Exotic Woods

Carl mitchell

Member
Messages
15
Location
Yemassee South Carolina
So I recently purchased some exotic wood to laminate and try to make a bowl with. I got some Bloodwood, Purpleheart, Wenge, and Padauk. Hopefully I will end up with a nice piece. Any helpful hints before I start
 
Watch for splinters from the Wenge, painful and plentiful. The Bloodwood and Purpleheart will bleed if you're not careful sanding/finishing - although you're mostly listing darker woods there so its likely not to much of a problem except maybe you'll get some red into the Wenge if you don't seal the pores first (on the plus side if you know anyone into wool or silk dying they'll be really happy with a few oz of shavings off of the red ones for dye stock).

One thing I've noticed looking at a bunch of other peoples segmented/built up bowls (I'm not really a segmented guy myself) is that quite a few people seem to have problems with differential wood movement. You'll see this cause problems in the joints opening up in the worst cases and some other cases you can often feel the join between the two woods where one has expanded more/less than the other. This seems to be acerbated if the grain directions have alignment problems and the pieces the bowl is made out of are larger (smaller pieces of wood == less movement per piece). I've seen some bowls and pieces that were seriously fantastic and had not problems years later as well so this isn't a "don't do that", more a "pay attention to wood choice when you pick what goes with what" and "think about wood movement when designing how the pieces go together". I don't know enough to say what kind of specific guidelines to be aware of.

Unfortunately the padauk and purpleheart will almost inevitably turn brown over time (although a few rare pieces seem to hold color for no obvious reason). The causes are basically light (UV) and oxygen so if you can exclude those as much as possible with your finishing schedule the color will last longer.
 
I did find out that the Purpleheart tends to turn easier at high speeds. I was toying around with a small piece and it seemed easiest to turn at about 3500 rpms. I’m not sure if it is because it is such a hard wood or because of the pore size. And I can tell there is going to be ALOT of sharpening involved in my bowls.
 
I'm not sure about those particular woods, but some folks can have allergic reactions to various exotics. If you don't know whether you are one of those folks, be sure to wear a dust mask/respirator when machining/turning these.

Also, many exotics need special treatment to get good glue adhesion because of their oily nature. Generally, a wipe-down with acetone before glue up will take care of that's

Good luck, and be sure and post some pictures!


Sent from my iPhone using Tapatalk
 
Sounds like a fun assortment of wood. :thumb: I agree with Ryan's comments. Wenge has some wicked stickers. Purpleheart is also prone to give you splinters that are a bear to remove. And I'll reinforce the comments about watching grain orientation. I've learned the hard way that if you don't keep the grain orientation the same, things can get ugly. I made an end-grain cutting board years ago and put a face grain border on it. Because the end grain expands and contracts in one direction, and the face grain does it in another direction, the board eventually cracked so bad it broke the wood.

I did find out that the Purpleheart tends to turn easier at high speeds. I was toying around with a small piece and it seemed easiest to turn at about 3500 rpms...

Keep in mind that the RPM number isn't nearly as important as the surface speed at the cutting tool edge. A 1" diameter spindle spinning at 3500 RPM has a surface speed of about 10 MPH. But a 10" bowl at the same speed is traveling at 104 MPH. Almost all woods are easier to cut cleanly at higher speeds, but you have to be careful finding the balance between "fast enough" and "too fast". Even a minor catch at 100 MPH can be pretty catastrophic. (Especially with a segmented piece.) Add to that the centrifugal forces on the outside of a bowl, which just helps make it blow up that much bigger. ;) For bowls especially, IMO it's safer to just cut carefully at lower speeds and get good at keeping your tools sharp. With practice, you'll find getting clean cuts at moderate speeds isn't real hard. Personally, I seldom exceed the 1100 - 1300 RPM range on bowls, quite often lower. Even lower than that on bowls over about 10". I know there are a lot of guys who run faster than that, but that's the comfortable balance spot for me.
 
Ok so after a couple hours at the wheel and some trial and error I made some discoveries about turning exotic woods. The first is extremely sharp tools. Tools you can shave with. And the second is that the faster it spins the easier it is to work with. Apparently when spinning slowly the wood catches ALOT. But when I raised the speed substantially from 800rpms to 2800rpms it became as easy as turning a soft wood. Yeah it was a little scary at first due to the extreme hardness of the wood but once I figured out how to work it, it became extremely enjoyable and rewarding. These are the pictures from the start to the finished product. Let me know what you think
 

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Looks pretty good from here! :thumb:. You got it up to a pretty good gloss as well.

I'd add taking absurdly light finish cuts to that list (but that kind of works pretty well for soft woods as well so not really specific).

Have you seen the bowl from a board trick where you cut out rings at an angle and stack them? Search for "bowl from a board angles" on Google for some good articles. That would both stretch out the wood a little and require less hollowing work (which I personally find a bit tedious with dry wood).
 
Personally the hardest part about hollowing is that my tool rest is only 6 inches long so that means I can only get 2 5/8 inches inside the bowl. Everything over that is a stretch cut that causes a lot of chatter if I’m not careful
 
Yeah, getting to far off of the rest is both tiring and a bit of a ride the lightening experience.

I foresee more tool rests in your future :D Having both larger and smaller ones as well as a curved one (or three) can help a lot. I've also gotten so I appreciate more open bowl forms both aesthetically and for ease of turning (although I can't claim the latter hasn't influenced the former hehe).
 
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