Taper Drill Bits

[Retief]

This should be pretty obvious, but it's not. I need to put in a fair number of wood screws and bought a Lee Valley set of taper drill bits, countersinks, and counterbores. Although the shanks of the taper drill bits match the shanks (unthreaded portion) of my wood screws(common Home Depot wood screws), the bits seem to taper much too slowly for the screws so that very little of the screw actually bites. For example, with a two inch #12 screw, the screw stops engaging the wood about one half inch back from the point. I know that you can drop down a few sizes (but then the countersink is the wrong size) and can not drill all the way to the end of the screw, but these taper bits seem to be a very poor match for the screws. Am I doing something wrong?

[shamus]

Are these the flat metal type of bit? If so you could regrind them to suit? Can't see how you could be doing it wrong, unless they're meant for a slightly longer screw.

[Nicholas Carey]

My experience is that regardless of what Fuller sez, I seem to use a bit two sizes under. For instance, for a #10 bronze wood screw, I a Fuller C8 tapered bit and countesink seems to work rather better than the C10 that Fuller 'recommends'.

[Chris Coose]

Depends on whether I'm into old white oak or fresh white pine, what size I'll use.

[Scott Rosen]

What Nicholas said. For soft wood I go down two sizes, hardwood one. You can buy countersink bits of any size to fit any drill bit. Check out the Fuller catalog.

The best solution is to use a stepped bit, if you can find someone who sells them. Or you can have stepped bits custom ground to fit the particular fasteners you are using.

[Bruce Hooke]

You are not doing anything wrong -- in my opinion tapered bits are just plain not a great solution to the problem of drilling a screw hole in one go. I prefer the design where the cutter for drilling the clearance hole for the shank of the screw is integral with the countersink, and then inside of all of that is a drill bit for drilling the pilot hole for the threads. This is still an imperfect solution because changing to a larger pilot hole drill bit for very hard woods is not possible and changing to a smaller pilot hole drill bit moves the bit off center unless you jury rig a shim around the bit. Also, the length of the clearance hole for the shank is not adjustable so it is usually too short. Still I think it is a a better solution that the tapered bits. Stepped bits are the perfect solution in a sense but to really get it right you would need a different stepped bit for each size and length of screw and you would need different stepped bits for hardwood, softwood, end grain and green wood, so if you commonly use, say, 10 sizes of wood screw you would need 40 stepped bits...

I recently picked up a drilling and driving system based on the prinicple described above (clearance hole and countersink together), that also pops out and reverses to become a screwdriver. While not perfect, for the reasons listed above, it does a fairly good job and is very efficient. It's made by Makita and they call it a 'quad-driver':

http://www.schlossertool.com/Sm_tools_2/784831-A.jpg

This image is from Schlosser Tool and Machinery, who I had never heard of until I did a search for this item on-line a few minutes ago. I'm not sure who else has it available by mail-order because I got mine at a local woodworking store (Beaver Woodworking in Brockton, MA).

[reddog]

Retief;
I believe this issue was addressed in a recent letter to WB by Sam Manning along with an article he did for WB back in the 80's.Stepped bits are the way to go if you can find them.If not you could have a machine shop turn down bits to your specifications.You would need a separate bit for each screw size,depth and variety of wood.
Of course you could always get by with two drills and bits.One set for the required counterbore/countersink and clearance hole and the other with the pilot bit size.
All the best;
Earl

[Dave Fleming]

To the best of my recollection, Fuller will grind bits any way you wish. It was not uncommon on new builds to get the screws in the yard and send a couple of each size to Fuller to use as patterns for drill bits. Worked very well, IIRC.

Off the shelf Fuller bits seem to do OK for me but I do a few 'samples' in scrap and see how it goes before beginning the real thing.

Another point is a person has to work at learning how to drive a screw. Electric screw drivers are not that easy to handle, IMOOP. No matter variable speed, 2 speed ranges and reverse, you have to make sure the screw driver bit really fits the head of the screw well and one of the worst offenders is a worn driver bit. Ayup even 'silly bronze' screws will wear out a driver bit over time.
Now air tools is another story all together. With the ability to regulate the air flow right at the tool with the addition of a small painters style valve one can really tweak the torque of the machine..
For me a combination of Fuller bits/countersinks and Apex driver bits and a good power tool, either air or electric are what makes things go.

Years ago Greenlee made a fine selection of drill bits and counterbores/countersinks but the line was sold to Forrest City and after that just seemed to fade into memory.

[Tom Lathrop]

The standard Fuller taper bits work OK for me with a couple of exceptions. They are self leading (pull themselves into the wood) and this will sometimes cause either splitting the wood or overheating of the bit in hardwood. I never use them near the end where they can split woods like teak easily. I've never had the problem stated by the original poster but I usually use a caliper to determine the proper size bit and ignore their labels..

By the way, I happened to have an old wax commode base sealing ring lying around and tested it as a lubricant for driving screws. It's low viscosity makes it easy to coat the tip of a screw and it really works well. Better and far cheaper than anything else I've tried. Busted it up and stuffed it in a jar and it will last me and my heirs our lifetimes. It looks like there is a lot of beeswax or something similar in it.

[ 09-23-2002, 12:41 PM: Message edited by: Tom Lathrop ]

[Mac_Muz]

Don't forget you can get odd sizes like 5,7,9 and so on.... When I replace old screws, I like to go a size bigger or two at times...mostly I do..

If there was a 8, I may run a 9 drill and use a 10 screw in worn wood...

