smoothing end grain on a bowl?

[Jake Truxal]

what is the secret to getting the end grain on both the interior and exterior of a bowl smooth? I'm using a scraper and getting the feather like shavings but the end grain always is rough and has some tearout. The degree of roughness seems to be related to the species and grain tightness. e.g in the past few days I turned a walnut, cherry and maple bowl. The end grain on the maple bowl I turned last night is much smoother than the walnut and cherry but still not great. I've seen posts about sanding in reverse (my lathe does not have reverse) and hand sanding with the grain. I also think i may have been running the lathe at a higher speed when I ran the scraper on the maple bowl so that may have contributed to it being smoother too? My problem there is, I don't have the greatest lathe and when I run at high speeds with a chuck (ie the bowl 4 inches from the headstock (have a spindle adapter too) ) I get alot of vibration in my headstock. The walnut and cherry bowl were larger diameter so the vibration was unbearable at higher speeds.

 

[MichaelMouse]

I'm not a scraper if there's another choice. Sometimes the angles just aren't there, so you have to use one, I suppose.

The theory of edges and wood says to cut across, lift down grain. A scraper presented broadside lifts to cut, while a gouge on its edge will cut prior to lifting the waste. You want a nice low sharpness angle for end grain, which can be really lowered by using a long bevel, or more commonly, effectively lowered by presenting the edge at a skew angle. If you can get both, Katie bar the door.

My preferred is to use a broad radius gouge with a constant bevel presented at a skewed angle to the travel of the tool. Some like to do the same with no bevel to guide them, but I like the support.

http://s108.photobucket.com/albums/n28/MichaelMouse/?action=view&current=CherryPeelIn.flv

http://s108.photobucket.com/albums/n28/MichaelMouse/?action=view&current=CherryPeelOut.flv

 

[Jake Truxal]

I'm not sure I know exactly what you mean by this: "You want a nice low sharpness angle for end grain" ?

A big part of the reason I'm using the scrapers is that I have a fingernail profile bowl gouge which I have not mastered yet (I've made a total of about 10 bowls) and I get alot of catches with it. Seems that whenever I try to do my final smoothing with it I get 90% finished and I get a catch and put a big gouge in the bowl, mostly I'm never exactly sure what angle I should be holding the gouge at so I can at least minimize the damage by using the scrapers.

 

[MichaelMouse]

An attempt to get to standard terminology, I guess. Though Hoadley on wood is about as good as you get in my experience.

http://www.sover.net/~nichael/nlc-wood/chapters/caop.html

Those "bowl" gouges are a problem, no doubt. I just refuse to try and adapt to their shortcomings and shave the way it was done before someone made a cylindrical gouge. Problem is fairly obvious, if you look at what most people do now versus what used to be.

http://i35.photobucket.com/albums/d160/GoodOnesGone/Gouge-Curves.jpg

Standing the gouge up on end rather than using the belly with the heel ground off, which was the first workaround I encountered back when, means that you're supporting the gouge, not the rest. It bumps a bit, you lift a bit, and if you overcompensate, it's a "catch." Another thing you'll hear a lot of is to cut above centerline inside. This means that wood, and disaster is right up close to the nose of the tool. Cut below center, and the compensation finds air for a distance that's hopefully enough to avoid the catch.

I just opt out, use the gouge that gives the same edge presentation with close support from the rest, not me. Plus, I give it a bit of skew so the initial edge contact near the bottom of the gouge curve cuts as close to directly across as possible. No broad shavings on finishing cuts, and certainly no chips!

Edit : On end grain versus mixed (faceplate) orientation, a hook or ring tool can be used as a gouge at 90 degrees to the stick, using the same principle.

 

[rsser]

Some other things you can try Jake:

Sort out the vibration prob. A smooth cut is a clean cut.

Get your tool rest as close as poss to the wood; overhang tends to create chatter which doesn't produce a clean cut.

Take smaller cuts, pref with a small gouge freshly sharpened. Hog out with a big gouge by all means but make your last few passes light ones.

Play around with different gouge presentations; see if you can get the cutting edge at a smaller angle than 90 degrees to the travel of the wood.

Good luck.

 

[Mark Warden]

Hi Jake if you have that much play in your spindle your bearings are probably shot.It's not that hard to change them and if you have a bearing shop locally you can get them alto cheaper than going to the manufacturer.My other suggestion would be get Bill Grumbines bowl basics video he shows a couple shear scraping techniques that help a great deal with tearout when I get it right I can start sanding at 180 grit. This is his website http://www.wonderfulwood.com/

 

[Joe Greiner]

I've had best results, even though not perfect, in cutting end grain in a somewhat slicing mode, like cutting celery stalks (very fibrous, like wood), or tomatoes, on a vegetable cutting board. Same with cutting end grain with hand chisels on a bias - called a "paring cut" if I recall correctly, and more side movement than direct.

