Virtual Designs in Sketchup #7: Corner Splines Without a Tablesaw

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Blog entry by rance posted 08-03-2011 09:03 AM 8378 reads 5 times favorited 4 comments Add to Favorites Watch
« Part 6: 3 Legged Workbench Part 7 of Virtual Designs in Sketchup series Part 8: The Inevitible Push Block »

I’ve seen questions here on LJ asking how to cut accurate splines with weapons other than a table saw. The obvious next choice might be a router. But what if you wanted them thinner than you could get with either of those?

I’m gonna suggest a good hand saw. Some can do them freehand with a hand saw. I’m not that good yet so my choice would be to build a Jig. (Or at least a SU drawing :).

First order of business would be saw selection. Although some of the larger saws might work, I’m gonna suggest a nice Dovetail Saw. If we are cutting corner splines on a nice mitered box, then we will be ripping. Therefore, we would prefer a saw with a rip tooth configuration. In actuallity, I’ll bet a Tennon saw would work pretty well too. The main requirement for the saw would be that it have a spine. You might suggest that it would rule out the Japanese pull saws but I say they could be configured to work. Alls ya godda do is configure a spine for them. That shouldn’t be too tough of a task for most folks. I’d say clamp the spine with the smallest of clamps to not increase the weight of the saw too much though.

On to the jig (my favorite part). Here’s an initial design that I believe would fit the bill for most woodworkers. It is not too difficult to build and should accomodate most any appropriate saw.


Lets break this down a bit. The basic jig starts with a corner brace attached with a butt joint:


Dimensions are not all that critical. Just use what you have available in the shop. Mine happen to be 4” x 8” x 3/4”. As with most jigs, I would suggest either MDF or some Baltic Birch plywood.  

Next are the saw blade guides(Refined):

These are are a glue-up of a 1/2” strip and two 3” triangles. These are glued up separately, lightly planed, then installed. Note the grain direction for maximum strength if using solid wood.  

Attach the Blade Guides. Draw a perpendicular line on the corner braces and attach the blade guides to the corner braces. You could glue the first one and wait till the glue dries or glue them both at the same time. Either way, you’ll use your saw to accomodate for the gap between the two guides:

To accomodate for the set in the teeth on the saw, you can add strips of tape on the blade. What you are after is to have the two saw blade guides perfectly parallel. Use the saw alternataly on both slopes to set the width of the kerf gap. You’ll want this snug. If it is too tight after gluing, you’ll easilly be able to remove the tape on the saw and saw through to open it up properly.

Now for the fence. The fence determines how far from the top/bottom of the box that the saw kerf will be. I just used two 4” x 4” blocks fastened together:

This fence will be held in place with a small C-Clamp when using the jig:

I suppose you could screw it in place as well. Actually, that’s probably what I would end up doing.  

Preparing the jig. First, you must place the saw between the saw guides and saw through the corner pieces that we began with. You can see from underneath where the saw has made its way through:

It wouldn’t hurt to put a backer board in there to prevent any tearout. That is important because those corner boards will act as backer boards when you do the sawing on your actual boxes.

Now you can adjust the fence to where your saw kerf will be at the top of your corner spline and clamp or screw it in place. Then place your box in a vise with one corner facing up and place the jig on the box, making sure the fence rests up against your box and make your first cut:

Repeat this for all four corners. If you intende to have both lower and upper splines, turn the box over and cut those now as well. Now make a shim equal to the thickness of your desired corner spline minus the width of your saw kerf. So if your saw kerf is 1/32” and you want a 1/8” spline, then make your shim 3/32” thick. I’ve shown my shim here as 5” x 5” with the lower corner nipped off to accomodate the box being held in the vise:

Once the second kerf is cut, the waste would be removed using a narrow 1/8” chisel. You can undercut the waste removal to assure that the splines meet both edges when installed.

To accomodate a shallower kerf, simply add shims to the top of the saw blade guides.

This is but one way that this can be accomplished. There are many other ways that could work equally as well. I’m just presenting this one as it would probably be my first choice, given my skill level and available weapons. Feel free to provide any and all comments or constructive criticism. :)

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

4 comments so far

View Joe Lyddon's profile

Joe Lyddon

10091 posts in 4046 days

#1 posted 08-03-2011 05:43 PM

Nice Approach!

Sure beats a Table Saw when all you want to do is a small spline…

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: ... My Small Gallery:"

View rance's profile


4258 posts in 3155 days

#2 posted 08-04-2011 12:22 AM

Thanks Joe. I have some future applications for thin corner splines and I think this will be just the ticket.

I tried to make the SU file available with a link, but with no success. I also tried uploading it to the 3D warehouse. I kept clicking the “Accept the Terms Of Service”, but it acts like I forgot to check a checkbox. I even turned off PopUp blocker, still no go. Hmmmmm?

Edit: Note also that I changed the build-up of the Saw Blade Guides to make them easier to build and stronger.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View Joe Lyddon's profile

Joe Lyddon

10091 posts in 4046 days

#3 posted 08-04-2011 12:47 AM

I’m running into that type of thing more & more… Junior grade programmers that do not know how to debug anything is my guess… or they think they are SO Perfect that they don’t have to test run programs…

If I had seen the kind of stuff I run into on My Watch (back then)... they would’ve been fired on the spot!

Very frustrating!

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: ... My Small Gallery:"

View gfadvm's profile


14940 posts in 2684 days

#4 posted 08-04-2011 03:28 AM

That looks like a lot of work and Im a power tool guy. If I needed really thin splines , I would use a thin kerf [1/16”] 71/2” circular saw blade in my table saw using my existing spline jig and I’d be done before you got your jig built. You could also cut thin splines on a bandsaw or REALLY thin splines on a scrollsaw. Anything to keep from using hand tools. No offense intended to those gluttons for punishment out there who LOVE hand tools.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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