Boxland: Work Stations and Boxing Tips #3: Cutting Spline Slots

  • Advertise with us
Blog entry by Boxguy posted 05-18-2012 11:40 AM 14652 reads 46 times favorited 17 comments Add to Favorites Watch
« Part 2: Spline Making Jig Part 3 of Boxland: Work Stations and Boxing Tips series Part 4: Separating The Top and Cutting a Hinge to Fit »

Boxguy’s Spline Slot Cutting Jig

Want to add corner splines like this?

You need a jig like this!
This hard working (and dusty) jig is used on almost every box I make, and is quick and simple to build. It has a wide plywood board for a base, a long “trough” supported by 45 degree triangles cut from a 2X6 and a handle so you can pull it back to you. (I just made the handle out of a forking branch.) The long trough lets me use this for boxes that are large or small. The wide base lets me run the jig along the saw fence. Sliding the fence over so it is snug along the jig removes all the play in the slide and makes the jig extremely accurate.

If you spread the two sides of your “trough” apart a little, your box will touch both sides, but rests on the bottom. Touching the box to the bottom board is important because it lets you set the height of your saw cut accurately using the base of the jig as a starting point for your cut. I can now set the slot depth using those long square brass spacer bars to raise my blade to the proper height by just sliding the jig forward and setting the bars on top of the jig base. (Hint: when you are making the jig. Affix the back side of the trough so it aligns with the back end of the jig, then just set a box into the trough to align and set up the front side so the box touches the jig base and then fasten the front trough board in place.) There are two important things to notice in the above picture. First, I have drawn a pencil line on the jig that aligns with and is as wide as the dado blade. Second, there is a strip of 2 inch masking tape running across the back side of the trough. More about these next…

You can see the tape and the line on the outside top of the trough here. (The mark on the trough takes little looking, sorry.) Though I have posed this with a finished box, you can get the idea.

First, I mark where I want each spline cut to be made on the box blank itself with a pencil. (In this case I would have marked three 1/4 inch wide lines for the three splines.) Second, I align these penciled-in marks for the splines with the pencil marks on the trough that indicate where the blade will cut. Third, using the box itself as a ruler, I draw a line along the top of the box and across the masking tape. This pencil line across the tape will now become my indicator for locating the box on the jig for each cut.

I draw one line across the tape for each row of splines (in this case three marks) and put a number next to each line. (If you don’t number the lines, I find it is too easy to lose track of where you are in the sequence and accidentally cut the same slot twice.)

To cut the slots I hold the box blank firmly in place with both hands, and use my body to shove the jig forward and over the dado blade. Do not bring the box blank backwards through the blade. Instead, after cutting the slot, lift or tilt the box blank up and above the blade then pull the jig back into place for the next cut. Making more than one pass through the dado blade will widen the slot slightly and you will not get a nice, tight fit on your finished spline. I cut all three slots in one corner then roll the box to the next corner and cut three more slots.

I like to use the back of the trough as a foot so I can stand this large jig out of the way on the floor next to the saw. That is why I cut the hole-handle in the base board.

This shot shows the back of the jig. Notice the maple stop at the top so you don’t push the jig too far forward with your body as you make the pass over the blade. It also shows the runner that fits in the saw’s miter slot.

This jig and careful work will let you produce corner splines in your boxes that fit like a glove.

For instructions about making the splines themselves click here.


It took me far longer to tell how to cut slots than it takes me to actually cut the slots in my boxes. With practice, blade height set up, locating the slots on the box blank, marking the lines on the masking tape, and actually cutting the slots with the dado blade only takes 5 to 10 minutes.

If you have questions or comments, just ask. Thanks for reading.

-- Big Al in IN

17 comments so far

View Philzoel's profile


303 posts in 3680 days

#1 posted 05-18-2012 01:34 PM

VERY, VERY nice and simple jig. Clear and detailed. Thank you.

Is the miter slot and fence redundant? Can I just use fence? Is miter slot bar loose? and therefore you need fence.

-- Phil Zoeller louisville, KY

View Roger's profile


21055 posts in 4141 days

#2 posted 05-18-2012 03:39 PM

I do like the handle on the back and the larger base

-- Roger from KY. Work/Play/Travel Safe. Keep your dust collector fed. [email protected]

View Boxguy's profile


2905 posts in 3604 days

#3 posted 05-19-2012 01:14 PM


The runner in the slot is needed for the fence to push against. Without the runner the jig would wander across the table and not stay in place. The longer plane of the fence and jig help keep the back and forth motions exactly on track.

