Simple centre finder

[NOBLNG]

This is an easy was to find the centre of any round rod for when you need to drill a hole in the end of it. Find something that is very close to half the thickness of the rod. Butt the rod up against the spacer and scribe a light line with a hobby knife. Rotate it approximately 90 degrees and scribe another. Do this four times and you will have a double set of crosshairs straddling the exact centre. A light rubbing with a pencil will make them more visible. To get a relatively centered hole clear through a short piece, I drill from both ends and let them meet in the middle. This is likely as close as you’ll get without a lathe or drill press. YMMV.

[Brutalform]

Great idea. I sometimes dread when I have to perform this kind of drilling. I’ll definitely be trying this next time. 

[peteski]

Good trick.  I have one of these from Micro-Mark, but it will not work for very small diameter materials.

 

 

[Skip]

I have a center finder from Starrett that does the job too.  If you don't have a Center Finder the other way to do this is use a set of dial or digital calipers, first measure the O.D. of the Rod.  Second, divide that measurement in half if it was 0.500" (1/2") then the center is at 0.250" (1/4"), set your calipers at 0.250" and lightly tighten the set screw.  With the little ledge between the moving jaw of the caliper and the fixed jaw at the top of the caliper, set the rod on the top of the moveable jaw.  Next, mark straight across the rod, turn the rod 90 degrees and mark again.  The intersection of the two lines is the center point of the rod.  If you want to prove this out, rotate the rod 45 degrees and mark, if the line intersects the first two you have found dead center.  This is really easy to do as well, just sounds harder than it really is.

If you don't have a set of Dial or Digital Calipers, Harbor Freight sells a 6" set that is perfect for modeling if you watch the sales you can often find them for under $10, I've had my set so long I think I paid something like $8 on sale.  I use those and leave my Brown and Sharp, Starrett and Mitutoyo measuring equipment in the machinist chest, they are every bit as accurate as the name brands.  Just make sure that you hit the off button every time you finish measuring with them or they will eat batteries.

[peteski]

16 hours ago, Skip said:

I use those and leave my Brown and Sharp, Starrett and Mitutoyo measuring equipment in the machinist chest, they are every bit as accurate as the name brands.  Just make sure that you hit the off button every time you finish measuring with them or they will eat batteries.

The OFF button doesn't preserve battery life by much.  ON most calipers it only shuts down the display (which used only small fraction of the total power used by the digital circuitry).  If the power button really turned it all off, the caliper would have to be re-zeroed every time you power it back on. Not only that. With the power off move the jaws to another location and turn it on - it will correctly show the new position - if it was off, it would not do that.  Yes, my digital calipers are inexpensive Chinese ones.

Here is some good info http://fliptronics.com/tip0006.html

[NOBLNG]

I recommend getting a dial caliper. They are super easy to read and calibrate, and can be had for about $20. and up. You also don’t have the expense or reliability issues of the batteries.

[peteski]

Eh, I much prefer a digital caliper. Direct readout is much more convenient, plus the ability to zero it out at any distance, then get direct readout of the offset dimension. 

I bought my original Harbor Freight one for $20 about 20 years ago and it still works well.  The battery needs changing about once a year - I can handle that.  But old-school calipers work well too. I still have my original veneer caliper - that one was a bit more difficult to deal with, but that was all that I had at the time.

Edited December 5, 2020 by peteski

[BuilderX]

great tip thks!

[JohnU]

On 11/29/2020 at 9:17 AM, NOBLNG said:

This is an easy was to find the centre of any round rod for when you need to drill a hole in the end of it. Find something that is very close to half the thickness of the rod. Butt the rod up against the spacer and scribe a light line with a hobby knife. Rotate it approximately 90 degrees and scribe another. Do this four times and you will have a double set of crosshairs straddling the exact centre. A light rubbing with a pencil will make them more visible. To get a relatively centered hole clear through a short piece, I drill from both ends and let them meet in the middle. This is likely as close as you’ll get without a lathe or drill press. YMMV.

I like this idea! You could use a feeler gage set to stack up the exact amount you need for the radius of the rod to scribe the center!