioned. What size rod or dowel is available to you? Use that whether it is 12mm or something else. What size hole would you like in the center? Use that whether it is 5mm or something else.

Hashem_Mehyar (author)Phil B2016-01-25

it's OK, its my job to do the conversion on my own, its just that my petpeeve is the imperial units

Phil B (author)Hashem_Mehyar2016-01-25

I would have been glad to give metric measurements, except my limited experience tells me the drills and rods available in metric are close to English sizes, but probably rounded up or down to an exact number of millimeters.

streetrod88 (author)2016-02-22

You could use any shape of metal for your guide as long as it is thick or long enough.

Phil B (author)streetrod882016-02-22

You are correct. I used 3/4 inch round stock because it is what I had on hand from a garbage day curb find.

cjbrockus (author)2016-01-31

ok why not just drill in a piece of strap iron and then you can have several different sizes of hole, both inner and outer size holes also the thicker the strap the less you might angle your bit

Phil B (author)cjbrockus2016-02-01

I had the 3/4 inch round stock. I do not have the kind of strap iron you are talking about. I know I will use some rod/hole combinations much more often than others. Individual guides can easily be replaced as one becomes too worn to be accurate. If I tried for a set of guides on one bar, I could not easily replace holes for one guide without discarding the whole bar. But, try it and let us know how it worked for you over time,

steinie44 (author)2016-01-27

Better to chuck the rod to be drilled in the drill press chuck. Put the drill in the vice vertical. The spinning rod will cause the drill to self center as long as you have fairly close to begin with. No center punch is needed.

Phil B (author)steinie442016-01-27

Two or three others made the same comment. I am not sure how y keep cutting oil in the hole to help the bit cut and keep it cool. I wanted something like what I described here for times when a drill press is not near or the rod is too long to fit onto a drill press. I also wanted something people without a drill press can use.

ventura38 (author)2016-01-23

would it be more accurate to drill the 3/16 straight through then drill half way stepping up the size with a 1/4 then 3/8 drill. this could even be done with just a hand drill

Phil B (author)ventura382016-01-23

That might be a good way to proceed if you have only a handheld drill. I imagined that the person without a drill press could use a guide, like a couple of small squares or square pieces of wood to keep the bit drilling straight, even if only as a visual reference. My main interest in doing what I did was to have the 3/16 inch bit automatically center itself in the cone left by the 3/8 inch bit.

magallegos (author)2016-01-16

The definition of genius! Simple, practical and accurate. One of those things that make you slap your forehead and say "why didn't anyone think about this before?!"

Phil B (author)magallegos2016-01-17

Thank you. In regard to not seeing something earlier, there is a story about Thomas Edison and Charles Steinmetz I really like. Steinmetz was working for Edison when Edison asked him to calculate the volume of the glass envelope for a very large light bulb, Steinmetz noticed part of it was a sphere. He knew the formula for that. Part was a cylinder, and he knew the formula for that. There was also a transition area between the two and he guessed as best he could. He gave his best figure to Edison and explained what he had done. Edison looked at him and said, "Why didn't you just fill it with water and then measure the water as you poured it out?"

ElvisM7 (author)Phil B2016-01-19

Phil B .. Excellent !

Phil B (author)ElvisM72016-01-23

thank you. I hope you can use it.

JeffB67 (author)Phil B2016-01-19

Well, Edison should have asked him to "MEASURE", rather than "CALCULATE" the volume. ;)

Phil B (author)JeffB672016-01-19

See my response below to msemtd.

msemtd (author)Phil B2016-01-19

I'm guessing because Edison asked him to "Calculate" and not "Measure" :D

Phil B (author)msemtd2016-01-19

it was more than 30 years ago that I heard this story while driving in my car. I have not checked on corroborating it. I cannot say for certain exactly what word was used, but tried to relay it as I understood it.

jakwagenaar (author)2016-01-22

Thank you for a safe, practical and virtually foolproof method to drill a centre hole. Using the centrefinder on a combination square set, it is possible to actually find the centre of the workpiece accurately and then, to guide the drill in the initial stage of drilling, mark the actual centre with a centre punch.

Phil B (author)jakwagenaar2016-01-23

I have discovered I may think I have the center punch on the mark I made with the center finder, but I am a little off to one side. Then my drill bit may skate or drift a little.

jakwagenaar (author)2016-01-22

Thank you for a safe, practical and virtually foolproof method to drill a centre hole. Using the centrefinder on a combination square set, it is possible to actually find the centre of the workpiece accurately and then, to guide the drill in the initial stage of drilling, mark the actual centre with a centre punch.

texdanl (author)2016-01-20

I used to make these for production drilling in a machine shop. They are called drill guides. The only thing you might do to improve it is when you are done heat it cherry red and drop it in water. This makes it hard as heck and so will last longer. I cut them on a lathe but your way will work just as well. Good Ible.

Phil B (author)texdanl2016-01-21

I may need to try heat treating these. The process I used is easy and quick enough that I could just make a new one, too. I know I will use these drill guides only occasionally.

danb35 (author)2016-01-21

Surely the easiest way to do this is to chuck the rod in a lathe (3-jaw, 4-jaw, or collet, depending on tool availability, time availability, and degree of precision demanded), put a center drill in the tailstock chuck, and have at it. Faster, easier, and more accurate--but it requires a lathe. This is a good method when you don't have access to a lathe.

Phil B (author)danb352016-01-21

I try to be aware that not everyone has access to a lathe, or a welder. I published an Instructable today that is a 2nd version of the first copy I made. The first copy was steel and welded. But, I did a 2nd version for the sake of people who can really use it, but do not have access to a welder.

redrobin12 (author)2016-01-19

I have a little trouble understanding ?, a little video would be a great idea.

shallnot (author)redrobin122016-01-19

I also had trouble divining what the writer had in mind but I did figure it out. The confusion comes with the line "beveled center at the bottom of the 3/8 inch hole automatically centers a 3/16 inch drill". I couldn't figure out how the 3/8-inch drill hole could "automatically" centre the second 3/16-inch hole.

