Turning blanks with cast and wood can create the most beautful works of functional art, but it can be tricky. It takes a careful touch to turn pens with blanks that have a mix of materials because your cutter can dig in if it encounters a different density material than it was cutting previously. This makes tear out or chip out almost inevitable if you aren’t careful, worse case your entire blank will blow and it will be wasted. Turning cast wood is definitely better for the experienced turner but even the most experienced turner is still new when it comes to turning cast material for the first time. Here, I will give you a few tips and examples of what to do to minimize the failure rate.
Prepping your tubes. I know this is pretty standard for turning any pen, not just cast wood pens, but I wanted to express how important it is with cast blanks to be sure your glue up is solid. Your tubes need to be rough sanded for a better bond. The walls of a pen are extremely thin in most cases and keeping the material from caving in or cracking really needs the support of your pen tube. If there isn’t a good bond on your tube then it will likely chip or break apart.
Speaking of a good bond, let's talk about glue. I usually use medium CA glue for making a pen. It works, dries quickly and holds well. However, when making a pan using cast wood I have found that CA glue is strong enough, but epoxy is better. So when I turn a cast pen blank, I use a simple 5-minute epoxy. Whether you use epoxy or CA glue, it is imperative that you make sure the entire tube area inside the blank is coated with adhesive. I slide the tube in and out several times from both sides and then I look inside the cast blank to be sure all of the walls are covered. This is why I use epoxy, I have a little more time to be sure the blank is fully supportive. Cast blanks can be brittle, then add stabilized wood which can also be brittle, so every precaution should be handled. Especially when using a higher cost pen blank.
Turning the blank. Now that you have your tube in, you have it barrel trimmed flat, mounted to your lathe, and the excitement you’re feeling is off the charts! What’s the best way to have success here? You don’t want to blow such an amazing blank that cost you more than the $2 bargain bin at your local Woodcraft. Well, you can be cautious for starters. Turning tools are interesting beasts. They come in all shapes, sizes, and several different materials. I have many of them myself. I use them differently depending on the task. For this particular task, carbide tools are the clear winners. I know, you’re going to say...I’m pitching carbide tools because I sell carbide tools. That would be an awesome reason right there to do just that, but in this case, it’s just the best option period. Why? Catches, that’s why. It’s extremely difficult to get a catch with carbide and no matter how skilled you are with HSS tools, you will still get a catch on occasion. It’s just the nature of the beast. If your tools are slightly dull or your bevel isn’t exactly perfect, you will have a catch. Not a huge deal on something larger like a bowl because you can usually fix it with a small change in design. With a pen, you just don’t have room for error. Carbide gives you more fine control, the tools stays sharp, and the edge stays consistent. It makes for a better tool in this case especially. Carbide works well for all projects, so definitely worth a look! <--That's last me pitching my tools!
Hope these tips help you find success.