9

While not the focus of the question I wanted to point out that when it comes to drill presses I almost always see forstner bits suggested here at WW (for good reason of course).

Much to my surprise in this answer from Graphus he suggested using auger bits instead. He mentions that depth of cut and price are key factors in choosing auger bits. Albeit a drill press was not the tool he suggested but I was still surprised.

Understandably spade bits would be at the bottom of choice but when it comes to making holes in wood what criteria would make me choose auger bits over something like a forstner? The latter I have come to understand are superior. Maybe they are but only under certain conditions?

It is possible those are the answers and that maybe forstner bits should only be used in drill presses. If nothing else this can be a place for that answer.

  • 1
    There's no reason to put spade bits at the bottom of the heap. They have their own advantages. It all depends on what you need. – Caleb Jul 20 '15 at 5:19
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    (Offtopic: Man walks into a repair shop with a busted snowblower and announces "This does not auger well...") – keshlam Jul 20 '15 at 18:27
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The problems with forstner bits is that they only have a portion of the bit (half an inch or so) that is as wide as the hole you are cutting. Whereas with an auger the entire length of the auger is as wide as the hole. This helps keep the hole straight.

Forstner bits usually have short shafts (though there are shaft extenders). Augers on the other hand are much longer.

The result of this is that an auger bit is better to drill deep holes and when you can't control the drill as well.

  • On the other hand, forstner bits can cut part of a circle, a flat-bottomed hole, and some other things the typical twist drill has trouble with.. Tools for tasks.... – keshlam Jul 19 '15 at 15:13
  • It may also be worth mentioning that auger bits usually have a screw-tipped "snail" at the business end that helps pull the bit into the wood, reducing the effort needed to push the bit as compared to a forstner or spade bit. – grfrazee Jul 20 '15 at 17:02
  • @keshlam - I've never seen an augur bit with a twist drill point. – WhatRoughBeast Jul 22 '15 at 3:06
  • @WhatRoughBeast they are mostly seen on larger diameter augers – ratchet freak Jul 22 '15 at 13:40
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One of the greatest advantages of an auger bit is in its name--it works like an auger, carrying away the chips and shavings that it produces. Auger bits are also available in very long sizes and are very rigid (i.e., they won't flex as easily as spade bits). They work best in low-speed, high-torque tools, including both power drills and hand braces.

Because the design clears chips better than a twist bit and you can buy auger bits up to 2 feet long, you can often drill very deep holes all the way through without having to take an extra step for chip removal as you would with a long twist or Forstner bit. Bosch has an article outlining some benefits and common applications of auger bits.

As ratchet freak pointed out, the design also inherently allows you to drill a straight hole once the hole is started.

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Augur bits generally have longer shafts and can have much longer shafts, allowing for much deeper holes. They also tend to be MUCH cheaper than Forsner bits, so often if you don't need what the Forsner bit is best at, nice flat bottom holes and very smooth sides, the Augers are perfectly fine.

As rob and ratchet said, augers also are designed better to drill straight holes when drilling by hand. Such as through studs for running electric. I only use my Forsner bits in my drill press.

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    +1 for Forstner bit with drill press and auger bit with a brace. – Ast Pace Jul 20 '15 at 22:02

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