Hidden wooden hinge jig / Cosman hinge jig

Hello all,

I saw a video on youtube of Rob Cosman making a lovely box with a hidden hinge. He used a little jig for putting holes in the dead centre of the dowel used to make the hinge. I have a metal lathe so I figured Id make a jig myself. It wasnt too hard so perhaps I should make some to sell on here.

I have ordered a few parts and have some material on hand but I would like to find out what preferences you all have if you would like to buy this jig. I have ordered grub screws to retain the drill bit, the drill bit, tig rods, router bits (cheapies but they dont need to do much work) and I will make a little case on my cnc. I planned on making 1/4" and 1/2" sizes for small and large boxes. The tig rods are the hinge bolt and the 1/4" takes a 1.6mm while the 1/2" takes a 3.2. These size rods are readily available at welding shops or hardware stores. I plan on including a few in the kit. Each takes me about 2 hours all said and done. Turning, altering the drill bits to appropriate size, tapping and prepping the box. I am hoping to provide a ready to go kit but without the dowel making jig.. maybe.


So, I would like to ask you the following - If you were interested in purchasing would you prefer

1. Metric or Imperial?

2. Sizes? 4, 6, 8, 10, 12mm? or 1/4- 3/8 - 1/2" I would prefer to stick to two sizes only. Or charge extra for custom sizes.

3. What would be a fair price? Cosmans jigs are awfully expensive and the shipping is a killer. I imagine shipping will be $10 Australia wide and parts around $10. It would be around 2-3 hours work per jig everything considered.

4. What else would be nice to have included? I thought about a dowel making jig. There are a few 3D printed designs I could print or make my own but it would be around $30 or so extra depending if I go with a planer blade or router bit as the cutter.

5. Are there any other tools that people are after that could be made on a lathe?

Thanks all,
Paul

Making one for your own use is one thing, selling them is quite another. Have you checked with Rob that you’re not violating some IP?

It isnt patented or copyrighted.

It isnt novel or non-obvious. Its the technique that is novel and even then its a twist on traditional wooden hinges. Its a tool that enables a technique to be used.
He tells you how to make one in one of his videos. This is a bit of metal with two holes drilled in it. Its not a Festool Domino.

His is designed differently than mine even though it is ostensibly the same principle. A short piece of round bar stock with two holes drilled in it. I didnt reference or copy his design. I looked for a way for me to accomplish the same outcome. Looking at his now it has interchangeable heads which is quite clever but again, not something that can be patented.

I see Bridge City and Woodpecker copies on Aliexpress and TEMU. The infringement there is not that they both shave wood or measure. Its that they seek to encroach on innovation and aesthetic of the established brands. There are many other options to achieve the same ends. Aliexpress and TEMU seek to hijack the brands reputation and in turn damage their company as a whole.

I am not trying to sell these as Cosman replicas.

I am making my own solution to the same problem which is not novel and is obvious.

As such, I dont feel it necessary to get permission to make and sell something like this.

I understand your concern but I dont consider this unethical. The maker community is just not like that. How many dovetail hand saw jigs are there out there? People sell plans for obvious and easy things if they want to make money solely off the idea. If youd like to purchase his then you are very welcome to do so. If you think me selling my version of the jig is unethical then you are welcome to contact Rob regarding this matter.

Chill out mate, I was posing a simple question. No need to jump down my throat. Your post was written very much like you were replicating Rob’s jig. And in previous threads where you’ve suggested selling them whether or not you would be replicating them exactly, you refer to making ‘Cosman hinge jigs’. Would you like me to link those threads here?

I gave your post a lot of thought and posted my reply. There was no personal attack or jumping down your throat. This thread is titled with Cosman in the name too so I understand the confusion. I should have titled it Cosman style hinge jig or just not mentioned his name at all.

Anyway. I don’t want to derail this thread. If mods deem my plan to be unethical they can close this down without protest.

I have the Cosman one in metric. i bought it before Covid and the large increase in freight cost. It was still expensive. I have the full set but have only used the smallest one so far. Sounds like a good idea. It’s not like you would be competing with Rob. I would be interested in a dowel making jig.

If you make a metric kit of varying sizes I’d be happy to be a Guinea pig to try them out as the ones from the states are expensive along with shipping

Cheers
Nathan

Id join Delbs in guinea-pigging. :)

Hi Paul, I'd be interested in 1/4" and 3/8". I have a veritas dowel maker kit so I can make any size dowel I want. Being Nth American, it's imperial. I can adjust it to make metric dowels but it's easier just to go with imperial.

Ok great. Ty to the volunteers.

I am thinking $40 a piece with $10 postage. This would include the jig, case, allen key, 3 drill bits, a cheapy ball nose router bit and 2m of tig rod cut up to fit.

Not looking to make a million. Just some extra funds to help pay for this moneypit of a hobby.

