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Some days it's just too much!

C

Chris Dinsmore

Joined
Feb 7, 2011
Messages
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Location
Renton WA
Website
lumberjocks.com
I have been turning a bunch of bowls the past few weeks for a charity auction and some gifts. The bowls have been turning out really well. Like the walnut bowl attached. They have been utilitarian bowls made of local hardwoods sized from 6"x2" to 12"x5". I have finished about a dozen so far.

I have used pretty much the same technique for all of them, as far as the hollowing goes. I use the a slight variation of the method Jimmy Clewes uses in his bowl turning video. When I get down to within an inch of the bottom I use a big 24" handled round nose scraper to get to the proper depth and blend in the sides. It causes a bit more sanding but using a bowl gouge kept leaving me with funnels, which have no real value to those seeking a bowl.

So the scraper has been doing great for me, up until yesterday. Then every time I was working on any part of the middle of a bowl every tool started catching. Starting from the top planing cut and hollowing all the way down the center mass. The scraper, Bedan, spindle gouge, the only thing that would cut the center mass was a bowl gouge coming from the side. But even the bowl gouge would start catching in the very middle. I sharpened the tools to make sure they weren't dull but still, boom.

The final straw was tonight, a beautiful piece of Cherry was turning into a 10"x4" round side bowl. Once I got down to the last inch every time I tried even the lightest cut, boom, dig in huge catch. The last one I followed with a baseball swing type "cut" from above 😉

Tomorrow I am gonna try tuning up my Jet 1642EVS-2. Clean it, tighten the tool rest and see if that helps. I am thinking that maybe the tool rest is slipping on me.

Not so much a question as a venting rant.

Walnut Bowl.jpg

Bowl Black Banner.jpg
 
I would suspect that you are doing something different. You may have your tool rest lower than normal, or are doing something different in tool presentation.
 
Lots of us get used to pretty much centered rings in our turnings. Makes us complacent, because sometimes the near center features a single or asymmetrical section of rising grain. That'll grab a casually presented edge as it passes, especially an edge presented at a high pitch angle. Since we're generally at max extension over the rest (why move it for this last little bit?) at that point, the tool has a lot of leverage on us. It moves, not the rest.

I twisted out little dimples in so many bowls early on that I just leave a button about an eighth proud and maybe a half inch broad at the very bottom now. This comes out either with an inside out cut/scrape or with the sander. Since the bottom's the broadest sweep in the average bowl, it works either direction. A climb in the grain responds best in to out.

Now that you've tried several methods of attack, why not give surrender a try.
 
It's been a decade since I last used a scraper on the interior of a bowl.....😉
Gouges do such a better job.
Scrapers are necessary for other purposes, but gouges excel for this particular purpose.......

A gouge ground to the proper shape is the ticket! (Sharp, of course, but, I'm sure you get that part!) Sometimes 3 or 4 differently shaped and shaft diameters are required, and you can negotiate just about any shape you want with a minimum of sanding......if you are using the right tool for the job.

In an attempt to make this understandable and simple.....the angle of the bevel is what's important here. Generally, the smaller that angle is, the better it will negotiate a steep side of the interior (a 2-step bevel is very useful for many cuts)......and, the more blunt or larger that angle is, the better it will work for the bottom of the interior.

MM is correct that you'll never get a perfect surface without any undulations, so expecting that is beyond reason. But.......you absolutely can get a near perfect surface with the right tools and practice.

ooc
 
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holmqer said:
I would suspect that you are doing something different. You may have your tool rest lower than normal, or are doing something different in tool presentation.
Click to expand...

Ditto

If the wood can drive down onto the tool you get a catch.

I position my tool rest height so that with the tool level :
Bowl gouge cuts at center
Scraper cuts a bit above center inside a bowl
Scraper cuts a bit below center if used flat outside a bowl

If you are cutting too much in the bottom. Measure where you want the bottom and drill a hole a 1/4 inch less than that depth.
As you turn out the inside never go below that depth. Then remove the last 1/4 inch with your finish cuts.

After a while you won't need the depth hole.

