The good old fashioned drill bit question

I have a couple good sets of drill bits.  I have them in a few flavors - cheap black oxide for wood, Ti coated for harder stuff, but they're all standard sets that go up to 1/2"  I need a good set of bits for the press that does 9/16" up to 7/8" or 1".  I bought a cheap Cobalt set ($35) off Amazon for a project that included two holes in 1/8" steel.  The first hole made it, but it was a lot of metal chips, not corkscrews.  The second hole mostly made smoke and the bit snapped in the hole.  I returned them.

I'm not finding many bit sets that shoot the middle.  I don't need a $250 Irwin drill set, but I also learned my lesson on the $35 set.  I'm hoping there is something out there for like $75 that will work?

Also, I assume I'm looking for Cobalt, right?  The TiN bits I have are fine for steel, but once the coating wears off they're kinda toast.  They can be resharpened, but without the TiN coating.  Can someone explain the finer points (pun intended) of the different alloys?  Different point angles?

That's the unfortunate reality of it, you either buy junk or buy good, but there's not enough profit in trying to make one that's "sorta good," it takes 95% of the effort as making it decently, but you can only charge half for the product.

If you're familiar with grinding, you can often take a crap drill and give it a good grind to cut a lot better, but if the material they used sucks, then it'll go dull really fast and need constant resharpening.

Are you using these in a machine like a drill press/mill or just in your hand with a cordless drill or whatever?

Cobalt drills are unarguably better than HSS, but they're also going to cost 3x as much.  The good news is if you have good control over feeds & speeds, they last a LOT longer, like in a CNC machine.

On the tip angle:

A 118° tip is easier to start by hand because it's a sharper point so you can press it into the material and make your own little pilot hole, just a spring punch point.  In a mill or drill press, though, you don't need to do that, go with a 135° tip instead.  The down side here is because you're drilling with a sharp point, it's easier to get the tool to walk instead of drilling true, you're also concentrating the cut in a smaller area so the tip will wear out faster.

A 135° tip is much more stable and last longer in the cut because you're engaging a significantly flatter cutting edge into the material. Depending on the quality of tool, tip profile, material,etc., you'll want an equivalent spot drill so you have a nice even hole to start in, otherwise you'll probably not push it in straight by hand.   If you have a nice rigid setup (Mill/really good drill press), you often don't need to spot a 135° drill bit, especially a cobalt or carbide one.  If you're doing it by hand or on a wiggly drill press, definitely spot or you'll likely wear out the tool prematurely.

One suggestion when out in the field trying to drill by hand is to use a drill bushing to keep the bit from walking around.

I'm currently testing the 135° drill bit set from harbor freight for my little CNC mill, it's a TiN coated HSS, but so far they seem to cut as well as the DeWalt kits I normally buy. 

I wouldn't buy cobalt for a hand drill, you'll snap it or destroy it before its time.  I'd stick with TiN coated HSS unless you have a specific hole you're drilling a lot of, and plan on them being consumables.

Edit: sorry, just saw you're using them in a drill press.  For a 7/8 drill bit, you might be running too high of RPM and burning up the tip. In A36 mild steel, my calculator says you really want to be around 315 RPM and be moving around 4.5 inches per minute, so slower speed and a bit more pressure downwards. That's asking a LOT of a drill press, so I'd probably go down to 159 rpm and try to hit about 1"/minute.    Don't forget to use some cutting fluid.

Pre-drill with a smaller diameter bit if you can.  Progressively work your way up to the diameter you ultimately want.  It takes a lot of pressure off of the zero velocity center web of the bigger bit, lowering the overall axial cutting forces.  Also, see what your local Grainger store has on sale for bits.  You might get lucky there.

For TiN coated HSS bits in structural steel, run about 75-100 (max) surface feet per minute SFM), using cutting oil.  RPM is calculated from the SFM based on drill diameter as follows ...

circumference = 3.14 X diameter;

RPM = (desired SFM x 12) / circumference.  