I will provide pics once the parts come in so you know what youre getting. Shouldnt be more than a fortnight or so.

Thanks all.
Paul

Hi Paul, I would also be interested in any two of the following sizes you decide to make, 1/4", 3/8" or 1/2".

Slight hiccup with Aliexpress (who'd have thought?). Turns out I ordered 6mm shank router bits instead of 1/4". Also, their 1.6mm drill bits are 1.44mm and their 3.2mm drill bits are 3.1. You get what you pay for. It doesnt seem like much but because the drill bit sticks out as far as it does and its captured within a cylinder it has no room to self correct. This means the hole will be off centre and with the bits I got delivered it will be too far off centre for the purpose.

I have ordered some Makita and Sutton bits locally, however, that means local pricing. Ive ordered 1/4" shank router bits which are 2 weeks away. Given Boonings sells the equivalent for more than this jig in total I figure its worth the wait. Quality is not as good, sure, but they are doing very little work. I have also sourced bright steel for the round stock. Tricky to drill a 1.5mm hole dead centre (quite a few broken drill bits so far meaning quite a few blanks chucked out with 1/2 a drill bit in them) but it is more resilient to marring in the drill chuck.

I was hoping to keep the price at $40 plus shipping but reputable drill bits x2 adds $5 to the costs. First round of orders will be $40 and next batch will be reappraised with maybe a $5 increase to cover new costs.

Cheers,
Paul

First few are finished. 1/4" and 1/2". I have a dozen or so of each almost finished waiting for me to buy a new 4mm tap tomorrow to tap in the grub screws. Taps are so fragile.

I am planning on making 3/8" size next week using 16mm bright steel round stock as my prototype squished in the vice due to the walls being too thin in 12mm stock.

Based on testing from forum member Bendigo Bob, the 3/8" (9.5mm) might be the sweet spot for shoebox sized boxes. I’ve also drilled the main hole oversized by 3-5% to allow for easy insertion of the dowel and also to prevent marring/burnishing of the dowel.

Router bits and quality drill bits are about a week away so they should be good to go shortly after.

I am still working on a dowel jig. Tricky to produce one cheaply that also makes accurate and tidy lengths of dowel. There are jigs on Temu for $20 but by all accounts they are pretty rough. Look nice but don’t produce good results.

Again, the kit will include the jig, 2x drill bits, Allen key, cheap router bit, length of stainless tig rod and a box.

Pricing for this first round of jigs will be -

1/4" $40
3/8" $45
1/2" $55

Postage $12

I will sell here and on eBay for those who prefer but with a 10% surcharge to cover fees.


Attachment 537810

Nearly done. Should be good to start selling in the marketplace by next Monday.

Attachment 537974

Another hiccup.

I finished about 3/4 of the batch I had planned before I checked for accuracy. I assumed that my lathe was still in alignment. It was not. This has meant that about 1/2 of the jigs are out of tolerance as the holes are not concentric from both ends. Some are perfect, some are within tolerance (Ive actually tested them on a mock up hinge) but the rest are scrap.

With a well tuned lathe, you can drill from one end, flip the part, and drill from the other and the holes will meet up almost exactly. For especially high accuracy parts, like a hole that a rod needs to fit snugly in without wiggle room but can still travel freely, it is best, no matter how good a lathe, to drill the complete hole from one end and then turn the outside diameter in the same setup so that the hole and OD are perfectly parallel or concentric. Generally the drill bit diameter to hole ratio is 5:1. The 3/8" uses a 2.4mm drill and the 1/2" uses a 3.2mm drill. Drilling through 45mm of steel isnt so hard with that diameter drill even with a ratio of 18:1 and 14:1 respectively. However, the 1/4" jigs use a 1.6mm drill meaning a ratio of 28:1. Not only do I not have a drill bit long enough to drill 45mm but even getting half that depth resulted in many, many snapped drill bits and trashed blanks. Shortening the jig would also mean having to shorten the drill bit. Sharpening 1.6mm drill bits by hand is ... beyond me. 2.4 and 3.2 I can do.

Further, in trying to get my lathe aligned I have ... unaligned it even more. 3 days sunk work and Im exactly where I started and still confounded on how to fix it. I have reassembled my lathe to put the final touches on the remainder of the jigs. This is only cosmetic details like chamfers and finish sanding so the misalignment will not effect usage.

With that said, I am currently printing out the rest of the cases needed and putting the final touches on the jigs that are within tolerance. I dont want to sell crap and would rather make no money and sell quality tools than make a little money and sell tools that only kinda sorta work well.

There are about 6 of the 1/2" jig, 10 of the 3/8" jig and 15 of the 1/4" jig. The router bits and drill bits have arrived an I have printed about 10 more of the mini cases to print.

All things going to plan, the jigs will be up by Wednesday. Thanks for your patience.

Paul

PS I also have a dowel jig designed. I will be testing it later this week. Only has a few parts you cant get from Bunnings