I’ve not pull tested anything but so far everything I’ve used with them remains sturdy. I will eventually buy a new set of straight countersinks – but to be fair so far so good. OH and one thing – MAKE SURE YOU SET THE SCREW LENGTH. Which is important regardless of the countersink you use.

Good points. I too find that the tapered bits are MUCH more fragile – and cry and swear when I break one (usually the size for which I don’t have a replacement bit.) They really benefit from a steady hand or use at the drill press – and don’t do well with off-axis loads.

And tapered bits? I guess they’re still useful for brass screws as fred says, which are still tapered for some reason. They may have those advantages that other people point out, but tapered holes are a disadvantage for straight screws.

As far as my own preferences, I have a couple of import bits that I use infrequently, and if I had a project coming up where I knew I’d need a good countersink drill, I’d get Snappy. Snappy also has a depth stop attachment that can aid in repeatability and consistency, something I occasionally have difficulty with when using drill bits or self-drilling screws with separate countersink bits.

We are going to use this little trapazoid to cut a helical path through the bulk material by using the "coil" feature. First of all make sure that your trapazoid shape is selected as the "profile" and then select the appropriate axis. there is an option withing the coil feature window to select the "axis" direction, make sure it is going the right way. Next set the function to 'cut' (the second button from the top on 2013 version) and make sure the coild direction is correct. (most threads in the world are right hand threads, meaning as it rotates clockwise it travels away from you).

How to calculate speeds and feeds using FSWizard CNC Machinist Speed and Feed Calculator · Click on the Material button to select the work material · Select the ...

Work hardening (strain hardening) manifests as the increase in stress that is required to cause in increase in strain as a material is plastically deformed.

Good info and great article! I started using traditional countersink bits years ago and then went with Dewalts Tapered bits and love them for wood. No serious woodworking or furniture maker here but only a Handyman retired contractor. Great info in the comments also!

Amana Tool – (55227) Carbide Tipped 82° Countersink with Adjustable Depth Stop & No-Thrust Ball Bearing, 3/8 Dia x 1/8 Drill https://smile.amazon.com/dp/B00BJFK6N6/

– The tapered bits are noticeably more fragile, and need a bit of care in use, not always possible on-site where tools tend to get abused.

Shown above is a 5pc set of Snappy countersink drill bits, and it has always looked to me like they use straight drill bits for the pilot holes.

Although Snappy’s other countersinks are not explicitly described as having straight drill bits, it seems to be a fair assumption based on appearances. With this brand at least, it seems that if their countersinks are not described as tapered, it should be fair to assume the pilot drills are straight.

So I think the reason there are more “countersink bits” with tapered bits is that there is no other use for tapered bits, while straight bits can be used for everything.

I used tapered only because they are much easier to start on an angle for toe screwing and to make countersinks. I have used them for 15+ years now. If I need the pilot hole to be smaller, just slide the countersink up the bit a little to the desired depth. I know there was a comment on somebody returning them because of bit making too deep a hole, and this is what I do to use the bits for everything. I have several sets of these with the countersink at varied heights for different lengths of screws. Works great for me, but not everyone.

Personally, if I grab a bit from an index to place in an accessory like this, chances are I’ll forget to take it apart and put the bit back in the index.

I have a set of Fuller tapered countersinks . Only problem is i only use smallest drill size mostly .It is very difficult to sharpen properly

NPT threadCalculator

A reader recently wrote in about countersink drill bits, and I am hoping some of you can share your experiences to help in answering their question.

And as I said earlier, I often use a manual countersinker, which is fast, cheap, and leaves a very clean hole. (Though if I’m lazy and I’m using #6 screws, I just use a phillips head screwdriver.)

1/8. 27. 21/64 ; 1/4. 18. 27/64 ; 3/8. 18. 9/16 ; 1/2. 14. 11/16.

NPT threaddimensions PDF

I’ve loathed every tapered bit I ever used. I also am the odd man out that doesn’t like the W. Fuller countersinks very much. I’ll take them (and just about anything) over snappy, however. I like the no mar depth stops, at least the ones that work. The Festool one was my favourite (and overpriced as usual), but Amana came out on top with their carbide one. I haven’t used the one with the plastic no mar part, I’m vouching for the one with the brass colored bit. I haven’t used a combined drill/countersink that wasn’t like the Festool or Amana in eons. No point. I do hower use standard ol’ metal countersinks (the kind with the hole) quite frequently.

