red Elm tear outs and other problems

[Perry Hilbert Jr]

I got some red elm leveling cuts off of a huge tree that came from the grounds at President Buchanan's home. So I have sap wood as well as heart wood. The heart wood is soft and prone to tear out and the sap wood is softer, but has less tear out. I have 4 bowls turned, but the sandiing to final smoothness is killing me. I have been starting with 60 and working up through 100, 150, 220, 300, to 400. I get about as far as 150 and when I step up to 220, the cross grain portions get rough again. On one I tried a sanding sealer and it did not seem to help. What can I do to stop these rough spots where the cross grain spots are.

[Richard Coers]

If you insist on sanding out all the tear out, you are evidently not removing it all with the 60 grit and moving on too quickly. I've can't imagine any way to get more tear out with sandpaper.

[Jamie Buxton]

I'm guessing, but perhaps the wood is punky -- that is, already partially rotting. That might explain why it is so soft, and why you get odd results when you cut or sand it.

Elm trees are killed by Dutch Elm Disease. Most elms in the US were killed in the twentieth century. Perhaps your huge tree has been dead standing for a long time, and rotting too.

[Richard Coers]

I'm guessing, but perhaps the wood is punky -- that is, already partially rotting. That might explain why it is so soft, and why you get odd results when you cut or sand it.

Elm trees are killed by Dutch Elm Disease. Most elms in the US were killed in the twentieth century. Perhaps your huge tree has been dead standing for a long time, and rotting too.

American elm were killed out, but people planted a ton of hybrids or other species. Siberian elm and slippery elm are everywhere.

[Perry Hilbert Jr]

Maybe I am using the wrong term. Where there is the harder sap wood, I sand with 60 until it is smooth, then with 100 and 150. There are no rough spots. When I go to 220 grit, there are fibers that stick out between the grain. As if the hard area between the fibers if sanding away but not the fibers. they stick out I have the opposite effect with OAk, where the fibers pull out leaving furrows in the wood between the grain. It take a bit of sanding to wear down the grain so it is even with the fibers in between.

[Jamie Buxton]

Do you have a plan for what you're going to use to finish it? You might put a couple of coats of that on the rough-sanded bowl to act as sanding sealer -- that is, stabilize those little fibers that are giving you trouble. Then continue on through your sanding schedule. You may well sand off most of the sealer, but that's okay. It will have done its job.

[Perry Hilbert Jr]

This elm died at Wheatland. and was cut and hauled to a place owned by a member of a Lancaster PA wood working club member. In April of 2019, members of several area wood working clubs got together, hired a portable saw mill and cut up a dozen or so trees from area parks and historic sites. The elm log was over 44 inches in places. Just one limb was almost 20 inches. As it tuned out the limbs were cut into planks, but the trunk was far too big for the mill. We also cut a huge avian cherry and a fir that was nearly 28 inches in diameter. The elm was eventually cut into large planks and volunteers made benches for parks and public buildings out of the planks. There was also a copper cable running up the trunk a few inches beneath the surface of the wood. Apparently that had to be cut out before the miller would cut it into planks.

[Dave Mount]

I'm not sure I have good understanding of the problem, but a couple thoughts.

If the problem is something protruding from the surface, then either you're wearing away the soft parts (e.g., punky wood) or failing to cut the harder parts (or some combination). Suggestions above for stiffening the soft parts include adding finish to areas to stiffen the fibers, or wood hardeners (which I believe are really just finishes thinned with a quick flashing solvent so they soak in well then cure quickly, e.g., Minwax "wood hardener"). I'm also not clear on whether you're having trouble on localized spots or the whole piece. Thin CA glue does a good job of hardening punky wood, but it can leave a little bit of a shadow on the finished piece where it soaked in, depending on the wood and finish. When I use it, I apply it like I'm drawing on the wood, applying it to specific areas and using application boundaries that follow that natural contours of the punky spot or other color variations -- the purpose here is to apply it in a way such that if it does leave a shadow, it looks like it was natural to the wood rather than applied.

One thing to look at is where on the piece the problems are happening. A lot of grain lifting problems show up on the "back side" of the end grain, meaning on the end grain just after the centerline of the grain. This is because you're cutting against the grain in this area. If the problems are there, then it's a cutting problem, not a soft wood problem. Soft or punky wood can occur anywhere.

On the flip side, the problem could be things that should be getting cut off than aren't -- one cause of that is dull sandpaper. If you haven't done it already, I would suggest a fresh piece of sandpaper. Sandpaper is a cutting tool, and like all cutting tools it gets dull -- it doesn't work well when it does get dull, and it gets that way far faster than many appreciate. Using a piece of sandpaper too long is one of the great false economies in woodworking. Same is true if you went up a grit and are having trouble clearing the scratches from your previous grit -- sandpaper is probably dull. Pushing harder, as we all reflexively do, is not a solution. Also like cutting tools, sandpaper generates a lot more heat when it is dull. Light pressure and frequent paper changes are the way to go, IMHO.

Another aid to cutting high spots is to use a firmer backer when sanding. This is easier to do on convex surfaces than concave. If you are hand sanding, put the sand paper on a backer, like a piece of styrofoam that will keep the sandpaper from dipping in and out of low spots. If using power sanding, most suppliers have backer pads of different densities; the firmer ones are good for focusing the cutting on high spots. If you use a firm backer, keep the sanding moving or you can inadvertently create a flat in an otherwise fair curve.

A final thought is speed if you're sanding on the lathe. I keep decreasing speed as I go to finer grits. I can't explain the physics of it, but it's clear to me from observation that fine sandpapers don't do as good a job if they are used on a fast moving surface, while coarser grits will cut quickly, as long as it's not so fast that things are heating up.

Best,

Dave

[Ron Borowicz]

I have turned a considerable amount of Red Elm. It is a very soft wood without being punky. My sugestion is similar to the above. I used a mixture of laquer and laquer thinner 50/50 thruout the turning. I applied another coat of this mixture prior to my final cut with, you guessed it, a sharp gouge. I did not have any problem applying a finish.