What material to use for reinforcing mitered corners

[tom coleman]

I plan on making numerous mitered frames and want to reinforce the corners with splines.
I will be cutting the grooves with a slot cutting bit on a router table and I want to select a bit size and slot material that will give a good fit.

Someone told me that hardwood plywood makes a good spline (YorN) If I used typical unddersozed 1/4 inch ply then I'll need a slot cutter sized to that plywood.

Suggestions appreciated.

[Dave Gaul]

Any kind of hardwood will work just fine. I usually use a wood that contrasts the frame's wood nicely. Maple with purple heart or walnut splines or reversed.

I would only use plywood if the splines are hidden. YMMV.

[David Hawxhurst]

are you talking about splines you won't see or the kind on the outside that you do see. for either i would probably just use solid wood and make them to the size of cutter i would be using. i personally like the look of visible reinforced splines made from contrasting wood.

[Norman Hitt]

If you don't use a solid wood that you can easily size to fit the slot as mentioned above by David, then you can get an adjustable slot cutter from Amana that you can easily adjust to fit the thickness of the spline, (Threaded adjustment, NO Shimming). They make two size ranges. I have one of the sizes and they are well made and should be worth the money to you if you are going to be using it a lot. They are a little expensive, but not outrageous. I have had mine since they first came out and can't remember what I paid for it, but have not regretted the purchase.

[Jamie Buxton]

If you're talking about splines that are not visible, a biscuit joiner is a good approach. The joiner easily cuts the slots. The biscuits are readily available. It is my standard approach for mitered cabinet doors.

[John TenEyck]

If you're talking about splines that are not visible, a biscuit joiner is a good approach. The joiner easily cuts the slots. The biscuits are readily available. It is my standard approach for mitered cabinet doors.

+1 If you don't own a bisquit joiner you can buy a 5/32" router bit to cut the slots.

[John Tallyn]

As others have said, plywood will work, if the spline is not visible, although finding plywood in the "thickness" you are looking for may be difficult. Almost any hardwood will work, just need to decide if you want a contrasting look, or want to try to blend the spline into the existing wood. The biggest thing with splines is making sure you orient the grain of the spline properly, as I'm sure you are aware of, can't count the number of times I've cut some beautiful splines only to realize that I've got the grain running the wrong way. I've not tried using a biscuit jointer, although I may try it in my next splined miter joint.
John

[Chip Lindley]

Concerning hardwood splines, make sure grain runs crossways to the slot. otherwise there is no strength. As said, you can size hardwood splines to the slot width; much easier than trying to match cutters to undersize ply.

For utilitarian splines, 1/8" hardboard fits right into the kerf of my Freud 50T combo blade. Jus' sayin'....

[Mike Henderson]

I use biscuits and cut the slots on my router table. I made a jig that holds the piece at 45* so all I have to do is set up a piece to slide the jig along, and use my fence to control the depth of cut. That way I get a strong corner without the visible splines.

Mike

[Dell Littlefield]

I used some 1/8" masonite on some boxes. A couple of them full of heavy objects fell about 4 feet. The hardboard splines split along with the joint. I replaced with hardwood and probably won't use use hardboard again. As far as strength is concerned, I think I would rather use just about any wood than plywood. Nothing scientific about my answer, just an opinion.