Amboyna Burl Woes

[TonyL]

Hi Folks:

My first two Amboyna pens (total of 4 barrels) turned fine.

However, I have blown 3 barrels since then..always the upper barrel of the Jr Gent or Baron. This happens as I approach the bushings. I do use very sharp skews (sharpening at least twice per barrel), very thin shearing cuts, and I do coat thin CA (no accelerator) at least 3 to 4 times during various stages of turning.

Is Amboyna burl known to do this? I may have just been lucky the first two times. Or I may not know what the heck I am doing!

 

[Magicbob]

Amboyna burl is my go to wood, I have turned a bunch and never had a problem, knock wood.
I use a gouge and a carbide R2.
I can only suggest the obvious, make sure your tubes are clean and sanded, I only use epoxy on anything that is not 100% stable, I sand the ends square, and turn.
I always cut from the center to the ends, never the other way. Not sure if it makes a deference, but someone told me to do it that way when I started and it made sense.

Good luck

 

[Sabaharr]

Its burl. Vacuum stabilize it. Closest thing to being a solid piece of plastic as you can get.

 

[KenV]

Good Morning Tony

What do the blowouts show?

I presume these were new or current prepared. Did the wood fail, or was there an adhesive failure?

Did you CA seal the ends of the blank during prep or not?

Approaching from the center or from the end?


Have had a few where there were fine cracks that were hard to see and lost a divot while turning.

 

[TonyL]

Hi Ken and folks. Thanks for your responses.

Great line of questions:

What do the blowouts show?

Bare brass. They all occurred toward a bushing when I am about a mm proud of the final dimensions. The blown-out fragment usually has an edge with a natural fissure/figuring.


I presume these were new or current prepared. Did the wood fail, or was there an adhesive failure?

I would say it was the wood failing even though I stated above that the blown-out fragment leaves bare brass exposed. It's always when the wall is relatively thin. Most of the time, it is the cap of a Jr Gent (12.5mm) or Baron (15/32nd inch). I use epoxy most of the time or BSI Insta-Flex CA. All new..as I am preparing (1800 to 2000 rpms with a very sharp Thompson skew).

Did you CA seal the ends of the blank during prep or not?

Always..two coats of thin - no accelerator.


Approaching from the center or from the end?

I always start away from the end and I never use a peeling cut...always a shearing cut.


Have had a few where there were fine cracks that were hard to see and lost a divot while turning.

Yes...like a piece of a puzzle has fallen-out.

None of the Amboyna burl is stabilized. They are in the $9 to $11 range.

Well, I am going to try something different in the future. As silly as this sounds, I may just sand when I get close. It has never happened on the lower barrels.

I tell you what I have done to recover. I bought some of that turquoise crush stone or whatever is. Crushed stone and enough CA to bathe a small dog...and I'm in business. They actually turned-out nice..but not my intention.

Thanks guys!

 

[jsolie]

Hi Tony,

It almost sounds like there might not be enough adhesive (either kind). I tend to over-glue tubes on my pens (and have to spend the time clearing dried epoxy out of the tubes later on). The times I've seen separations like what you're describing have been where there wasn't enough adhesive. The last one I saw was a really nice olive blank nearly explode on my son-in-law where he didn't get enough epoxy between the tube and the blank. We recovered by turning away the blown out area and replacing it with some maccassar ebony.

 

[thewishman]

Sanding is a legitimate method for shaping touchy materials. There is so little "meat" left on the tube, that a tiny error has big ramifications.

 

[jcm71]

Tony, I can usually tell when I have not done a proper job gluing in my tubes. As the blank gets smaller the cut begins to feel different to me. It begins to pick up a slight vibration as I get closer to the bushings. Thats a warning sign to put down the skew and pick up the sandpaper. Don't fall into "I'll just do one more light pass" trap. That's when the blank will blow. DAMHIKT

 

[KenV]

The bare brass and fissure suggest that the end of the tube is glue starved. and there is likely a bit of space between the wood and the tube.

The only place that really really really needs the glue and the support it offers is the end 1/4 in (6mm or so) of the blanks. That is where there is the most likely stress and generally the thinnest wood.

