Using a Round Cross Grain

[Richard Line]

I want to make a round bottom dado across a piece of 2x4 and I'm wondering about using either my 5/8" (#10) wood round plane or the 1/2" round blade for my plow plane (a 45). I don't recall ever hearing about using either of these across the grain. I assume there would be a need to score along the edge of the dado and probably a good idea to plow a normal 'guide' grove in the middle of the dado to help guide the round plane.

Or is this a no-no as I'm likely to do harm to the round or the round plow blade. The wood is a construction grade 2/4, probably a fir of some kind, but not Doug Fir. The section where this would go is free of knots.

What is the thinking on this.

[Jim Koepke]

The planes might produce blow out on the ending side of the trough.

It might be easier to do this with a gouge of the size needed.

There may be a few other ways to do this, what is the use of this going to be?

jtk

[Derek Cohen]

Making a rounded dado is straightforward .... simply knife the boundary lines, deeply knife the centre of the "dado", and then chisel a vee to guide round plane (H&R, Stanley #45, Veritas Combination) to remove and shape the dado. But what is this for? As Jim asked, I am puzzled about the purpose.

Regards from Perth

Derek

[Richard Line]

Jim and Derek, thanks for your comments and help. I don't have a gouge, so I will probably go with Derek's approach. I've thought about the blow out and will probably clamp a backer board over the end of the grove to control the blow out.

What is it for. Well, I was hoping to not have to reveal that. The end product isn't to do with wood working, furniture. This will be the grip on a work stand for my bicycle. The horizontal frame tube will set in the grove and be clamped with a mating piece on the top. I've got a couple of fall back ideas, but they wouldn't be as elegant (not sure elegance really exists here).

[Jim Koepke]

[edit]

What is it for. Well, I was hoping to not have to reveal that. The end product isn't to do with wood working, furniture. This will be the grip on a work stand for my bicycle. The horizontal frame tube will set in the grove and be clamped with a mating piece on the top. I've got a couple of fall back ideas, but they wouldn't be as elegant (not sure elegance really exists here).

It would likely be just as easy to make your groove longways on a pair of 2X4s and use that to support a bike by the top tube (horizontal frame tube).

Another way would be to clamp your two pieces together and carefully drill them out with a large auger bit. The frame tube is likely bigger than 1/2-5/8" unless bikes have really changed since my riding days.

Derek's method may be the easiest. A large half round rasp would also be useful.

jtk

[Richard Line]

The frame tube is an ellipse with major and minor axis of approximately 2" & 1.5", with the major axis vertical. My plan was being driven by my available tool set. I was going to do 2 groves of 1/2 or 5/8 with about a 1/2 space between them. However, Jim you got me thinking again about drilling out the majority of the material.

I clamped the 2 pieces together, got out my expansion bit (the small size), set it to 1-1/4 dia., and got the brace going. I was able to keep the hole more square than I thought I could. To avoid blow out on the back side, I turned the assembly around once the lead screw peeked through. Then I found out how bad an expansion bit is at drilling once the lead screw can't do its work. Well a bit of chiseling took care of that. I am now in the process of widening the width of the grooves to fit the tube, with some space for cushioning material (rags).

Thanks again for the advise on this little job.