Round-over Question

[jsburger]

Is there a method (other than trial and error) for ensuring the round over is equal?

My sense is that if I carefully align the very lowest portion of the cutting surface of the bit (remember I'm using an overarm router) with the exact mid point of the stock, it should end up uniform and centered when I flip the work piece over.

Is that right?

Not unless your stock is exactly twice the thickness of the round over bit radius.

I don't have an over arm router but the procedure I use on the router table should work fine, just upside down.

I use a SS ruler on edge and raise the bit so the bottom corner of the cove is flush with the table. The bearing will keep the other edge of the cove flush with the stock. You will always be centered regardless of the thickness of the stock. This way you will always get perfectly rounded over corners. Unless your stock is EXACTLY twice the dimension of the round over bit you wont get a perfect bull nose if that is what you are after. If the stock thickness is very close a little sanding will make it perfect.

With the over head router you don't need the ruler. Just lower the bit so the top corner of the cove is flush with the top of the stock. I make a test cut to be sure I have it correct. Tweek if necessary but usually only once. With a router table the stock thickness makes no difference when tweeking. I just use a piece of scrap. With the over arm you need a test piece the same thickness as the final stock.

What you want is the cove to just meet the surface of the stock. Too high and you don't get a complete curve. Too low and you get a square corner at the surface of the stock. Of course you know that because that is why you asked the question.

[jsburger]

I leave the start/stop details for others to address, but I think a reference point would be 1/2 the bit radius (distance from the bit rotation center) to be used with a reference line on the router table.

I believe I would use a smaller radius round over.

I think under shoot is preferable to over shoot(slight extended squared off).

I totally agree with all the above. 1/2 the bit radius is the perfect way to start and then can be adjusted depending on how much square edge one wants left.

Great wood working takes time. Jigs, test cuts, jigs, thinking, jigs. Oh and dreaming.

[algale]

Thanks JPG and JSBurger. Very helpful hints/tips.

I think I will hold off and look for a 1/4" or 3/8" round-over. The 1/2" I have is too large, I think, for the 3/4" thickness of the stock I am working with.

[reible]

Keep in mind the bearing needs something to ride on. The bearing might be OK on the first pass but the second pass on the other side might result in the bearing riding on cut away material.... You would have to look at that if do try it. On the other hand I think you will be happier with the 3/8" and you will not have that issue with it.

Keep in mind that sandpaper can reshape the area where you hand grips, and a nice grip is more importation then looks alone for tools you will actually use.

Ed

[jsburger]

Thanks JPG and JSBurger. Very helpful hints/tips.

I think I will hold off and look for a 1/4" or 3/8" round-over. The 1/2" I have is too large, I think, for the 3/4" thickness of the stock I am working with.

Yes it is. I would use a 1/4" as I don't think I would want a full bull nose that the 3/8" would give you.

[rpd]

If you have a 45° router bit, another option would be to chamfer the edges.

[masonsailor2]

I know you said you wanted to do this with the overhead router but this is a lot easier with a small trim router. With a 1/4” round over bit you can carve out the roundover up to a mark and then blend it in with abrasives. The small base of the trim router will follow the different variations in the thickness of the pieces of wood easier than trying to hold it absolutely flat against a table.
Paul

[algale]

I do have a trim router, so that's an option!