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Thread: Countersink drill bits

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    Default Countersink drill bits

    Ideally, the drill bit would drill a pilot hole in the chine log to prevent splitting, larger hole in the plywood to pull the plywood tight against the chine log, and countersink the flat head screw.

    Do they come specifically for 1/4" plywood and 3/8" plywood?

    Any recommendations for good quality countersink drill bits?

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    Default Re: Countersink drill bits

    Fuller

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    Default Re: Countersink drill bits

    Quote Originally Posted by Canoeyawl View Post
    Fuller
    Amen.

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    Default Re: Countersink drill bits

    Quote Originally Posted by Canoeyawl View Post
    Fuller

    They are the best I've found but when using the depth stop collar it's a pain to clear out the countersink flutes every 4th hole...is there anything better out there?

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    Default Re: Countersink drill bits

    The new carbide ones look cool. Not sure how well they work.


    B4CBDBCF-77E3-4F19-921B-8C66081E8D96.jpg

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    Default Re: Countersink drill bits

    I use this Dewalt set for pilot/ countersink and they’ll bore if I want to later over plug it. Depth adjustment adjusts with little allen key. Comes with a quick release thingy. Seems to work perfect and wasn’t much.


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    Default Re: Countersink drill bits

    Quote Originally Posted by StevenBauer View Post
    The new carbide ones look cool. Not sure how well they work.


    B4CBDBCF-77E3-4F19-921B-8C66081E8D96.jpg
    Fuller makes a high speed steel version and I have shattered them trying to mount hardware and reseat the 82° angle on the hardware itself while for the perfect fit in situ, which is the way of it.
    The old standard Fullers may still be the best.

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    Default Re: Countersink drill bits

    If you really want the larger hole in the plywood, Stanley made some countersinks called Screwmate which did a pilot hole, larger hole in the top panel for the shank and a top countersink/ counterbore to draw things together. I’ve seen them on ebay nos but are pretty spendy as a set unless you get lucky. Individually about 10-15 dollars. If you click this one, it gives a photo on the back which shows you which screwmate part number is which for the right screw then you might be able to buy just the one you’re needing.

    https://www.ebay.co.uk/itm/203458196...kAAOSwC1FgpFbu
    Last edited by Edward Pearson; 06-06-2021 at 04:03 AM.

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    Default Re: Countersink drill bits

    I have Fuller bits in various sizes. They are about 40 years old now. Been used, abused, and sharpened many many times. They still work great although the set screw in one is stripped. One can use either the tapered bit that is sold with them or a regular constant diameter bit. Depends on the purpose. It's easy to load a clearance bit into another battery drill to make clearance holes if your tapered bit isn't set deep enough. I never use the depth stops. I find them unreliable and they imprint onto the stock.

    Jeff

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    Default Re: Countersink drill bits

    I frequently use the depth stop, (it can leave a mark, but by the time you put in a bung and clean that up the mark is moot) sometimes I mount the collar backwards to use a stop but not a counterbore or countersink.

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    Default Re: Countersink drill bits

    Countersinks are easy enough to come by but counterbores seem to be harder to find. Maybe I haven't looked hard enough.

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    Default Re: Countersink drill bits

    Thank you all for your recommendations. So Fuller, Dewalt and maybe Amana carbide tipped are recommended.

    The Stanley "Screwmate" listed by Edward Pearson is exactly what I had in mind. I remember using them about 40 years ago and they worked well but I couldn't remember what they were called. Thanks to Edward now I know. From my current research, it appears that they don't make countersink bits like those anymore. Is it not necessary to have the hole in the plywood larger than the pilot bit size, to pull the plywood tight?

    Are the tapered bits the substitute for having a larger shank hole for the plywood? It seems that the taper at the top of the pilot hole would not have as much holding power being larger than the correct pilot hole size. For instance this snippet from a chart of wood screw pilot hole sizes

    Snippit of taper vs straight bits.jpg

    The pilot hole in hard wood for a #6 screw straight bit is 7/64" while the tapered bit is 9/64". It seems that the upper portion of the pilot hole will be larger than the optimum diameter pilot hole. Unless the screw is tapered from tip to shank.

