I like a debate and thank you for posting this because your points are important to all in balancing the viewpoints than with the information posted letting everyone make a fair choice. Welcome to the forum, my response is in debate and discussion for the good of all interested and to learn more from the
point counterpoint.
Bullet bits are fine for wood and plastic, possibly even superior for it. I don’t drill much wood or plastic anymore, it’s aluminum, steel, brass, bronze and stainless in all types of hard nesses for me now so a more balanced use drill
bit, especially one with superior coatings such as TiCN or TiALN work better on the more common sizes than also last much longer in steel and have a chance with stainless steel or tool steel. Just yesterday I was cutting and drilling some 1/4"x2" mild steel plates to mount a
mirror ball motor off an I-Beam. The 48"
mirror ball weighs 120# so not only did it require sizable materials but accuracy in drilling for it’s mounts. This required multiple ½" holes
thru a double
thickness of plate and tap drill bits for bolting the plates together. For a homeowner like a school, that is not doing much refined work or does not have the time to properly drill the hole with pilot holes, correct speed and lubricant so as to preserve
bit life, the bullet tip might be useful. It takes some training to learn proper drill speeds, oil
etc. Without that training even expensive drill bits bite the dust. But for anything major, that bullet tip with it’s chrome finish would not last long. This is my opinion, you speak well of your use and knowledge on the subject and would intend not to infer anything different, this is still my opinion and training not a judgement.
Depends upon the material you are cutting and who is cutting it. I don’t know about you but I prefer to use a center punch to
mark my hole while I’m laying it out, than step or
walk up the bits in size if not using a TiCN (titanium coated) Uni-bit step
bit for anything 1/8" or less in
thickness. It also depends upon the cutting angle of the drill
bit point angle 118° or 135° as to how clean of a cut verses how much walking it can do, plus the proper speed. With some practice, stepping up your drill
bit can be about as fast as sitting around heating up the single drill
bit as it cuts, but less heat means longer life no matter what the finish or brand. Your
point is correct that the bullet tip is possibly better than a solid split
bit if it’s the only drill
bit used, but drilling with a single twist
bit is not that smart to do often anyway in metal.
Bit walking... not with a center punch much less walking/stepping up your drill
bit sizes and a 135° tip. They will walk more commonly if the above is not followed as you state - perhaps more than the bullet tip.
The problem I mainly cite with such bullet bits is that you can not use them for stepping up the hole in size. Let’s say you want to drill a ½" dia. Hole in 1/4" plate mild steel. Very common in the lighting industry that size for structures and clamps. With a bullet
bit you would have to either use that ½"
bit for the only
bit which would more quickly dull it, or figure out what size the center
point is drilling at so you can use that size
bit or one smaller first. That means two bits used. Now granted, with stepping up split tip drill bits, you would have to use at least three sizes of drill
bit to get the job done, but it’s a lot easier to drill say a 3/16" hole first, than a 5/16" hole than the final ½" hole than a single ½" hole with a bullet
point bit or say a 3/16" than the ½"
bit. I would normally go with four bits, but it all depends upon the hardness of the materials. You really don’t have that option with a bullet tip
bit.
Let’s say your hole is 3/8" and you discover you need it to be 13/32". Much less 25/64" which would probably be hard to find in the home center/local supplier along with number and letter sizes where appropriate such as for a
tap and die set or specific hole size. Bullet bits are not very good at stepping up holes due to the
flat or negative angle of their secondary cutting surface and now due to a lack of center positioning, it won’t center too well without something for the
point to center on. In other words, one hole and don’t try to improve upon it in going slightly larger unless you have more normal drill bits also in
stock. You cannot accurately use a bullet
bit to make a already 3/8" hole into a 13/32" hole, much less to make a 3/8" hole into a ½" hole. Can’t use it to make a 10-32 mounting
bolt for a 3"
Fresnel C-Clamp into a 1/4" mounting
bolt hole given you could find a #7 sized Bullet
bit for the 1/4-20 tap.
In addition to this drill at an angle and the stepping bullet
bit is also much more likely to walk. With a normal
bit you start the hole dead on than once started you can move the
bit to the desired angle or
block something up against the surface to balance the
bit at an angle. This would not work to well with a bullet
bit because of the interrupted tip.
I would also cite that the standard bullet tip is available in chrome, black oxide if you can find it from Black & Decker for the “premium bits” and perhaps titanium coatings if available though neither are listed on the website, just chrome. Who do you get such even TiN coated bits from given production drilling where you need say 60 or 100 holes in a hard surface without replacing bits? Much less Cobalt and solid carbide bits are not available for special purposes such as drilling pipe - something we don’t do much of in the theater. Schedule 40 black water pipe tears up normal drill bits but I admit I have not tried it with a Bullet
bit.
I know I had a pamphlet on the Bullet
point somewhere but could not find it to tell me what types of
bit other than Black Oxide I believe in a economy off shore brand and most commonly chrome coated were available. The website was not of much use either on this type and coating question. Must be that one drill
bit is as good as any other and last just as long in all materials and applications. It would seem that no major suppliers such as J&L, McMaster Carr, Grainger, or Fastenal sell the bullet tip
bit either for
ease in getting them. Funny, unless I go to a home center, I just can’t find the Bullet
bit. That takes time, faxing in an order for same day delivery is much quicker. You would think other suppliers such as industrial suppliers and metal working suppliers will have caught on to the Bullet
Bit’s usefulness. If that home center is out of
stock... plus the extra prices, what do you do drive around to find more? Now a Bullet
Bit proper might live up to more abuse than a standard home center twist
bit, bought one at 5/16" once a few months ago, I believe Tool Shop was the brand. Funny, I never had a drill
bit shatter before. J&L frequently puts a 64 piece TiCN
bit set with index on sale for $30.00. Decent quality 135° plus the index. Might try shopping there than comparing for a general purpose drill
bit.
