I am making beds for my garden and am using treated wood with steel bracket like things. I need to make holes in them and the wood. I am doing 12 of these beds, what bit will hold up and cut through both the wood and steel.

  • HSS drill bits are designed for drilling ordinary steel. This is either off-topic for woodworking or a duplicate of How to identify a wood drill bit from a metal drill bit - and does it matter? – RedGrittyBrick Apr 28 '16 at 10:47
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    I voted to close as this is not about woodworking. But the type of bit you're looking for is typically a twist bit which perhaps you might already have? You can read more about this on machinist's forums but you should use a centre-punch to put a dimple into the steel to help prevent the tip from wandering and also lubricate periodically during drilling (e.g. with 3-in-One or motor oil, fresh or unused) to prevent buildup of excess heat. The steel may drill much more slowly than you're used to but don't press hard to get it to pierce it, as always it's best to let the bit do the work. – Graphus Apr 28 '16 at 10:50
  • On a related note if you have not already this would be a better fit for the Blacksmith and metal working proposal. Consider getting yourself commited! area51.stackexchange.com/proposals/88630/… – Matt Apr 28 '16 at 13:14
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    Actually, woodworking does sometimes require some amount of working with metal... Depending on the speçific application, this could be on topic. Or might not be. – keshlam Apr 28 '16 at 14:17
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    I thought your question was a reasonable question for woodworking area. Sorry that some people were rude to you for simply posting a question. Hope you found your answer. – TAMMYE S May 4 '16 at 23:46
up vote 1 down vote accepted

I thought I might as well convert my Comment above seeing as nobody else posted an Answer specifying the exact bit type.

Bit type
The bit you're looking for is a twist bit which perhaps you already have?

These days they're commonly available in three finishes, bare steel, black oxide and "titanium-coated" (more accurately, coated in titanium nitride).

Twist bits/twist drills

Most bare steel bits will be HSS, short for high-speed steel, a hard and durable alloy that is highly resistant to softening at high temperatures. Both of the other types can be HSS under their respective coatings too.

It's still possible to buy carbon-steel twist bits today, especially if they're very cheap. The durability of these bits when boring into steel can be low, especially if heat is allowed to build up during drilling (this can literally cause a bit to go blunt the first time it's used — if the tip goes blue it got too hot and will have 'lost temper', becoming little harder than the steel brackets you're drilling into).

Method
When preparing to drill into the steel a centre-punch must be used first to put a dimple into the metal. This is to to help prevent the tip from wandering, but even so some care must be exercised to keep the bit on the mark before it starts to cut and form its own hole.

Even though HSS is very heat-tolerant you may need to lubricate periodically during drilling (e.g. with 3-in-One or motor oil, fresh or unused) to prevent buildup of excess heat. The steel may drill much more slowly than you're used to but don't press hard to get the bit to pierce it, as always it's best to let the tool do the work at its own pace.

Once the bit has gotten through the steel and enters the wood expect it to suddenly increase its boring speed, so be prepared for this as the drill may jerk which always comes with the risk of a snapped bit.

Personal protection
Wearing eye protection is advisable, and especially if doing the drilling indoors ear protection too (common foam earplugs are fine for this level of noise).

  • Did anyone else notice that those are left-handed bits in the picture? – AaronD Dec 2 '16 at 6:10
  • @AaronD LOL, apparently not. Probably the picture just got flipped. – Graphus Dec 2 '16 at 7:45

As it was said in the comments you are going to need a HSS (High Speed Steel) drill bit which just means that the drill bit is extremely hard and resistant to heat. There are also titanium HSS bits which are just covered with a titanium oxide but then you wouldn't be able to sharpen them if you ever needed to do so.

It sounds like for what you are doing the HSS bits would be fine for drilling through the metal and wood but depending on the materials you may want to look at a step bit such as this but I doubt that would be necessary.

Edit: To add on to what I said before, step bits are a good choice of drilling if you are only drilling sheet metal or metal that is relatively thin (1/8" -1/4"). Also when drilling metal at anytime to counter the extreme heat generated you are going to want to use a lubricant such as motor oil or just look up "metal drilling lubricants" into google and you will find many available for purchase that are more specific to metal drilling.

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    My understanding is the titanium oxide coating will come off after awhile, so by the time you need to sharpen one of those bits, it'll be as easy to do as any other HSS bit. I'm having trouble finding a source for this information, though. – Charlie Kilian May 20 '16 at 2:54
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    You might consider editing your answer to include when a step bit would be necessary, and what it excels at. – Charlie Kilian May 20 '16 at 2:58
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    Note that when cutting metal, an appropriate lubricant is needed -- basic household oil will work. – keshlam May 20 '16 at 12:37
  • Yup, any light household oil like 3-in-1 oil will work. You can even use water, though you'll probably have to apply more of it as it's low viscosity means it will be thrown off more quickly. At least the clean up with water is easier... – FreeMan May 24 '16 at 16:35

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