drilling a thru hole

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Forum topic by trz posted 08-25-2013 12:21 AM 1153 views 0 times favorited 8 replies Add to Favorites Watch
View trz's profile


90 posts in 2511 days

08-25-2013 12:21 AM

I’m trying to drill a thru hole centered on a piece of 3×3x12 in. stock. I mark X on each end then set it on the drill press table and hold it with a hand clamp. before I drill I line the bit up next to the stock to make sure it’s plumb with the bit. Drill one end flip over and repeat. And the holes NEVER meet. I’m using a 7/16 bit and try to stick a 7/16 dowel thru when I’m done and it never meets from each end close enough to send the dowel thru. I always have to ream it out so I can get the dowel thru. I would think by marking the x’s on each end I would be close enough but it’s not . Have any suggestions?

8 replies so far

View lew's profile


12102 posts in 3780 days

#1 posted 08-25-2013 12:29 AM

Do you have a lathe? Drilling a centered hole on square stock is much easier with the lathe and a chuck.

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View badcrayon's profile


38 posts in 1846 days

#2 posted 08-25-2013 12:36 AM

Put a sacrificial wood top on your drill base drill into it with the bit but not all the way thru. Then drill as far as you can in one side. Put a piece of dowel into the wood base and use it to line up the holes. If this sees like too much work Harbor Freight sells 18 inch drill bits

-- Bad Crayon Studio

View JAAune's profile


1802 posts in 2342 days

#3 posted 08-25-2013 12:46 AM

It’s quite possible that your drill bit isn’t cutting straight down but is drifting to one side. This is especially likely in woods like oak that have areas of high density surrounded by low density earlywood filled with pores. To minimize this, make sure the bit is really sharp and use a brad point. The standard drill bit configuration is geared towards metal working and isn’t the optimal shape for wood.

Another trick is to use a stone to dull the flutes of the bit so it’s less likely to bit into sides of the hole you’re drilling.

-- See my work at and

View firefighterontheside's profile


18351 posts in 1882 days

#4 posted 08-25-2013 12:53 AM

Cut the piece in half at the band saw or table saw. Use a fluting bit at the router table and route down the middle of each half. Glue pieces back together. This will give you the best chance at having the hole centered in your stock. Even with a really long bit, it probably won’t come out in the center of the other end.

-- Bill M. "People change, walnut doesn't" by Gene.

View gfadvm's profile


14940 posts in 2715 days

#5 posted 08-25-2013 01:56 AM

It is nearly impossible to drill that far in end grain and have it come out perfectly straight. I would either do as Bill M suggested OR rip a dado on the tablesaw and then glue a filler strip in the kerf to give you a perfectly centered square hole which you could then ream to round with the drill if you need a round hole.

I do all my Shipwright hinges this way and some of them are 18” long.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View RobsonValley's profile


31 posts in 1788 days

#6 posted 08-26-2013 05:25 AM

Buy an Irwin Installer’s bit = 18” long. Clamp in the vise straight and level.
Add electric drill and tighten chuck. Organize a bubble level with tape on the drill
body. Open the vise = you’re good to go.

View ADHDan's profile


800 posts in 2133 days

#7 posted 08-26-2013 07:38 PM

If this is something you may have to do repeatedly, this seems like a situation where the investment in a specialty bit would save a ton of time and effort spent trying to find a perfect workaround.

Plus if you get an extra-long undersized bit, you might be able to use it to drill a thru pilot hole and then drill out the larger hole using your current method. I.e., drill a small thru hole and use it to center the bit on your drill/flip/drill operation. With the right bit, hopefully it won’t wander and you’ll get the holes lined up. (Caveat: I’ve never done this before and have no idea if it would work.)

-- Dan in Minneapolis, woodworking since 11/11.

View shampeon's profile


1775 posts in 2208 days

#8 posted 08-26-2013 07:55 PM

badcrayon has the right technique. Use the a dowel or a cut off nail head the same diameter as the drill bit as an indexing pin to keep the bit centered, then drill in half way on both sides. You must have square stock, and the table must be squared to the chuck to do this.

But 12” is a long, long way to drill a perfectly centered hole.

-- ian | "You can't stop what's coming. It ain't all waiting on you. That's vanity."

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