What the bottom bevel of the 3/8-inch drill hole does do is make it easier for you to manually find the centre and ensure that both the smaller and larger hole share a common centre.

By slipping the completed jig over the 3/8-inch rod to be drilled the centre of the 3/16-inch hole is automatically at the centre of the rod.

Really, the 3/4-inch rod as material for the jig is a red herring as it could just as easily have been a 1-inch square 1/2-inch thick piece of plate steel. For that matter trying to drill the original pilot hole near the centre of the 3/4-inch rod is not necessary as it only has to be far enough away from the outside of the rod to ensure that the 3/8-inch hole is entirely contained within the material of the 3/4-inch rod.


Phil B (author)shallnot2016-01-19

A twist drill is not flat on the cutting end, but is pointed with a 59 degree bevel from each side. If you look closely at the first photo of the drilling procedure, you can see the hole has a beveled bottom that leaves an inverted point in the center. The smaller bit for the second hole will automatically slide into this point at the center. That is why I said it centers itself. That is also the key principle of what makes this work.
As regards the 3/4 inch stock, that is simply a description of what I used and a way of distinguishing it from the 3/8 inch rod into which I wanted to drill on cente.
In writing Instructables, there is a constant tension between keeping it simple so as not to be so wordy that no one will read it, and being complete enough to be understood. After many years of dealing with verbal communications, I am convinced someone will always be able to misunderstand something.

Psalms116 (author)Phil B2016-01-21

Well spoken Phil.

Phil B (author)redrobin122016-01-19

A video would not help, trust me. Look again at the photos, especially those showing drilling while making the accessory. As you think about it, I believe you will understand it.

shallnot (author)Phil B2016-01-19

A video may not help but a better description of the process would. If I have to re-read, re-look, and "think about it" you have failed to explain it properly.

rch (author)shallnot2016-01-20

Gee whiz, it took me all of 20 seconds to understand what he was talking about. Great, informative Instructable.

bluerosei (author)shallnot2016-01-19

Wow, Seriously? If you have to re-read, re-look or think about it, it's not well explained? I understood this perfectly just by skimming over it quickly with a fast look at the pictures. What part did you not understand?

Cut it, drill it, pass through drill it, use it., simple.

While it's true many people want instant gratification and everything handed to them, I personally am not that person. I don't mind studying something I'm interested in. This not a case of a bad teacher, it a case of a lazy student.

Phil B, Great post Sir.

Phil B (author)bluerosei2016-01-19

Thank you.

Zville (author)2016-01-20

Great idea. It did take a couple of minutes to visualize this, but it was awesome when the light bulb went off. Thank you.

jeffatha (author)Zville2016-01-20

Too cool!

telfon (author)2016-01-19

The best way to drill a perfectly centered hole in a small diameter rod is to put the rod in the drill and spin it. Keep the bit fixed and it will self-center into the rod as it drills in. It is why they use lathes for round parts.

Phil B (author)telfon2016-01-19

A couple of people below made the same comment. I responded to at least one of them.

streetrod88 (author)2016-01-19

There is a much easier solution to the problem. Chuck the drill bit in the drill press backwards. lower into a vise and tighten. Release the drill from the chuck . Now chuck the 3/8" rod. Just turn the drill press on and bring down over the drill bit. It won't drill anything bot a perfect centered hole.

JeffB67 (author)streetrod882016-01-19

Doesn't work so well for a hand drill, though.

Phil B (author)streetrod882016-01-19

Because of the flutes in a twist drill I have never been able to get an accurate and concentric grip on a drill put into a chuck cutting end first. Perhaps you have been successful. But, see also the second paragraph of my response to ToGrin.

ToGrin (author)2016-01-19

Are you familiar with the principle of gun drilling? It's a process of drilling deep, concentric holes where the drill is stationary and the work rotates. This makes the drill self center in the work, which is a real plus for a gun barrel. :) Try holding your drill in the vise and the 3/8 rod in the cordless drill. I think you'll be pleasantly surprised at how well it works.

Phil B (author)ToGrin2016-01-19

read about making a gun barrel in the Foxfire Books series. In that case, they began with a rod form. Steel was heated and twisted around the rod form and hammer welded. Then the barrel turned on a long bed lathe while a stationary drill was fed into the bore. I think there were lathe dogs to keep the barrel on center. I found the most interesting part to be cutting the rifling grooves in the barrel.
What you say is very fine if you will always be near a drill press and the rod is no more than a few inches long. My little accessory is very portable and can be used anywhere on any length of rod. Also, I like to use plenty of cutting oil when drilling like this. Bringing the rod down onto the bit makes it very difficult to keep oil on the bit while drilling,

schabanow (author)Phil B2016-01-19

> ... cutting oil ...

I use mixture of water, kerosene, mineral oil and oleic acid. White water stuff if shaked well (for a week or two, then goes apart a bit). Elixir. )) Oleic acid may be replaced by pork fat.

ToGrin (author)Phil B2016-01-19

Length doesn't matter Phil. If you spin the rod against a stationary drill, the drill will self center throughout the drilling process. Give it a try, I have. In fact, I'm about to drill a .22" diameter hole through a 24" long rod for a rifle I'm building. The only difference is that I've using a hollow gun drill to force coolant into the hole for lubrication and chip removal.

Mark 42 (author)ToGrin2016-01-19

Drill bits can wander, even when the work is spinning - but it's a lot less pronounced.

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Bio: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying ... More »
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