Box Joint on a router table

[Justin Rapp]

Any good plans for a box cutter jig for a router table. I built one based on a this design https://www.youtube.com/watch?v=G01hhn-kQnc from wood magazine. However when I route the cuts, I am getting a pretty bad cut due to some vibration, which is chewing up the wood making the joint useless. I am using a double flute 1/4 router bit (1/2 inch shank). The wood is 1/4 thick and 1.75 wide. Any thoughts on a better router bit and should I go with a smaller joint, maybe 1/8 or 3/16"

[Lee Schierer]

I am using a double flute 1/4 router bit (1/2 inch shank).

In the video they are using a upcut spiral bit.

[Thomas Wilson]

The fence opening needs to be really tight to the bit. The workpiece needs to be secure to the fence. I cut multiples and clamp them to the fence. I use an Incra fence for spacing but your jig should work too.

[glenn bradley]

You can minimize vibration in a few ways on this type of jig. First assure that the tolerances of the jig's moving parts are good; you don't want any slop there. Your bit selection is important too. A spiral would be my choice. With that out of the way we come to material handling. Some 200 grit sandpaper fastened to the face of the fence will improve your grip. Clamping the work before each pass will help as well.

[Stan Calow]

I think every one of the woodworking magazines has featured a plan for a jig at least once. I'd do some searching on their websites, maybe starting with Woodsmith.

When I've used a jig, I found the major problem was supporting the workpiece (especially a long one on end) so that there was no back & forth wobble to it, as you're pulling it through. I think the spiral bit wants to give it a little rotation when it bites too, so I use a straight bit.

[Charles Lent]

For really clean cuts using a router table, you need a sacrificial backer, applied to both sides of your workpiece, because the bit cuts one direction on one side of the bit and the opposite direction on the other side of the bit. I ended up switching to the table saw because of this, since the table saw cuts the whole notch in one direction and a backer is only required where the blade teeth exit the work. I've made a lot of box joints and a lot of box joint jigs, but then bought an Incra I-Box jig and all of my shop made jigs went to the burn pile. They worked, but not as well as the I-Box jig, and it's easy to adjust for different size box joints, so no need for shop made jigs for different size box joints. Most of the time I'm now using the Freud SBOX8 blade set for 1/4 and 3/8" box joints, but also have a Freud FTG ground 1/8" ripping blade that works well for smaller box joints. The sacrificial backer is a piece of 1/4" MDF that is part of the jig. I just move it sideways to an uncut position just before cutting a new set of box joints. A few that I've cut in Baltic Birch are posted below. I was once told "You can't cut Box Joints in Plywood", but I do it frequently.

Charley

[Lisa Starr]

While I cut my box joints on an old Craftman Table Saw with a quick and dirty jig, I think many of these tips are universal.

1) I keep 1/8" masonite around and always use it to back the cut.
2) Slow, steady feed rate
3) Clamp or other method to keep stock absolutely vertical and tight to fence
4) No play in slide of jig.

Like Charles said, it is possible to cut box joints cleanly, even in plywood. I just finished cutting joints for 16 new shop drawers in 1/2" borg plywood. I only chipped two cuts and that was when I got sloppy.

[Justin Rapp]

What I am getting from this is - use my table saw. I made a box joint once before on my table saw and built a jig a while ago for it but it wasn't 'great' so it was repurposed.

For the jig I made, it's got no slop in it and using a piece of popular as my sacrificial fence. My woodpecker router table is showing up today so I might give this another try with a spiral bit, clamp between each cut, sandpaper on the fence and maybe a more solid router table then my old rockler setup. If it fails to be as good as I want, i'll build a new jig for my table saw. I just looked at the I-Box jig and if I made boxes all the time I would absolutely invest in one of these.

Thanks all for the input.

[Thomas McCurnin]

While I cut my box joints on an old Craftman Table Saw with a quick and dirty jig, I think many of these tips are universal.

1) I keep 1/8" masonite around and always use it to back the cut.
2) Slow, steady feed rate
3) Clamp or other method to keep stock absolutely vertical and tight to fence
4) No play in slide of jig.

Like Charles said, it is possible to cut box joints cleanly, even in plywood. I just finished cutting joints for 16 new shop drawers in 1/2" borg plywood. I only chipped two cuts and that was when I got sloppy.

+1

I prefer table saws for box joints but made this jig and a dedicated little router table for these types of 1/4" joints using a small DeWalt 611 Router. Yeah, back the cut, go slow, clamp the stock.

[John TenEyck]

I use my router table for cutting box joints because the corners are really square. Unless your dado set has flat ground blades (not just chippers) it will leave a little point in the corners. Also, spiral bits tend to cut undersized so the fingers won't fit into the slots when I use my Incra jig so I use straight bits. If you use a custom built jig then that won't be a problem. And as many others have said, backer boards are key to clean entry and especially exit cuts. I stack up common parts, clamp them against my jig, cut them all in one pass at full depth, index and repeat. Plywood, solid wood, they all come out fine.

John

[Stan Calow]

" . . . Also, spiral bits tend to cut undersized so the fingers won't fit into the slots when I use my Incra jig so I use straight bits."