I don't think that the wider threads do much holding either in the plank on frame... it is the frame part of the screw, and so the upper thread has little work to do in reality..... But then I may be all wrong as my whole name is not here.... Mac

[ahp]

Pardon my ignorance, but are taper drills really intended for wood?

In my experiance taper drills are used to drill into metal to receive a matching taper pin. This is one way of locking a wheel onto a shaft. After the tapered hole is drilled through both shaft and wheel (or gear or pully coller) then the matching taper pin is driven in to lock them together.

[Dave Fleming]

Go here... Counterbores and Taper Drills (http://www.wlfuller.com/)

[Bruce Hooke]

Originally posted by ahp:
Pardon my ignorance, but are taper drills really intended for wood?

In my experiance taper drills are used to drill into metal to receive a matching taper pin. This is one way of locking a wheel onto a shaft. After the tapered hole is drilled through both shaft and wheel (or gear or pully coller) then the matching taper pin is driven in to lock them together.We are talking about a different type of taper drill bit that is most definitely designed for wood. The taper drill bits used by boatbuilders are mostly made by Fuller and, rather than having a uniform taper (which is what I would guess the ones you are talking about have), they have a varying taper:

http://www.jamestowndistributors.com/store/pix/TPD564.jpg

[Bayboat]

Tapered drills are not tapered because screws are tapered. If you look carefully at a standard cut thread screw you will see that it is not tapered. The shank (the smooth part between the head and the threads) is a certain diameter, and the outside measurement of the threads is the same diameter except at the very tip. Step drills make the best pilot holes for the threads and clearance holes for the shanks, but as said above one would need several dozen. The adjustable tapered bits are a reasonable compromise and for most work on small boats you only need about 6 or 7 (for #6 to #12 screws). Follow Tom Lathrop's advice and don't always try to match the number on the bit to the number of the screw. Use a drill gauge to fit the bit with the screw. With those bargain bits from Lee Valley, dropping down a size or two works OK. IRRC, the counterbores are either 3/8 for the smaller bits or 1/2 for the larger. Either way, a standard bung works.
Tom is right about drilling for screws near the ends. For these, it is critical for the clearance hole to have at least the same diameter as the shank of the screw. The best way is to drill the pilot holes and clearance holes separately, then make the countersink or counterbore. It takes a little longer, but there is a lot less danger of splitting.
Stanley makes an adjustable bit/countersink/counterbore that makes a pilot hole, clearance hole, and countersink or counterbore all in one operation. You just need one for each diameter of screw, and the lengths of both the pilot and clearance holes are adjustable. The main trouble with them is that the pilot hole bit is flat, does not drill fast, smokes in hard wood and breaks easily. I used them for quite some time but finally turned to the Fuller type.
For the beginner the best way to avoid trouble with sinking screws is to try the bit and a screw in a piece of scrap wood like what you are fastening. Before long you will learn which is the suitable bit/countersink/counterbore for a particular kind of wood and screw size.
Another tip that takes a bit more time but does a better job: Don't drive screws with an electric driver set at a high torque. Use the lowest torque that will drive the screw, then change to a hand screwdriver or brace & bit to tighten down.

[Retief]

Thanks, everyone, for the responses. I suspect that the Fuller set does at least a little better than the set I have. Shamus, they are round bits, as Bruce Hooke illustrates. I will take a look at the Makita quad-driver, since it sounds like the best compromise.

[capt jake]

Makita is no comprimise to the Fullers. I have to get another set, as mine are all broken. :

[JMAC]

MAXIM- if you are joining piece A to piece B with a screw, the screw should be able to slip through the hole in piece A and thread into piece B. That is imperative!

REMEMBER?...those old log splitters that you would bolt onto the hub of the drive wheel of your old pick-up truck? Well they miniturized them and now sell them as tapered drill bits!They still split wood quite nicely.

DID YOU READ...? The recent WoodenBoat article on broken screws? After all the metalurgy talk, near the end of the article, it was mentioned that the builders who were experiencing excessive screw breakage were using tapered bits. Put your tapered bits in a lower drawer and forget about them! And that is my rant, somewhat shortened by restrictions of time.

[Tom Lathrop]

Originally posted by JMAC:

DID YOU READ...? The recent WoodenBoat article on broken screws? After all the metalurgy talk, near the end of the article, it was mentioned that the builders who were experiencing excessive screw breakage were using tapered bits. Put your tapered bits in a lower drawer and forget about them! And that is my rant, somewhat shortened by restrictions of time.[/QB]Yeah, I wonder why they don't make the bits in the same shape as the screws, straight with a taper on the end.

[Sailing-Randy]

Okay, guys, I seem to remember reading somewhere that some one used to grind drill bits to fit the screws they were using. Mounting the bit in an electric hand drill and while it turned, grind it down to size and shape.

Seemed like a good idea when I read it. :D
Does anybody else remember this - hopefully with better recall than I have as to where it was written?
Has anybody tried it?

[Ron Williamson]

Randy
I tried it and it worked well enough.It is a little tricky to get the shape right,without being undersized and weak.I think I was using a #9 countersink(3/8"plug size)and a 9/64 or 5/32 drill bit,ground down to a tad under 1/8 for about the first inch-and-a-quarter.
Have fun
R

[JMAC]

What is so hard about having two drills set up and ZING and then ZING again, if you only have one drill then look for a deal in one of those ever-arriving tool catalogs and get another one. A big joy of woodworking is tool buying- admit it!Thus I end rant 2.