Cracks after turning

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Jon Nutting

Jon Nutting

Member
Joined
May 2, 2020
Messages
58
Location
Dallas, TX
Hi All,

I'm brand new to the site and also brand new to pen turning. I've turned 3 blanks so far with decent results but this last one I did has a crack that I can't seem to fix. Any ideas on what causes this and how to fix it? This particular blank is snake wood. I've sanded it down with grits 150 to 600 including lateral sanding at each grit.

Thanks in advance for your feedback
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Hello Jon, welcome to the site, I've never liked turning Snake wood. It is brittle, and it does have a tendency to crack. Well it did on me, and I was afraid to sell the pen because of issues I had with another one I turned. For the issue with this one, you might try packing the cracks with fine dust from a piece of the wood, and then apply CA glue and refinish it. Good luck.

Len
 
Hi Jon. First - Welcome to IAP. 🤣 . We'll help as much as we can.

OK, so I'd say if you have turned only 3 pen blanks, and this is you're 4'th and being snakewood, you are in over your head... .:eek:.

Snakewood is... "fussy," not a beginners blank. Snakewood is a blank that is very finicky to turn, I'd say a moderate to advanced level.

I would suggest you get a bunch of "practice" blanks (local woods, pine, walnut, oak, maple, etc...) and simply practice turning these. If you are well practiced as a woodworker, may be this is not necessary. You can judge you're skill level.

As to the blank you posted above: The cracks may be easily fixed with some CA and wood shavings. I would certainly try this.

And then the issue of the sanding... there are obvious radial sanding grooves. This is from the
sandpaper/method. Easy to see, and also easy to correct. :p

I would suggest repeating your sanding grit sequence. Slow speed, lowest choice of grit, hopefully at 320 or above. Then stop the lathe and hand sand the blank while hand turning the blank - sanding horizontally. Repeat this for all subsequent grits (320 - 600+, then additional sanding/grits for different materials).

There are many, many procedures for finishing, so keep poking on the IAP site and you will get one that works for you. No magic here, just a trial and error process. You'll do fine!

Cheers, Mark
 
Snakewood is notorious for cracking. One of the most frequently cited issues is heat buildup while drilling or turning. Because snakewood is very dense/hard, when it is glued to a brass tube the changes in humidity/temperature cause the materials to expand at different rates and the result is a crack. It is more than just the hardness, as there are other woods that are similar hardness that don't crack, but usually woods that are likely to crack are also very hard.

This particular crack looks like it was probably there before you started. However, I would be worried that it could get substantially worse if proper precautions were not taken in the early steps.

Another issue with extremely hard woods is that they will often crack during assembly due to the slight expansion of the tube when the fittings are pressed in. There are several ways to prevent or minimize this risk, I usually sand the inside of the tube until it is close to a slip fit and then use a little blue threadlock to keep the fittings in.

As Mark mentions, filling with CA is probably the approach I would try. That said, I would probably put the finished pen on the shelf for a year or so before giving it away to make sure it's not going to crack, and I wouldn't sell it without a strong warning to the customer (with a replacement guarantee). Just my 2 cents.

Good luck and welcome to the forum!
 
Jon Nutting said:
thank you all for the feedback. Ill give the CA a go and see what happens! Appreciate it guys. 👍
Click to expand...
In case it isn't clear from what the other folks have said - you have to slow right down with snakewood. I don't fold the sandpaper deliberately so I can feel if it starts to get warm. Fresh sandpaper (never use it more than once!), slow speed, light pressure. And as Mark said, you can get rid of those circumferential scratches by stopping the lathe and sanding up and down the blank, turn a few degrees, sand up and down the blank, turn a few degrees ... lather, rinse, repeat. Brush the sanding dust away with a toothbrush (or blast it with compressed air) so you can see that all the radial lines have gone before you move up to the next finer grit.
 
One other thing to note: once you are able to successfully turn and finish snakewood, which I enjoy, it will still eventually develop at least hairline cracks. They may even be hard to see but they will come. Maybe a week, maybe a month, maybe several months. I do not feel they detract from the look of the pen, but do let people know to expect them as part of the nature of the wood.

Welcome aboard, from Washington, Indiana.
 
Welcome aboard Jon.

I've been successful with snakewood, pink ivory and some ebony wood. They are all troublesome.

Here's my solution. When drilling, yes drill shallow cuts. Then let it cool.
Here's the key.
After drilling put it aside for at least a week. Then check to see if drill slides through, probably not. Redial and once again set it aside for a week... When you finally can push the drill through its ready. These woods need rest time to stabilize.
Remember to clean the hole in blank with DNA or other, and glue immediately.
Turning these wood also require careful slow cutting/turning, heat is the enemy. Let it rest and cool down while turning. I often apply thin CA between turning and sanding.

Sanding, same concerns, keep it cool.
 
Wayne said:
Welcome aboard Jon.

I've been successful with snakewood, pink ivory and some ebony wood. They are all troublesome.

Here's my solution. When drilling, yes drill shallow cuts. Then let it cool.
Here's the key.
After drilling put it aside for at least a week. Then check to see if drill slides through, probably not. Redial and once again set it aside for a week... When you finally can push the drill through its ready. These woods need rest time to stabilize.
Remember to clean the hole in blank with DNA or other, and glue immediately.
Turning these wood also require careful slow cutting/turning, heat is the enemy. Let it rest and cool down while turning. I often apply thin CA between turning and sanding.

Sanding, same concerns, keep it cool.
Click to expand...
Thanks Wayne!
 
I wanted to follow back and and share the results after following your suggestions. I use CA thin and some fine dust from a scrap piece of ebony I had to fill the cracks before sanding with 320 up to 1000 grit. If I hadn't marked where it was it would have been hard to find 😀. Thanks again gentlemen, appreciate it! Planning to use CA finish next week.
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I have had similar cracks in other woods, although not so many all in one linear area like that. I have always assumed its because pen blanks are so non standard - some are kiln dried some seasoned, and some are who knows ? Even from WoodCraft and PSI I have had blanks with cracks and checks from delivery, some with wax,some not - I think I even remember a company that sells blanks stating they might not be dry and recommend waiting a long time before using their blanks.

whatever causes it you have the right solution AND filling voids with wood dust and CA is the same trick to working with open grain woods like oak, walnut, zebrawood etc. . If you catch the cracks in time you can fill them with the same dust as the actual pen - just create some dust with 220 or 320 grit sandpaper on your actual pen and add the CA right on the sandpaper as you sand - I think a famous old pen guy had a video on youtube showing this back in the 90s the same guy that applied his CA with his wife's synthetic quilt batting - the grain filling doesn't always work for me but on the larger cracks its pretty good - I do save wood dust and I often like adding slightly darker woods to fill the cracks and grain
 
Forgot to say --- for what it's worth I would almost never sand any wood past 400/500 grit
the finest thousands of dollar furniture is probably only sanded to 220 or 320, maybe at most 400
the science is --- sanding finer than 500 burnishes the wood - this makes it hard for finishes to sink in and form a good bond - remember when you finish with poly you need to sand in between coats because the poly is too smooth for good tooth and holding power -same concept with woods being too smooth - save that 1000 grit to sand the CA finish
 
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