# Please HELP me (Box Joint Jig)



## Beok21 (Jan 9, 2021)

Hello, all! I am new to the community and fairly new to woodworking, I've been doing it for a couple of years now however I've only ever utilized butt joints, lap joints, and pocket holes for any of my joinery in the past.

I am trying to step my game up by creating more illustrious, stronger joints beginning with box joints. So I'll jump right in to my complications: I have a 24"x24"shop-made router table. I have a makita RT0701C Palm router mounted underneath the table. And I am using pine 'Premium Select' from home depot (not sure how but it seems they make these boards much harder than traditional common boards). 

I have created a box joint 'sled' type jig that glides squarely across my route table, and feeds work pieces into the bit to create box joints. Although I have had some success, as none of my issues lie in squared-ness, distance gaps, or any of the other common issues. 

However!! I continually get large chunk blowouts and tearouts not only on my joints, but when attempting to create a new jig template for different sized bits - mostly when I go to make the second mortise (or slot) and it tears out the tenon (tooth piece) [disclaimer : I only use parentheses because I'm not 100% sure I'm using these terms correctly] and leaves me with one large utterly useless slot either in my workpiece or in the template I am attempting to make for another joint size. 

I have tried tampering with lower and higher speed settings on the router, I have run the grain of my pieces both parallel and perpendicular to the router bit.. Is it because I'm using pine and it is too soft a wood to withstand a full box joint cutout in one shot? Could it be that my router cannot keep up with feeding a full 3/4" cutout into it at one time, and I need a larger router? 

I really don't know what else to do, please help me understand how I can correct this issue. Thank you in advance!


----------



## NoNails (Jun 6, 2016)

You have cut out a larger slot in the back of your jig than you are now attempting to cut. Provide a backer piece.


----------



## Pretender (Jun 22, 2019)

Are you using a backer board?


----------



## DustyDan (Dec 21, 2020)

Not really sure about my answer so if someone disagrees please chime in. My first thought is power. That palm router seems pretty small for a somewhat hefty cut. I think most people use a full size router in a table. The result could be that you are unwittingly forcing the cut with excess tear out being the result. Try multiple passes to compensate.

Guys, am I off base hear?


----------



## Beok21 (Jan 9, 2021)

Thank you all for your responses thus far, all very helpful! Regarding the backer board my answer is yes, as I have my jig itself backing up the creating of another size template or a workpiece. 

However as NoNails has pointed out and something I did not really consider : it could certainly be attributed to the fact that I've allowed wider bits to somewhat cut into my jig and so now when I am attempting to make lesser-diameter cuts in my jig templates or workpieces, I could see how that could easily create a blowout as it approaches the end of the slot creation, 'kicking' the remainder of material between the two slots right out. 

Also though, as DustyDan points out and is equally a concern of mine, is indeed my router itself. When I did my research and learned to make this jig and how to use it, I don't recall being able to see nor it being stated what an optimal size router would be for this application. My impression is that my router being rather small, has it's power and ability to maintain a smooth shearing motion severely blunted when pressing a 3/4" worth of material up against it and becomes more of a 'beating','hammering' motion instead, result in quite substantial tear-outs and blowouts. 

However, creating finger joints having to use 2-4 passes for each and every slot is also quite tedious and if that is what would be necessary for my current router to create these joints, I'd probably have to just wait until I can obtain a more powerful 1/2" shank router. 

I'd be very interested to hear more thoughts on both parts of this, or if anyone else uses a smaller 1/4" shank router to create box/finger joints? Also, if I am to create a new jig, should I be totally avoiding the allowance of the bit to go beyond any size bit diameter template - and not insert the jig at all, as it will inevitably create a larger-diameter cutout that will likely cause blowout to any future jig templates or workpieces? Some of the videos and even drawings I've seen of other jigs seems to display the bit inserting the jig slightly without cause for concern, nonetheless I can see how that would easily cause blowouts as stated above. 

Thank you all so much for your help, I've been on my own all this time - I have no mentor or anyone I personally know that I can reach out to that also does any woodworking; so I typically trial-and-error until I get it right, however this really had/has me stumped for about a week now.