While black oxide and chrome can be fairly durable on common materials if the proper oil is used and used at the proper speed, they will wear out in mild to hard steel plate unless stepped up so the single individual
bit does not get as warm and there is less effort to the motor - no matter what the tip type. What is the proper drill speed given two drill sizes
in one bit, do you need to slow down the drill
bit once you get to the second cutting surface or are you to run the primary cutting
edge at a faster than optimum speed? On small drill sizes it won’t matter much but once you get past 1/4" heat is going to become a factor.
As Black & Decker says about the
bit, [...eliminating waking which is common to “ordinary” drill bits. (Meaning 118° chrome bits.) Bullet drill bits drill up to four times faster and last seven times longer than “conventional” drill bits. (Or what specific type and size of drill bit was that rating in reference to? A 3/32" drill bit will drill plenty fast.)
These three new bullet sets meet the needs of “serious do-it-yourselfers” as well as “home owners” for all types of projects,]
While the diagram on
http://www.blackanddecker.com/ProductGuide/DocumentView.aspx?DOC_ID=PG_PR_10-01-1999_BulletDrillBits is true to some degree - at least as exaggerated for thin materials, the diagram would not look anything like it were the plate thicker, angle of tip different or speed increased. For thinner materials you are better off using a Unibit anyway.
As I said, I could not find the Bullet pamphlet, I did find one for the Vermont American Sidewinder Drill
bit. It says it cuts three times faster than standard jobber drill bits. I assume in their ratings that a standard jobber
bit is what Black & Decker calls a
conventional drill
bit, though I can find a jobber
bit in the catalog. Also I assume that the pilot
point bit cited is a bullet
point. Anyway, Vermont American says a standard drill
bit takes 51.7 seconds to drill 25 holes
thru 1/4" 1018 carbon steel w/o lubricant. The pilot
point 16.3 seconds and the Sidewinder 14.8 seconds. That’s at lest partial data given they did not cite the dia. of the drill
bit, rather than here say without any data to back it up.
In ½" 1018 carbon steel, again without lubricant, the standard drill
bit lasts 310 holes, the pilot
point 29 holes, and the sidewinder 953 holes. There is also data on what they say is 50% less drilling pressure to penetrate the work piece and showing without any specifications it’s less pressure than the pilot
point. Again, vendors will say what they want from we are the #1 car dealer to 7 times longer life but not really be specific about the testing to achieve that figure.
Sidewinder bits also are said to be self centering given a 135° tip, and are available in addition to chrome, in cobalt, titanium and their normal surface treatment what ever that is. Non walking it would seem is a common statement.
In other words, everybody has a claim, be it side winders lasting 3 times longer than normal, titanium 6 times longer
etc. Again the Vermont American
line is for DIY’er’s or like with the bullet not designed to be used all day long almost every day of the week. Industrial drill bits verses home owner drill bits, there is a difference.
I tend to believe un-biased info such as out of McMaster Carr where it’s not a cut sheet from one brand stating how much greater their product is, rather it’s a description of surface treatments, finish types
etc. and what each one is going to do for a specific application and no brand names cited. Specific bits for specific purposes.
“Coatings extend drill life by as much as 300% to 800% compared to uncoated tools.” I can about attest to that, depends upon the tip,
etc. Drill a few steel rivets out with a jobber verses a bullet tip verses a TiCN tip and see which will last longer and will be easier to use.
As for flipping the material over, I would think you can do so at any
point in having drilled your
pilot hole as normal in using twist bits. Note also that if you set your depth stop properly, you can flip the material over and continue boring from the other side. With a
pilot hole, it’s less frustrating because the smaller drill
bit does not need to be depth stopped. If with the bullet tip, that depth stop is not correct, or on the second piece of material cut with the depth stop, there is any metal shavings under the material that depth setting now will allow too deep of a cut given the size of the center drill and you will not be able to use it to guide the drill
bit from the opposing side without a sloppy cut. So setting depth cuts is frustrating in general but especially with a bullet tip. In the case that you have to flip your material over, than it’s easier without the bullet tip, instead just use a
pilot hole. Not that you normally would need to, what you don’t counter sink your hole’s sharp edges? Note: attempting to do a depth cut on unsupported material is just as difficult no matter what drill
bit you are attempting to use. For a centering hole it’s easier to use a smaller sized
pilot hole bit.
“A
page taken from woodworking technology.” What is this a commercial or did you forget to cite a source? That’s fine just let us know we have a vendor rep on
line instead of a “guest” if this is the case. All are welcome as long as it’s on a
level playing field. Freud is a good brand of forstner
bit, I
stock the titanium version of them. Costs more but stays sharper longer. Of note however on a forstner
bit is that there is usually a lot more tear out damage from too much pressure at the end of the cut when it’s not supported. In other words on a forstner
bit if not supported it can rip chunks out of the back surface. Are we to infer that a bullet
bit is or is not like a forstner
bit when working unsupported on that tin plate? Not to mention they don’t work very well either in enlarging holes.
Good debate, neither of us will be absolutely right either because its’ subjective and personal opinion for much of the debate. Still interesting to spar with someone taking the time to explain his viewpoint and state it so well. I look forward to your saw blade descriptions and further info on drill bits.