Thank you for that John. I thought it was my imagination. I have the Incra jig now, and am still fussing with it.

[Justin Rapp]

I use my router table for cutting box joints because the corners are really square. Unless your dado set has flat ground blades (not just chippers) it will leave a little point in the corners. Also, spiral bits tend to cut undersized so the fingers won't fit into the slots when I use my Incra jig so I use straight bits. If you use a custom built jig then that won't be a problem. And as many others have said, backer boards are key to clean entry and especially exit cuts. I stack up common parts, clamp them against my jig, cut them all in one pass at full depth, index and repeat. Plywood, solid wood, they all come out fine.

John

I was just scratching my head one this. I have a 1/4" shank 1/4" upward spiral bit that I was going to try and it was a bit loose in the finger joint I made with my strait bit. I put calipers on it and it's .240 vs .250.

[Jim Becker]

I was just scratching my head one this. I have a 1/4" shank 1/4" upward spiral bit that I was going to try and it was a bit loose in the finger joint I made with my strait bit. I put calipers on it and it's .240 vs .250.

Not unusual, honestly. It's a reason that those of use who use CNC absolutely must measure physical tooling and make adjustments in the tool inventory of our CAD/CAM software so that the actual diameter of the tooling is taken into consideration when the toolpaths are created.

[Charles Lent]

Justin,

That .240" router bit will work, if you design the jig to fit it. You need the pin width to be .240" as well as the space between the pin and the bit. If all three are .240" and there is no side play in your jig, the bit will work for you.


The reason why I ended up buying an Incra I-Box jig is that, once calibrated, you can dial the width of the bit (even.240") and it adjusts the other dimensions to keep all three critical bit, space, and pin equal dimension. Changing from a 1/8" to a 3/8" box joint is simply a matter of making the one adjustment to fit the bit or blade. Then make a test cut to assure it's what you want. Calibration of the jig is easy too. You adjust it to just touch the cutting edge, then dial the desired width of the cut, make a test cut to assure that it matches the cutter size, move the sacrificial backer to a fresh position, and begin cutting your box joints. Any width from 1/8" to 1" is possible. For me, the Freud SBOX8 blade set cuts perfect 1/4 or 3/8" flat bottomed box joints. For larger than 3/8" I use a Freud Dial-A-Width DADO blade. It doesn't make perfect flat bottomed box joints, but it's less noticeable in these larger sizes. My latest addition is a 1/8" kerf Freud Ripping Blade LM72R010 that also makes perfect flat bottomed cuts. This is great when the need for small box joints for very small boxes need to be made.

The additional plus from going with the I-Box jig is that I didn't need to store the 10 Shop Made box joint jigs that I had built any more, so I reduced the needed storage space in my shop since the I-Box jig requires much less storage space. Although I have a Leigh D4R dovetail jig, I rarely use it since getting the I-Box jig, because it's so easy to set up and make strong boxes with box jointed corners than trying to get the dovetail jig set up just right to build the same boxes with dovetails. I now only use the Leigh D4R when dovetails must be cut to satisfy the job requirement.

Charley

[Justin Rapp]

Justin,

That .240" router bit will work, if you design the jig to fit it. You need the pin width to be .240" as well as the space between the pin and the bit. If all three are .240" and there is no side play in your jig, the bit will work for you.


The reason why I ended up buying an Incra I-Box jig is that, once calibrated, you can dial the width of the bit (even.240") and it adjusts the other dimensions to keep all three critical bit, space, and pin equal dimension. Changing from a 1/8" to a 3/8" box joint is simply a matter of making the one adjustment to fit the bit or blade. Then make a test cut to assure it's what you want. Calibration of the jig is easy too. You adjust it to just touch the cutting edge, then dial the desired width of the cut, make a test cut to assure that it matches the cutter size, move the sacrificial backer to a fresh position, and begin cutting your box joints. Any width from 1/8" to 1" is possible. For me, the Freud SBOX8 blade set cuts perfect 1/4 or 3/8" flat bottomed box joints. For larger than 3/8" I use a Freud Dial-A-Width DADO blade. It doesn't make perfect flat bottomed box joints, but it's less noticeable in these larger sizes. My latest addition is a 1/8" kerf Freud Ripping Blade LM72R010 that also makes perfect flat bottomed cuts. This is great when the need for small box joints for very small boxes need to be made.

The additional plus from going with the I-Box jig is that I didn't need to store the 10 Shop Made box joint jigs that I had built any more, so I reduced the needed storage space in my shop since the I-Box jig requires much less storage space. Although I have a Leigh D4R dovetail jig, I rarely use it since getting the I-Box jig, because it's so easy to set up and make strong boxes with box jointed corners than trying to get the dovetail jig set up just right to build the same boxes with dovetails. I now only use the Leigh D4R when dovetails must be cut to satisfy the job requirement.

Charley

I did figure the .240 will work just fine. Today my job is setting up my new router table, so I won't get back to the box cut till maybe tomorrow or the weekend. I am gonna retry my jig if it works with the new table and set it up with a .240 pin and gap. Ironically, the Freud Ripping Blade LM72R010 is already in my cart since I have a feeling these small boxes I am making will look better anyway with 1/8". That means incra I-Box or I make yet another jig.