Al
 
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If your scraper is catching you probably have the tip higher than the handle. A scraper needs to be presented to the wood with the tip lower than the handle. Then take light passes until you get used to how it's cutting. You may also have had too much tool hanging over the tool rest. The forces tend to want to pull the tool down and into the wood. You should also be cutting at or slightly above center.
If the bowl gouge is leaving you funnels your not moving the handle to guide the bevel. The handle steers the cut much like the tiller of a boat steers the boat. If your getting catches that means you are not rubbing the bevel or you have what we call an unsupported cut. This is where the cut wants to rotate the tool and pull it into the work. Rotate the gouge so the flute is about 45 degrees pointed in the direction of travel and use the handle to steer the tool making sure that you are rubbing the bevel. If you watch my video on cutting coves it might help.
http://www.youtube.com/watch?v=DSybPNw4F1o

This one on Shear Scraping may help you also.
http://www.youtube.com/watch?v=7oeiVQLeOd4

This one on the new Hunter Hercules tool might also help
http://www.youtube.com/watch?v=vzrLN8SQ8ms
 
None of us knows how you use your scraper, so to try and resolve the conflicting information above, I'd like to remind the advisers and you that scrapers are prepared in three particular ways, two of which are similar to the way a cabinet scraper is prepared - burr from the grinder and turned burr. These don't actually scrape when used properly, they sand or shave. The burr from the grinder is unpredictable, so you'll have to start differently than with a turned burr formed at a known angle. Bring it in slowly - always slowly - somewhere as close to 90 horizontal degrees to the surface as possible, then raise the handle slightly as it begins to engage to find the sweet spot. You're really sanding more than cutting, so nearly 90 is a decent place to start.

The turned edge is actually a low angle planing edge, so if you turn the edge at 12 degrees with your burnisher, expect to engage it for best use near that angle to the work. HSS alloys aren't normally the best candidates for burnishing, as they tend to be a bit more brittle than carbon steels, but if you get a burnished edge properly engaged it's a thing of beauty. You skew the edge a bit as you advance, just as you would your plane, because you're slicing.

A third option is to simply have a smooth, sharp edge created by honing both bevel and upper surface, leaving no burr. This is a wonderful tool to use as a shearing edge, where a small shear face can turn little translucent twists. It is also, In my opinion, the best option for HSS alloys. It's the most forgiving of the three when it comes to a point where the surface is not fair, and likely to bite and grab with the other presentations.

Oddly enough, this third "scraping" option is available to you without a tool designated as a scraper. You simply remove the grinding burr with a slip.
 
MM,
I only know two ways to get a catch with a round nose scraper inside a bowl.

1. is to let the bevel ride so that the wood can drive onto the tool which causes the tool to dig in. And big catch.
This happens with the tool rest too low or as John said you have the tool rest above center and drop the handle. With the tool rest above center you have to have the Handel up to reach center and this gives a nice space between the bevel and the wood and lets the burr work.


2 is to scrape up the sidewall of the bowl of the bowl where there is some vibration and the endgrain climbs onto the tool even though there is no bevel riding.

While it is possible to use a scraper as a flutless gouge cutting tool it is not something that should be tried by anyone who has gotten a catch in the last two years. It is just asking for disaster.
Al
 
As I said, it was more of a rant than a question. It is almost impossible to get an answer like this from a board. Without being here to see exactly what was happening it is impossible to know all the factors that contributed to the issue. Plus it is dependent on my not so good ability to communicate in writing!

I imagine that everyone has an answer to what they "think" the issue is. They base this on their own experiences. Some answers will be helpful, some are well meaning but written without really reading the original post, and others will come off as arrogant and belittling because the author is concerned with showing off how knowledgeable they are. I honestly appreciate them all. That people are willing to attempt to help is great!

In this case THE Issue was my tool rest was slipping. When making a cut we typically rest the bevel on the wood which adds support to the tool and takes pressure away from the tool rest. The way I was scraping the bottom the support of the tool is completely on the tool rest. I was using a curved tool rest right up against the wood. My tool rest was slipping under pressure which cause the tool to dig in just a bit deeper with each scrape, causing mayhem! I just wish I would have figured that out before I killed a beautiful Cherry bowl..

Thanks to everyone who took their time to respond to my post. Looks like things are going much better now. Happy Turnings!
 
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Thanks for enlightening us on the problem. I've had a tool rest slip a time or two over the years. It gets your attention real fast. 🙂
 
hockenbery said:
MM,
I only know two ways to get a catch with a round nose scraper inside a bowl.
Click to expand...

Apparently the op has found another.

Once again, it's important for those offering information on scraper positioning to mention which form of edge they are employing. There is a difference.

That said, the information on climbing grain is important to remember. If you look at the walnut example you actually see the ultimate in climbing grain - a knot. They make it easy to dig or peck out the point at which the edge enters the endgrain. If you're hanging out too far, it'll roll and tip a gouge. If you're shear scraping with a no-burr you can nick the surface, while broad scraping can dig and pop.

I always say the first thing to do to avoid a catch inside is to stay below centerline. Tougher to get caught under the wood if there's no wood over you.
 
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