Bowl turning issues

[Tiger]

Dear all,

I haven't made many bowls, platters etc. but when I have tried I usually have 2 recurring problems.

1. When I'm roughing out the bowl with the bowl gouge, I usually at some point (when the blank is square or squarish), get chunks of wood splintering off. Is this because of incorrect presentation of the gouge? Usually, I hold the gouge close to my hip in a fairly vertical orientation.

2. I reach a point where I cannot remove the torn end-grain entirely no matter how sharp the tools I use and how light my cuts are. Do you also reach a point where you say close enough is good enough or do you try some other method? This seems to be more prevalent on softwoods.

[rsser]

Re 1. try speeding up your lathe, take light cuts and start with the heel of the bevel rubbing. Then gently raise the handle til you are cutting. Set your tool rest about a thumb's thickness below the point you will be cutting when it's at the equator.

Re 2: yes, this is hard to avoid. Usually caused by tool chatter, or not rubbing the bevel (but that's hard when you're 'turning the corner'). Reduce the overhang as much as you can. (If you can afford a seperate gouge grind it with a short bevel for the corner). Take light cuts; speed up the lathe. Play around with flute presentations (inc. shear cutting on the bottom wing with the flute facing left).

[Edit: Finishing cuts with a small gouge also help. What size (diam of shaft) are you using?

You can also play with spraying some water on the end grain of soft wood to help swell and support the fibres, or use clear sanding sealer.]

Most of us end up using some kind of scraper to clean up.

[PAH1]

RE1 Use a scoop cut in from each edge, rather than a cut parrallel to the edge. This reduces the chances of levering a piece off.

Re2- Sometimes shear scraping can help but some woods have a propensity to tear and there is little to be done other than sand.

[Tiger]

Thanks, Ern and PAH,

Ern, I start the speed on the slowest setting when the bowl is not round. The shaft on the bowl gouge is about 15 mm from memory. I do use a scraper in the end and I do use it in shear scrape form ie at 45 degrees to the rotating wood.

[rsser]

In terms of roughing out, do you start from the centre of the flat and work out? This will reduce chipping and overall turning time. How slow is the slowest speed and how big is the blank?

Re tear out, an unsteady tool or a big cut will contribute to this. That doesn't matter much until you get to fine finishing cuts. A smaller gouge is recommended, or if you can afford it a superflute style gouge which has a tight inner and wider outer radius allowing both fine and rough cuts.

One way to negotiate the corner is to really push your gouge up in a high tight arc, then roll it clockwise bringing it down to the centre.

On the other hand, some soft woods don't ever turn well. What are you using?

(Work is slack at the moment; PM me ... I'd be happy to come out and help.)

[Tiger]

Thanks, Ern. I usually work from right to left on a bowl making sure that I go downhill. I might have to get you to demonstrate the high arc motions as it's a little hard to understand unless you see it.

[rsser]

Yes, on the inside you work 'downhill' but have options about how you position the flute.

On the outside while roughing the blank you can work uphill.

Happy to demo.

[Hickory]

All of the previously mentioned are true, might check to see of you have the tool rest set too high or low. This will create the problem, Also (especially with bowls) it is difficult to keep the tool rest as close to the work as we need to do. Reaching out with a tool creates slight chatter which tears fibers.

Re-set the tool rest, is my suggestion to add to the superior knowledged fellows' responses. Sharp tools , correct speed and rubbing the bevel are all influenced the tool rest placement. They work in conjunction with each other. The height of the turner can cause a problem, Short turners seem to point the tool upward as they stand low compaired to the center. As a result the tool rest needs to be lower. Same holds true with Tall turners, the tool rest needs to be higher due to the angle of the holders position.

I hope this helps.

[Skew ChiDAMN!!]

Sharp tools , correct speed and rubbing the bevel are all influenced the tool rest placement.

And my 2c worth...

Changing the speed can make a major difference to some timbers. If adjusting the tool-rest and bevel rubbing make little difference, then incorrect RPM would be the next most likely culprit.

Don't forget that the closer to the centre of the bowl, the slower the effective cutting speed. RPM's that work well on the outside of a largish bowl are often too slow for the centre... and it shows in the finish. Thank god for easily changed variable speeds. ;)

[CameronPotter]

Thank god for easily changed variable speeds. ;)

And curse belt changed (and severely limited) speeds...:o

[rsser]

Tiger, a few afterthoughts after our practice session today:

Clean up the bottom with the smallest scraper you've got with a fresh burr and held flat (not sheared) ... to deal with that punky grain at the bottom of the bowl.

When you sharpen your gouges, try to ensure the tops of the two 'wings' are on a par (looking straight down into the flute with the shaft at 90 degrees to line of sight. Make sense? Now you know why Darlow uses technical language!).

Insulation: http://www.concertinafoilbatts.com/

Happy to do another practice session ... with an easier bit of timber next time ;-} . Or bring that one back and we'll finish it off. PM me.

[Tiger]

Thanks, Ern. I'm looking to increase my supply of bowl blanks. As you say, that particular bowl was too small. Once I've got some reasonable wood, we'll try again.

Thanks for the insulation reference, it was so cold yesterday that I could barely stay in the garage for more than a few minutes at at time.

[Skew ChiDAMN!!]

..And take yer camera next time Tiger! ;)