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

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

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

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

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

Step 5: 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

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]

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]

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

[Bill WW]

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]

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]

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

[Phil B]

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]

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

[Phil B]

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]

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]

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]

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]

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]

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]

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]

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]

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]

Phil B .. Excellent !

[Phil B]

thank you. I hope you can use it.

[JeffB67]

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

[Phil B]

See my response below to msemtd.