# Spline Miter Joints



## Jophus14 (Aug 21, 2012)

I am going to be building a keepsake box and I want to have splined end miter joints. However, I do not want the spline protruding through the lid of the box. I built a 45 degree jig to cut the spline slot on my router table, but I wanted some input on which bit would be best to use. I was thinking of using an 1/8" straight bit and setting up a block to ensure that I don't go through the lid, but now I think an 1/8" slot cutter bit might work better. Cutting the piece from the bottom towards the lid will be easy since I can set up a stop block, but when I flip the piece around to cut the opposite miter and have to start from the lid and cut toward the bottom.....I will have to make sure both cuts line up. Any help will be appreciated. Thanks.


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## Dave Paine (May 30, 2012)

You can make either option work.

The nuance with a slot cutter is having to spend the time to curve the spline to fit. I have done in the past, or you stop the spline at the curve and have a hidden gap. I spent the time to hand sand the spline to match the curve of the slot.

I do not expect you are going very deep. I think the 1/8in straight bit will be adequate. The difference is some potential tearout, but this will not show since the surface will be glued.

You do not state the box height. I think you may be able to clamp stop blocks for the start and end and just start with a plunge cut. Easy for such a small diameter bit.


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## Jophus14 (Aug 21, 2012)

I will be constructing the box out of 3/4" X 4" walnut. I think I would have to lock the board in the jig and lower the entire jig down to plunge the bit into the wood. I would do this to ensure that the board stays at a 45 degree angle. If I set up a stop block on both sides of the bit and let the walnut "ride" the block down to start the cut, the bit should plunge at the same place on every board. Do you see any issue with doing it this way? Here is the jig.


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## Dave Paine (May 30, 2012)

Nice looking jig.

I see the piece underneath to use as your reference against the edge of the table instead of using a fence. This should work well.

I think lowering the entire jig onto the bit can work. If the hole is a little enlarged it should not be a problem for the joint.

I do not expect your spline grooves to be very deep.

You would set a block and rout all the same sides, then change the block to the other side of the jig and rout the other side.


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## FrankC (Aug 24, 2012)

I would plunge it close to the center of the board and have stops at both ends, run it to one end then back to other end. This will give a straight slot across the length so both ends are locked, the excess width in the center from the plunge action will not matter.


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## Jophus14 (Aug 21, 2012)

Thanks for all of your help. I actually cut a slot in my router table to insert a miter gauge or feather board so the strip of wood attached to the bottom of the jig will fit securely into that slot for these cuts. I think plunging into the middle of the board is a good idea in case there is any play prior to moving in either direction. I am open to any other advice that you may have regarding keepsake box construction. Thank you all.


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## redisette (Nov 11, 2012)

*Hidden Spline*

Jophus14,
I am wrestling with a similar problem... Seems like we've arrived at a similar solution. I've never used internal splines... Hope they're strong enough. http://www.woodworkingtalk.com/f5/vertical-grain-carcass-44658/#post398330
Good Luck,
Redisette


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## Midlandbob (Sep 5, 2011)

I just did a whole bunch od mortises in stool legs for half a dozen stools. Sometimes the bit would chatter enough to give slight imperfections in the walls. It was also a lot of work for the router bit. I finally used the drill press to drill 3/8 inch holes along the mortise for 1/2 inch mortises.. This made the final routing much more pleasant and clean. I think the overall time was less as the holes did not need to be very precise while the mortises were more precise.


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## TimPa (Jan 27, 2010)

if the spline is not going to show, maybe use a biscuit/jointer?!?


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