Thuis next step seems little but it is important for creating realistic threads, put a small chamfer around the outside edge of your threaded profile. make the chamfer 45 degrees and about 1/3 to 1/2 the thickness. (this could be built into the profile but doing it this way is less complicated.

Lets say that we know how to model everything else except the threaded part, if you dont know how to model the rest of it dont worry about it, you make threads the same way for any kind of part. I said the first step was to determine whether the threads you are trying to model have male threads of female threads, this one clearly has male threads so we will start there.

“But if straight countersink drills are better for modern wood screws (an assumption for now), why are there so many more tapered countersink drills on the market?”

Yes, and better. As fred points out, there are Martin or Welden style countersink-only bits that have a single cutting edge, created by drilling a skewed hole through the tip of the conical bit. Those bits don’t chatter and leave a very clean hole. The combined countersink attachments you show are the fluted style, which are probably faster but can leave a ragged hole in wood.

I’ve never used a tapered bit. I wonder if there are any real world test on pull out strength. Straight vs. Taper. I have a Dewalt set that has served me well. It’s the flip set with a phillips driver on the other side.

I’m wondering if you have any info on countersink pilot bits? I bought a pack of three sizes from Dewalt recently and found that the pilot bits did not properly match the countersinks. If you drilled deep enough to achieve a proper countersink the pilot hole became too wide due to tapering in the drill bit. Returned them. So trying to figure out who is producing decent countersink pilot bits.

https://www.popularwoodworking.com/tools/comprehend-the-countersink/#:~:text=A%20straight%20bit%20pilot%20hole,cut%20deeper%20into%20the%20wood.

I always use straight bits. Straight bits work for everything: wood, plastic, metal, etc. They make holes for bolts, self-threading screws, wood screws, or sheet metal screws. They make holes which can be tapped. They make holes which can accept pins or dowels. And when you are using countersinks or depth stops on the bits you can position them anywhere along the bit that you like. A tapered bit can only make holes for wood screws, and they are limited in terms where you can place the depth stop or countersink.

Anyway I have tapered bits becasue that’s what I found first. As said they were made for older style wood screws that are tapered. and short of brass reproduction screws and a few plated ones I don’t know of any tapered wood screws you find these days.

Sheet metal comes in various gauges and is often connected via rivets rather than screws. Dimpling using a punch (manual, hydraulic or machine) is often use to provide a recess to accommodate the rivet head.

You can buy countersink bits and separate straight drill bits, but there’s not much advantage in having to source things separately.

Cabinet maker here. I use only tapered bits when building carcasses. Two reasons I prefer them. The taper allows the drilled hole to self clean to some degree. There is room for the drill dust (or whatever it’s called) to eject itself. This also allows the bit flutes to not get impacted with the wood remains. Anyone who has used straight bits with a countersink has had to pry the burnt wood from the bit. The other reason is I like the adjoining wood to have a larger hole as I feel like the screw head sinks better.

The first thing we need to do is create an accurate profile to cut the threads into. We know from the previous step that NPT connections all have a specific O.D. but they dont maintain that I.D. through the whole length of the threaded section, the "T" in NPT stands for 'Taper' which means NPT threads are on an angle. 3.576 degrees to be exact. The taper is defined as 1/16" of drop in radius for every 1" of thread length. What I do to make this simple is I define my vertical drop as (horizontal length/16).

I like the snappy brand straight bit countersinks, they’re consistently good and seem like a good value for the price. For the occasional times I want a tapered bit (fancy brass screws, etc.) Fuller is the way to go, expensive but top quality. I keep a few of those in a nice case in the shop, hidden away from meddling hands.

The Tapered bits are useless and cause standard bugle head screws as used for interior carpentry to be way too lose in the hole. So buying what was only available quickly one day created some weak joinery without any good reason. This is kind of akin to software engineering where things are messed with for no good reason, and due to incorrect assumptions about what is ” good.” I did not like the look of this product in the package and this is the exact reaosn why. They do not work well in the majority of cases being used in my shop currently.