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    Default Re: Countersink drill bits

    If you don't have a clearance hole through the outer piece,how would you expect to know that it was properly seated?I think that printed chart can be largely disregarded and would suggest that anybody needing to know what sizes to use should buy a cheap digital caliper and see what sizes will correspond to the size of the parts of the screws being used for any particular job.There can be differences between what the nominal screw size ought to be and the actual size of the screws in the box.If you should ever find a #2 screw,it will have head that will look lost in a 1/4 inch countersunk hole.

    The Stanley Screwmate mentioned earlier had a cousin-the Stanley Screwsink and the version for a No 6 screw left a 1/4 inch counterbore.

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    Default Re: Countersink drill bits

    Quote Originally Posted by John Meachen View Post
    If you don't have a clearance hole through the outer piece,how would you expect to know that it was properly seated?
    Precisely what I was asking about.

    I think that printed chart can be largely disregarded and would suggest that anybody needing to know what sizes to use should buy a cheap digital caliper and see what sizes will correspond to the size of the parts of the screws being used for any particular job.
    The actual diameters are not the issue I was asking about. The issue is that the larger diameter at the upper part of a tapered bit would be bigger than the optimum pilot hole diameter. IOW, if the ideal pilot hole diameter is 7/64", then the upper part of a tapered bit being 9/64" would not be optimum.


    There can be differences between what the nominal screw size ought to be and the actual size of the screws in the box.If you should ever find a #2 screw,it will have head that will look lost in a 1/4 inch countersunk hole.
    The chart includes the #2 screw but that's not what I would use to secure 1/4" or 3/8" plywood. Of course I would use the drill bit diameter to correspond to the optimum pilot hole diameter for the screws used. Meaning that I would not go strictly by the chart but by actual measurements.

    The Stanley Screwmate mentioned earlier had a cousin-the Stanley Screwsink and the version for a No 6 screw left a 1/4 inch counterbore.
    Thanks for this additional information.

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    Default Re: Countersink drill bits

    I use the Fuller counterbores. Many times I dispense with the tapered bit and substitute a straight bit the same diameter as the screw shank. This bit will be positioned just long enough to penetrate the plywood. I use a second drill with a straight bit that matches the root diameter of the screw. This bit will have a masking tape flag attached to use as a depth stop. A little experimentation with different bits soon finds the optimum diameter. The charts are good as a jumping-off point, but actual conditions often dictate a different bit diameter. For instance, long screws need bigger pilot holes than shorter screws of the same gauge.

    The tapered bits are useful, but the tapers are a compromise and work better for some screw lengths than for others.

    Hope this helps.

    Jim

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    Default Re: Countersink drill bits

    Quote Originally Posted by Jim Ledger View Post
    I use the Fuller counterbores. Many times I dispense with the tapered bit and substitute a straight bit the same diameter as the screw shank. This bit will be positioned just long enough to penetrate the plywood. I use a second drill with a straight bit that matches the root diameter of the screw. This bit will have a masking tape flag attached to use as a depth stop. A little experimentation with different bits soon finds the optimum diameter. The charts are good as a jumping-off point, but actual conditions often dictate a different bit diameter. For instance, long screws need bigger pilot holes than shorter screws of the same gauge.

    The tapered bits are useful, but the tapers are a compromise and work better for some screw lengths than for others.

    Hope this helps.

    Jim
    Hi Jim,

    Excellent info and very, very helpful toward my drilling and countersinking goals for optimum effectiveness for securing plywood on boats.

    Have you tried it the other way around? IOW, use a countersink with straight drill bit for the pilot hole and then on a second drill have a proper size bit to drill just the plywood for proper clearance to pull the plywood tight? If so, did you find the method you described above to be better or easier?

    I'm thinking about having a small piece of wood on the drill bit to act as a spacer to drill just the plywood. Then there would be zero chance of the bit biting and drilling beyond the plywood.

    The Stanley Screwmate sounds ideal if the proper size bit for the plywood thinkness and pilot hole can be found. It's hard to know the actual pilot hole size without having an actual sample in hand.