Most of us, while learning to shave, discovered that a slight bias helps to sever the whiskers better too. Try it; you might like it. Except for you, Ern.

Cheers,
Joe

 

[MichaelMouse]

Bearings may or may not be bad, you imply it's a runout problem shaking your headstock. Rattle the spindle or listen/touch test for bearings. Bad ones have slop, make noise or excessive heat. Then get the speed DOWN and get the energy out of the system so you don't shake things as bad, regardless.

Joe's "bias" is the skew angle the article and I mentioned. The great thing on a lathe is the motor brings the wood to the tool to be sliced.

Sanding in reverse merely lifts what was pushed down and pushes down what was lifted when you were going the other way. Use water to stand everything up and hand sand uphill/upgrain to defuzz.

 

[Jake Truxal]

I think the bearings are ok, the headstock does not seem to be 100% stable, I can just smack it with my hand while the lathe is not running and it will vibrate a bit. My lathe is in the corner of the shop, I've considered just jamming a lennth of 2X4 between the wall and the headstock but was concerned that might throw the spindle off center if the 2X4 is too tight and cause more runout.

I did come across a video on ehow last night which maybe illustrates how you guys were trying to tell me to how to try using the scraper. I currently use the scraper sitting flat on the toolrest, in the video she only had the bottom edge of the scraper on the tool rest and was holding it on a 45 degree angle

http://www.ehow.com/video_4943916_woodturning-finishing-cut-bowl.html

is this what you guys were trying to tell me to do?

the other thing I picked up from this video, is she puts a new burr on the scraper by running the diamond hone up the cutting surface, somewhere along the line ( I have to go back and watch but I'm pretty sure it was in my Roberty Sorby video) they said to run the hone across the flat (top) edge of the scraper - which never made sense to me, i always thought that would take the burr off, not create a new one, but I was just doing what I was told...

so I'll give both those things a try today and see if I get a cleaner surface using my scraper that way.

 

[MichaelMouse]

That's what they do with scrapers. Now imagine doing the same or better surface without having to balance the scraper on its edge. This is a demonstration of swinging into an interrupted surface, in this case, a chunk of yellow birch which has been dried and is ready to turn back to round. You even get a bevel to help steady the tool, and you don't have to stand in the throw zone to do it!

http://s108.photobucket.com/albums/n28/MichaelMouse/?action=view&current=Gouge101.flv

Or if you want to pull your "bowl" gouge, it works fine outside. Just not as friendly as the broad radius, which works inside or out.

 

[Jake Truxal]

I've tried the scraper on a 45 degree angle and getting somewhat better results. I tried it first on a cherry bowl with a standard salad bowl shape.

Now I'm trying to smooth a walnut bowl shaped somewhat like this: )_(
This is a "faceplate" bowl with mixed grain. I'm having trouble determining which direction I should be scraping in. I know rule of thumb is cut downhill so does that mean on the outside of the bowl I should be cutting from both the top and bottom edges toward the middle of the side and on the inside from the middle of the side toward the top and bottom ?

 

[MichaelMouse]

Down grain or down hill, which are mostly the same. Makes the answer yes.

http://www.turningtools.co.uk/wtintro/wtintro.html One of the better explanations out there of why. Chapter seven.

 

[Jake Truxal]

Thanks Mike, great reference.
But doesn't figure 7.9 indicate to do the opposite of what I asked? It seems to indicate on the exterior to cut away from the axis of the lathe (from narrowest part of bowl to widest part) and on the inside to cut toward the axis of the lathe. or are there other factors involved here?

I think my diagram is correct for spindle turning?

 

[rsser]

Uphill and downhill is shorthand for cutting or scraping in such a way that the fibres you're severing get the most support from those behind them, and so consent to be cut rather than be chipped out.

So have a look at what direction will give you that.

(And Joe, I think my face would require a York pitch ..)

Added: sometimes with interlocked grain you get a better result with the scraper flat on the rest by the way.

 

[Jake Truxal]

yea, I understand that concept, just not sure how to implement as far as determining which direction is best

 

[MichaelMouse]

You got it right, Jake, but look at the figure, and you'll find the shapes are convex. Yours are concave.

Spindle or faceplate is really the same thing. Every time you round down the end of a spindle you're really turning the outside of a bowl. You cut across and peel down, no matter if the wood comes to the tool in a line or an arc.

 

[Steve Worcester]

The idea is to cut in the direction that give you the grain suporting the direction of the cut.

Lets look at it this way, out side of a bowl, cut little to big, or inside to outside.
Inside of a bowl, cut big to little or outside to inside.
That only works if it is a side grain bowl, or grain perpendicular to the bed.
On an endgrain bowl, with the grain going parallel to the bed, you would have to actually cut the opposite to make sure that the grain beneath is longer the grain you came from.

 

[Jake Truxal]

thanks for the clarification Steve.