If there is space between the tube and the wood, and the bevel is pressing the thin wood flexes and a piece breaks out.


I have had some glue failure -- the glue became brittle and broke -- with some old blanks that were in the back corner for a few years (or more). These breaks showed glue on the brass and glue on the wood.

 

[TonyL]

Thanks all. I would heed your advice.

 

[Sabaharr]

Hi Tony,

It almost sounds like there might not be enough adhesive (either kind). I tend to over-glue tubes on my pens (and have to spend the time clearing dried epoxy out of the tubes later on). The times I've seen separations like what you're describing have been where there wasn't enough adhesive. The last one I saw was a really nice olive blank nearly explode on my son-in-law where he didn't get enough epoxy between the tube and the blank. We recovered by turning away the blown out area and replacing it with some maccassar ebony.

I had fits with epoxy in the tubes till I got some sheets of dental wax to press into the holes. Even when it builds up a dam of epoxy and completely envelopes the end of the tube none gets inside. If you are epoxy generous as I am you should try this out. I got 25 sheets for $7 on ebay and have still been on the first sheet for a month, about 40 pens. When you square the blank all the excess epoxy is gone and the wax pokes right out with a punch. No more time spent scraping out epoxy with an exacto knife and hoping the parts won't get stuck if I miss some.

 

[TonyL]

Thank you. I do use bee's wax sheets (bought from Exotics). They work great!

 

[nativewooder]

Go to a local dental supply office (where they make false teeth) and you can probably get a lifetime supply of wax in exchange for one of your pens!

If you are turning pen blanks that you consider special or valuable, don't be cheap on applying epoxy glue. Make sure the inside is fully coated and allowed to set for 24 hours before proceeding.

 

[KenV]

Tony - one of the negatives to the push and twist with wax is that it leaves a wax smear or residue on the outside of the tube. I have a process step to clean the contamination by wax with an abrasive or solvent.

 

[pianomanpj]

Also make sure you scuff up your brass tubes with sandpaper before you glue. That little bit of extra tooth will help.

 

[TonyL]

Thank you. If not pre-scuffed, I scuff the tube using a dremel with an 60 grit sanding drum. Thanks though.

 

[KenV]

Tony -- if you scuff before wax, the wax has grooves to reside in. I scuff after wax in the ends becuase I was seiing that glue was not sticking to the end of the tubes on thin barrels == and asked my self why that might be happening. Wax blocks glue bonds. A good mineral spirit wipe or two seems to get of most residual wax on the ends also.

 

[TonyL]

Thank you Ken. I will practice your process.

 

[Skie_M]

Put some CA round the back end before you glue your tube in as usual. It sounds like you're not properly spreading the glue through the blank and that's causing you issues.

Don't forget to ream out any excess glue before you set up on your lathe, of course.

 

[jsolie]

I had fits with epoxy in the tubes till I got some sheets of dental wax to press into the holes. Even when it builds up a dam of epoxy and completely envelopes the end of the tube none gets inside. If you are epoxy generous as I am you should try this out. I got 25 sheets for $7 on ebay and have still been on the first sheet for a month, about 40 pens. When you square the blank all the excess epoxy is gone and the wax pokes right out with a punch. No more time spent scraping out epoxy with an exacto knife and hoping the parts won't get stuck if I miss some.

I swab a lot of it out while it's still gooey and it only takes maybe a minute or two with a round file to file the rest out of the tube when it's hardened.

Will keep this in mind if I have a large number of pens to make at once. It's not too bad doing a couple of pens, but having to do a whole bunch at a time--yeah, I can see where the dental wax would be a huge time saver.

 

[TonyL]

Thanks folks...all great advice and things to be aware of!

 

[janet0]

has been bookmark, this seems like a very interesting thread

 

[campzeke]

Great thread! I have my first piece of amboyna burl in the shop right now waiting to have the tubes glued in place. Thank you to everyone that contributed here hopefully saving me some time and frustration. If all goes well maybe I will post a photo displaying the results of all the great advice!