Countbore centering jig for the drill press

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I'm in the process of building a second deck chair to match the one in this blog series.

The project is going much faster than the first since I have all of the required templates and jigs pre-made.  The build process requires a number of bolt holes in the side assemblies to be drilled from the inside out.  The holes require a counterbore on the outer surface.  On the initial chair, I tried to line-up the forstner bit over the 1/4" drilled hole - this worked okay, but it was fiddly to get the bit centered.   For this chair, I made a little centering jig.

It has a 1/4" dowel pin on one side and a counterbore on the other.  With the pin inserted into an existing hole, the at-rest bit is lowered until it seated into the jig.  While holding the bit down with one hand, I clamped the work down with the other.  Raise the bit, remove the jig, and drill the counterbore.  Worked like a charm.  

It is purpose built for specific diameters for the hole and counterbore, so it will be stored with the jigs for this chair.  I gave it a handle so it would look like a tool and not a piece of scrap that might accidentally get tossed.  
Any easy solution.  Is there a reason you cannot drill the counterbore first and use the Forstner bit's center for the location to drill the 1/4" hole?  

--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.

Ross,

Took a fee minutes of thought and looking at the pics to get it.  Good solution.

daveg, SW Washington & AZ


 Lazyman
 commented about 2 hours ago
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Any easy solution.  Is there a reason you cannot drill the counterbore first and use the Forstner bit's center for the location to drill the 1/4" hole?  
That would be ideal, but the bolt hole goes through a floating tenon of a mortise that is cut on the inside, so there's bound to be a little bit of variability in both the mortise location and the position of the hole in the tenon.   I know generally where the outer counterbore will be, but not precisely.  If I drilled it first, I'd likely be off-center once the bolt hole was drilled.


 gdaveg
 commented about 2 hours ago
new
Ross,

Took a fee minutes of thought and looking at the pics to get it.  Good solution.
Yeah, I think I could have sequenced the pictures better to make its purpose clear.  
Nice, simple solution. You’ve become quite the jig master, Ross.

 Ron Stewart
 commented about 18 hours ago
Nice, simple solution. You’ve become quite the jig master, Ross.
Thanks, Ron.   The jigs come with their own sense of accomplishment, with repeatability thrown in as a bonus.  😀
Wonderful solution Ross.

Main Street to the Mountains

Thanks, Eric.

I meant to point out that while I used a CNC to cut out the jig, it can easily be done on the drill press by,
  • Clamping a piece of scrap for the jig onto the DP table
  • Drill the 1/4" through the scrap
  • Without moving the piece, swap the 1/4" bit for the forstner bit of the required size
  • Drill the counterbore part way through. 
  • Add a short stub of 1/4" dowel for the centering pin