I have this curved piece of walnut for a piece I’m making (picture is attached). I would like to soften all four edges using a round-over router bit but the best I can tell this isn’t possible without running into end grain. It seems to me that if I route on my table or by hand this is unavoidable. Everything I’m finding is telling me this to be true. Is there something I’m missing here? Do I just break out the spokeshave and sandpaper?
Thanks,
BobE
Replies
A very sharp bit and starting with shallow cuts is your best bet. As wonderful and labor saving as routers are they also have the ability to destroy in a nano second a whole day's work and a precious piece of wood. If tear out on the end grain is a major concern you can always avoid those areas with the router and finish those spots by hand. A reversible router and a corresponding set of bits would solve the problem. Oh, wait! They haven't invented that yet!
Size the end grain areas with dilute hide glue. Use a brand new bit. Try climb cutting (on scrap first) to get the feel.
You can use this bit with two height setting having either the uper or lower bearing working against the part. https://toolstoday.com/v-10644-54190.html
You know I think that might work but without going into the reasons why not I think I'll pass on it. I do appreciate you taking the time for the post though.
Normally, router cuts are made by moving the router left to right. Because the cutter is rotating in a clockwise direction (looking from the back side), this causes the cutter to be pulled into the work as it cuts. Occasionally, the grain comes to the surface at an angle against this normal motion. When this happens, the tendency is to tear out the grain. This can usually be eliminated by taking shallow cuts and reversing the direction of the router to what is called a climb cut. By doing this, the cutter is cutting downward on the grain which tends to push the router away from the cut, but also reduces the tendency of lifting the angular grain. Sometimes it is necessary to combine these cut methods on the same board due to the grain going in different directions.
How do you reverse the rotation ?
You don't. You reverse direction of the whole router; right to left rather than left to right.
Please don't tell someone to climb cut without explaining the perils of doing so. That's how someone really hurts themselves.
https://www.finewoodworking.com/2022/10/06/video-what-the-heck-is-a-climb-cut
https://www.finewoodworking.com/2011/07/15/climb-cutting-dont-believe-the-naysayers
FW's current stance on it, is that if at all possible climb cutting should be avoided. Get a bit with two bearings and flip the piece over.
I think right to left / left to right still does not keep an inexperienced user safe. Feed direction can change relative to your belt buckle when you turn a corner or mount a router in a table.
Cross the equator?
I've found that a spiral cut router bit (up cut or down cut) can reduce tear out.
He's running a molded edge.
Thanks to everyone for the suggestions. I'm not a big router user so for this one I'll use the spokeshave and some sandpaper. I know what climb cuts are and have had to do some using a Leigh jig I used to own. I do have another application where climb cutting could be useful and have read the links provided by Ben and done some other research. I may do some testing with this in a controlled environment and see whether it's for me.
Again, thanks to everyone.
BobE
I'd do the same. The router is not always the best tool for the job. When it is, great, and otherwise, avoid it since it failure with a router can often wreck your part.
I think if you were making many of these, you'd have some options. One is to make a fixture to hold the part rigid against a form. You'd need two, one for the inside, one for the outside.
A second option would be a CNC machine, again with the part held rigid to the table.
But those approaches only make sense if you're making a bunch of parts.
One way to reduce the likelihood of an edge being routed spitting out a big spelk as the router bit goes against the rising grain is to first make a series of "stab" cuts along the problematic edge.
You set up the router and bit as you would for making pass-cuts but then begin by pressing the spinning bit into the edge at right angles to the eventual along-the-edge cuts you're going to make to finish the profiling.
This makes a series of bites along the problematic edge, which greatly reduces the chance of a big spelk being torn from the workpiece edge as you later run the router along it.
The technique doesn't eliminate the chance of a spelk breaking out but, if you make enough careful "stab" cuts, the final edge cutting pass of the bit has less to chew off and is more likely to cut the rising grain parts without them spelking. The trick is to cut as slowly as you can (with both stabbing and edging cuts) without the bit burning the wood.
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If you initially set the bit (via a slightly larger guide bearing) to take a smidgen less than the final full profile-bite, this lets you put back the "proper" guide bearing that's just a teeny bit smaller in diameter so that a safe climb cut can be the final pass. This will give a smoother finish and also take any burn marks off that may have occurred when you made those slow stab and edge cuts.
A bit of a faff, all that - but it can work well if there's not an option but to route such a difficult-grain edge.
I’ve been working on a side table with walnut legs and stretchers. I debated whether to ease the edges either with a chamfer bit or a round over bit or do it by hand with a block plane. I decided on the latter. It’s amazing how fast a spinning piece of metal can screw up a piece of wood. In using the plane I rediscovered the pleasure of experiencing the wood. And the joy of using a finely honed plane.
I have used a double-bearing flush trim bit on a Demi-lune table top with an adhered template and then just flipped the workpiece to accommodate grain direction. I then used a block plane to shape an unequal aris curve to the top and bottom edges.
Using a very sharp bit and starting with shallow cuts is crucial. While routers save time, they can quickly ruin your work and precious wood. If end grain tear-out is a concern, avoid those areas with the router and finish by hand. Too bad there’s no reversible router to solve this!