Bolivian Coffeewood: My arch-nemesis

[mgatten]

I managed to get a good deal on a chunk of beautiful Bolivian Coffewood and cut it down to about twenty pen blanks. I was excited to get started on some really nice pens.

But, try as I may, they keep blowing out. Some times I get lucky and they blow up on the drill press before I've put much work into them, but mostly it's as I near completion of the turning.

Is this wood known for being particularly brittle? I see many other Bolivian Coffeewood pens out there, so I know it's possible. But I've blown out twelve blanks in a row now without a single success.

I've turned pens from many kinds of wood, and I've had my fair share of blowouts, but I've never seen a wood that blows out every single darned time.

 

[egnald]

Although I have never turned any, the Janka that I have found for it puts it up there at the top of the scale where lignum vitae and the the ebony families live, so I am guessing that it is really hard and may be prone to cracking because of it's density. I would also guess that heat buildup might be a real problem when drilling and maybe even when turning. I hope you are able to get a pen or two out of it, I would really like to see the end product! - Dave

 

[jttheclockman]

Never used it and never seen it. I can not recall anyone with a pen with it here. If anyone has one I would like to see it. It could be one of those woods that just does not want to be turned into a pen such a snakewood. Wonder if it is in the Bolivian rosewood family? If so I love the rosewood and never had a problem with it. Oily yes but very stabile. I saw photos of the coffeewood as a flooring and man that looks sweet.

 

[Painfullyslow]

I have no experience with that wood however I did make a few pens from black palm which I am told is a real PITA to work with and is prone to blowing out. I took the pen down to about 1/16th from the bushings with a carbide skew and then used sandpaper to get to final dimensions. Slower for sure but it does prevent the dreaded blowout.

Maybe something like that would work for you?

 

[MRDucks2]

I do have some Bolivian Coffeewood but have never turned it. Have a habit of picking up wood I have never heard of when I come across it.

 

[PatrickR]

Cook woods list this as Bolivian Ebony (not a true Ebony). I have never worked with it. With twelve lost blanks it would seem to be a very poor choice for pens. I think I will avoid it.

 

[MRDucks2]

When I bought this wood, I thought it was identified as a turning wood and research shows it to be well suited for such. Maybe more detail on how you are turning it would help us help you. Lathe speed, tools used, tool approach, the more info the better.

 

[leehljp]

Blowouts: Can you see the glue on the inside of the blank pieces that came off? Can you also see where the glue was on the tube? Does it look like it was perfect adhesion or spotty adhesion? A number of people have been surprised after a blowout at how little adhesion has taken place between the tube and blank. FAR more air is introduced than one would be believed. Next, what kind of adhesive/glue were you using?

To help prevent blowout, the glue/adhesive that holds the best and hated by many and used the least is polyurethane glue. CA has the most failures. Epoxy holds better than CA, but no matter how well one coats the tube and inside of the blank with epoxy, it still has air spots inside.
Polyurethane glue expands after a time and gives 100% coverage in its adhesion between the tube and blank. The downside to poly glue is that it is STICKY on the fingers and anything it touches; Next if the blank is not taped on the ends with the tube inside, sometimes the expanding glue will push the tube out and the blank/tube will be lost. And last, Polyurethane glue requires about 12 to 24 hours to cure properly. But it has the least blowout of glues.

Note: Gorilla Glue is the most popular polyurethane glue but Not all Gorilla Glues are Polyurethane (expanding) glues. Be Careful in selecting the glue, if you decide to try this. Make sure it is P

 

[mgatten]

Thanks, everybody, for the input.

Lucky thirteen was the one that stayed together. For this one I coated the tube with an obscene amount of medium CA like I usually do but then also took the extra step of coating the inside of the wood blank with an obscene amount of thin CA. After a full 24-hour cure I took it to the lathe and turned it down to where it had nearly an eighth of an inch of thickness left and then pulled out the 80-grit paper gouge.

After a depressingly long time grinding wood off with the paper (depressing because it felt like cheating), it got very close to final thickness so I started up the grit ladder and everything finally stayed together.

A brazilion coats of CA/BLO finish later, it was ready for assembly. My kit was the Executive Rollerball pen from Penn State, which I hadn't seen before. I'm pretty disappointed. When the cap is in place, it looks like it wants to snap on further or like some thing is missing. I won't be buying this kit again (or this wood), but the wood does look pretty nice.

 

[leehljp]

Since you use CA, and reading your first post in this thread, Blowouts are not uncommon for you. That points to the lack of adhesion that results from CA. Just because a blank is stuck to the tube with CA does not mean that it has full adhesion contact between the two. There are lots of air spaces in that minuscule space between the blank and tube. The cure is just what you did, or changing to epoxy (which can still have air bubbles all through it, or poly glue.

Always coat the inside of the blank with medium or thick CA if using CA, and on the tube. Same for Epoxy and it works best for poly glue too. Overdoing the gluing has a great payoff that is not really noticed, and that is a good thing.

 

[Alan Morrison]

I agree with Hank in #8 above.
It sounds like you spent more on CA glue than on the blank!!!

 

[mgatten]

I've been considering switching to epoxy for a long time. It's just so much more work, and since I'm usually only making one pen at a time, a lot of epoxy gets wasted. But this episode may be the one that finally pushes me over the edge. I'll just have to start doing a lot more pens at a time.