Bird Mouth Joinery: the 8-side router bit 

+Malcolm Webster Hi Malcolm! Thanks for the comment! Glad you're enjoying bird mouth joinery.

Thanks, Donovan! Any problems, give me a shout!

+Lynn Wright Thanks for the kind words, Lynn! I hope that you find the bits locally; in the past I have only seen them online. If you do locate some at a local store, let me, and a lot of other interested parties, know. I often get questions about where to buy them.

Thanks for your kind words, Shayne!

Thanks, fletcher3913! Glad you liked it!

Walter Reuter Sr. Walter - thank you for the thoughtful comment! Yes, I have considered the idea of a flush top, but not yet applied it to a decorative box; I think it's an excellent idea. Using a similar idea however, I did make an 8-side BMJ coffee table a couple of years ago. I used a beautiful piece of 3/4" pecan veneer ply as the table top and dropped it into place; I was very pleased with the result and the table is in our living room now. Now that you bring it up, that project might make a good video!

Thanks, Wayne!

+twoweary Thanks for the kind words and the useful comment! Yes, the bird mouth angle is 90 degrees. And yes, using a tilted straight bit should work perfectly well. I would be very interested in your result. The possible problems I see would be having a router table with angled bit capability (I don't have one!) and getting the angle exactly right. As you probably know, bird mouth joints can also be cut on the table saw but getting the perfect angle can be a problem.

How about a router table sled with a 45 degree bed?

My above question was answered when I viewed your "A unique tool box" video. Again, your video was very informative.

Thanks for the comments, PepperJack! Also, I appreciate the suggestion; I should have caught it myself.

+Jeremy Grefe Hi Jeremy! I have no experience with painted surfaces so can't give any direct help. However, my best guess for laying down polyurethane over paint would would be to scuff the paint surface well with steel wool or 320 grit sand paper, spray or wipe on a coat of shellac, and then use the poly. The scuffing probably wouldn't be needed for milk paint. Good luck!

Hi T Bone! Sorry, but I've never seen a 1/4" shank bird mouth bit. Thanks for your encouraging comments!

+davidhenry32 Thanks. Yes, after searching on Google for an hour I came to the same conclusion. So, now I'm in the market for a new router, HA. Thanks for your help and your great videos. Keep 'em coming.

This is a response from several years after the original post! With the mass of that bit I think it would dangerous on a 1/4 inch shaft and that is why you not finding a 1/4 shaft bit of this design.😁🛫

Hey, Rich! Thanks for the question, and good luck with your new bit. The bit height setting is proportional to the thickness of the stock. For 3/4" stock it is about 3/16", as I mention in the video. So for 1/2" and 1/4" stock the settings would be 1/8" and 1/16" respectively. The height is a sensitive setting to get just right; I always do tests to make sure that it is exactly as I want it, and frequently have to make very small microadjustments to get it just right. This is likely a problem stemming from my primitive router table setup! I'm sure that a simple formula for calculating bit height for a given stock could be worked out; just haven't done it.

davidhenry32 Thanks for the reply David. So, for 3/8 stock, would the height be 3/32?

Hi Donald! I have a new video ready to upload as I write this; thanks for asking! Subject: BMJ: Eight-sided decorative bowl with highly tapered staves. Should be available in a couple of days.

You're really paying close attention, Roger! I'm surprised that you could make it out with the resolution of my videos. It is a project from a "think-outside-the-box" design class that I took at the Palomar College woodworking school several years ago. It is unrelated to BMJ but is made of stacked plywood cutouts of diminishing size; hard to describe without a photo. It was a great class!

+Katheryn Lamarche Hi Katheyn! Glad you enjoyed the video! I hope you do get the 8-side bit and try a few projects; you'll have a lot of fun with it!

Hi Vicente! Yes, there are 16-side bits. I have one from Yonico that works well.

Hi Vicente! Yes there are 16-side bits available. I have one from Yonico that works well.

fred vferreira. Olá Fred, você encontrou essas fresas em alguma loja aqui no Brasil? Poderia por favor me passar o nome da loja ou ou o link, ficarei muito agradecido.

Olá Fred, você encontrou essas fresas em alguma loja aqui no Brasil? Poderia me passar o nome da loja ou o link? Ficarei muito agradecido.

Hi Mark! Thanks for the comment, and sorry for the difficulty you've run into. I've had a number of viewers tell me of similar problems. Conceivably, it could be your router table, but if your router table works well for other routing tasks then that's very unlikely. The problem isn't the fault of depth or height adjustments: such adjustments affect the amount of stave overlap at each joint, but don't affect the angular fit at the joints, and your problem is angular fit. In other words, the angle of turn at each joint is slightly more than the required exact 60 degrees. I suggest two things. First, do a simple test. Using your 6-side bit, cut a V-groove down one side of a single piece of stock a foot long or so. Then cut it into 6 equal length pieces and try to make a hexagon shape (perhaps you've already done this.) If you have the same problem you've already described, then you very likely have a defective bit (made with a slight angular error) and there is no cure for this except a replacement bit. As a second check, try the 8-side bit in the same test. Make an octagon from a single piece of stock. While there is no guarantee that the 8-side bit couldn't be faulty also, that seems a remote chance statistically, and I don't remember any communications about bad 8-sided bits, only 6-side. If the 8-side bit gives good results then that pretty much pins the problem on the 6-side bit. Contact me again if the problem isn't solved. Good luck!