So for a 1" diameter bit, running at 75 SFM, that equates to 286 RPM.  

Hope that helps.

How about hole saws? Milwaukee 9/16" up to 1" except for 5/8" $5.00 ea. Hole Dozer Bi-Metal Hole Saw

In reply to VolvoHeretic :

I have a full set of those Milwaukee hole saws, keep them lubed and not much can stop them.

Real cutting fluid, too. WD-40 is often worse than dry. Tap magic or honing oil will help a lot, and it works great with hacksaws, too.

Was wonkothessne said. Get the speeds and feeds right. 
 

years ago I used to be able to buy msc import brand drill bits made in Poland.   They were good. 
 

Stuff is now Chinese and garbage.   Damnit I'm old. 

Most of this is in the drill press, but I snapped the cheapy 9/16" bit with a cordless hand drill adding a winch plate on my trailer.  Couldn't really get the trailer in the drill press.

I always use a dedicated cutting lube which is different depending on the metal.  For the steel I use Oatey cutting oil with high Phosphorus but for aluminum I use WD40 or paraffin.

Drill press belt is on the lowest speed, but I'll have to check what that RPM actually is.  My musician brain says 400 rpm or close to that.

I always pre-drill.  For the 9/16" hole I went 1/4, 7/16, 9/16... or something close to that.  I often use the less-common sizes for stuff like this so I don't over-use the eighth and quarter-sized bits too much.  I probably chose something like 13/32" for the middle size.  Critique me on that if I'm doing that part improperly.

I don't have a coolant setup and don't really see the cost/benefit for the home hobbyist, I just keep adding lube and try to not apply enough pressure that it goes up in smoke

Unless your drill press has absolutely no ass at all behind it, that amount of pre-drilling may be hurting you.  Yes, you are reducing the amount of metal the drill has to remove, but you are also reducing how much stock there is to both slow down that (too high for steel) surface speed, and to dampen any runout/chatter.

Step bits.  Using a twist drill in sheet metal will not give you a round hole.

Step bits are hugely important as are the small holesaw-esque cutters you can buy these days. Get a gallon of real cutting fluid from NAPA and some lab bottles when mixed per instructions a gallon lasts a long long time. The HF silver and deming bits are way better than they should be for $50. 

Until a couple of years ago while working with a pipe fitter drilling through thick metal and SS when he somewhat explained drilling speed, I always drilled at the maximum speed the drill could achieve, because HIGH speed drill bit, right? I had to look up SFM (Surface Feet per Minute)- Selecting the Best RPM for Drilling. Too bad my hand drill doesn't have a tack on it.

travellering said:

Unless your drill press has absolutely no ass at all behind it, that amount of pre-drilling may be hurting you.  Yes, you are reducing the amount of metal the drill has to remove, but you are also reducing how much stock there is to both slow down that (too high for steel) surface speed, and to dampen any runout/chatter.

Quoted for truth.   Since you're on a press, I'd recommend getting a 135° spot drill, then 135° drill bits and have straight at it.   Obviously, if you're cutting with a 7/8" drill bit, you need to have the part CLAMPED.   The other problem with doing a lot of steps is that you only end up using the outer edge of your drill point, which means you're notching it, causing you problems in the future. 

You want to engage enough of the flute to pull an actual chip, not just grind the outside down.   Remember that the feed & speed calculators work on the whole diameter being used, if you're only using the very outer edge, you're doing what's called "chip thinning" and you need to increase your feed & speed appropriately to match.

In the field, you're generally stuck by how little force we as humans can apply accurately, and you end up putting a bit of angle/twist on the drill bit and that's why it walks & snaps.   That's also why 118° works better by hand, you're pressing your little bit of force on a smaller point.  If you can, clamping a bushing to what you're cutting will help tremendously, even if that bushing is just a decent scrap piece of wood you drilled a hole in with the same drill bit.

In practice, for field work, I've been quite happy with the DeWalt brand drill bits sold by lowes, they're HSS with TiN, but again, you just have to treat 'em as a consumable.