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Drill bit quality

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  • Drill bit quality

    I'm a woodworker and sailor by hobby but find occasional use for metal work. The sailing requires stainless steel work at times, always 304 or 316 SS. I'm puzzled from my reading of types of drill bits and how to use them. Just about anything works OK in wood, but with steel I've melted several bits and have rarely gotten through SS. (An exception is a set of 5 DeWalt bits with a stepped cutting edge.)

    What kind of bit should I get for general metal use including stainless steel?

    How do I know if a bit set is quality? Is price a reasonable assurance? Do I get what I pay for? Are there manufacturers that reliably produce quality products? Suppliers that reliably sell quality products?

    Can you lead me to articles or forum threads that will teach me more about drilling and, more specifically, how to use the drilling process properly?

    Thanks for any help you can give.


  • #2
    I can almost guarantee that your rpm is too fast for drilling stainless. Drill at the slowest rpm you can and use plenty of pressure otherwise you work harden the stainless and it will just melt your bit.

    My Web Site


    • #3
      Simple rule, The harder the material, the slower you need to run the drill bit , and the harder you push !

      Simple rule # 2, The cheaper the drill bit, the lower the quality. Those "gold" plated full sets of drills for 20 bucks are garbage

      If you want a drill that will help you with stainless steel, get a Colbalt drill with a 135 degree lip angle, and look for American drills, like Cleveland, Chicago Latrobe, or Precision (PTD) or Japanese like OSG. The Germans make good drills (Bosch)but are harder to find..
      Make sure you read the shank of the drill. If it says " USA", you have it. If not, then beware !

      Green Bay, WI


      • #4
        You can get what you pay for if you're careful.
        For good cutting tools I always buy "Made in the USA"
        Niagara cutter for end mills.
        Dormer for drill bits.
        Available everywhere.
        Not cheap

        Look here.

        My Dad always said, "If you want people to do things for you on the farm, you have to buy a machine they can sit on that does most of the work."


        • #5
          Use a cutting lubricant on metal, saves bits and a sharp bit means less work for you. Doesn't have to be fancy, something like thread cutting oil (available at Home Depot) will be OK.


          • #6
            It's all good info you've gotten so far. And with stainless, not only do you need good drill bits, but you need to keep them cutting while in the hole. You can't dwell even for an instant or some types can work harden and then burn up the best HSS drill bit made. You don't want the bit to rub at all. Depending on the exact grade of stainless your working with, Machinery's Handbook lists drilling speeds from 20 feet per minute up to 90 fpm.



            • #7
              what the other guys said.....and.... those grades of stainless workharden very easily. Unless you keep up an aggresive feed or you're done. If you can, 303 or 416 are a treat to machine.... unfortunately both have poor weldability.


              • #8
                You do get what you pay for in drill bits. Harbor Freight and Home Depot bits will last a fraction of the time of a good set of Precision Twist, Cleavland, OSG, or Hertel bits will.

                The subject of drill bits is huge, I've covered some of the basics below, but this only touches the surface when it comes to drill bits.

                The three common material drill bits are available in: high speed steel (HSS), cobalt (HSS with cobalt), and carbide. There are other exotic materials, but probably are not what you are looking for. HSS if for general purpose drilling in most materials, cobalt for tougher alloys such as titanium and stainless and carbide for really tough materials or production work.

                In the drilling range of 1/16 to say 1/2" you generally have three common styles that only differ in length: jobber, stub, extra long. Jobber style are the most common and stub length are used when rigidity and head room are paramount.

                In the range below 1/2" you have fractional, lettered and numbered bits. (ya just gotta love the English system). The fractional, numbered, and lettered bits cover all your tapping needs. If you are not planning on tapping holes, then a fractional set might be all you need.
                If you go larger than 1/2" you enter into the world of taper shanks and Silver and Deming (reduced shank) bits. Silver and Deming are good when holes are relatively short and head room is at a premium. Taper shank will grip until they twist in two and thus are great for hogging material especially in deeper holes.

                Point type
                118 degrees, split point, and spade. 118/split points: lots of personal preference in this area and conflicting data from data sheets. Generally split points won't walk as much as a 118 when first contacting the material to drill. The rest is a subject of debate.
                Spade bits are generally made of carbide and are for drilling lots of tough material.

                If you are drilling lots of stainless and other materials, I would suggest jobber length cobalt bits. They will last much longer when drilling in tough materials like stainless. There is a cost differential, but then your time sharpening drill bits has to be considered too. Use coolant if you got it; it works wonders.