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    Default Re: Countersink drill bits

    Quote Originally Posted by DayTripper View Post
    Hi Jim,

    Excellent info and very, very helpful toward my drilling and countersinking goals for optimum effectiveness for securing plywood on boats.

    Have you tried it the other way around? IOW, use a countersink with straight drill bit for the pilot hole and then on a second drill have a proper size bit to drill just the plywood for proper clearance to pull the plywood tight? If so, did you find the method you described above to be better or easier?

    I'm thinking about having a small piece of wood on the drill bit to act as a spacer to drill just the plywood. Then there would be zero chance of the bit biting and drilling beyond the plywood.

    The Stanley Screwmate sounds ideal if the proper size bit for the plywood thinkness and pilot hole can be found. It's hard to know the actual pilot hole size without having an actual sample in hand.


    In actual practice the pilot hole is often drilled first, followed by the shank hole, but this is not the best. The larger diameter bit will try to screw its way into the pilot hole and must be held back from doing so.

    Don't put a block of wood on the bit, it's clumsy. Just use a masking tape flag to indicate the depth. You do want to drill the shank hole right through the ply, not almost through. If there's a chance of the bit splintering the inside of the ply try holding a softwood block over the breakthrough point.

    Forget the Screwmate, get the Fuller counterbores and use them with the tapered bits or the straight.

    Get hold of a digital caliper if you intend doing much of this work, it'll pay for itself very quickly.

    Jim

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    Default Re: Countersink drill bits

    Quote Originally Posted by MoePorter View Post
    They are the best I've found but when using the depth stop collar it's a pain to clear out the countersink flutes every 4th hole...is there anything better out there?
    If you are using the Fuller bits you need to buy one of the other counter sink bits that have a hex shaft. I bought one at the orange box in size 10. Use the Fuller to drill the hole without the stop collar. Just sink it deep enough to establish the counterbore. Take bit out of the other one and use it with the stop collar to the finished depth for your counter. Without the bit in place the flutes stay clear of chips.

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    Default Re: Countersink drill bits

    It's all about the allen-screw for the traditional round-shaft units. Buy the best product you can. A cheapie will just strip, and then the tool is useless.

    I prefer the non-tapered bits, personally.

    Tangent: For a simple drill-stop I cut a piece of 1/4" brake tubing to the appropriate length, and tape it to the chuck. (Nice to have several drills in use if the job is big.)

    Dave

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    Default Re: Countersink drill bits

    Quote Originally Posted by Jim Ledger View Post
    In actual practice the pilot hole is often drilled first, followed by the shank hole, but this is not the best. The larger diameter bit will try to screw its way into the pilot hole and must be held back from doing so.

    Don't put a block of wood on the bit, it's clumsy. Just use a masking tape flag to indicate the depth. You do want to drill the shank hole right through the ply, not almost through. If there's a chance of the bit splintering the inside of the ply try holding a softwood block over the breakthrough point.

    Forget the Screwmate, get the Fuller counterbores and use them with the tapered bits or the straight.

    Get hold of a digital caliper if you intend doing much of this work, it'll pay for itself very quickly.

    Jim
    Thanks for your additional suggestions. How do you use a digital caliper when drilling pilot holes?

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    Default Re: Countersink drill bits

    Quote Originally Posted by Dave Hadfield View Post
    It's all about the allen-screw for the traditional round-shaft units. Buy the best product you can. A cheapie will just strip, and then the tool is useless.
    I prefer the non-tapered bits, personally.
    Thanks for sharing your insights. I will buy a reputable brand of countersink bits.

    Going for the straight bits because for my simple Jon boat, my chine log will be about 13/16" x 1-1/2". When screwing the sides into 13/16", I want the entire length of the screw in the chine log to have maximum holding power. It appears to me that using tapered bits, the portion of the screw just below the plywood will be too loose. And with only about 3/4" of screw in the chine log, I want the entire screw to have maximum holding power.

    Thanks.

