Effects of electrical etching
Effects of electrical etching
(OP)
We had a problem with some custom tools that we made breaking for no apparent reason. We electrically etched the tool # on the shank. Is there a disturbance caused in the area by the electrical current that could cause the tool to be weaker there?





RE: Effects of electrical etching
Any surface defects will act as stress raisers to reduce sevice life.
nick
RE: Effects of electrical etching
Keith Durkee
www.toolgrinder.com
RE: Effects of electrical etching
As you probably know, untempered martensite is very brittle. It you can't use some other marking method, then retemper the tools after you mark them.
RE: Effects of electrical etching
nick
RE: Effects of electrical etching
Keith Durkee
www.toolgrinder.com
RE: Effects of electrical etching
One thing isn't clear to me. Did the etched tools break AFTER you ground off the etching or did the grinding save them?
RE: Effects of electrical etching
The tools still broke after grinding the etchings off. The etchings were done with an electrical DC etcher. Not electro-chemical. We have a new one that was never etched running right now, bet we also left the neck .015" bigger in diameter. We also broke this one in by running a couple of cycles at 50% before running full speed. We changed too many things at one time to know for sure.
Keith Durkee
www.toolgrinder.com
RE: Effects of electrical etching
We tried resistance brazing WC years ago and never could do it without damaging the carbide. What you are doing may relate to that.
Several ideas come to mind.
1. If it is standard cobalt matrix cemented WC then there is a significant difference in electrical resistivity between the WC and the Cobalt. We cover this pretty well in
U. S. Patent 5,624,626 where we use current to remove either the Co or the WC. Removing the Cobalt would leave it weaker.
2. For some reason the term eta phase comes to mind. You may be affecting the carbon and creating an eta phase embrittlement I can’t explain why but this idea seems as though it might apply. Typically this is a sintering problem.
3. I would think that a simple stress crack is more likely.
4. Maybe just forget it and try a straight chemical etch.
Our last newsletter had some good pictures of carbide defects. If you don’t get the newsletter and haven’t heard me speak lately please email and I will send you info.
Tom
Mr. Thomas J. Walz
President
Northwest Research Institute, Inc. / Carbide Processors, Inc.
3847 S. Union Ave.
Tacoma, WA. USA 98409
800 346-8274
Ph (253) 476 1338
Fax (253) 476 1321
tomwalz@email.msn.com
www.carbideprocessors.com
RE: Effects of electrical etching
Thanks,
Keith
Keith Durkee
www.toolgrinder.com
RE: Effects of electrical etching
Good question.
I have no idea if this makes sense but I think of EDM as passing the current by and / or though the part while etching forces the current into the part.
I first learned about etching as a problem when we tried etching our name into some of our ceramic tipped saw blades. We truly spent whatever it took to make the very finest saw blades we could. We didn’t even label them because we didn’t want to fool around with clearances measured in tenths of thousandths. However we were sold an electro-etcher absolutely guaranteed not to affect the plate. Well it warped the plate so that one or maybe two teeth out of sixty stuck out about 0.001” which left just beautifully clear marks in the wood when it cut. Of course we didn't check before we shipped so we had a recall nightmare for a couple dozen saw blades.
Tom