Zero Clearance Router Table Miter Spline Jig

  • Advertise with us
Project by PaulfromVictor posted 09-12-2009 10:03 PM 16861 views 13 times favorited 14 comments Add to Favorites Watch

...that’s a mouthful.

So, as I am in the shop working on this my wife comes in and asks, “what are you making?” To which I reply, “Do you really want to know?”. She said “Yes” So, I told her I was making a router table miter spline jig. Her response was a 10 second silent pause as she did her impression of a deer caught in headlights. Then she proceeded to talk to me about what she really wanted to talk about.

Someday I may find the inspiration to start an “Andybox”. When I do, I will use this. I did this as a router table jig instead of a table saw jig for a couple of reasons. First, I do not have a flat grind sawblade, only ATB. Second, using this with a slot cutting bit set I will be able to make spline of various thicknesses, including smaller than 1/8”.

The jig is made out of all MDF. The base is two thicknesses (1.5”) . The right angle portion is made out of 1/2” paper coated MDF (because I had plenty of scrap of this). These pieces are replaceable. I made a batch of 8 of them to last me for a while. Also, the 45 degree bevel is cut on each end, so after one end is used, you can swap sides and have a fresh end for a new zero clearance. The replaceable pieces are attached with quarter inch bolts and phenolic knobs. A quarter inch grove is cut into the pieces that runs almost the full length of the piece so they can be adjusted as needed. An additional grove of a half an inch is cut over the top of that groove as a counter sink for the bolt head.

There are a couple of downsides I see to this jig. One is that the height of the slot cutting bit will limit how far up a box a slot can be made. The other issue is that it will be neccessary to slide the removable pieces out to capture the bit, then adjust them in to cut out for the zero clearance.

Next time I make replacements for the disposable part, I will make them taller, so I can put two sets of grooves, and they can be flipped for a second cut, and then switched to the other side for two more cuts. 20/20 hinsight.

14 comments so far

View papadan's profile


3584 posts in 4179 days

#1 posted 09-12-2009 11:46 PM

Jig looks well made. I just don’t understand what you do with it. I need a picture of a splined miter from the jig. LOL

View bobthebuilder647's profile


128 posts in 4063 days

#2 posted 09-13-2009 01:52 AM

Nice jig. I never thought of doing this on a router.

-- Rick, Pa. Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen.

View a1Jim's profile


118104 posts in 4388 days

#3 posted 09-13-2009 01:55 AM

Cool Idea how about some photos of how well it works.


View cabinetmaster's profile


10874 posts in 4369 days

#4 posted 09-13-2009 01:57 AM

Great idea. I had never thought of that either. Great thought about the 20/20 hindsight.

-- Jerry--A man can never have enough tools or clamps

View dustyal's profile


1319 posts in 4286 days

#5 posted 09-13-2009 01:57 AM

I was wondering if someone had a router jig for spline miters. I made a jig for my table saw and it worked, but I really want to use the router since it is quieter and cleaner than my table saw. I do not have a flat top blade for the TS and it shows. Don’t intend to buy blades until I get a new TS.

Nicely done… but I can already see that this jig might get a bit complicated for me.

I didn’t think to go with a slot cutter… I kept thinking straight bit. I had what was an unusual sized bit… a 1/2” shank, 5/32” bit. I broke it… can’t find a replacement. In looking… didn’t see anything smaller than a 1/4” straight bit… but now that you made me look, I see the smaller slot bits. Not important… just drifting off there for a moment.

Thanks for posting.

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

View PaulfromVictor's profile


230 posts in 4157 days

#6 posted 09-13-2009 04:43 AM

I don’t have anything milled up for current projects just yet. It will probably be a couple weeks till I have a chance to try it out.

You could make a vertical form of this jig for traditional router bits and dovetail bits (for Dovetail Keys). Straight router bits would be a bit thick for most applications though.

View PaulfromVictor's profile


230 posts in 4157 days

#7 posted 09-13-2009 04:56 AM

One thing that may not be clear in the photo is that the part clamped to the fence has a portion hollowed to make room for the spinning arbor of the slot cutter.

View papadan's profile


3584 posts in 4179 days

#8 posted 09-13-2009 05:45 AM

OK, now I understand what you do with it. I was thinking of the bit coming up into the wood, didn’t catch the slot cutter part.

View Innovator's profile


3589 posts in 4224 days

#9 posted 09-13-2009 06:26 AM

Nice looking jig, it looks great.

-- Whether You Think You Can or You Think You Can't, YOU ARE RIGHT!!!

View Splinterman's profile


23074 posts in 4172 days

#10 posted 09-13-2009 10:34 AM

Sweet jig…...good job.

View blockhead's profile


1475 posts in 4119 days

#11 posted 09-22-2009 06:00 AM

Now that’s a sweet jig! Great job!

-- Brad, Oregon- The things that come to those who wait, may be the things left by those who got there first.

View Rich99's profile


60 posts in 3983 days

#12 posted 10-07-2009 09:11 AM

looks great, paul, but i just can’t visualize how it works.

so the bit is partly buried in that block that’s clamped to the fence? and the workpiece sits right in the ‘v’?

you’re putting the spline across the miter?

yeah, i really don’t get it. but it looks good… see my sander-mounted chamfer jig… my first attempt at an original jig.

-- Far-North Wood-Works (a fantasy company)

View PaulfromVictor's profile


230 posts in 4157 days

#13 posted 10-08-2009 02:16 AM

It is used with a slot cutting bit. The blade spins on a plane parallel to the table. A traditional bit will not work because it is vertical. The spline goes accross the miter

A picture of a slot cutter might help visualize. Here is one on Amazon:

View Blackie_'s profile


4883 posts in 3323 days

#14 posted 04-10-2013 12:09 PM

I’ve been wanting to do 1/4 splines as I already have a thick kerf flat bottom 1/8 TS blade so this would work great and I see you’ve already touched on the spline placement limit, Andy mentioned a spiral bit so I’m assuming the box would ride the router table as does a TS thus giving you more flexibility on placement, I don’t have a spiral in my inventory but I do have slot cutter. Nice jig.

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

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