----------



## DustyDan (Dec 21, 2020)

Maybe a pic or your jig and a description of how wide your fingers are for the box joint. What bits are you using?


----------



## Terry Q (Jul 28, 2016)

You should design your jig so that the backer board is an easily replaced part of the jig


----------



## Outpost22 (Nov 8, 2020)

RE: Pine
Having just built my first box joint jig and experiencing your same issues, even with a backer, I would ask if you are cutting the joints in one large cut? I found if I cut half of the joints depth and then went back a second time and finished the depth of cut to its final depth, there was no tear out. 
Then, when I went to oak and walnut as my work pieces, I was able to do full depth of cuts with no tear out. I attributed it as an issue dealing with a softwood like pine vs. hardwoods. 
Anyway, that's the way it worked for me.


----------



## Rebelwork (Jan 15, 2012)

You might also try Router Forums


----------



## Beok21 (Jan 9, 2021)

Thank you all for your responses and experience, it is super appreciated - I'm not one to typically reach out for any help (probably hence half of my problems 😂)

Anyway, attached are a couple pics of my current setup. I am in the process of creating T tracks for both my jig and my fence for greater stability and reliability (this is a new endeavor for me and I did not foresee the potential issues with my sled having rails that glide along the edges of my table, nor the slots I've made for my fence) I am using 1/4",3/8", and 1/2" MAX (given my rather small router) straight bits when attempting to make finger joints, at a depth of 3/4" as that is the thickness of my boards.

I believe it is a 3 part issue for me : my small router being tasked with 3/4" depth cuts in a single pass, at any diameter really. The choice (or lack thereof) in stock, being a softwood. And lastly, although I did have some success with my initial joints, I am now seeing multiple areas that could be re-engineered to become more stable and reliable. 

As for doing finger joints in multiple passes per each 'slot', I had this same thought - as I typically do any routing in ~1/4" passes at a time given that my router is not very heavy duty. However, with finger joints using a jig that requires a 'key' to index the spacing, if I were to do multiple passes per slot, that would require a ton of going under the table and shifting the router up & down - making it not only tedious but creating great room for error in the depths of my slots (as I'd have to reset it at the exact same depth for each slot after adjusting for multiple passes)

Lastly, I had thought that my jig itself would provide essentially a backer board function in and of itself, however I think part of that issue may also lie in the fact that if I use say a 1/2" template on my jig, it cuts into my jig slightly - then when I switch back to a smaller diameter (ex : 1/4") because I have created a greater sized void behind my 1/4" template, correct me if I'm wrong but it seems that would create a circumstance where as the pass is about complete, it will want to "bat" out the remaining material between the slot currently being routed and the previous. 

Which leaves me with the question, then, should I be creating a new backer board for each and every time I make a set of finger joints? Which with my current jig, would also entail drilling holes thru the backer board so my thru-bolts can pass thru it? Or am I making a mistake by allowing my bit to go into my jig itself whatsoever? 

Thank you for your inputs, and hopefully this serves as an aid for others with this issue because it seems to be a rather tough subject to get detailed instruction on given all the variables here. 

Below are my setup, a couple half-decent successes, and a few failure blowouts.

I feel as if 90% of these variables can and are answered via articles & videos, however that remainder 10% seems to be a vital yet evasive set of guidance that these articles and videos lack.. I've done many hours of research and watching videos and none really detail things like router size, bit choice, or stock type when using a box joint jig for a router - it's either a how-to build or how-to use article/video; but not the other smaller details.


----------



## Beok21 (Jan 9, 2021)

Also another note, the one picture with the much higher slot was my attempt at trying to create deep slots with a long straight bit, as I was going to try to use finger joints to joint together 2x4 which would require much deeper slots given it's thickness. Nonetheless it shows the type of blowouts I am experiencing. 

Also, a back view of my makeshift jig - I know it isn't a very traditional build, however I was attempting to make this work without having T track in my table - which is what I am now working on doing. It seemed to work at first but also if I am to build a new jig more suitable for backer board changeouts, I may as well put the work in and run it on T track


----------

