Drill bits

I will point out that "titanium bits" are steel bits with a gold colored titanium nitride coating on them. Actual titanium is too soft and flexible to make a good cutting tool.

TiN is an inexpensive process that a lot of really bad Chinese drill bits are treated with to give the (false) impression that they're good tools. In that case, it is almost purely decorative.

In soft abrasive material such as plastic and wood, the coating improves the life of the tool and reduces cutting temperature.

Most non industrial users, using non industrial tooling and non industrial machinery to work steel are going to blunt the cutting edge through gross edge damage from imperfect alignment and uncontrolled feeding, not through gradual wear, which is where TiN is of benefit.

I would look at the quality of the steel and grind in the bit before the coating.

You will notice an improvement in life using a cobalt HSS bit. The longest life is with carbide - but most users will not like the life they receive if they're not used within a narrow processing window.
 
What I think Nathan meant was: If you do not have a very rigid setup and spin the bit at the right speed it will break. A cheap drill press is not a good way to go with carbide bits. They are extremely brittle and any real side load and they snap. If you have a rigid setup like a milling machine and a good vise and spin them at the correct speed and presure they will drill tru a fully hardened piece no problem. When I first started using carbide end mills I was very frustrated because I broke them so often. Then I started spinning them a LOT faster and breakage dropped to nill unless I did something stupid.
 
ib2v4u said:
What I think Nathan meant was: If you do not have a very rigid setup and spin the bit at the right speed it will break. A cheap drill press is not a good way to go with carbide bits. They are extremely brittle and any real side load and they snap. If you have a rigid setup like a milling machine and a good vise and spin them at the correct speed and presure they will drill tru a fully hardened piece no problem. When I first started using carbide end mills I was very frustrated because I broke them so often. Then I started spinning them a LOT faster and breakage dropped to nill unless I did something stupid.
Click to expand...

Thanks... that makes sense. I have a number of solid carbide drills that I use for drilling through hardened steel using my HF drill press. I have drilled quite a few holes and have never broken (or been concerned about breaking) a carbide bit. I do, however, always make an effort to securely clamp the piece. I drill all holes on my drill's lowest speed setting (~180rpm) and let-up on the pressure as the bit goes through the bottom of the piece (to avoid binding). I have no experience with milling, bit imagine that the lateral stresses involved require that a lot more attention be payed to speed and feed rates. Carbide drills are not used with great frequency in my shop... but when they are needed, they do their job well. :thumbup:
Erin
 
There are three main differences between steel and carbide.

One, carbide is stiffer than steel - so you get a better finish and accuracy (think about this - the steel in the bit is deforming as much as the steel being cut, up to the yield point of the work piece)

Two, carbide is harder than steel - so it can cut harder things, and resist wear.

Three, carbide will withstand higher temperatures than steel - so higher cutting speeds can be used that get into a SFM range where steel doesn't weld onto the cutting edge of the carbide, giving improved finish and accuracy and life.

You don't always have to use all three properties to justify the use of carbide.

The major down side to carbide is the combination of stiffness, and zero ductility makes it unforgiving of errors. A slight misalignment of a drill bit to a work piece (caused by flexibility in a fixture, table or vice, or runout in a tool holder or chuck) the stiff tool doesn't comfortably conform to the illregularity - but breaks or (more commonly) the very cutting edge chips.


There are basically three types of carbide drill bit:

One, the circuit board bit or similar has high relief and rake angles to cut fibrous material or plastic without delaminating it or creating unnecessary heat. It is very sharp. It is used in production machining of plastic, aluminum and other soft abrasive materials.

Two, the straight flute bit has a square (or nearly square) cutting edge designed to drill hard steel.

Three, the concrete bit, with is like a split point spade bit. It is not very well suited to drilling good holes in steel.

Most carbide bits fall under the first category and are fairly fragile in use, especially in steel. Over feed them on exit and the cutting edge fails. Underfeed it and squeak it, the cutting edge crumbles. Get it chattering during the start of the cut, it falls apart. So for most non production users, the additional life of carbide is frequently never realized.

