End-grain gluing

[Jerry Lawrence]

This seems like a simple basic question, but I'm going to ask it anyway. I'm building a football trophy for some friends, and on top of this trophy will be a glass football supported on a three sided tapered stand (think super-bowl trophy). Each of these three sides will be four inches at the base, tapered to three inches at the top and six inches tall. The three sides have 60 degree bevels on the edges cut on them to glue together to form the topless pyramid shape for the football to sit atop. The football itself is hollow (yet still quite heavy) and will have a steel rod epoxied into it which will be run down the inside of the pyramid and through the box shaped base of the trophy itself...therefore the weight of the football will mostly be supported by that rod. Ok...enough of the lengthy set-up, here's my question: The beautiful piece of curly maple I have for the pyramid shape will look best if crosscut, with the grain wrapping around the pyramid. However that would mean cutting the 60degree bevels into the end grain and glueing end grain to end grain. Knowing the end-grain glueing is usually not the strongest of joints, do you think this will be strong enough under this circumstance?

[Jamie Buxton]

End-grain gluing isn't as strong as edge-grain gluing, but it can work anyhow. I've built boxes with glue only on beveled endgrain, and they've held together.

And if you're still worried, you can put all sorts of joint reinforcement hidden inside the base. For instance, you can put glue blocks in there, or plywood gussets. They'll help hold the joints together.

The bigger issue is how you're going to cut a 60-degree bevel....

[Jerry Lawrence]

Jamie, that is indeed another issue. So far the only way I've come up with is to tilt the blade 30degrees, and run the tapers through on edge. With a couple feather boards to hold them tight against the fence, and to minimize their tendancy to want to ride up on the blade, it still feels like a dicey operation. Any suggestions in that regard too?
Thanks for the vote of confidence on the glue joint itself though. Hopefully since it's not an overly stressed joint, it won't peel apart.

[Jamie Buxton]

Jamie, that is indeed another issue. So far the only way I've come up with is to tilt the blade 30degrees, and run the tapers through on edge. With a couple feather boards to hold them tight against the fence, and to minimize their tendancy to want to ride up on the blade, it still feels like a dicey operation. Any suggestions in that regard too?
Thanks for the vote of confidence on the glue joint itself though. Hopefully since it's not an overly stressed joint, it won't peel apart.

If you run the tapers on edge, they're resting on the offcut while you make the cut. When you fully sever the offcut, the stock is going to fall into the blade slot in the table, and jam against the blade. Bad things happen quickly. Perhaps you just burn the cut, but perhaps the blade kicks the stock at you. One way to avoid this is to fasten the fancy maple to something else. The something else bears against the rip fence and the table. Sometimes you can clamp the maple to the something else. Sometimes you can screw the two together, because the screw holes in the maple are on the inside of your box.

You also might want to make an auxiliary fence which is taller than the OEM one, so that the stock doesn't wave around in the air.

[Mike Heidrick]

Could you use a lock miter bit of some kind?

[Jerry Lawrence]

I'd wondered about a router bit, but haven't found one like that which work for a 60 degree angle.
Any other good suggestions?

[Jim Becker]

Jerry, is there "room" in the joinery for splines, loose tenons or even dowels to reinforce the end-grain to end-grain joints? They don't even need to be large...something small will add a lot to the strength.

[Dan Cameron]

You might want to consider clamping the boards in a tenoning jig instead of using a rip fence.

Dan

[John Thompson]

Blind spline if the inside won't be seen..

Sarge..

[Jim Finn]

[quote) For instance, you can put glue blocks in there, or plywood gussets. They'll help hold the joints together.....[/quote]..........I have done this often in making domed top trunks. Works for me.

[Alan Schwabacher]

Make test cuts on cheaper stock. 60 degree angles won't fit.

[Jamie Buxton]

Make test cuts on cheaper stock. 60 degree angles won't fit.

Hah! You're right. If you tilt the sides of the box in at the top, the bevel angle on the sides becomes less than 45, not more than 45.


....ooops... You're doing a three-sided box. I was thinking four-sided box.

[Jerry Lawrence]

Make test cuts on cheaper stock. 60 degree angles won't fit.
60 degrees is the correct angle for a three sided object regardless of taper. 180 degrees divided by number of sides = 60. Just like a square box...180 divided by four sides means 45 degree cuts. The taper of the sides shouldn't change the degrees of the mating corner pieces.
Now that I've said that....usually when I make a statement as fact, I'm instantly proven wrong...lol.

[Jerry Lawrence]

I was thinking of cutting two or three complete triangles out of thin stock and using them as blind splines glued into grooves on the inside of the 'semi pyramid'. Not only would that give glue support for the edges, but also help support the rod running down through the center. That's the best "better safe than sorry" kind of solution i could think of so far.
Sound good?

[Jamie Buxton]

60 degrees is the correct angle for a three sided object regardless of taper. 180 degrees divided by number of sides = 60. Just like a square box...180 divided by four sides means 45 degree cuts. The taper of the sides shouldn't change the degrees of the mating corner pieces.
Now that I've said that....usually when I make a statement as fact, I'm instantly proven wrong...lol.

Try this mental experiment. Take your three-sided object and push the top down until the whole thing is flat. Now what's your bevel angle? It is ninety degrees. The point is that the bevel angle does change when you tilt the sides in at the top.

[Jim Finn]

60 degrees is the correct angle for a three sided object regardless of taper. 180 degrees divided by number of sides = 60. Just like a square box...180 divided by four sides means 45 degree cuts. The taper of the sides shouldn't change the degrees of the mating corner pieces.
Now that I've said that....usually when I make a statement as fact, I'm instantly proven wrong...lol.....
Actualy aren't there are 360 degrees to get full circle? Four sides require four 90 degree turns and we make each turn in two cuts so we cut them 45 degrees each. Three sided objects still need to get all the 360 degrees included. 360 divided by the six required cuts =60 degrees at any taper.

[Jerry Lawrence]

Try this mental experiment. Take your three-sided object and push the top down until the whole thing is flat. Now what's your bevel angle? It is ninety degrees. The point is that the bevel angle does change when you tilt the sides in at the top.
I don't think the bevel angle changes, just the taper angle

[Jerry Lawrence]

....
Actualy aren't there are 360 degrees to get full circle? Four sides require four 90 degree turns and we make each turn in two cuts so we cut them 45 degrees each. Three sided objects still need to get all the 360 degrees included. 360 divided by the six required cuts =60 degrees at any taper.
Exactly, Jim! Either 360 divided by number of cuts, or 180 divided by number of sides.

[john bateman]

You should use the Polycut.exe program to determine the angles you need.

It's available from at least one of the other woodworking forums. It used to be a freebie from Badger Pond forum, and I think it's stored in Woodcentral's archives.

http://members.verizon.net/%7Epecker/60degrees.gif

[Lee Schierer]

Mitered corners in a picture frame are essentially an end grain joint. To get good strength in mitered corners you need to flood the joint with glue. The end grain sucks up considerably more glue than face grain will . Coat both surfaces with glue spreading the glue over the entire surface, then clamp the two pieces together. The joint should be strong enough for a trophy.

I agree that the tapered sided parts will not be at 60 degree angle when you cut them. You will need to use a compound angle calculator. This is one type of cut the Radial arm saw is superior to a table saw in cutting.