I caught this on another forum....explains why I try to be extra careful (it's less than a minute):

 

Have you watched Tim Yoder video on catches. He creates the catch and explains it.

 

 

Hard to tell because RPMs in a video are difficult to determine but it seems the lathe was running very slow. Slow RPMs can have the effect of making catches easier to happen. 

 

When I use a jam chuck, I also use strapping tape to secure the piece to the chuck. 

I loved that Yoder video, and i hadn't seen it before now.  Thank you.

On 9/12/2024 at 3:03 PM, Fred W. Hargis Jr said:

I loved that Yoder video, and i hadn't seen it before now.  Thank you.

Be sure to watch the second part

I've watched his stuff on catches through part 5. I was most interested in his relief grind on a scraper. I did finally buy one and it's a "flat grind" (Tim's words). I'm considering doing the relief grind on it, but doesn't angling that tool down in use do the same thing?

1 hour ago, Fred W. Hargis Jr said:

but doesn't angling that tool down in use do the same thing

Yes, it sorta does, but typically scrapers are help "flat". The change in the grind makes it so you don't have to adjust your "stance" when working on a bowl. And the scraper is less aggressive when removing material.

 

Many of the carbide cutter companies put a "negative rake" on their cutters for the same reason- to make them less aggressive.

 

 

I guess it is all in how you learned to turn. If you look at Richard Raffan, he uses scrapers almost everywhere. If you watch his sharpening videos, he doesn't add the relief grind to his scrapers. 

 

According to Stuart Batty angling a flat scraper does not equate to a negative rack grind. I have changed two of my scrapers to negative profile. Yes it does not allow you to hog off material but it is almost catch proof and I think gives a cleaner finish. As for angles I think I have 70degree for bottom and 25 on top. when you sharpen you just grind the bottom till top bevel gets too short and then grind the top bevel.

Here is a very good video on scrapers.  Good info here.