-- Big Al in IN

View DocSavage45's profile


9071 posts in 4179 days

#4 posted 05-22-2012 02:44 PM

Looks well used. Which means it’s a good tool. Like your solution for the fence rail. :-)

-- Cau Haus Designs, Thomas J. Tieffenbacher

View DeLayne Peck's profile

DeLayne Peck

669 posts in 3538 days

#5 posted 08-27-2012 03:46 PM

Thank you for sharing your wonderful art and methods.

-- DJ Peck, Lincoln Nebraska. Lord, keep your arm around my shoulder and your hand over my mouth.

View dustyal's profile


1322 posts in 4812 days

#6 posted 08-28-2012 02:59 AM

Big Al, is there any reason you don’t use a stop block to hold the box in position? i.e., keep the box against the block and do slot cut on on four corners. Then, move the stop to do the next slot on all four corners, then move stop again to do the third set?

Your method of using layout lines for dado location and the top of the box positioning is good… just thinking I would tend to clamp a stop block… so, just wondering out loud.

-- Al H. - small shop, small projects...

View Boxguy's profile


2905 posts in 3604 days

#7 posted 10-24-2012 09:05 PM

Dusty, good question about a stop. I find that a pencilled line gives enough accuracy for my needs and is a fast easy way to work. I do use a V shaped stop clamped into the trough for small items like trays because they tend to wobble when I cut them on edge.

I find that wood workers tend to get obsessed with accuracy in a product that moves with every change in moisture. Building a box is not the same as building an engine. My motto for wood is, “If you can’t see it with your eye it doesn’t count.” Don’t misunderstand me. I work carefully, but my tolerance tends to run between a 32nd and a 16th.

-- Big Al in IN

View BadDavid's profile


86 posts in 3369 days

#8 posted 11-22-2012 10:48 PM

The runner, it looks to be made out of a hard plastic. Is that true? And if so did you cut it out of a plastic cutting board?

-- BD, where bad wood finds a home. Va

View The Box Whisperer's profile

The Box Whisperer

678 posts in 3407 days

#9 posted 12-09-2012 11:28 PM

Very nice jig, would make a very nice upgrade to my little plywood one. I;ll try to make it pretty.

-- "despite you best efforts and your confidence that your smarter and faster than a saw blade at 10k rpm…. your not …." - Charles Neil

View Blackie_'s profile


4883 posts in 3849 days

#10 posted 02-06-2013 12:16 PM

Big Al, how do you handle tear out?

-- Randy - If I'm not on LJ's then I'm making Saw Dust. Please feel free to visit my store location at

View Boxguy's profile


2905 posts in 3604 days

#11 posted 02-06-2013 02:30 PM

Randy, with most wood it is not a problem. Since there are fewer teeth on my dado blades, I slow the rate of feed a bit. It helps to have sharp blades. Some of my walnut has a real problem with tear out and I solve that by rounding over the corners of my boxes and just sanding the tear out away. I really prefer rounded corners anyway.

I think Andy’s idea of tape would help. If it is a real concern, I would design my V trough with some extra width and have a half inch plywood backer board that I could replace and slide side to side for fresh use on the back side of the pass.

-- Big Al in IN

View Ken90712's profile


18099 posts in 4525 days

#12 posted 02-17-2013 04:32 PM

Well done I sue the same technique when doing this.

-- Ken, "Everyday above ground is a good day!"

View Chad256's profile


131 posts in 3223 days

#13 posted 05-20-2013 01:17 PM

Thanks for the great tutorial! I’ve been wanting to “teach myself” how to do splines….I’m sure this will help a lot!

-- -- Chad -- T&C Woodworks

View Boxguy's profile


2905 posts in 3604 days

#14 posted 07-24-2013 11:51 PM

Bad Dave, the runner is 3/4 inch HMD plastic that I bought at the Peachtree booth at the last Woodshow that I attended. I cut a strip lengthwise. HMD doesn’t swell with moisture and is self-lubricating.

-- Big Al in IN

View Jacob's profile


85 posts in 3615 days

#15 posted 08-11-2013 12:56 AM

Built a jig inspired by yours Big Al. Makes for some happy stress free spline cutting.


showing 1 through 15 of 17 comments

Have your say...

You must be signed in to post the comments.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics