How I solved the problem of centering a drillbit in an existing hole

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Blog entry by George_SA posted 12-19-2012 10:21 AM 1563 reads 1 time favorited 9 comments Add to Favorites Watch

Usually when I want to countersink a larger hole in a smaller hole I use a Forstner bit to drill the larger hole first. The Forstner tip leaves a nice little center hole which enables me to accurately drill the smaller hole all the way through. Sometimes I get overeager and forget to drill the larger countersink hole first. One is then faced with the problem of centering the Forstner bit on a hole. Not so easy!

This happened again the other day and thinking about the problem for a while, I came up with the following solution. Put a dowel in the hole after marking the center on the dowel. After drilling the countersink hole, just remove the dowel.

-- There are some things that money can't buy - Manners, morals and integrity

9 comments so far

View GerardoArg1's profile (online now)


814 posts in 1030 days

#1 posted 12-19-2012 10:32 AM

Great Idea George!!!!! I had the same problem several times … and never came across the solution. I’ll use your system to the next.

-- Disfruta tu trabajo (enjoy your work) (Bandera, Argentina)

View HalDougherty's profile


1820 posts in 2273 days

#2 posted 12-19-2012 11:56 AM

I had the same problem drilling a hole in a 9/16” aluminum rod to make pillars for bedding in the gunstocks I carve. I don’t have a metalworking lathe, so I worked out a simple jig to center the hole. I drill the 9/16” hole in a block of maple using a 9/16” plunge router bit in my drill press. Then I cut a slot with my bandsaw so a bolt will clamp the block around the 9/16” aluminum rod. Next I clamp the maple to the drill press table and center it by lowering the 9/16” router bit into the hole and lock the maple in place. Then I replace the router bit with a .260” diameter drill bit and drill the hole. It’s centered and the jig is so easy to make, I don’t worry about the cutting fluid messing up the maple jig, I just make another one in a few seconds each time I need one.

-- Hal, Tennessee

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110 posts in 1689 days

#3 posted 12-19-2012 01:17 PM

Great idea. I could have used this tip about a month ago. Merry Christmas!


View ChrisK's profile


1407 posts in 2118 days

#4 posted 12-19-2012 01:30 PM

Simply genius! I hope I remember that next time I have the same issue.

-- Chris K

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Ben Simms

191 posts in 1328 days

#5 posted 12-19-2012 01:33 PM

i made this mistake the other day. nice fix!

-- I played with Legos as a kid and I never had the part I thought I needed, so I learned to improvise. Now I'm an engineer with a woodworking hobby.

View a1Jim's profile


113725 posts in 2613 days

#6 posted 12-19-2012 01:36 PM

Well done.

-- Custom furniture

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Charles Maxwell

1046 posts in 2843 days

#7 posted 12-19-2012 01:45 PM

I often have need to open the size of a prior drilled hole. I’ve used your method in the past with good results but, I found that a stepped or tapered drill bit with a follow on forsner bit is a far better solution. And, my need for accuracy is important as the hole I open is typically in a clock. Give it a try.

-- Max the "night janitor" at

View Adam's profile


80 posts in 2098 days

#8 posted 12-19-2012 01:51 PM

Good idea, another soulution is to drill a hole through a piece of scrap, say 1/4 plywood, with the larger forsner bit you wnat to counter sink with and then clamp that hole over the smaller hole. The walls of the pre drilled hole in the scrap will guide the bit into the workpiece without wandering.

-- Adam, St. Catharines, Ontario, Canada

View exelectrician's profile


2285 posts in 1464 days

#9 posted 09-27-2014 11:11 PM

Good thinking…

-- Love thy neighbour as thyself

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