How to work Black Locust

[Eric Schmid]

First a quick introduction since this is my first post in this section. I have been reading here for a while as I integrate more hand tools into what has primarily been a machine driven shop. Woodworking in my vocation primarily consists of building structures/furniture that live outdoors (decks, arbors, benches, gates, etc.). Some of my work has been evolving towards minimizing steel fasteners in non-structural applications (e.g. mortise and tenon gate/door construction) and I am finding hand tools to be a better fit.

On to the present conundrum. I have acquired some Black Locust, milled from a couple of fairly large trees that blew over onto my shop last winter.

This wood is like nothing I have ever worked with steel knives. It dulls chainsaw cutters, chisels and plane irons so fast that I wonder if it's worth the effort (and I'm fairly stubborn). It tears out when planing with the grain, but planes fairly well cross grain. High speed steel knives seem to work best, but I'm sure those will be dull in short order. A short session with the smoother and the edge was gone.

The grain, once revealed, is quite beautiful. Getting there is anything but a beautiful experience.

I did a search and saw that Juan Jovey (sp?) did a workbench top using Black Locust. In the thread he indicates that it was easily milled, but my experience has been just the opposite; at least with steel cutters. I offered a burl to a wood turner friend and he declined for similar reasons.

Since I have read both good and bad reviews on the workability, I can only assume that the difference in experience boils down to two possibilities. The wood takes on different characteristics depending on where it's grown (soil conditions), or the craftsman are using different methods.

Is there a plane iron set up/technique that might make planing a reasonably fruitful effort on this wood?

And if Juan is still around, it would be good to hear how the bench top has held up.

[Jim Koepke]

Howdy Eric and welcome to the cave by the Creek.

You may have the answer about the difference between a wood being easy to work or not so easy, location, location, location.

Some species are prone to pick up silica in the soil and disperse it throughout the living tree. This spells bad news for edge tools.

There may also be other factors to consider:


Overall working characteristics for Black Locust are mixed: although the grain is usually straight, its high density and hardness can make it difficult to machine. Black Locust also has a moderate blunting effect on cutting edges. Responds very well to both lathe turning and steam bending; glues and finishes well.

That is from: http://www.wood-database.com/lumber-identification/hardwoods/black-locust/

Looks like a pretty wood. Not sure if blades of PM v11 from Lee Valley would be of any help.

jtk

[Nicholas Lawrence]

As a kid I used a lot of locust for fence posts. My experience was that it was easy to cut when green, but once seasoned was very resistant to decay and hard as a rock.

[Warren Mickley]

Black locust is one of those tame domestic hardwoods that Derek used to tell us about. I have worked it occasionally. It is hard, but I never got the impression that it had silica in it. In general it is harder than white oak. Some oak species that are lumped with white oak are close to black locust in hardness. Hickories are generally a bit harder. Locust has nice color (the yellow gradually changes to brown) , but not as much depth and luster as our best cabinet woods.

My guess is that you are the one dulling the tools, not the wood itself. A lot of people react to one of the harder woods by using the plane or chisel in a rough manner, which is what is hard on the edge. The edge can only take so much brutality. Think instead of working in smaller bites and using the same force that you would use for a softer wood.

[Rob Luter]

In these parts they call it ironwood. It's like working with stone when it's dry and seasoned. I've seen it throw sparks when cutting it with a chainsaw. It has more BTU per cord than most firewood. It dulls anything you try to cut it with. As some have noted, it makes great fence posts.

I'd suggest light cuts and A2 plane irons. Plan on sharpening often.

[William Adams]

It’s a bow wood, so if you have long, straight-grained pieces, might want to offer it to bowyers.

[Al Weber]

I've cut it with a chain saw and almost always get sparks due to the silica in the wood. I think it is just the nature of the beast and you either put up with the difficulty or make fence posts which really last a long time.

[John K Jordan]

I like it for woodturning, no more difficult that some other hard woods we use. I can't imagine enjoying working it with hand tools.

It does make good garden stakes although I prefer Osage Orange for that.

[Robert McNaull]

This is an interesting thread as I have been contemplating black locust for building a deck and wondered how hard it was to work. We used to cut a lot of firewood from it growing up but it was always wet. Plac out of Wisconsin sells decking materials out of it and same as the OP was thinking of it for outdoor furniture.

Eric, if you get some stuff built I would love to see pictures.


Bob

[Jeff Heath]

The best way to tell when a black locust fence post is in need of changing is to set a rock on top of it. When the rock crumbles naturally, the post needs changing.

Black locust is a beautiful wood and is a long lasting choice for decking material. It's a bit harder to work than normal, but the experience you're having is not typical. It's definitely harder on planer and sawmill blades, but I've not experienced the extreme dulling you speak of when putting a hand plane or chisel to it. More frequent sharpenings; yes, but not instantly.

[Dave Anderson NH]

I've turned Black Locust without any special problems and the results were beautiful. I've also worked it by hand without any difficulty though I did have to sharpen more often than normal. A friend built a strip sailing dingy hull from it though the transom and dagger board box were mahogany. It was quite heavy though the strips were only 1/4" thick. It is an absolutely beautiful boat.

Here in NH we say that one Black Locust fence post will outlast 4 post holes.

[Chris Hachet]

Other than having to sharpen more often I have not had any unique problems with this....but then I like working with hickory, Quarter sawn white oak, and hard Maple.

[george wilson]

It is supposed to last 10 years longer than STONE!:)

[Bill White]

Jeff has it wrong. Don't worry about the stone. When the soil around the post rots away it is time to replace the soil. The post will still be there. :)
Jeff, I'm just jerkin' your chain.
Bill

[Eric Schmid]

I'm not sure I can think of another wood that elicits such a varied opinion as to the work-ability. To be fair, my tentative stance began when we bucked up the fallen trees and may be effecting my view of its work-ability. I have never sharpened so many cutters in such a short period of time and I'm fairly certain I saw/heard sparks at one point. Hard to be sure with all that orange saw dust flying around. I have never been puzzled by a species/specimen of tree, but I find this wood quite unusual (not quite sure what to think of it).

I am curious how it would perform as a decking material. It seems very sustainable. There are a hundred sucker shoots coming out of every root and stump from the area where these trees came down; it propagates its own groves. I came across an article and apparently it is being farmed in eastern Europe for outdoor wood projects. Its rot resistance is legendary. I have not seen it sold here in the Pacific NW yet.

I'll sharpen the plane iron and give it another go, although this particular specimen may be better left to carbide cutters. I was initially planning on making a large raised garden bed with it. It is an uninteresting wood in its rough sawn state. When I exposed the grain a little I was surprised. That strange orange saw dust I first encountered had evolved into a beautiful face grain. There are a lot of Honey Locust here, but strangely in over 25 years of working outdoors I am not sure I have ever seen the inside of a 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.