                If you are drilling stainless day and night you might consider carbide spade bits, but I would only go that path if I was drilling lots and lots of holes since the per bit price is high and sharpening carbide requires special grinding wheels.

                As far as sizes: If you plan on doing lots of tapping in the 4-40 to 1/2-13 range you might as well get a whole set of jobber bits that include fractional, lettered and numbered bits to avoid not having the bit you need. If you just need to punch a hole through some random materiel every once in while then a simple set of jobber fractional bits will most likely suit you fine.

                If you take care of your tools and learn to sharpen your bits, most will last a lifetime (the small ones will occasionally shatter and disappear into thin air). I've lost a #78 just putting it in a chuck.

                Over time I have collected almost every conceivable style of drill bit, right hand, left hand, carbide, spade, taper shank, aircraft, coolant through, Silver and Deming, stub length, jobber, etc. I have found uses for all of them, it just depends on what your needs are and you don't need all the styles right off the bat.

                One could write a whole volume on drill bit styles and their use. Hopefully this gives you some useful information to start your search.


                • #9
                  My suggestion would be that you stop at a few yard sales, flea markets, auctions etc and keep your eye out for the boxes, jars, tubs etc of old drills that you can buy for <$10. Buy/acquire/find a good quantity then clean them up (nylon or brass wire wheel works wonders), and use them to practice sharpening on the bench grinder. You dont need a dedicated drill bit grinder, just a bench grinder and a bit of patience, practice, and eyesight. Once you learn to grind them properly (many online tutorials), keeping an eye on what dulls them quickly vs slowly will teach you a ton about drilling various materials.

                  You will be surprised how quickly and cheaply you can acquire a good set just by buying/cleaning up/sharpening others used odd drills.
                  "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."


                  • #10
                    McMaster Carr always handles quality drill bits. Their prices are fair, their delivery excellent, and they don't rip you off on shipping. Everything said earlier stands, but if your'e drilling with a hand drill and using a bit larger than say a 1/4 in, it will be difficult to obtain sufficient pressure in stainless. Bob.


                    • #11
                      Thanks much. Lots of good info. I thought I posted a reply earlier but don't see it. If there's a delay in posting there will be 2 replies. Oh well. I used your info and searched on line this afternoon. I've purchased from McMaster-Carr before with good results. They don't, however, say anything about origin or manufacture of their bits. However, considering your advice, their reputation, and the price, I suspect it would be a good place to go.

                      Thanks much for your help. This is a good forum. I don't have the knowledge to contribute but I'm sure I'll have questions in the future. I appreciate your help.



                      • #12
                        Geoff --

                        A lot of folks, including me, find "Cobalt" twist drills -- which are made from a "high speed steel" alloy containing around eight percent cobalt -- hold up better when drilling stainless than other high-speed alloys do. Most cobalt drills come from the factory with a "135 degree split point", which is well suited to stainless.

                        Shorter drills (according to my instructors of way back when, "drill" is the metalworker's term for what the woodworker calls a "drill bit") are usually better than longer ones, especially when they are chucked in a drill motor (metalworker's term for the woodworker's "electric / pneumatic drill") or "eggbeater". The typical hardware store or home center usually sells "jobber length" or longer drills; industrial distributors or mill-supply houses can get -- if they don't stock -- the shorter "mechanic's length" and shorter-again "screw machine length" drills.

                        I've been a fan of Norseman-brand and Viking-brand drills, which come out of the same plant in St. Paul, Minnesota, and are probably identical until they are marked with the brand name. Triumph Twist Drill, which changed their name from Minnesota Twist Drill after buying Precision Twist Drill Company's economy line, Triumph, also makes a good drill.

                        As the others have already said, when drilling stainless you need to turn the drill slowly and feed it aggressively. Here in the US, drill speed is usually measured in "SFPM" -- Surface Feet Per Minute, which can also be abbreviated "SFM" -- while the speed of the drill press or drill motor turning the drill is measured in "RPM" -- Revolutions Per Minute". Since you know how big a drill you're going to use, you need to calculate the RPM . . . using the SFPM appropriate to the material you're drilling into.

                        Good drill makers publish literature with recommended cutting speed ranges for their various types of drills, into various types of materials. For example, Norseman recommends 15 to 50 SFM when drilling stainless with a high-speed alloy drill. For the work you and I would typically do, slower speed leads to longer tool life. So let's use the 15 SFM value, and calculate RPM to drill a 1/2 inch diameter hole:

                        RPM = 15 SFM / (0.5 inch x Pi / 12 inch/foot), which is reasonably approximated as 15 SFM / (0.5 inch / 4) = 120 RPM.

