Grinding the point off a forstner bit

maxvintage

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We re-did our kitchen about 12 years ago and went with IKEA cabinets and drawers. They held up ok but it's time to replace them, so I made new doors out of Birch ply.

The Ikea hinges fit into a 1 3/8 round pocket in the door. The issue is the Ikea doors are a non standard thickness--they aren't even standard metric sizes, and I could not find good plywood on the right thickness--3/4 works, but it's a little heavy. 5/8s looks better.

So I have it all done and working fine, but the hinges are just slightly too deep for the pocket hole. I drilled 13/8 holes as deep as they could go without drilling through, and the hinges are solid but no quite flush with the back of the door, by maybe a 16th-8th of an inch

I was thinking--grinding the point off a forstner bit and then drilling into the existing hole would get me right where they need to be. Take the doors off, grind the point off a forstner, mount it in a drill press, set the depth, and I'd get a much better fit.

Anyone see and problems with this?
 

trapdoor2

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All I can add is that I would probably wax the sides of the bit (a little for each hole) to make things go a bit more smoothly. Sometimes Forstner bits get a tad sticky. Use a drill-press if you can...more control.
 

telemnemonics

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Even with a drill press you're likely to get some oval-lization when drilling without a brad point. If you do try this method, first work with some scrap wood to make sure the results are acceptable to you.

The right tool for the job is a plunge router.
What I would do is drop the pointless bit deep into each hole with the motor off, then start it running and proceed to deepen the last 1/16".
Not going to alter the rest of the hole as there is no cutting edge back there.

Try to start each one with motor running though and all sorts of hell will rain down!
 

maxvintage

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What I would do is drop the pointless bit deep into each hole with the motor off, then start it running and proceed to deepen the last 1/16".
Not going to alter the rest of the hole as there is no cutting edge back there.

Try to start each one with motor running though and all sorts of hell will rain down!
yes that's the plan. the existng holes are almost 1/2 inch deep
 

telemnemonics

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I was actually installing the first gen of these hinges created by the Hafle or Hafele brand in the '80s, and we drilled with proprietary bits sold by the (German?) hinge maker.
Must have had a very short brad point since it was the same basic problem of drilling near all the way through doors.
Once other brands produced similar hinges I think you had to buy odd size metric bits?
Some nutty size like 33.3mm?
Very cool revolutionary hinge design though!

Hard though to shorten an existing brad point and keep it centered.
I've sharpened a lot of forstner bits and it's easy unless the brad point gets dinged.
Those bits can run for decades if sharpened, and if you don't hit metal.
Old ones at least, designed to be sharpened over and over.
Pretty sure I have a couple from the 1970s that still work, but not in constant use of course.

I'd be cautious of the middle of the hole where the two main cutters don't quite go to center, and the brad point was removing that small portion of stock in the middle of the hole.
If no cutter clears the middle, pressure on the quill could heat/ burn/ crack the front face there.
 

Peegoo

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Ovaling of the existing hole is not a factor because Forstners don't cut on their side faces.

I have ground the point off of a Forstner. I did this to make flat-bottom holes when I made a honeycombed pine Telecaster in 2020. It worked fine.

The only caution is there needs to be a small bump in the center to push the wood fibers in the middle sideways so the blades can slice them off.

Also, the lack of a point makes it difficult to spot holes accurately because you have no center reference. But in your case, you're deepening existing hinge mortises so you're golden.
 

telemnemonics

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Here’s a couple of excellent Austrian made bits (1 1/4” and 1 1/2”)
6F6BE8E2-3968-412B-8293-E028C3FA8D99.jpeg
6DB0D5DF-1DAC-4A60-B497-47EFF9200FB0.jpeg
and if you look close you see that the two main cutters don’t quite meet in the middle, so clearing stock there falls to the brad point.
Lose the brad point and you start burning there and applying pressure to maybe a 1/8” spot.
 

Peegoo

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That's why you need a little bump in the center to push the wood outward from the center. A Dremel with a 1" diamond wheel is the ideal tool to do this job.
 

telemnemonics

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That's why you need a little bump in the center to push the wood outward from the center. A Dremel with a 1" diamond wheel is the ideal tool to do this job.
Right but I'd still be wary of the results with hardwood ply where the grain may not want to be pushed if thin birch plys saturated with glue.
If there's white formica on the other side and some heat is generated in the middle by the bump trying to push the grain?
Cold get little brown burn spots on the face!
Or even cracks.

Half the time I'm making stuff I'm thinking of all the ways it could go wrong!
 




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