Broken Arbor Cap

This slitting saw arbor cap broke. I was a little surprised. I put it in a drawer with a saw on it since I was going to use it again in a minute. The saw bound slightly closing the drawer, but I didn't force it. I shifted it so it wouldn't bind and closed the drawer. When I opened the drawer a few minutes later it took a moment for my brain to register what I was seeing.

I left it for a few days, but I did notice right away that black staining that clearly shows a defect. Rust I could understand. This has run with flood coolant. Oily I could understand. I have used the arbor with cutting oil. The defect is clearly (in person anyway) dry and black. Finally it occurred to me that whatever they used to blacken the tool holder when it was new likely soaked into the defect then. I haven't used it much, but I'm sure its out of warranty. I guess I will be making a new cap for the tool holder soon. Thank goodness I have a lathe.

Possibly cracked during heat-treating, or just flawed steel would be my guess.
If it's a TORMACH toolholder, they may replace it for free.

My first TORMACH 5" vise totally cracked and blew-out along the fixed-jaw keyway area.
I sent it in for them to look at, and they gave me a free replacement.

I sent them a couple pictures. They said it was out of warranty, but it never should have failed like that. They sent me a replacement for free. It arrived yesterday.