I actually turned this pen last week. Was no cracking when I assembled this one. I just went to use this, twisted it and it cracked and the nib fell out
Any idea why this could have happened?
Quite common. Ebony! Pen turners have been asking "Why" for years!
Ebony as a blank can crack but usually doesn't. Extreme care in drilling "seems" to help some, but that doesn't prevent it. My opinion is that it needs to be drilled 1/64 inch too large and use flexible glue. Ebony, under heat or cold or wide humidity changes does NOT like to be constricted. Ebony will fight constriction. 1 in 25 or 1 in 50 will not crack under wide changes and there is always one person that says theirs has not cracked under wide environmental changes. But in most cases, it is a given that it will.
Why do unturned and undrilled blanks not crack as much as those on pens? They can expand and contract on their own; Drill them out and constrict them with glue and nature will win. That is the nature of wood.
Your Pen: The fact that they both cracked on the same side "suggests" that they probably received too much heat equally - Sunlight, heater? Then again, it might be that you aligned the grains perfectly in their natural line and that was the weak spot.
More on this phenomena: laminates and plywoods do not expand and contract like solid wood. 3/4 inch plywood will be virtually stable. 3/4" thick red oak, cherry, white oak, walnut will expand and contract considerably, especially on a board 12" wide and 8 ft long. I have had boards crack when glued together side by side and then screwed down. Wood moves and likes to move.