SolidWorksNPT threadexternal

I have had people ask me on here how I model npt threads for some of the parts I make, so I figured I would put it out there for others to see as well. Note: if you look at the threaded models I have on this website you will see that I have clearly taken more time on some of them than others, this tutorial will teach you how to do it the right and proper way.

Most if not all of the wood screws I tend to use have straight shanks and even threads, and so I have always assumed that tapered drill bits could cause problems when drilling deeper holes – exactly the type of issue that Rich has been experiencing.

I don’t know the answers to your other questions (not that you were necessarily seeking my knowledge, which is paltry and dim!)

In really hard wood (I sometimes use lignum vitae – but more often maple) – it is important to pilot the entire length of the screw if you are planning on using brass (relatively soft) screws. An old trick is to first run in a steel screw to ease the hole and then lubricate the brass screw with candle wax. All this helps prevent brass screw breakage or buggering the slot as you try to drive them home. But a properly drilled clearance/pilot hole reduces the number of steps in the process and helps insure good results. Of course you still need to hand drive the brass screws and back-off if the going gets too tough.

Collets - Morse Taper, R8, 5C, 3C, ER and Brown & Sharpe. Many collets are available individually and in sets from LittleMachineShop.com.

“I’m also not seeing any quality “countersinking gizmos” where you need to supply your own drill bits.” I don’t either, and they might not exist. I thought you were talking about countersink-only bits. So I guess I was wrong earlier. (And I don’t use them, because both countersink-only bits and hand countersinking are better, in my experience.)

I understand that tapered bits do have a theoretical advantage for classic style wood screws, but I’ve never encountered a situation where normal straight bits didn’t work for me. Sometimes I’ve had the hassle of having to drill twice, once for the shank and again for the threaded part of the screw so I could see the tapered bits being a time saver there, but I don’t do enough fine woodworking to justify the cost of one trick pony bits like that. And these days I tend to use modern screws which aren’t tapered anyway.

Note: I tagged this as intermediate but only because there are several steps, once you get the hang of it this isn't hard and I will walk you through this one little bit at a time. Lets say we want to model a fitting of some kind that has 1" NPT threads, we could just use the "thread" tool that inventor comes with, but it doesn't truly model threads it just overlays an image on your part that kinda looks like threads and in a drawing can be called out as such. If we want to make it right we need to actually model them as they would be on a real physical part, that means the first thing we need to do is determine if the threads are male or female (male means the threads are on the outside, female means the threads are on the inside) I will teach you how to do it both ways.

Yeah, people say the single-edge countersinks are smoother and make less chatter, but I sometimes use a manual countersink, and there the rosette style is much easier. Just a few twists and you’re done.

The second thing to determine is what size threads your part has. NPT pipe sizes can be confusing since the dimension it is called has very little to do with its actual dimensions. In step (1) I just stated that we will be making 1" NPT threads, if we look up "NPT dimensions" on the internet we find that all 1" NPT pipes, fittings and anything else have an actual O.D. (outside diameter) of 1.32". The I.D. (inside diameter) varies with pipe schedule, so once you know what schedule you have you can look up the I.D. by searching the internet for "schedule ** dimensions" (where ** is the pipe schedule you are working with). Once you know the O.D. and I.D. of your part we can begin making threads.

NPT threadangle

The Snappy looks to use standard user-replaceable twist drill bits. For drilling wood, are there much better options you would use?

If you dont have a part in front of you to measure its a good bet that the length of your threaded section is going to be just slightly longer than the maximum thread engagement for your pipe size. (this information can be found by searching the internet for "NPT thread engagement")

Is there a difference between using these in hard and soft woods? E.g. maybe a taper could be used in construction-type applications in soft wood where the end of the screw can compress the wood easier for a more solid fit.

I mentioned these Amana (no-mar) countersinks under Stuart’s recent post about best in class tools. Like you. I find these very useful for cabinetry, installing cleats etc.

But if straight countersink drills are better for modern wood screws (an assumption for now), why are there so many more tapered countersink drills on the market?