Turning your spindle as slow as possible might help prevent chatter and squeal that damage carbide, but carbide likes to turn fast. Turn it fast enough and the steel can't weld to the cutting edge, pulling craters off the carbide as it pops loose, and you're less likely to overfeed it on exit, which is where most damage occurs. Carbide almost always does better when used in the recommended SFM range, which in our applications is usually between 90-200 SFM - which is pretty fast. Faster than most sears drill presses can turn a bit without chatter due to flexibility issues.

I have spent several thousands of dollars already this year on carbide cutting tools, but I don't use carbide drill bits in steel. But if I did, I would probably turn a 1/4" bit about 3000 RPM, and feed it about 10 inches per minute.

I do use carbide drills in production machining of plastic.
 
Getting a bit off-track here...

Simply put, most here on the board will get the best overall utility out of cobalt bits- that is, assuming you buy bits that actually have a given percentage of cobalt in them, and aren't just Chinese scrap-metal drills called "cobalt".

Keep in mind that a lot- way too many- drills you find in retail and box stores will use buzzwords like Titanium and Cobalt as brand names, not descriptions. "Titanium Brand Twist Drills" is considerably different from "Titanium-Nitride Coated Twist Drills".

Cobalt drills are simply HSS (high speed steel) with upwards of 8% Cobalt added- an alloy called M42. I raises the "red hardness" of the steel, so that the drill retains it's strength even at elevated temperatures.

In terms of cost, HSS and "black oxide" (which is just a coating on HSS) are the cheapest. Cobalt adds a bit of cost, but tends to make the drill last longer and perform better. Carbide, on the other hand, is anywhere from three to six times more expensive than even cobalt, and if you don't have the rigid setup and flood coolant virtually required of carbide use, you won't get any significantly longer life out of it before the edge chips or it breaks entirely.

And even then, just straight HSS will work for 90%+ of all your drilling needs. Just keep an eye on your spindle speed, and use a lube of some form (doesn't have to be anything fancy- cheap motor oil is often just fine) and keep the bit sharp.

And that last part is the key; drill bits wear in use just as grinding belts do, just as the knife edge itself does. They need to be periodically sharpened for best performance, which is why I noted, as others did, in the other thread that it's very much worthwhile to learn how to sharpen your own drills. (Or to buy a Drill Doctor, although doing it by hand is cheaper, and often just as fast.)

And because of that, exotic coatings like "Titanium" (titanium nitride, or 'TiN') have very little use outside the mass-production arena. Properly applied over good steel, TiN will help the bit stay sharp a little longer, and will reduce chip welding at the cutting edge, but the sad fact is, unless you buy them from a reliable jobber- in other words, if you get them from places like Home Depot or out of the cheap end of an ENCO catalog, you won't get what you paid for.

They'll either be plated with something not TiN- we've seen cases where the gold coloring is actually a thin copper flash- or is, in fact, Titanium Nitride, but applied so thin it's basically just a color wash. Literally only molecules thick.

So all that said, while it's handy to have a couple of exotic bits on hand for emergencies (I keep one particular carbide drill on hand just for drilling the ends of taps to use a tapping-point guide) you'll do just fine with standard HSS and the occasional M42 Cobalt drills. Personally, I have well over 10,000 drills in the shop, ranging from 0.050" to 2", and out of all those, there's fewer than 20 that aren't simple black-oxide HSS. And with them I do everything from brass and Delrin up to annealed carbon steels and cast irons.

Which is, now that I think about it, one of the other benefits to learning to hand-sharpen drills; You can, with just a few minutes on a grinder, change the point angles as well. A steeper angle (sharper point) for softer materials, a shallower angle for harder materials. It makes a difference, but is worth a whole books' worth of posts all by itself. :D

Doc.
 
Let me confess that I'm among those fooled by (maybe fake) TiN coated drill bit.
It also had stupidly (I can recognize it now) unusual shape of cutting edge.
After the miraculous coating has went off, it was just a normal HSS drill.
Actually less than normal HSS drill because of funny shape of the cutting edge.

I did grind off it's funny shape and put normal cutting edge on it.
But as you may imagine, it never held it's edge as well as normal HSS bits.

After this lessen, I mainly use normal HSS drill bits, sharpened by myself.
 