Thanks for your reply David.I have done as you mentioned and used the 8 sided bit. Although it wasn't perfect, the 8 sides went together. But what I have noticed, that I never noticed before trying these bird mouth bits. Is my router table doesn't lock off the bit once set, and during the cut the bit dropped around 3 mm during the cutting. Not sure if that would make the difference. I took a picture of the 6 sided piece to show you, but I can't insert it into this chat.Maybe a new router table is the answer?Regards. Mark.

Hi Mark! Unfortunately, if your router bit changes adjustment in any way from the initial setting while the router is in use, any cutting it does will be flawed. More importantly, this could be a dangerous situation; if the bit comes out during use it could cause serious harm to you and/or your shop. A new router table, or at least a reliable repair, definitely sounds like a good idea!

Thanks for the great comments, and good luck with your upcoming BMJ projects Reslan!

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Lou Turcotte Thanks, Lou!

davidhenry32 qq

Hi William! Tapered staves can get complicated but they work just like straight staves if there is not too much taper. If the churn you have in mind is the familiar round one about two feet high, with a smaller diameter at the top than the bottom, then I think tapered staves would do fine. Just off the top of my head, this would need 12 two-foot long staves that were 3" wide at the bottom and about 2 1/2" wide at the top. Good luck with it; sounds like fun!

Hi Willian! Thanks for the comment! Regarding the finish, I use (for almost everything) a sealer coat of shellac followed by (typically) 3 coats of wipe-on polyurethane. The polyurethane is made by General Finishes and is called ARM-R-SEAL Oil & Urethane Topcoat. There are many oil-based urethane topcoats available and all would probably work reasonably well, but I prefer this one because it levels (smooths out) exceptionally well as it is applied, and also builds the finish rapidly. Unfortunately General Finishes products are not sold in Brazil, according to their website. Perhaps you could get it online? Good luck! Oi Willian! Obrigado pelo comentário! Em relação ao acabamento, eu uso (para quase tudo) um revestimento isolante de goma-laca seguido por (tipicamente) 3 camadas de poliuretano limpe-on. O poliuretano é feita por Acabamentos Gerais e é chamado ARM-R-SEAL Oil & revestimento superior de uretano. Há muitos acabamentos de uretano à base de óleo disponíveis e todos provavelmente iria funcionar razoavelmente bem, mas eu prefiro este porque os níveis (suaviza) excepcionalmente bem como é aplicado, e também constrói o acabamento rapidamente. Infelizmente Geral Acabamentos produtos não são vendidos no Brasil, de acordo com seu website. Talvez você possa obtê-lo on-line? Boa sorte! Dave Henry

hedorah99 Hi hedorah99! Thanks for the question, and for sharing my video! In theory, for a given stock thickness, there should be an exact height setting. Unfortunately, in practice, this isn't usually the case and some trial and error will probably be necessary for any specific project. I blame this on subtle factors: the hardness of the wood; almost invisible amounts of warp or twist; different routing setups; different routing techniques; small variations in stock thickness, etc. For the 8-side bit I set the height at 1/4 of the stock thickness and then do test cuts with the same stock that I plan to use for the project. It usually works out that the final bit height is a shade higher than where I start. For example, today I routed a redwood project in 3/4" stock and the optimum height came to an estimated 1/64" more than the 3/16" that I started with. It's worth the trouble to get it right. Good luck with your work! More questions? Just ask.

Hi Luiz! - Sorry to be so late with a reply. I didn't realize how easy it was to get a translation until now. Thank you for your generous comment. However, I can't answer your question because the computer translation (Portuguese?) was a little confusing. Please ask the question again and I would be happy to respond. Hopefully the translation will be better a second time!

Hi David, I was thinking about my comment, and of course mortise and tenon and cross lap joints are cross grain joints, where as table tops require a breadboard end, I wonder where the cut off it? How wide a board can you cross glue before it's a problem? (I know it is also species dependent!)

Thanks for your question, Richard. I'm glad you found the video helpful and hope that you give BMJ a try. You are not the first to ask about my crossgrain glue joints; many observant viewers have questioned me about it. There is no doubt at all that long crossgrain glue joints are a bad idea; wood moves and such joints will almost certainly fail eventually. I originally used such joints for their decorative value in small projects, figuring I'd soon find out if it was a serious problem. I have used the technique a lot but have yet to have a failure in several years of use; the longest joint has been about six inches in length. That was used in a unique octagonal tool box, and I did a video about that construction (accessible through my RU-vid channel.) I can only guess why it continues to work for me. Certainly the fact that bird mouth joints have two glue surfaces adds strength beyond a simple miter/butt joint. Also I stay away from soft woods that expand a lot with high humidity. And it is not unthinkable that the common wisdom of the woodworking world has overemphasized what is clearly bad technique for large panels, but may be more permissible with smaller projects. And your comments about M&T and lap joints are also very pertinent.

Thank you David. A six inch joint sounds like bigger than I would be using, so I'm probably safe!! Thank you for you responce

Francisco de Assis Obrigado, Francisco! Os seus comentários são muito generoso!