Is this an issue of the depth of the stop not being set correctly? That’s the first thought I had and quickly reading the article JeffD posted seems to support that a potential problem.

Koko – no, dimpling means “denting” the sheet metal to make a funnel shape indentation. No cutting involved. It’s used for thin metal, like .024″ or thinner where there isn’t enough meat to use a cutting tool.

NPT threadchart

As my final bit of info – folks may know that countersinks come with different cutting angles for different specs and applications. The common ones that I can recall are 60, 82, 90, 100, 110 and 120 degree points. Unified screw thread standards are 82 degrees – while ISO specifies 90.

Die and Straight Grinders · Other Tools · Dust Extraction · Heat Guns · Impact ... /Burrs. Burrs. Categories. Back to Other Accessories. Burrs; Cutting Lubricants ...

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1NPT threaddimensions in mm

As far as I know- the pilot hole doesn’t need to go as deep as the fasteners. It’s primarily to prevent splitting; but please correct me if I’m mistaken.

Lets say I want to make a camlock adaptor (if you dont know what that is dont worry about it this technique can be applied to anything) Note: I'm not actually measuring this part I'm just making something that looks close for demonstration purposes.

Good stuff! I notice the second item you mention is called a “combined drill and countersink” (because the countersink is only the conical part of the tool.)

Categorized under Flat Rolled Shapes, Nec, Aluminum. Our records show it was established in 2010 and incorporated in Virginia.

And technically, a “countersink” is just the conical hole at the surface to accomodate the screw head (and a “counterbore” is a cylindrical hole for things like capscrews.) The hole that accomodates the threads and shank of the screw is a pilot hole.

@Rich – I would think that the Snappy set would be a good option, and readers might have alternate or even better suggestions and recommendations.

If you use old-style brass wood screws that have tapered shanks, then the corresponding taped drill bit would be the first choice. They have an advantage of drilling both the proper diameter clearance hole for the un-threaded upper shank of the screw and a smaller diameter hole – for the tapered threaded lower portion of the screw. Brass screws of this sort – with flat (rather than Phillips , Robertson or Torx) drive slots are my choice for reproduction furniture. So for that use I choose a tapered set – my choice being the W.l. Fuller brand. Having the tapered hole seems to help – especially with hard maple or even harder woods like purpleheart or lignum vitae. But for most other wood screws – these days – they don’t have tapered shanks – and come with more efficient drive styles (like Robertson or Torx). So when I’m driving something like a Spax screw – I’ll use a straight shank drill bit for a starter hole.

3/8npt threaddimensions in mm

Depends on the fastener. If I’m installing a machine screw then it’s a straight countersink but if it’s wood screw then it’s tapered.

Yes, you can mark all your holes, drill all your holes, and countersink your holes, maybe even countersink and counterbore your holes, but it’s less work with a single drill bit assembly.

“Personally, if I grab a bit from an index to place in an accessory like this, chances are I’ll forget to take it apart and put the bit back in the index.” I would do that too. But I have many sets of standard bits, so that’s no big deal. And you can still use the drill bit while mounted in the countersink attachment for shallow holes.

Definitely. Soft woods are usually more forgiving. But don’t let that fool you. Some soft woods are actually harder than hardwoods and if using different woods look at charts that show wood expansion for your climate. Basically softwoods are trees with needles, hardwoods are deciduous (trees with leaves). If using teak, oak, ipe. You’re going to want to pick a very specific counter sink, length with and counter depth. If going into pine it’s no big deal unless it’s finish work.

Either way make sure your shape protrudes down into the revolved profile you created in the previous steps, use the "project geometry" tool to project the tapered line from the profile onto your currecnt sketch and constrain the top edge of your trapazoid (or whatever shape you are using) to be colinear with that tapered line. Make sure the trapazoid is close to the beginning of the taper but not on it.

I’ve always used tapered. Can’t explain why it’s just what I’ve had for years and years. I even have a set passed down from my father.

By Weldon, are you specifically refering to the kind with the single round “flute” (more of a hole, if you ask me) vs the 4 and 6 flute designs? The ones with the hole are my favourite in metal and wood. I pick up Norseman, locally , for next to nothing and get beautiful results.

