Drill bit quality

[Treeview]

I buy 1/8" double ended drill bits in 10-12 quantities. Mostly I've found them at flea markets for a few dollars. Now I need to order on-line. The choices are overwhelming...and this lead me to wondering about drill bit quality in general.

How do we know what is used to make the bit?
How do we know how tough the bits are? I bought a small assortment one time and the bits were about as tough as nails...in the drill bit sense. Dulled and broke them all quickly.

Years ago I bought a DeWalt set in the plastic box...from three sizes below an 1/8 up to half inch. They're been good performers.

Does anyone have a favorite source for jobber bits?

Tom

[eamarquardt]

Bits in the order of quality are carbon steel, high speed steel (HSS), cobalt, and then carbide. HSS should suffice for most uses but cobalt last longer per sharpening. That said who knows what you're buying now-a-daze with so much crap being made in China. If the bit is made in the USA I think you'll be good to go in most materials with HSS. I recently drilled some holes in Stainless Steel and got three holes per sharpening using a cobalt bit. The SS was nasty stuff.

I bought 5# of cobalt bits on EBay that I use for general drilling. They're in the 0.090 to 0.150 range so I use them for drilling pilot holes and then follow up with the proper size bit. Better to drill pilot holes for accuracy of the finished hole size and location.

Here are some items on EBay.

Yeah 5# is overkill but I give them to friends and make their lives just a bit better.

http://www.ebay.com/itm/50-pc-1-4-11-10 ... 3cd40eb179

http://www.ebay.com/itm/COBALT-DRILL-BI ... 3cd414376f

http://www.ebay.com/itm/3-75LBS-ASS-6-H ... 43ad35c15b

I bought one of these and it works great for sharpening bits perfectly and also thinning the web on industrial bits with thick webs:

http://www.drilldoctor.com/index.php?pa ... Itemid=144

[asianflava]

I've never had luck sharpening on the grinder so I got one of those Drill Dr rigs. It works like a champ, actually takes me longer to get it out and plug it in than it takes to sharpen half a dozen bits.

[halfdome, Danny]

Years ago I bought a DeWalt set in the plastic box...from three sizes below an 1/8 up to half inch. They're been good performers.

I've never had luck sharpening on the grinder so I got one of those Drill Dr rigs. It works like a champ, actually takes me longer to get it out and plug it in than it takes to sharpen half a dozen bits.

Same here.
I found the Harbor Freight tin coated bits don't hold a point for long.
It will be interesting to see if someone has a source that's a good performer.
Danny

[CarlLaFong]

Hanson, Cleveland and Vermont American used to be good quality bits. However, they are all Chinese now. As a sidebar, how many Americans used to work at these factories???? Anyhoo, here is a company that still cares about delivering a quality product at a fair price. https://www.americanmadedrillbits.com
Harbor Fright bits are worth every penny you pay for them

[Treeview]

I bought the large Drill Doctor...what a great tool! yesterday I made a shelf to mount on the pillar in my workshop so that I don't have to go to the file cabinet when I need to sharpen.

I need a few single drills to keep my sets complete. Buying the singles from the American Made drill bit company is economical.

Thanks for the info on bits,

Tom

[halfdome, Danny]

Thanks for the link, it's now in my favorites.
Danny

[Kody]

I don't know what brands of drills you fellas have over there, so I can't comment on the quality of the brands. However, High Speed Steel drills are not all the same in quality. Yes, they are made from High Speed Steel (HSS) but there is both high and low quality to be found in this material. I will never buy a drill made in China as 99% of these are junk. The best drills are made in the US and Australia and these are the easiest ones to obtain. Cobalt drills are made from HSS with the addition of Cobalt to add extra hardness, heat resistance and especially toughness. The bad thing about Cobalt drills is that they are rather brittle and can snap if they are dropped onto a concrete floor. You will also pay more for these drills but they are certainly worth the extra expense. If you want the best drill of all for drilling metal (and also wood) buy the "TiN" coated style. These are recognized by the beautiful bright "gold" plating on the drill from the cutting point to where it is held in the chuck. The coating is Titanium Nitride and produces an intensely hard and "slippery" surface, slippery means a surface with an extremely low coefficient of friction. These drills are wonderful for drilling aluminium and deep holes in steel. The TiN coating is also applied to the end of the drill when it is made. Don't be afraid to sharpen these drills, The TiN coating on the end is lost when sharpening, obviously, but the quality and performance of the drill still remains. It is the coating on the surface of the flutes that does the work. This is where the swarf/cuttings slide up to be expelled from the hole. The drills cut so much better than anything I have used. However, some manufacturers (like in China) coat their cheap and nasty drills with TiN so you need to be very careful of what you buy and where you buy it from. The best guide to quality is the price but look to see where it is made.
Some drills are completely black in colour when you buy them. This is an oxide coating but I'm not certain what it consists of. The advantage of these black drills is that they resist corrosion much better than a standard form of HSS drill. There are other coatings on drills but they start to become cost prohibitive, an example is Titanium Carbon Nitride (TiCN) and Titanium Aluminium Nitride (TiAIN). These drills are superior to the standard TiN coated ones and you will pay a lot more for these. They are not necessary in the home workshop.
When you sharpen your drills, it is best to grind them down on a "coarse" grit wheel as this is much quicker to do. When you complete the finish grind, always use a fine grit wheel to produce a fine smooth finish on the cutting point and the edges of the flutes. A smooth finish adds greatly to the life of the cutting edges and cuts better with more accuracy.
Every drill I now buy either as a new size or as a replacement, is TiN coated, they are definitely the best. Cobalt drills are also available as TiN coated.
Hope this helps a bit more,

