[OP]
Member
Tonight I was making a light cut on the bottom of a bowl when my bowl gouge broke. It wasn't very eventful, it just fell off and landed on the ways of the lathe. It was a nice bowl gouge, and I would be lost without a 3/8" bowl gouge. I'm going to order another one like it tonight and try my luck with a second one. Has any one here had a bowl gouge basically just fall apart?
bowl gouge.jpg
Member
I have not, but we have had at least two instances in our club, both powdered metal, major brand tools (same brand). One happened at a demo that I was at, light cut on the outside, no catch. The vendor replaced the first one, not sure about the second, but they commented that they had only ever had two break and the same guy (our president) was using them! I think he opted for a different brand when he replaced the gouge. His were larger gouges, 5/8" or 3/4" IIRC.
Retired - when every day is Saturday (unless it's Sunday).
Contributor
Never had it happen to me but if it did, in the manner that you describe it did, I would contact the manufacturer and see if they would offer to replace it. I would think any reputable maker would want to keep the customer happy, find out how their product failed and why and do their best to see it wouldn't happen again. You didn't mention the manufacturer of the gouge and the picture offers me no clue but if this was one of the more "economical" brands, before spending any money to replace it with the same thing, I would consider a different maker (think Sorby, Thompson, D-Way etc.)
Call me Jim, James seems so stuffy.
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[OP]
Member
It is a D-way gouge, and I don't expect him to warranty it as I have gotten a lot of good use out of it the last couple years. After sitting here thinking about it, I think I'll just re-grind it where it broke and keep using it. Here is what the end looks like where it broke. The metal looks as it though it is twisted. There was no catch either, it just fell off.
gouge.jpg
Contributor
I can assure you that Dave wants that gouge back to inspect it. He builds quality tools and that looks a defective heat treat. In fairness to him, you should contact him.
Member
I second John's post on contacting Dave at D-way. He would be very interested to see any tool he sold that failed in such a manner. He is a very honest stand up guy and you should not have any reservations about contacting him. I would be interested also to see if he has any thoughts as to why it failed like that.
Rich
Member
I'm with John, Dave needs to know about this for his quality control.
Comments and Constructive Criticism Welcome
Haste in every craft or business brings failures. Herodotus,450 B.C.
Member
That is certainly a defect and I would want it back to study it and show my supplier. Dave is a good guy and, I feel certain, will replace it for free. I would not resharpen it as it might have more defects in it and the next time you might not be so lucky.
Do or do not, there is no try.
Member
There is a larger issue, Dave who is a good guy and who I am sure will make it right, needs this back to find out what happened and to have a chat with his steel supplier. This could have been a tragic occurrence with our friend John's professional brothers (and sisters) involved. This really needs analysis.
Member
My Thompson 5/8 bowl gouge did that and Doug replaced it immediately for me. He said that there are sometimes (rarely) defects in the powdered metal and there is no way to know it until it breaks.
Two issue come to mind.
First, I agree with others that Dave (or whoever the vendor of a broken tool is) should be notified.
Second, some folks have the mistaken impression that any "overheated" tools (from aggressive sharpening) should be quenched in water. While this was the case with carbon steel, it should not be done for newer HSS, including the high vanadium and cobalt alloys. Quenching these steels will result in micro fractures that can propagate and result in catastrophic failure under minimal stress.
Member
What you are stating is only a part of the story.Originally Posted by Jeff Gilfor
HSS should not be quenched from red or near red heat and above. If grinding the tool makes it too warm to comfortably hold, dipping it in water will not cause microcracks to form. The theory behind the formation of microcracks is that the large temperature gradient that occurs from the rapidly cooled thin edge across the thicker slower to cool body causes the thin edge to shrink more than tne thicker section and the difference in the shrinkage exceeds the ductility of the material and the shrinkage cracks occur. A difference of 100 degrees f between tbe thin edge and the body of the tool will not be sufficient to cause microcracks.
HSS was originally designed for metal working at higher surface speeds and consequently higher working temperatures than carbon steel. Most HSS has a high red heat hardness, meaning that the actual edge of the tool retains it's hardness when red hot. In metal working, the actual edge of the tool can be red hot while just a few thousnadths of an inch back from the edge the tool will be much cooler. Often times a coolant is used, and the temperature just back from the edge will be at or near ambient. This large of a temperature gradient in such a short distance does not cause microcracking. Aggresively sharpening HSS and causing the steel to become red hot does not appreciably affect the temper in the tool.
The powdered metal tools with a high vanadium content are actually more of a wear resistant steel than a high speed steel. These tools should not be sharpened or shaped aggresively enough to cause the edge of the tool to become red hot. The temper of the steel will be affected if the steel does become red during grinding. Again, dipping in water when the tool is uncomfortable to the touch will not cause microcracks. Dipping in water when the tool is at or near red heat should be avoided.
I don't know what material the gouge in question is made from, but the fracture is so far back from the edge that is seems unlikely that heat from sharpening could have played a part in the failure.
Member
Yea, what others have said, contact Dave. He would want to know. That is, to me, a metal failure. Dave's tools are not powder metal, but some times there can be flaws in the steel. Dave is a great guy to work with.
robo hippy
Contributor
Dale, it is my understanding that Dave uses M42 Cobalt steel, which is a super cobalt high speed steel which may be heat treated to HRC 68, and that is the range he treats to from what he has explained to me. It would seem that any metal can be subject to a metallurgical defect, and that appears to be the case here. Those defects are not usually discernible and are rare, but do happen.
I use Dave's gouges on a regular basis, and enjoy the hardness and durability. I have no doubt Dave will replace this gouge and will want the broken one returned for his inspection and so he can speak with his metal supplier.
Member
John,
I have no opinion on what caused the failure, just wanted to add to the comment on dipping a tool after grinding. In order to determine the cause or even come with a swag, a close visual inspection or pehaps microscopic look see would be needed. In some instances, an internet photo of the failure is enough for a guess, but in the photos posted the cause it not readily apparent to me.
M42 is good stuff, the cobalt adds to the red heat hardness capability. I have one tool from d-way, a thin blade parting tool and am happy with it. It was a gift, so not much looking into the horses mouth was done regarding material.
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