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    Default Re: Countersink drill bits

    Quote Originally Posted by DayTripper View Post
    How do you use a digital caliper when drilling pilot holes?
    It comes in handy when you're choosing a drill bit that's sized to be just a tad larger than the root diameter of the threaded portion of a traditional wood screw.

    Or a tad smaller if that's your preference, depending on the wood species you're working with and whether you prefer to use some kind of screw lube or not.

    The clearance bore diameter needed in the top-most workpiece can be gauged better with one also but as previously stated once a pilot hole's been drilled a larger twist drill needs to be held back or it simply acts like a really coarse screw thread, the flutes don't do much cutting as it just pulls itself into the pilot hole.

    Along with that digital micrometer one also needs a chart of number and letter drill sizes. A bonus is having metric on there too but of course this inevitably leads one to desire access to a ready source for those odd bits, that best match the digits that come up on the micrometer's display.

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    Default Re: Countersink drill bits

    Quote Originally Posted by sp_clark View Post
    It comes in handy when you're choosing a drill bit that's sized to be just a tad larger than the root diameter of the threaded portion of a traditional wood screw.
    Or a tad smaller if that's your preference, depending on the wood species you're working with and whether you prefer to use some kind of screw lube or not.
    Oh, now I see. Using a digital micrometer to check the drill bit diameter.

    For that what I've been doing for my normal drilling (not boats) is to hold up my drill bit gauge against the light (the kind that has a lot of holes) and position the screw threads against the holes. I look for the hole that just fits the screw shaft not including the threads for the bit to drill the pilot hole. And the hole that is larger than the threads to drill the clearance hole in the outer piece. Then I use the drill bits per the fractional size markings on the gauge and a countersink bit for flat head screws. No micrometer needed.

    For occasional screwing, this 3 step operation works. But for screwing hundreds of screws to fasten plywood on a boat, that method is much too slow. At least a countersink bit can do two of the operations. I hope to find countersink drill bits that can do all 3 operations in one shot.

    The clearance bore diameter needed in the top-most workpiece can be gauged better with one also but as previously stated once a pilot hole's been drilled a larger twist drill needs to be held back or it simply acts like a really coarse screw thread, the flutes don't do much cutting as it just pulls itself into the pilot hole.
    Totally agree. ..... I have a small plastic bottle that holds a bunch of small wooden blocks of various lengths with pre-drilled holes in them. I use the wooden blocks to limit the depth of drilling in the outer pieces. The wooden blocks work well to positively limit the depth of drilling. And they avoid scoring the surface of the outer piece since I hold the block with my left hand while drilling. The scoring only happens on the wooden block. .... When drilling pilot holes in a 3/4" thick wall to mount hardware, the wooden blocks insure not drilling the pilot holes all the way through the wall. .... I do also use tape flags to limit drilling depth when the depth of drilling is not that critical.
    Last edited by DayTripper; 06-07-2021 at 03:59 PM.

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    Default Re: Countersink drill bits

    I have heard that Fuller will custom make drill bits with multiple dimensions. You send them a sample of the screw you will be using and they custom grind the bit for a perfect fit. I have no idea how much this costs or even if they still do it. But you could give them a call and ask them.

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    Default

    Quote Originally Posted by StevenBauer View Post
    I have heard that Fuller will custom make drill bits with multiple dimensions. You send them a sample of the screw you will be using and they custom grind the bit for a perfect fit. I have no idea how much this costs or even if they still do it. But you could give them a call and ask them.

    Page 33 in the catalog:

    https://www.wlfuller.com

    https://www.wlfuller.com/html/Catalog25small.pdf
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    Default Re: Countersink drill bits

    Depending on the thickness of the plywood and the type of glue used (thickened epoxy is noted for this) you can end up with the dreaded "quilted pillow" effect if you rely on just the screws to pull up the plywood. This is a hateful scenario when it happens.
    I usually use a stiff batten over the plywood joint with longer self drilling screws to pull up the plywood join and then after the glue is "off" remove the batten and fasten it with the real fasteners whatever they may be. A piece of plastic between the batten and the plywood can keep you out of trouble, clear plastic packing tape will work.

