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+-- Thread: Carter bowl gouge split down the middle.... (/showthread.php?tid=7210783)
Carter bowl gouge split down the middle.... - EightFingers - 02-03-2016
Not sure what she was actually doing, but LOML was working on a bowl and then she had a catch. Must have been pretty bad, because the tool was pretty much split down the middle. Never seen anything like that. I'll post a pic tomorrow.
Re: Carter bowl gouge split down the middle.... - sniper - 02-03-2016
Holy hand grenade Batman, I hope she's alright (other than having to go change). Can't wait to see the pic.
Re: Carter bowl gouge split down the middle.... - AHill - 02-03-2016
A split like that sounds like a catastrophic failure due to some inclusion or void in the steel. If the split is longer than 1/4", that's my best semi-educated guess. It's possible the catch jammed the tool between the bowl and the lathe, striking the lathe very hard. Either way, even for the kind of steel you have in a turning tool, it should have bent before it split. I'd call Carter and tell them what happened. They would be interested if there was a defect in the steel, as there might be other tools out there that have similar defects. The next event for someone else might result in a serious injury with the potential for a lawsuit. Glad your wife is OK. Things like that are scary.
Re: Carter bowl gouge split down the middle.... - Arlin Eastman - 02-03-2016
Seeing this it makes me wonder if it was the tool that made the catch and not her. That is pretty bad when a bowl gouge Splits down the middle and I have never heard of that before and I googled it too.
You have to tell Carter about it and see what they say.
Is the wood salvageable? O and how is your wife.
Arlin
Re: Carter bowl gouge split down the middle.... - EightFingers - 02-03-2016
She's ok, just a little embarrassed that it happened. She was turning some very hard eucalyptus. I bought the gouge at Craft Supplies so I'll give them a call tomorrow.
Another thing, this was not on a "big" lathe, it was on the Delta 1 HP lathe, she said it was set at speed "4", (10 is the fastest)
Here's a pic:
Re: Carter bowl gouge split down the middle.... - Gregory of Sherwood Forest - 02-03-2016
I can't even imagine how that happened, unless there was a metal defect. I doubt I could replicate that big a failure with the tool held lengthwise in a vise and some big swings with a sledge.
Re: Carter bowl gouge split down the middle.... - AHill - 02-03-2016
After seeing that, I'm now 95% sure there was a defect in that tool. (I'm a metallurgical engineer by education.) The long jagged edge is classic of something we call brittle fracture. Brittle fracture occurs when things happen very quickly and the stress applied overwhelms the ability of the tool to bend or yield. Kind of like when you pull silly putty quickly. It breaks vs. stretches. It's possible, but unlikely a catch by itself resulted in brittle fracture. If you look at the surface of the crack, and see a bright part next to a shiny part, that's evidence of a void prior to the mishap. If there are lips on the edge of the crack that make a 45 deg angle to the tool, then it's ductile fracture (i.e., it stretched some before it cracked).
EightFingers said:
She's ok, just a little embarrassed that it happened. She was turning some very hard eucalyptus. I bought the gouge at Craft Supplies so I'll give them a call tomorrow.
Another thing, this was not on a "big" lathe, it was on the Delta 1 HP lathe, she said it was set at speed "4", (10 is the fastest)
Here's a pic:
Re: Carter bowl gouge split down the middle.... - Angus - 02-03-2016
I've heard of that happening on benjamins best tools before. friend of mine sharpened a gouge and found a void
Re: Carter bowl gouge split down the middle.... - Ruler2112 - 02-03-2016
WOW - that's crazy! I've never seen anything like it before. Showed it to my father, who was a professional metallurgist for 30+ years and has a good functional grasp of how steel behaves under various conditions. (He knows a hell of a lot more than I do about it...) A synopsis of his explanation is as follows:
When steel is formed, it starts as a large billet. This is drawn through a series of progressively smaller and smaller dies under extreme pressure that reduces the diameter while increasing length. Sometimes the steel doesn't go through perfectly and forms seams - basically where the outside of the steel folds into the bar somewhat. It's also possible that the metal will tear apart between dies; it's smashed back together when it goes through the following dies so tightly that while it appears to be a solid piece, there are really two pieces that are simply pushed together. In extreme cases, voids can actually be formed inside the steel.
Samples are taken from each batch when steel comes into the plant and tested. They run them through a magnaflux machine that makes these seams glow under black light; if there are too many seams or if they run too deep, the steel is rejected. Seams are uneven and go in and out throughout the bar longitudinally. If the seam goes farther in than is ground off during the grinding of the rod, there is a natural stress-riser created. During heat-treatment, a microscopic crack was likely formed where this seam was.
Most of the time, these tiny cracks go unnoticed for long periods of time until just the right amount and type of stress is put on them. The impact of the catch your wife had was enough to open up the preexisting (invisible) crack and cause catastrophic failure of the tool. The wavy edge on the part that opened up and that it runs the length of the tool supports this hypothesis.
In short - it was probably a defect in the steel that was provided to the people who made the tool.
Re: Carter bowl gouge split down the middle.... - robo hippy - 02-04-2016
I have seen a number of gouges that snapped across the flutes, but never one down the length of the flute. I would call both Carter and Craft Supplies. I don't think I could make some thing like that happen, and I make my tools sweat when I turn...
robo hippy