How to work Black Locust

[Tom M King]

I built a grape arbor out of it in 1978, and it finally died a couple of years ago, so it lasted about 35 years in mostly red clay soil. Parts of it above ground didn't last much longer than what was in the ground. I think it would have lasted longer if I had taken the bark off, but I was young and foolishly in a hurry.

[John K Jordan]

...Hard to be sure with all that orange saw dust flying around.

One odd thing, I have never seen orange saw dust from black locust. Perhaps because the trees grew in an entirely different environment? The color of the wood and the sawdust on the black locust I'm familiar with is kind of bland light brown.

Not doubting you, but orange saw dust sounds like osage orange. When I cut osage I get bright orange/yellow sawdust and shavings. Osage is often confused with black locust since the end grain looks almost identical. A sure test: black locust fluoresces a bright green under UV light while osage doesn't glow at all.

Another test: if you put some osage orange shavings in water it will turn the water yellow. Black locust shavings won't. People who like natural dyes for fiber arts use osage orange for the color.

For a sanity check I just now walked down to my shop and made sawdust from two pieces of black locust and a piece of osage orange. One piece of black locust has been drying 2 years now and the other for about 8 years. I cut both myself so I'm sure of the species. Both pieces made tan/light brown sawdust. The piece of osage orange has been drying for about 10 years and was uniformly brown on the outside. The sawdust was bright yellow/orange.

Both are very hard and dense with osage a little more dense than black locust. Both are difficult to work with hand tools but easy to turn and cut cleanly.

BTW, the flowers of black locust have a heavenly smell. My honey bees think so too.

JKJ

[Phillip Mitchell]

I've cut many a black locust tree down. For firewood and for saw logs. Around here there are tons of locusts; there is a borer bug that is killing most of the locusts so most of them are standing dead at this point. For that reason, the percentage of trees that I've cut that actually had logs worth sawing into lumber was quite low compared to any other common species around here. BUT, the logs that were good were worth it. I've sawed locust for many outdoor applications. Bridge decking and supports, decking material, outdoor bench material, trailer decking, etc. There are some locust fence posts still standing on my property that I believe to be from the 1940-50s.

I have sawn locust lumber for decking (outdoor deck boards) and took it from rough sawn and milled it into 3 1/2 and 5 1/2" decking, with a round over. It's a tough thing to do because you really only want to attempt that when the wood is still green, but it's pretty tough to plane green lumber as far as dust/chip collection. It clogs a planer pretty easily, but if you wait until it's dry then it turns extremely hard and will dull your cutters very quickly and put a lot of stress on your machines. I would suggest laying down the decking a bit tighter than you may space decking that is dry, but not quite as tight as you would put down wet PT decking. It will shrink and gap some after it's screwed down.

I've cut tons of locust firewood, and can honestly say that in the dead of winter, I prefer it over any other wood. It's the only tree I've personally cut for firewood that can actually be dry (12-18% moisture content) on the stump if standing dead. If you get logs that are standing dead and solid, you can have one of the highest BTU/longest burning firewoods that is dry and ready to burn immediately. Oak and hickory take 1-2 years to dry in this climate and can rival locust in heat output, but you obviously have to wait much longer for seasoning. I have also seen sparks fly when cutting locust. It will dull a chain quicker than anything else, but I've had the best success cutting locust with a semi-chisel chain with fairly aggressively sharpened rakers. Dirt/rocks in the thick bark will dull a chain much quicker than actual locust will. The bark is bad for this because it's quite deep and tough. It can hide a lot of rough stuff. Around here, the sawdust from fresh cut locust is a distinctive yellow.

In summation, most locust should be used for firewood and fence posts, but if you have sizable, solid (not rotten) logs/lumber and you need superior rot resistance or outdoor application then it's hard to beat. Just know that it's going to fight you and your edge tools every step of the way.

[Eric Schmid]

John, you are correct. I am not sure why I said orange. The sawdust was bright greenish-yellow when the wood was green. Since it has dried out a bit the saw dust is more of a light brown. I had quite a reaction to the saw dust when we were bucking it up. I got some in my eyes and the wife thought I contracted Pink Eye.

It's definitely Black Locust. The trees were towering over my shop for many years before their unfortunate demise.

I was standing 30' from where they fell, when they fell. They came down so fast that I never would have gotten out of the way. Heard a crack and by the time I turned around they were already in the apex. There were three of us working outside and fortunately none of us were in its path. Seven roof rafters were busted clean in half; under a layer of plywood over car deck. These were fairly good size; at least 50' tall and 26" diameter at the base.

[Eric Schmid]

In my quest to tame this wood I have spent some time over the past two weeks trying out various honing modifications for a number 4 Stanley plane. I figure if some can work Black Locust successfully I should challenge myself to seek improvement in skill and knowledge by trying different techniques.

So I focused on one plane and began with the iron. It started with a simple honing and ended with a back bevel, to increase the angle of approach, and a convex bevel. There were quite a few intermediate iterations. I was able to take fine shavings in hard maple, but still no luck with the Locust. Lots of tear out and very difficult to push the plane.

Then I moved on to the frog and sole. The sole had always checked out quite flat. I did some work on the frog and decided to make a few passes over sandpaper on a flat plate. Looked a little high on the toe and heel. Quickly got scratch marks on the sides, toe, and heel, but a little concave in the center; maybe .001.

The sole had some pitting so I had the bright idea of speeding up the process and tried to remove the pitting on a belt sander. Not because I thought it needed it but I was trying to narrow down all the variables. Went pretty well until it didn't. That plane might be toast. Oh well, I wanted a new smoother anyway.

I found a new #4. Unpacked it and did nothing to it except flatten the back of the iron and hone the edge. Hard maple...check. Black Locust...Hmmm, suddenly taking clean shavings with minimal exertion. No tear out, although card scraper is still needed to get the surface as smooth as maple.

I have no idea what the difference is? The new plane has a thicker iron and chip breaker, but otherwise seems identical. The new plane is a bit heavier. The new iron might have a slightly keener edge, but both slice through maple with ease. I haven't tried the old blade on the new plane as my daughter was having too much fun using it as a carving tool.

[Juan Hovey]

Eric - I'm still around and kicking, somewhat against the odds.

The black locust out of which I made the workbench you mention was green at the time and hence easily worked. I worried when building it that the green wood might go nuts on me as it dried, so I took great care 1) to seal all end grain with soft wax, 2) cinch together the three planks that comprised the top with staggered lag bolts, and 3) attach the top to the base with splined through tenons.

Last time I saw the bench, which is in my son-in-law's shop in the Bay Area, it was drying as expected. There were no end-grain cracks or splits anywhere, for starters. The leg tenons had come proud of the surface of the bench about 1/16 inch, and the three heavy boards comprising the top remained tightly cinched up and showed no sign of cupping or warping. I plan to wait six months or so before I take a plane to the top.

As it happens, I came across an offcut of that black locust recently and spent an hour or so yesterday testing out the irons in two new planes - and I can tell you for sure that the stuff hardens as it dries. I'd been thinking I might take some black locust with me to the L-N open house in Maine next month, to show off what my planes can do with ornery wood. Now I'm thinking...maybe not, as I'd have to sharpen my irons after every pass or two.

In any event, the fact that the wood was green was key to the ease with which I worked it in making my son-on-law's bench. I wouldn't attempt any such project with dry black locust, as the stuff just gets too ornery, and I will salute you if you carry on.