[JustinAhrens]

Hello everyone,

I am working on my third segmented bowl, and I am having a problem with "checks" appearing on my bowl. I don't know if it is my technique, my tools, or my lathe.

I have a '80s Delta 46-700 variable speed, which seems to have a poor reputation. I turn mostly with a 1" wide 3/4" thick round nose scraper at 500 rpm. I sharpen frequently, but haven't tried to put a burr on it with a burnisher.

I've attached a photo of the checks. You can see them on the second ring from the bottom which is hard maple. They don't really appear until I put some shellac on the bowl.

Any help would be great!

Justin

 

[DaveTTC]

It could be your chisels. How sharp are they?

Not being familiar with your timber I would be curious about the grain and how hard or brittle that piece might be.

With some timber that I have found to be problematic I have resorted to using a scraper pointing slightly down and a little below centre.

Hope that helps.

 

[JimBobWay]

I'm a rookie with this as well and have had the same type of problems on hard wood. For me, I see it's the sharpness of the tool and speed. I tend to get carried away and try and take too much at one time. I think it's fun to see the massive amount of chips flying. That's OK for roughing it in but I had to slow up and take lighter cuts. I get that chatter if I don't take the time to move my rest in closer. So much to learn, yet so fun... Hope that helps some from a rookie stand point.
Jim

 

[JustinAhrens]

Thanks guys, The wood where the checks are most pronounced is hard maple, but they also appear in some of the softer woods like lacewood. I will sharpen again and try some of your ideas.

Thanks

 

[laxin213]

I'm not a pro but I've had this issue and people have emphasized to me that scrapers scrape away the wood while a tool like a bowl gouge cuts the wood away. I always see a bit a tear out and checking with scrapers, so at the end I make several light passes with a bowl gouge and this will clean it up and smooth out your surface in my experience

 

[john lucas]

I had a 46-700. It was not a terrible lathe, just not up to todays standards. I did a lot of segmented work back in those days because I didn't know you could turn green wood and couldn't find thick wood so I glued everything up.
Have you tried shear scraping? Here's my video on the technique. https://www.youtube.com/watch?v=7oeiVQLeOd4
I normally use bowl gouges on my segmented work these days. However segmented work actually works well with scrapers. YOu probably need to sharpen more often. The burr wears off really fast and needs to be re established frequently. Stewart Batty claims the burr only lasts 90 seconds on his V10 steel scrapers. A HSS scraper should last less. I must not be as picky as he is because my burrs seem to last a little longer. Can't put numbers to it but I stop and feel for the burr and if it doesn't feel sharp or I'm not getting those wispy hair like shavings then I resharpen.

 

[Dave Paine]

Watch John's video on shear scraping.

You need to put a burr on the scraper. I do not sharpen my scraper often, but I do refresh the burr often.

Get a Veritas burnisher. Very fast to refresh the burr.
http://www.leevalley.com/US/Wood/page.aspx?p=20266&cat=1,330,49233&ap=1

Also try increasing the speed.

Light cuts.

As John mentioned a sharp bowl gouge may give a better surface.

 

[DaveTTC]

Watch John's video on shear scraping.

You need to put a burr on the scraper. I do not sharpen my scraper often, but I do refresh the burr often.

Get a Veritas burnisher. Very fast to refresh the burr.
http://www.leevalley.com/US/Wood/page.aspx?p=20266&cat=1,330,49233&ap=1

Also try increasing the speed.

Light cuts.

As John mentioned a sharp bowl gouge may give a better surface.

interesting, never seen one of them before. Took me a couple of minutes to work out what it does and how it works

 

[JustinAhrens]

Thanks guys,

I'll try a freshly sharpend bowl gouge, along with putting a burr on my scrapers.

John, thanks for the great videos you have put up on youtube. I will also try sheer scraping.

I thought my lathe was part of the problem until I watched this video by Rob Millard http://www.shopwoodworking.com/build-a-portsmouth-side-table-dvd

He has the exact same model lathe and does quite well with it. I am sure with practice, I will continue to improve.

Justin

 

[SGalley]

Sharp, speed, light cuts. Are you working from the right towards the headstock? Also if you can put a piece of wood against the lip and put pressure on it with your tail stock it'll help with chatter. I put a rag in between to help with scratches.

 

[firehawkmph]

Justin,
after looking at your pic, I wouldn't call those marks 'checks', that's tearout. I don't use scrapers much anymore. I'm with John on shear scraping with a sharp bowl gouge. You have to take extremely light cuts and be patient. The wood coming off the tool should look like angel hair on your christmas tree. Very, very light cuts. When you get done, you should have hardly any sanding to do.
Mike Hawkins

 

[JustinAhrens]

Thanks guys,
I wasn't sure what to call them. I agree that "checks" is not the right term. I suppose it is tearout. I tried the shear scraping without much success. I also tried a bowl gouge, but still got the marks. I got to the point where I didn't want to make the wall any thinner, so I ended up sanding the heck out of it. It turned out pretty good, but I will continue to practice my technique and hopefully get to the point where I don't have to sand too much.

Regards,
Justin

 

[DaveTTC]

Agree with mike on the 'tear out'.


To remove it you obviously have to remove timber form the entire form to the depth of the tear out. It is a game of patience. You may want to go back to the grinder a few times and touch up your edge on your scraper as you go

regards