Getting a ridiculous amount of tear out in a segmented resin and wood bowl I’m turning. The wood is cutting just fine but the epoxy looks awful. I’m using Ecopoxy and cutting with Robert Sorby carbide cutters. Both the round and square heads do the same and they are new. I’ve adjusted the lathe speed all over the place with no change. Not sure why it’s so bad…
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That is unusual, I also use carbide scrapers to cut epoxy filled wood blanks . The mix ratio could have been wrong and gave either a too soft or too brittle result. Carbides never are as sharp as a carbon tool steel, I would try a freshly sharpened carbon steel scraper.
Yeah, I was leaning toward the epoxy being too hard. I’m very precise with the mixtures, so you think maybe this brand just isn’t good for turning?
What Ecopoxy product did you use ?
It's called Ecopoxy Flowcast
That would be the recommended product, did you feel the mixing container heating and the product starting to cure prematurely, leading to some foaming while curing ?
ohh you might be on to something. I made a 24x12x1" form, poured the mix in and covered it with cardboard to prevent dust from getting in it. Later I felt a TON of heat on the cardboard so I removed it and noticed some of the epoxy was harder than I think it should have been so early. I then put a box fan behind it...I bet all of that made it cure prematurely.
That is what happened, when epoxy is mixed in a large quantity, it kicks an exothermic reaction that builds heat fast and changes the end product, sometimes even foaming. That is why there is a maximum pour thickness but sometimes the reaction starts in the mixing bowl. When I do large quantities, I mix throughly but rapidly and then separate the mix in a few plastic cans so as not to get that reaction, the pour thickness should also be checked as not to exceed the manufacturers recommendation.
Great idea. Thanks for the help!
I can't speak to the epoxy but as to the turning, I would not use any carbide replaceable tip tool.
These tools are for the most part, scrapers. If the epoxy is still soft, this is what can happen. It scrapes up a small ball and then pulls it out.
First address the epoxy issue, then try a shear cutting method.
The chalenge with turning a wood/epoxy piece with shear cutting tools such as a sharp bowl gouge is the sudden change in hardness between the two. The gouge will dig in deeper in the softer wood and hit the tough epoxy causing a catch. The scraper is easier to control in that manner and can be fed straight and slow, taking a minimal amount of wood but enough of the epoxy to remain under control. Even then, it’s my main cause of catches ahead of knots and voids.
In my experience, a higher speed and lighter cuts are what's needed to deal with woods (or other material) of different densities or hardness.
A scraper may be easier to control but it is an unsupported cut and can result in tear out. A high angle bevel rubbing cut can provide enough support to the fibers to avoid this. It may take practice but I know it can be done. Here is a piece I made 10 years ago from Purple Heart (janka 2500) and Poplar (janka 550)
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