                        Others have also mentioned coolant or lubricant, especially when drilling stainless. Most hardware and home-center stores sell "pipe threading oil" in small packages -- sometimes as small as 8 fluid ounces, to as large as a gallon -- that'll do what you need. But there are very workable alternatives from the kitchen, in the form of animal fats and vegetable oils. Lard (or bacon grease) is the figurative North American standard, but I've known English machinists who preferred beef tallow and a couple of Middle Eastern machinists who used mutton tallow for the tough jobs. Shortening (such as Crisco) and vegetable oils aren't as traditional, but they are also very effective.

                        The downside to the animal fats and vegetable oils is that they will, sooner or later, go rancid and STINK if not cleaned up.



                        • #13
                          Canola oil is my go-to lubricant for tough drilling, reaming, or tapping jobs. I'm still using the same $1.59 quart I bought in the grocery store back in the 20th century. Hasn't gone rancid yet.

                          The canola plant is a relative of the rape plant; I'm guessing the oil is similar to the "rapeseed oil" my antique machinist books talk about. Either way, it works great.

                          Downside: if you don't clean it up, a week or so later it turns into something that's basically glue. It is *slightly* soluble in acetone and laughs at gasoline, naptha, kerosene, Var-Sol, and various types of carburetor cleaner. I had it all over the shop before I discovered this, and spent most of two days cleaning it up.

                          It works better than anything else I've ever encountered. Just don't let it dry!


                          • #14
                            Good information so far; I'll try not to repeat what everyone else has already said. I used to do a lot of work in both 304 and 316 for particle accelerators components. I've done everything from hogging enormous amounts of material to tapping 2-56 holes in 1/4" 316 and never had any issues. Follow the advice already given and you'll have much more success.

                            Since it sounds like you are new to the game, consider this website for tools/supplies: They carry a decent selection of quality and low quality (e.g. import) tools and supplies. For a drill bit set, I suggest you start with a Hertel set. The general consensus is that the new Hertel is mid-range quality.They used to be an independent German company but a really big cutting tool company called Kennametal bought a controlling interest in 1993 and recently, Hertel has shown up in many USA supply catalogs (like Enco). I have a set of cobalt 135* split point drills from Hertel and have been very pleased with them. I also have sets by Lawson, Chicago Latrobe, Precision Twist and several sets of no-names. The no-name ones were still fairly expensive and they have held up surprisingly well; they sit next to the drill press and get abused. My good sets get used mostly in the lathe or mill.

                            I find that I prefer 118* points for thin work. Although you have to worry about it wandering at first more than 135 split points, they don't seem to chatter as bad as the split points. But, like others have said, this is a topic of debate. Look for a good set that is on sale and don't worry too much about point style. Coatings aren't too important either, but be aware that the "gold" coating isn't meant for aluminum. The aluminum will gall really bad.

                            Have a look through Enco. When you find a set you want, search the forum for "Enco Promo Code". I posted a code here a couple days ago that will give you free shipping and 10% any order of $99. As most of us here know, Enco regularly emails promo codes, so if you miss this one, there will probably be a free shipping or 10% code next month.

                            Here's a cheap set to get started with:

                            Once you get deeper into the hobby (or profession!) you will find that you want more sizes (letter and wire sizes) and better quality, but the above is a good general purpose set.


                            EDIT: Even better! Just got an email that you might find useful...
                            With the fall semester in full swing, it's time to save big on the essentials you need. From now through the end of the month, students, schools and educators can take an additional 10% off plus enjoy free shipping* on all orders - no minimums and no exclusions!

                            To take advantage of both offers, be sure to enter both promo codes prior to checkout. Simply enter promo code: TENOCT (then click apply) for 10% OFF, and then enter promo code: SHIPOCT (then click apply again) for Free Shipping!

                            Both promo codes can be combined, but must both be entered prior to checkout.
                            Hurry! Offer ends October 31, 2012.
                            Last edited by Fasttrack; 10-18-2012, 10:10 AM.


                            • #15
                              Something that hasn't been mentioned yet, step the hole up. If you want to make a 1/2" hole, start with 1/8" or maybe 3/16" drill bit. Then you can get enough pressure to keep the bit cutting. Once that first drillbit gets through, it gets much easier. If you try to start with the 1/2", you can't lean on it hard enough to keep it cutting.
                              I'm here hoping to advancify my smartitude.