boring a countersunk hole in rounded material

[jschiffr]

I am trying to figure out the best way to drill clean, centered, countersunk holes in rounded material.
The above picture shows a leg of a cabinet base (left) and small teak shelf support (right), both of which have been rounded-over with an OF 1400. I see now I could have tackled the holes prior to shaping the edges. However the bearing on my roundover bit might have sunken into the drill holes and caused a dip in the profile.

Either way, I'm now faced with the task of boring roughly 30 holes, the base supports are 6/4 oak, the brackets are 3/4 teak. The oak will accept round head bolts, the teak will accept countersunk brass screws which go through the wood and into wall mounted anchors. I don't have a drill press, and so far my tests on scrap with a General Accu-Drill Precision Drill Guide have been horrendous failures full of tearout.

What countersink bits do you festoolers recommend, and can I get these holes done using my 1400 creatively, or do I have to bite the bullet and spring for a drill press?

 

[paul_david_thomas]

I use my countersink drill bit with my festool drill C12... Don't remember the part number - always does clean holes for me. You can set depth of hole drilled and depth of countersink.

to be honest, i really don't think i've been very helpful

 

[jschiffr]

Maybe you have, and the solution is as simple as a countersink bit. I assumed I'd need some fancy rig to duplicate a drill press, but i've been wrong (often) before. I'll give it a shot.

 

[Guy Ashley]

Hi

I would suggest a Forstner bit in a drill press to make the initial cut, but make sure your stock is well secure, then a countersink bit.

Guy

 

[paul_david_thomas]

The festool one has a great device that limits the depth and does not mark the worksurface, the device that limits the depth has two large holes in it, allowing drilled material to escape... Mark the drill points with a pencil, then use a steady hand.. do a few practice ones first !!

OR

clamp a drill to and MTF/3... Where the drill point is - clamp some 'packing' material that you can rest the object to be drilled ontop of. Then turn the drill on and then slide the item to be drilled upto the drill. This (if all clamped) should mean a straight drill hole... I can see it in my head.. just hard to explain

 

[woodguy7]

As Paul said, the Festool countersink bit in a cordless drill should work fine for the teak.  On the Oak i would make up some sort of drilling jig with 2 sides & a top that will slip over the Oak.  Pre drill a hole with a Forstner bit completely through the top of the jig.  Slip the jig over the Oak & slide it so the hole lines up with where you want the bolt.  Clamp in place & drill through the hole into the oak.  The Forstner bit should not wander & will give you a clean flat bottomed hole.  Just drill through for the shaft of the bolt with a standard wood bit, from the centrotec set of course 

Hope you understand this as it is not easy to explain

Woodguy.

 

[Wood_Junkie]

woodguy7 is on the right track, suggesting a saddle jig.

Pre-drill your desired holes while the jig is still square.
Then, just create the opposite profile as your roundover, using a core box bit or something similar, so that it sets down nicely on the roundover lip.
One in place, clamp it onto your frame, and place that on some more scrap (e.g. 3/4" ply).  You should not get any tear out on top as the jig guide it, and the ply backing should prevent blowout.

 

[Wonderwino]

I am fortunate to have a DJ-1 from Bridge City Tools (bridgecitytools.com) which will perfectly center the holes I drill with my C12.  Once the pilot hole is drilled, You can either use a countersink or just use a larger bushing in the jig to cover the screw with a plug.