I was just thinking that screwing into pine or spruce, for example, is a different experience than oak. If you’re working with soft wood (not a hard softwood, but maybe a soft hardwood), the taper might help the screw bite more near the tip.

I think I misread you a little. So there are four things: regular twist bits, tapered twist bits, countersink-only bits, and countersink attachments that take twist bits (what I called “gizmos.”) Your pictures show twist bits mounted in countersink attachments. So:

I get it Mr. Creek. ? In this case I’m referring to wood that is physically soft or hard. Not necessarily a softwood or hardwood.

But for wood, if I were working with a lot of non-self-drilling screws or needed to counterbore many holes for flathead screws, I’d find a do-it-in-one-step operation very appealing.

Those fancy bits in the pictures drill both pilot holes and countersinks at the same time, but you don’t have to do it that way. And there are countersinking bit holders that will turn a regular bit into a do-it-all bit.

Buy Now: Snappy 5pc Set via Amazon Buy Now: Snappy Tapered Set via Amazon Buy Now: Dewalt Tapered Set via Amazon More Options via Amazon

Lastly doing threads this way leaves a definite stop point that looks bad, so the way I correct this is to draw another profile that covers up this area and then I revolve it aroud the same axis as everything else.

Fred, you are right as usual. Thin sheet metal = dimpled. Thicker material = countersunk. And yes, per your earlier post, I recently learned that metric flush head screws require a 90 degree countersink, which is not the same as the SAE/Fractional countersink. Since I am working with metric on my current project, I ended up buying a whole new set of 90 degree countersinks.

Some of you have expressed countersink preferences in the past, and so I’m wondering – do you prefer straight or tapered countersinks? Do you prefer a particular brand? Why?

so to add to Fred’s bits. It’s an interesting topic of straight vs taper. And the dewalt by the way are just like the Irwin countersink sets. as far as I can tell, I bought a dewalt bit to replace my #6 Irwin.

I’m a cabinetmaker and furniture maker who also does a fair bit of on-site carpentry. With little exception, I use straight bit countersinks for all my work, not because they necessarily work better but for convenience sake:

I try not to use tapered drywall screws in softwoods. And have come to depend more on grk cabinet screws or similar rather than these drywall screws.

Countersink drill bits, as many of you I am sure are aware, are drilling accessories that are designed for drilling a pilot hole for screw threads as well as a countersunk recess for flatheads screw heads. They can also counterbore a recess hole for screws to sit below a work surface rather than simply flush. Countersink drill bits are designed for completing all of these processes in a single drilling operation.

Apr 6, 2017 — A quick Google of brands of flutes lists over 80 flute makers from around the world! ... Flute brands to avoid... On EBay, many flutes for sale ...

However I have made a number of things with my tapered Irwin bits and modern dryway screws and construction screws (#10). and I find they work as well – but you have to recognize that the threads near the top ofthe hole don’t engage as well as the ones at the bottom. But they do go in nice and easy.

When I used to work in boat yards doing wooden boat restoration/repair I had some of the fuller bits with the taper. Great for using those traditional tapered bronze wood screws with flat heads. Since than I have a set of snappy counter sinks with straight bits. They works fine for most everything, even the occasional bronze wood screw in oak. But if screwing big woodscrews into oak frames was still a regular thing for me I would get another fuller taper set, as there seems to be less of a chance of splitting and the screws seem to set easier.

“The Snappy looks to use standard user-replaceable twist drill bits. For drilling wood, are there much better options you would use?”

“You can buy countersink bits and separate straight drill bits, but there’s not much advantage in having to source things separately.”

Now its time to make the threads. Create a sketch on the same plane you created the revolved profile on, and draw the shape that matches the space between your threads. If you want to be 100% exact you can look this information up but I find that a 1/16" x 1/32" x 1/64" trapazoid seems to work well for most applications. For bigger thread sizes you may want to make the trapazoid larger.

The Amana is the best I’ve used yet. I don’t bother with anything else. Personally I use the 5/32″ version, 55229 (8 and 10 screws, no?).