Here is what I use.
Mild steel and most other soft materials I use HSS bits. I keep a couple sets of fractional, numerical and lettered. I also have a coffee can full of old bits and every once in a while I sharpen the whole batch, separate into groups like up to 1/4, 1/4+ to 3/8, 3/8+ to 1/2 and 1/2+ up. Then if I dull or break a bit in my set I go to these and find a replacement and toss the dull bit into the dull pile.

For hard stuff I have a small selection of carbide drills and small end mills. I only use them in my milling machine
 
I just use regular black or gray HSS bits for everything, unless I get very good prices on cheap ti-nitride bits which I just use and throw away anyhow. Carbide is also very nice, of course, but it's painful to break one, so I use them only when I have something that won't drill with regular bits.
 
i'm thinkin you might could check with a local machine shop and find out where they get their drill bits. and just for fun, find out what thay do with their scrap steel suitable for knife making. could'nt hurt asking.:D
 
OK, I'm overwhelmed by all the information. Can anyone just recommend a brand/model of drill bits for general knife making drilling in a cheap drill press? I too am in the market for a decent set of bits; so, for us inexperienced folk, a brand/model might be more beneficial.
 
I can't make that recommendation, I just use whatever I get cheap. Unless you've got a drill doctor or are experienced in sharpening your own bits, higher priced non-carbide bits are a waste of money, in my opinion. Even with a system it's going to be tough getting an accurate resharpen on bits smaller than about 1/4", so I just scrap them.
 
Just get cobaly 135 degree split point bits. even the imports work ok! i use chicago -latrobe. very good bits (imo).
 
wulfshrunting said:
OK, I'm overwhelmed by all the information. Can anyone just recommend a brand/model of drill bits for general knife making drilling in a cheap drill press? I too am in the market for a decent set of bits; so, for us inexperienced folk, a brand/model might be more beneficial.
Click to expand...

I like the Dewalt cobalt bits. They can be bought in singles or in a kit of 13 pcs http://www.lowes.com/lowes/lkn?action=productDetail&productId=71226-70-DW1263 Z&lpage=none

Be very wary or extremely careful if using them on wood as they are very aggressive and will screw into the wood.

They also dig into steel if you don't get your speed and feed just right and the cutting edge can chip off but if you use a press and a vise you shouldn't have any problems with them.

I don't have a press, only a hand drill so I've gotten good at sharpening the pilot point on the big ones... but I should get better at controlling the speed and not digging them in and chipping the cutting edge :)

I actually bent one of them the other day, very surprising that it didn't break. Anyway, I still had a bunch of holes to drill in a burner tube and kept using the bent bit without a hitch.
 
I like the Rigid brand cobalt bits from Home Depot (even better than the DeWalt cobalt bits). I use more 1/8" bits than any other size... I have been using the same 1/8" Rigid cobalt bit for the last couple months without sharpening. Big thumbs-up :thumbup::thumbup:.

Erin
 
I buy the packs of 10 or 12 from Harbor Freight and after a batch of 4-8 blades I toss. They seem to last pretty good but at the first sign they are not cutting they get tossed, On sale they are $0.10 to $0.30 each.

I dont use them where precision is needed.
 
69_knives said:
I like the Dewalt cobalt bits. They can be bought in singles or in a kit of 13 pcs http://www.lowes.com/lowes/lkn?action=productDetail&productId=71226-70-DW1263 Z&lpage=none

Be very wary or extremely careful if using them on wood as they are very aggressive and will screw into the wood.

They also dig into steel if you don't get your speed and feed just right and the cutting edge can chip off but if you use a press and a vise you shouldn't have any problems with them.


.
Click to expand...


I'll second the recommendation for the Dewalt bits at Lowes, and also second the warnings.

I got in a pinch and put one of these in a machining center running production. New cutters arrived the next day, but I decided to leave the consumer grade drill bit in the mill until it started showing problems. It ran production for a week which is about 10X longer than I thought it would.

The Dewalt bits at Lowes, as of last winter, were good bits.
 
On a recomendation from Terry Davis I started buy screw length bits from msc or mcmaster carr. The latrobe bits from MSC in cobalt drill very good holes and the short length flexes sidways less than the others wich results in a straighter hole. For folder making this is very important.
 
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