JSK-Koubou Loose Tenon Joint Jig - My Build

[roy_okc]

I recently saw the Japanese Youtuber JSK-Koubou's build of a 3D printed loose tenon jig, YT link: https://www.youtube.com/watch?v=vdi3JxJpnZo, and offering plans and printable 3D parts models for sale. I can't at present justify the cost of a Festool Domino machine, but my early estimate was that it would run $50-75 in parts to build the kit, I already had a compatible router, plus probably a couple tools to aid in assembling.

The initial ZIP file that I got when I purchased the plans, which were about $12 I think, contained a link to a password protected web page that had the instructions as well as some updated files. When the video was initially released, there was only support for 65mm diameter routers, but I've since two more sizes added.

I first started printing using gray PETG, but this resulted in warpage on the large parts that were unusable. I then reprinted the unusable parts as well as the rest that I hadn't already printed in yellow and orange PLA which came out fine, only using a few of the PETG parts. Not counting the bad parts, print time was around 20-30 hours total across a few days. As I recall, the total filament used was over 1 KG but well under 2 KG.

I ended up buying two tools, a heat insert press and a HF 6" cutoff tool and discs, plus a set of metric drill bits large enough to clean up the holes for the rods.

The hardest part of this was finding suitable substitutes for his BOM, I have a feeling that there may have been a run on supplies due to this build release as a couple things that I had added to my Amazon cart but not yet purchased went out of stock before I finished the order. Additionally, I couldn't find exact matches to some of items and had to end up doing some hand modifications.

Below is the nearly finished tool, I just need to replace a couple temporary bolts when the correct ones arrive and glue some of the covers on knobs. Definitely need to adapt to my dust extractor, as I was getting a face full of sawdust.

Perspective View

Joint Jig 1.jpg (47.32 KiB) Viewed 12011 times

Not pretty results yet, the outer two were before I set the depth adjustment, I was going too deep. The middle one would probably be usable, if ugly, for alignment purposes. I definitely need practice with it. I was using a 1/4" CNC bit, not sure if that was too aggressive for this purpose; I plan to order a purpose-designed 1/4" shank bit from Woodpeckers in 5mm and/or 6mm cutting diameter.

First Cuts

Joint Jig First Cuts.jpg (36.93 KiB) Viewed 12011 times

One mod I made was instead of metal I used plastic linear bearings in the thought that they wouldn't have an issue with dust; this may be leading to some of my quality issues as I found it difficult to push although side to side was easy so I'm going to try replacing at least "Y" direction bearings.

I haven't yet totaled my actual BOM, it may have crossed over the $75 point; but with one or two exceptions, I have enough parts to build another one or two of these and still have a bunch of metric screws and heat inserts left over. I did not build the stand as I don't have a need for it, so that would add a bit to the overall cost. Nor have I printed the angle adapter, not sure if I will or not but that would be a couple more dollars in filament and a little bit of hardware.

Total assembly time was probably around 3 or maybe 4 hours over the course of several days with most of that time cutting and grinding the rods to length and modifying a too-large stop collar.

Let me know if anyone would like to have the BOM for the parts I sourced or more detail on the actual build.

[roy_okc]

Yesterday I swapped the Igus-style plastic linear bearings with metal ones on the Y direction rails; I left the plastic X rail bearings in place for now as they have been sliding smoothly. I then tried a couple new mortises with the Woodpeckers 6mm bit. The new bearings made a huge difference in operation, very smooth to push versus a bit too firm before. I still need to get used to the operation of the jig as I initially made 2 or 3 of the mortises less than full width; I didn't yet use the shims to try to get exact width. I need to make a gauge block of some sort to adjust the cut depth as the first couple weren't deep enough and after adjusting were a bit too deep. I added holes to the front part model before printing and put heat inserts in so I can put end stops on, still need to make the simple stops but those will just be something from scrap with appropriate sized holes. Also still need an adapter for the dust extractor and glue the top piece on to the front handle for just a bit more comfortable feel.

As you can see in the below pic, the cuts are much cleaner looking than the previous test. The one that appears to be the correct size is actually an accidentally super tight fit that I had to hammer the tenon in. As best as I could check with a straight edge, the two 2x4s appeared to be straight across on the top when connected.

I still need to practice a bit more in hardwood, with and without the limiting shims, and probably every time before I use it for actual work, but I think this will work out well enough for my present occasional needs.

15 May Pic

Joint Jig 2e.jpg (368.74 KiB) Viewed 11565 times

[GetterDone]

Thanks for Sharing the idea.

I watched the video and thats a great idea.

I am subbed for your projects with this.

I have a A1 Bambu and I love seeing things like this.

[roy_okc]

Thanks for Sharing the idea.

I watched the video and thats a great idea.

I am subbed for your projects with this.

I have a A1 Bambu and I love seeing things like this.

Dwayne,

Thanks for the comments. I'm on my 4th 3D printer, a Snapmaker U1, and what a difference this one is in quality and speed over the old printers. I'm probably close to having printed more on this in the 5 months I've had it than the other three combined going back at least 10 years. With things like this, it is paying itself off compared to buying. I've already printed a dust boot for my CNC, saving probably $150-200 on that, will have better ATC tool cups that will save a couple hundred more over less optimal holders, plus some misc stuff that I'm not even sure I could find the equivalent to buy; right now I'm printing a holder for my e-stop box for the CNC. I'm hoping I can get good prints from ABS and ASA when I get the official top cover sometime this summer, although I'll move it out of the house to do so.

Any projects will likely be infrequent. I have other tools that I will likely use before this, especially a PantoRouter, a huge CNC, and a couple higher end dowel jigs. I built this for those cases where I'm working on something that wouldn't be easily portable enough for the PantoRouter nor conducive to using the CNC and don't need/want precision of dowel jig; or just plain quick for alignment purposes such as edge glue ups. But I'll try to remember to post pics of at least the first couple things I do in here.

[GetterDone]

Cool.

The PantoRouter has the most interest for me.

You have a lot of Cool projects going on.