# drilling a flat bottom hole



## whiteshoecovers (Jun 7, 2015)

What are the options to drill a truly flat bottom hole?

I need it to be 1/4" in diameter. A very small dimple in the center would be acceptable. I'd like to do it in only one operation and with a hand drill. Using a guide bushing for the drill is acceptable but I don't want to limit it to having to use a drill press.

Thanks.


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## Kazooman (Jan 20, 2013)

Forstner bit.


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## JoeinGa (Nov 26, 2012)

Kazoo is right. I've used Forstner bits in a cordless drill before, you gotta have a very steady hand and be dead straight going into the wood.


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## Kazooman (Jan 20, 2013)

Forstner bit.


> Kazoo is right. I ve used Forstner bits in a cordless drill before, you gotta have a very steady hand and be dead straight going into the wood.
> 
> - JoeinGa


Yes, he will need to be careful, but a 1/4" hole should go well. I suppose using one of those guide devices that are intended to keep the drill bit perpendicular to the surface (I seem to recall one brand being called a "port-align") might help, but I have never used one and have heard mixed reviews.


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## waho6o9 (May 6, 2011)

https://www.biggatortools.com

This plus a forstner bit should get you in the ball park


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## canadianchips (Mar 12, 2010)

Plunge Router


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## Nubsnstubs (Aug 30, 2013)

What is the depth of this 1/4" ID hole??? ............. Jerry (in Tucson)


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## OSB (Dec 16, 2016)

Any "flat" bottom bit actually has a shallow inverted cone on the end. In CNC machining a flat bottom hole is created by plunging and then moving the bit in a circle so the edge of the cutter (which is square to the plunge) cuts the entire bottom of the hole rather than just the edge.


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## bandit571 (Jan 20, 2011)

!/4" brad point bit?


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## whiteshoecovers (Jun 7, 2015)

> What is the depth of this 1/4" ID hole??? ............. Jerry (in Tucson)
> 
> - Nubsnstubs


Good question, 5/8" or less.


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## Nubsnstubs (Aug 30, 2013)

If you have hundreds of these holes to drill, go to MSC, McMastercarr, and other machine shop tool suppliers, and look for a 1/4" plunge cut end mill with a shank that will fit your current drill press chuck. They make them, so no problem finding it. Cost should be under $20 for HHS, and over $30+ for carbide…......Jerry, (in Tucson)


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## splintergroup (Jan 20, 2015)

I use a Forstner bit in a DP when I need to drill a hole leaving only about 0.050" before breaking through the other side. The centering spike on the end of the bit would poke through in these cases so I use a standard Forstner bit to get close, then a cheap/old Forstner bit of the same size with the spike ground off to get to the final, perfectly flat bottom depth.

A hand drill makes your problem a bit more difficult, but if you don't work about the small digit created by the centering spike, a Forstner bit is probably the best choice.

If you have a drill press and a way to lock down your project, the end mill is ideal for a single pass solution.


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## whiteshoecovers (Jun 7, 2015)

Thanks for all the replies.

Do you think an end mill in a hand drill using a jig with a guide bushing would do well?


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## BigYin (Oct 14, 2011)

drill your hole with a normal pointed drill bit to almost full deapth, then flat bottom with another drill bit of the same size with the point ground flat.
not too quick but it works


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## splintergroup (Jan 20, 2015)

> Thanks for all the replies.
> 
> Do you think an end mill in a hand drill using a jig with a guide bushing would do well?
> 
> - whiteshoecovers


I wouldn't do it, the mill has no centering capacity and unless your guide gushing has a dead solid mount with the workpiece, the bit will be next to impossible to control.


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## Skunkwoodz (Dec 8, 2016)

I second the plunge router, its how I make perfect 1/4" dimples to inlay magnets. I always have to take a chisel and a clean up the little nipple it leaves in the center though to get the magnets to sit flush.


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## Cooler (Feb 3, 2016)

> !/4" brad point bit?
> 
> - bandit571


If you grind off the point and use it in a drill press, yes. A cheap way to go.


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## bandit571 (Jan 20, 2011)

Use a regular drill bit to hog the waste out of the holes, then flatten the bottoms of the holes with that end mill, using the drilled hole as a guide, just go down far enough to flatten the holes' bottom.


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## Cooler (Feb 3, 2016)

> !/4" brad point bit?
> 
> - bandit571
> 
> ...


Or use a brad point drill to start the hole and then use a second brad point drill with the point ground off to finish the hole. That way you can use a hand drill instead of a drill press.


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## whiteshoecovers (Jun 7, 2015)

Appreciate all the input. But I was serious about some of the criteria:

1. must be one operation
2. cannot depend on a mill or drill press

So far an end mill in a hand drill with a jig holding a guide bushing sounds most promising, but I'll have to try it to see how well it works.


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## Cooler (Feb 3, 2016)

> Appreciate all the input. But I was serious about some of the criteria:
> 
> 1. must be one operation
> 2. cannot depend on a mill or drill press
> ...


General makes a drill guide attachment for a hand held drill. It turns it into a mini drill press. That would be more versatile than a drill bushing. Drill bushings cost about $6.00 to $10.00 each. The drill guide is about $30.00.

See: http://www.homedepot.com/p/General-Tools-Drill-Guide-and-Chuck-36-37/100349264?cm_mmc=Shopping%7cG%7cBase%7cPLA%7cD25T%7cPowerTools&gclid=CNuY7Py5l9ECFc6Pswodg3sByA&gclsrc=aw.ds


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