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drilling a flat bottom hole

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Forum topic by whiteshoecovers posted 12-23-2016 07:21 PM 2431 views 0 times favorited 20 replies Add to Favorites Watch
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whiteshoecovers

63 posts in 1233 days


12-23-2016 07:21 PM

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.


20 replies so far

View Kazooman's profile

Kazooman

1151 posts in 2101 days


#1 posted 12-23-2016 07:24 PM

Forstner bit.

View JoeinGa's profile

JoeinGa

7739 posts in 2156 days


#2 posted 12-23-2016 07:38 PM

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.

-- Perform A Random Act Of Kindness Today ... Pay It Forward

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Kazooman

1151 posts in 2101 days


#3 posted 12-23-2016 07:48 PM

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.

View waho6o9's profile

waho6o9

8434 posts in 2726 days


#4 posted 12-23-2016 07:53 PM

https://www.biggatortools.com

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

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canadianchips

2608 posts in 3146 days


#5 posted 12-23-2016 08:06 PM

Plunge Router

-- "My mission in life - make everyone smile !"

View Nubsnstubs's profile

Nubsnstubs

1408 posts in 1879 days


#6 posted 12-23-2016 08:59 PM

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

-- Jerry (in Tucson) www.woodturnerstools.com

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OSB

147 posts in 675 days


#7 posted 12-24-2016 12:23 AM

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.

View bandit571's profile

bandit571

21314 posts in 2832 days


#8 posted 12-24-2016 12:31 AM

!/4” brad point bit?

-- A Planer? I'M the planer, this is what I use

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whiteshoecovers

63 posts in 1233 days


#9 posted 12-24-2016 02:19 PM



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

1408 posts in 1879 days


#10 posted 12-24-2016 02:53 PM

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)

-- Jerry (in Tucson) www.woodturnerstools.com

View splintergroup's profile

splintergroup

2313 posts in 1371 days


#11 posted 12-24-2016 04:02 PM

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

63 posts in 1233 days


#12 posted 12-24-2016 04:06 PM

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?

View BigYin's profile

BigYin

421 posts in 2565 days


#13 posted 12-24-2016 06:02 PM

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

-- ... Never Apologise For Being Right ...

View splintergroup's profile

splintergroup

2313 posts in 1371 days


#14 posted 12-25-2016 12:01 AM



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.

View Skunkwoodz's profile

Skunkwoodz

11 posts in 683 days


#15 posted 12-26-2016 02:47 PM

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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