1/2npt threaddimensions in mm

On the "coil size" tab within the coil feature window select "revolution and hieght" as the type and then input a hight that goes slightly beyond the tapered section you are trying to thread, for "taper" enter 3.577 (if you try to enter exactly 3.576 it wont work) then select the appropriate amount of revolutions. you can find out how many revolutions per inch your thread has by searching the internet, though this number often has to be modified slightly to appear correct in pictures.

https://www.amazon.com/Fuller-Tapered-Drills-Boxed-Set/dp/B0032YZ060/ref=sr_1_1?dchild=1&keywords=B0032YZ060&qid=1620747071&s=hi&sr=1-1

Straight bits for me I don’t use tapered screws and find the tapered bits easier to break towards the small tips. I have a Dewalt and old craftsman set that both perform well.

I love tapered for the non-walking starts. It starts excatly where I put it and that’s important because most of the time I’m using a tapered drill bit is to join cabinet faceframes together and I have to make sure I’m going where I need to go.

another thought. If the issue is enough ‘meat’ remaining to grab onto, I suspect with brass screws then my statement is going to be moot, but a smaller pilot bit with appropriate countersink head may solve the problem.

– I find that I snap or dull a drill bit once or twice a month and straight bits are far easier to replace, I have 12-packs of drills from C-L or Champion via McMaster in all the small sizes.

Standard Drill Sizes - Inches ; Drill. Size . Decimal. Equiv. ; 80, = .0135 ; 79, = .0145 ; 1/64, = .0156 ; 78, = .016 ...

This product works with mills with a R8 spindle taper including: Grizzly G0758 Mill/Drill; BusyBee CX605 Craftex Mini Mill; Cummins (Tools Now) 7877 Mini Mill ...

Oct 26, 2013 — Leave around 0.1mm or 0.004" material on the sides of the bore ( drill/bore 9.8mm for 10mm). From small to large bores ...

– Lately I’ve gotten some tapered bits where the point wasn’t ground on center. I think they were Insty or a similar mid-priced model so not the absolute cheapest Amazon trash.

Those self-countersinking screws you mention help too, though I find they don’t really sink fully flush. But they allow the countersink to be shallower or less clean, which makes the job go faster.

You can buy them separately, and still use them all at once. Mount a drill bit in one of those countersinking gizmos, and presto, you have a one-step countersinking and pilot hole drill.

I have the snappy set that have above with the rotating depth stop. I can recommend it although I only seem to use the size 6 and size 8 bits. I’ve never used the number 12. The depth stop height is fairly easily adjustable with a hex wrench that lives with that bit. It is a pain to move the depth stop from one bit to another so it just lives on my number 8. I wish that I had another depth stop for the number 6 and I’ll probably buy one later. I have broken the pilot bits but they are standard size and I was able to pick some up from the store.

I have both and when I grab the tapered set, I’m always annoyed. They’re fine and not noticeably different in almost all use cases unless you need to make a shallow hole, in which case you have trouble getting the countersink to sit properly on the tapered portion and they collect sawdust and can burn a bit because of it. I’m sure if I was using tapered screws, it would be worth it, but not for anything I do.

There’s plenty of advantage to sourcing the countersinks separately from the drill bits. The big one is that with separate countersinks, you can use your existing drill bits!

Next we are going to do a full revolve of our profile we just drew, something I didn't mention is that it is good practice to orient sketches on the origin that way you can revolve around established axes. When you are done youre part should look like the picture.

Tapered never made sense to me for the reasons that have been stated, I have found the snappy drill bit to be pretty exceptional compared to the ones at the big box stores, they tend to stay sharper and tighten much better than the dewalt and irwin ones ive picked up in the past.

Also under Stuart’s post about the best in class tools – I mentionned Weldon countersinks. Stuart had done a post about that style as compared to the perhaps more ubiquitous rosette style. Chatter is less of a problem with the Weldon style.

I’m using the snappy set (straight) and found it much better than the cheapie generic ones I initially tried. I would not hesitate to buy them again if needed.

So typically, I have one drill/driver with a drill bit for the pilot hole, another to drive the screw, and a hand countersink in my pouch (the flutes are sharp, and will tear up pockets. If I get to it, I might round over the corners of the edges, which aren’t important for cutting the countersinks.) No need for these countersink attachments.