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    Default Re: Countersink drill bits



    Well...check me out...I just got 3 new old stock Stanley Screwmates in a size 10 (1, 1.25 and 1.5 inch length) that I often use and a plug cutter for £5.99 for the lot on ebay! Rare these in the UK. I'm tickled pink. He listed as Screwmates...don't ya just love an Ebay typo.

    One day these might be just be the ticket.
    Last edited by Edward Pearson; 06-08-2021 at 07:31 AM.

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    Default Re: Countersink drill bits

    I used to use the Stanley plug cutters in conjunction with Fuller counterbores, they sometimes offered a better fit.

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    Default Re: Countersink drill bits


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    Default Re: Countersink drill bits

    They do. At £20-30 the ‘expensive’ ones last alot better than cheap ones (about two holes!). I find you get a bit of drift though and you aren’t always perfectly over the hole or perpendicular on a big hole by the time you finish if your not really carefully and not a little lucky. Just put some new stands together for my bandsaw and thicknesser and used one - quite big countersinking 8mm bolt heads.. Removing it to clear the hole seems doubly important with them and they seem to do well at a slow speed. Used a hand drill. In a pillar drill obviously straight as a die i’m sure. Never found a new source of proper brace countersinks.
    Last edited by Edward Pearson; 06-08-2021 at 01:26 PM.

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    Default Re: Countersink drill bits

    Quote Originally Posted by Canoeyawl View Post
    Depending on the thickness of the plywood and the type of glue used (thickened epoxy is noted for this) you can end up with the dreaded "quilted pillow" effect if you rely on just the screws to pull up the plywood. This is a hateful scenario when it happens.
    S’trewth!

    I have a bucket of hard maple 3/4 square x 6” long pieces, w/ a 3/16” hole drilled through 1” from each end.

    They get used as ‘cauls’ for gluing plywood edges to something (placed 1/2-1” apart) using 2” # 8 pan head sheet metal screws.

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    Default Re: Countersink drill bits

    Quote Originally Posted by Edward Pearson View Post
    ... pictures omitted to save bandwidth ...

    Well...check me out...I just got 3 new old stock Stanley Screwmates in a size 10 (1, 1.25 and 1.5 inch length) that I often use and a plug cutter for £5.99 for the lot on ebay! Rare these in the UK. I'm tickled pink. He listed as Screwmates...don't ya just love an Ebay typo.

    One day these might be just be the ticket.
    Hi Edward,

    Thanks for taking the time to post the pictures of the different sizes of screw-mates that could work for my build.

    I just ordered the 04-607 (#10 x 1") for my 1/4" ply sides and 04-608 (#10 x 1-1/4") for my 3/8" ply bottom from ebay. Bought them now since they are vintage and who knows if they will be available later. Not sure when I will start building my 12 foot Jon boat because there's no new 6hp outboards in stock in my area and the dealers aren't sure when they will be in stock. I want to have the outboard first to be sure my transom depth is correct. I've seen a post where the guy said the outboard was advertised as short shaft 15" but he received one with a 17" shaft. Not sure which outboard I will end up buying depending on availability and price, so shaft length is not certain.

    Anyway this just gives me more time to design my boat.

    Thanks,
    DayTripper

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    Quote Originally Posted by woodpile View Post

    That style countersink works better than any other. Doesn't make an oval like the "star" countersinks tend to do.
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    Default Re: Countersink drill bits

    Lots of great info and experience here. I am hoping that this is not too much of a thread drift but I have not been able to find any wood drill bits that are not the modern aggressive type that want to rapidly twist through the wood like the ones available today. The standard bits available when I was a kid seemed much better. Anybody agree and/or have a solution or source?

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    Default Re: Countersink drill bits

    What kind of drills were you using as a kid? I have always mostly used regular jobber's-length twist drills. High speed steel with a 118 degree point. These are definitely not the best choice for drilling wood, but it's what I have and, used with care, they get the job done. I haven't noticed any significant change in this type of drill during my lifetime. I'm 66. Maybe if you could describe the kind of drills you are looking for we could help you find them.

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