Need help with Epoxy Turning

[MarkDarby]

I am making my first attempt at turning a vase out of a piece of spalted maple (??) that I have encased in resin/epoxy. I am using a round carbide tipped tool for the work. The diameter of the piece is around 11" and I have the lathe set to around 400 RPM. I'm getting alot of tear-out in the resin. It appears to be chipping out rather than being cut or scraped off. I attached some photos. Can anyone offer advice?

 

[Stuart Kent]

1. speed up as much as you feel safe with

2. make a roughing pass to ensure the stock is centered before you start refining it

3. try negative rake cutters or present your tool with a slight negative pitch

4. treat the cut as you would with a bowl gouge, in that you want to move it through the material as a 'push cut' where the material is constantly supported by the material behind it. *do not present the tool perpendicular to the spinning mass, rather come at it from a sharply acute angle; beginning at the tail stock end and 'push' the cut in the direction of the head stock.

5. reduce your cut depth (pressure you are applying)

6. slow your feed rate (how fast you move your hand)

7. try raising the tool slightly above the axial center of the mass to aid your hands in achieving a less aggressive cut

hope this helps, let us know!

 

[mattfrit]

Negative rake cutters made a world of difference for me.

 

[MarkDarby]

Hi All,

I wanted to give everyone some feedback. My shop was around 70 degrees. I did use a vacuum chamber -- first on the resin itself and then once I encapsulated the wood in the resin. Additionally, I sealed the wood with a coat of resin and let it dry before hand.

I thought I'd try several things based on your feedback -- and that of others on Redit and ChatGBT. Changing the height of the banjo, changing the angle of the tool, and changing the rotation speed.

Before getting feedback from everyone, I did try different cutting tools -- and decided that was not a good idea. I used a roughing gouge -- and discovered that the material coming off the wood hurts. This didn't produce any better results. I then put on a left glove and tried a detail gouge -- whose edge is now totally destroyed. So, I went back to the scraper and tried various angles.

Increasing the speed helped greatly. I took the speed up to about 1000 RPM. I did have two issues with this: I have a midi-lathe and it did struggle to maintain speed as I made my cuts. Second, it did vibrate more - which caused the lathe to slowly creep across my floor. I have a fold-away wood shop, so I can't permanently place anything. Not enough space. This was workable, though.

The second thing was lowering the banjo and dropping the back of the tool. This, coupled with the increased speed, gave me the results I was looking for.

I shaped the outside of the bowl yesterday. This was going to be a vase, but I really liked the pattern of the wood and epoxy as it was... so went to plan B. Rigid flexibility in design is the best way to make sure your end product matches your design. Today's job is to hollow the inside of the bowl and hopefully sand and finish.

I definitely need to learn about negative rakes -- I've heard of them but not seen any videos on them yet.

Thanks for the feedback!

Mark

 

[mattfrit]

Negative rake cutters. 100% the way to go.

 

[SabertoothBunny]

Room temperature for cured resins isn't a big deal. Make sure your carbide tip is sharp, if not give it a quarter turn to reveal a sharp face. Keep a toothbrush with your lathe for resin, it is the perfect brush for getting those resin strings off the lathe and out of the way so you can see. The toothbrush works better while the lathe is running.

Negative rake cutter, that is a bit loaded. The negative rake carbides are great for finishing your piece as you're taking off the last amounts for the final look. I do not recommend them for shaping as that is not what they are designed for. Negative rakes work the same as regular carbide tips, they just offer cleaner finishing cuts like a steel scraper compared to a cutting gouge. Yes, negative rake can be used for shaping but doesn't work as well in that capacity.

As mentioned, higher speed for turning resins. 1000 is a good start but not high enough for large items so if you're getting those vibrations it is because the piece is out of center or the lathe isn't stable. Keep the 1000 until the piece if evened out and then turn it up more. Also, clamp your lathe down as tightly as you can to reduce bouncing that comes with your moving it around and not being on a permanent, heavy base. For mid sized lathes its easy to bog the motor down with heavy cuts so just take smaller, consistent cuts to prevent that. The piece will take a little longer to finish but that is reality of a small motor on a lathe.

Regular carbides are a better option to use for shaping and removing material. Make sure you have the banjo/tool rest set to the right height so your tool is centered on the piece when you go to cut. With carbide tools you want the tool to be flat on the tool rest to get cleaner cuts, not angled left/right or up/down. You are using the sharp edge to cut and the edge is flat so changing the angle on it can reduce effectiveness because you're now using less of that sharp edge. Start with smaller cuts, don't get too aggressive up front. Let the tool do the work, no need to force it because that is one thing that leads to chipping.

Hollowing, take your time. It is easy to get a catch inside the vessel which can cause it to come out of center or fly off the lathe. Be patient, don't rush.

If you have any questions feel free to shoot me a PM and I will help as best as I can.

 

[RDUcabinetbuilder]

Hi mark, we met at capitol city a week or so ago! I recognized the vase that you had showed me. Just wanted to say hey and nice work!

 

[MarkDarby]

Hi mark, we met at capitol city a week or so ago! I recognized the vase that you had showed me. Just wanted to say hey and nice work!

So glad you texted. Hope to see you at the lunch! And the picnic.

 

[MarkDarby]

Room temperature for cured resins isn't a big deal. Make sure your carbide tip is sharp, if not give it a quarter turn to reveal a sharp face. Keep a toothbrush with your lathe for resin, it is the perfect brush for getting those resin strings off the lathe and out of the way so you can see. The toothbrush works better while the lathe is running.

Negative rake cutter, that is a bit loaded. The negative rake carbides are great for finishing your piece as you're taking off the last amounts for the final look. I do not recommend them for shaping as that is not what they are designed for. Negative rakes work the same as regular carbide tips, they just offer cleaner finishing cuts like a steel scraper compared to a cutting gouge. Yes, negative rake can be used for shaping but doesn't work as well in that capacity.

As mentioned, higher speed for turning resins. 1000 is a good start but not high enough for large items so if you're getting those vibrations it is because the piece is out of center or the lathe isn't stable. Keep the 1000 until the piece if evened out and then turn it up more. Also, clamp your lathe down as tightly as you can to reduce bouncing that comes with your moving it around and not being on a permanent, heavy base. For mid sized lathes its easy to bog the motor down with heavy cuts so just take smaller, consistent cuts to prevent that. The piece will take a little longer to finish but that is reality of a small motor on a lathe.

Regular carbides are a better option to use for shaping and removing material. Make sure you have the banjo/tool rest set to the right height so your tool is centered on the piece when you go to cut. With carbide tools you want the tool to be flat on the tool rest to get cleaner cuts, not angled left/right or up/down. You are using the sharp edge to cut and the edge is flat so changing the angle on it can reduce effectiveness because you're now using less of that sharp edge. Start with smaller cuts, don't get too aggressive up front. Let the tool do the work, no need to force it because that is one thing that leads to chipping.

Hollowing, take your time. It is easy to get a catch inside the vessel which can cause it to come out of center or fly off the lathe. Be patient, don't rush.

If you have any questions feel free to shoot me a PM and I will help as best as I can.

Thanks, Sabertooth. I will. Working on a table now - but already have my next resin project planned.

 

[MarkDarby]

Negative rake cutters. 100% the way to go.

Heard about them. Going to have to try on the next project.