Kody

[Kody]

Just a short note about drilling Stainless Steel. There are as many varieties of S.S. as there are fish in the sea. Only a few of these steels are noted as being "common" and found in most workshops and shops that sell S.S. All of them have two properties in common, they extremely tough and resistant to machining/drilling and they are also quite soft. Yes! They are quite soft. Softness is not usually combined with toughness. It is this toughness that makes S.S. so horrid to work with. If the cutting tool (lathe tool, drill bit, saw blade) becomes dull, it won't cut but will instead cause the S.S. to work harden. If this happens you will end up ripping all your hair out. The secret to machining S.S. is to reduce the cutting speed, ie, the feet per minute the S.S. is passing the cutting tool. Normal steel (used for making cars, trailers etc) is machined/cut at a speed of 80 feet per minute and finished machined at 100 feet per minute (using HSS cutting tools). For machining /drilling S.S. the speed must be reduced to at least half of this (40 or 50 feet per minute). Sharpen your drills to a minimum front clearance as this adds strength to the cutting edge and leaves more steel at the edge to act as a heat sink. You absolutely must also use a high quality lubricant / coolant as a lot of heat is produced. The deepest holes I have drilled in S.S. were 9 inches with a 5/16" HSS drill. I had to drill an 18" length of 3/4" diameter S.S. from end to end so I drilled it from each end. The time it took for each 9" hole was less than 20 minutes. This could not have been done without an ample supply of lubrication and coolant. I also had to extent the drill length from 6" to 12" to drill the holes. It was a fabulous job to do.

Kody

[eamarquardt]

Re drilling SS. The 1/4" plate I was working with was a bear. I used a plasma cutter to cut it into about 6 inch circles. I then drilled three holes in it (for mounting) and a center drill in the center. As I mentioned, even with my drill press at its slowest speed the bits would dull after three holes. I then put screws in each piece to serve as lathe dogs and held it against my three jaw with a live center. Even with new carbide inserts I couldn't turn it round on the circumference. I finally gave up and ground the discs round with a 12" disc sander. You can grind virtually anything.

I'm not sure what this stuff was and how it was heat treated but I've worked a lot of SS and never seen anything like it. I had to make several other parts for this project out of SS (I was refurbishing 5 BBQs) and had no problems with the other SS pieces I had to fabricate.

I have one more piece of this stuff and I'm not sure how I'll work with it again, ha.

I recently refurbished a 30,000 truck lift. I wanted the rollers to be able to grease the rollers for the lift chain so I drilled some grade 8 bolts lenghtwise and then cross drilled them. No problem. I've also drilled grease passages about 7 inches deep in hinge pins for my dump trailer. Again, no problem.

Cheers,

Gus

[Shadow Catcher]

There are different grades of SS some with more chrome (what makes it SS) there are also other alloying components that can affect toughness. As for drill bits I would be looking for an industrial supplier rather than consumer.

[eamarquardt]

There are different grades of SS some with more chrome (what makes it SS) there are also other alloying components that can affect toughness. As for drill bits I would be looking for an industrial supplier rather than consumer.

Agreed and I was using industrial, American made, cobalt bits.

Cheers,

Gus

[Ron Dickey]

I just resharpen them.

[grantstew8]

I have a wide quality range of drill bits and this is the first time a bit has bent and not broken (I break lots particularly the little ones)
It looks like it missed the hardening stage in the manufacturing process......

[Kody]

The shank (end) of most drills is left soft. I think this is so the jaws of the drill chuck can hold it better and lessen the chance of the drill slipping in the chuck but I am not certain of this. It looks like the drill has been held at sometime by the extreme end by the look of the score marks on the end itself. We all do this at some time to get the greatest length of the drill to do what we want but sometimes it can be rather hard on the drill. Was this a high quality drill or a cheap one from Asia? If you are breaking a lot of small drills, you need to run them much faster, the highest speed of your drilling machine is usually still too slow for small drills. Just as an example, a 1/4" drill should be run at 1200/1500 rpm. An 1/8" drill is run at 2500/3050 and a 1/16" at 5000/6000 rpm. Anything less than the slowest of these speeds and drill breakage rate begins to soar. These speeds are for drilling mild steel.
Hope this can help you and others,

Kody