Eliminating tool marks in bowls

[Chuck Marsh]

I have been turning bowls for about 10 years now and I still cannot eliminate tool marks on the inside of my bowls where the grain is 90 degrees to the bowl (2 places). My tools are nice and sharp. I have tried everything from shear scraping to sanding the heck out of it and I still have tool marks and the surface is rough. Sometimes I get lucky and the inside surface comes out smooth but 75 percent of the time I have tool marks. Also, is there a filler I can apply on the tool marks to make it feel smoother? Would applying sanding sealer before I add my finish help? I would be open to any advice or suggestions. Thanks.

Chuck Marsh

 

[John Torchick]

Can't help but am going to monitor the answers.

 

[Dennis J Gooding]

I have been turning bowls for about 10 years now and I still cannot eliminate tool marks on the inside of my bowls where the grain is 90 degrees to the bowl (2 places). My tools are nice and sharp. I have tried everything from shear scraping to sanding the heck out of it and I still have tool marks and the surface is rough. Sometimes I get lucky and the inside surface comes out smooth but 75 percent of the time I have tool marks. Also, is there a filler I can apply on the tool marks to make it feel smoother? Would applying sanding sealer before I add my finish help? I would be open to any advice or suggestions. Thanks.

Chuck Marsh

Are these burnish marks or are they tear-out?

 

[hockenbery]

I run across people in similar situations who have turned a long time and developed Poor habits that limit the success they have in getting a smooth surface. A day practicing good technique puts a big smile on their face.

The tools used, how they are ground, how they are presented to wood, and body movement all affect the quality of the surface. Shape of the bowl, size, wood quality, and wall thickness affects how easy it is to get a clean surface. Vibration affects how clean a cut you can get.


common causes for tool marks and tearout
not holding the tool handle against your side.
Not riding the bevel
Too big a cut
Getting the bowl wall too thin near the bottom before finishing the wall closer to the rim.
Improperly shaped gouge.
Not grinding the heel off the gouge
Punky wood

also if you can’t sand it out you might want to consider your sanding technique


I can’t “see whatever you are doing wrong from here”
I can show you how I get a smooth surface using the Ellsworth ground gouge and a small bowl gouge to smooth the wall near the rim. If you have time to look at the video compare what I do to what you do.

View: https://www.youtube.com/watch?v=sCZWsHB4vlM


Let me know where you are doing things differently. May be able to offer a correction.

 

[Davis Stevenson]

Are the trouble spots in an area with a decently tight curve? I have a 1/2" (American Size) bowl gouge with a 50ish degree grind and the bevel ground off for the last few (light) passes while hollowing, which has really kept the tool marks/burnishing at bay. Feels like a precision surgical tool compared to the blunt rock feeling of the 5/8" gouge with the heel intact. My burnishing problems and sanding time decreased significantly when I downsized and ground the heel off... I do have to be much more mindful of the toolrest, though, as the smaller gouge can't take more than an inch of overhang, which can happen easily if you end up significantly less than perpendicular to the tool rest top.

 

[Mike Brazeau]

I have never had anything that sandpaper could not fix. If really bad static power sand with maybe 150 or 180 followed by sanding with the work rotating. Sometimes I apply Clapham's Sanding and Cutting lubricant and then a scraper. Lately I ground a one inch scraper with a negative rake profile. Totally amazing performance. Wisps of shavings you can almost see through and no tearout. Have a couple of P&N gouges ground with bottom feeder profile too, but now the NRS is tops in my charts.

 

[Richard Coers]

I'm going to give you some tips on tear-out. Hard to imagine only getting tool marks in two spots. You didn't tell us if this is mostly wet wood or dried, spalted or sound wood. Also no mention of tools used except for the shear scrape comment. So more information would eliminate a lot of guessing. Some people either use a wipe down with a damp cloth, or sanding sealer to change the cutting characteristics of the wood fiber for the last couple cuts. Personally, I'm a huge fan of the Hannes grind on my bowl gouges. A quick pass on the grinder for the final cut and I can slide the gouge down the wall to take an incredibly thin cut at a very high shear angle portion of the tool. Always amazed at how far that grind will let you cut on the side of the bevel. Often a smaller gouge will pull a finer curl and also reduced tear out. Also a quick wipe with a damp cloth before sanding helps. It swells the fibers and when dry, the sandpaper cuts the fibers more easily. You didn't mention if you are power sanding or hand sanding. You can lock the spindle and only power sand on the two torn spots, then run the lathe slowly and power sand to blend it all together.

 

[musky]

Have to say some of the same things as others.I grind the heel back so that you only have about a 1/8" of bevel, and grind a fresh edge more often than you think you need to. Take your final cut with very little bevel pressure. If your tool is sharp, it will virtually cut on it's own. Some turners like a large gouge, but my preferance for the final cuts on the inside of bowls and such, is for a 1/4" gouge for the outer rim area, and in, to about 1 1/2', and a 3/8" for the rest. I do use my 1/2" bottoming gouge alot for deeper bowls and vases, and sharper transitions. The bevel on my bottoming gouge is only about a 1/16" wide, and gives an extremely fine and smooth cut. As most of the walls on my turnings are 1/8" or less, I am not able to make one final pass over the whole inside, but will step it in as I gradually core it out, as I want the outer rim to be even. If the heel of your tool is not ground back enough, sharp edge or not, it's probably not on the bevel at the edge when making the turn, and would explain why you have tearout. I feel this is one reason why I get such great results from my bottoming gouge, as my bevel on it is apx 1/16" at the most.

 

[Donovan Bailey]

Agree with most/some of what's said above, however, I pass along a couple of tips definitely worth trying. 1) We have all heard the term "ride the bevel" over and over...but the fact is that you get beautiful tool marks if you "ride the bevel." This gets fixed by "floating" the tool (with a light touch) over the surface to be cut. Give it a little practice and see the difference. 2) the grain orientation says don't use a pull cut on the inside of a bowl...use a push cut. Give both of these tips a try and let us know if they work for you.

 

[Bill Blasic]

I use the hat makers grind on all my V gouges but even with that I sometimes get a real difficult piece of wood and have trouble through the transition area of the bowl (going from side to bottom). This is the only time that I ever use a U shape gouge. I take a Thompson 3/8 U gouge and grind the tip to about an 85 degree bevel, this slices through that transition area and gives a super clean cut.

 

[Roger Wiegand]

I just had a lesson that helped a lot with chatter and tearout in the unsupported end grain patches in my bowls. Three things made a huge difference:
1) Sharp, sharp, sharp tools. Honing the edge of my gouge with a diamond hone made a big improvement. Pick the general grind shape that works well for you, I doubt it makes much difference. Grinding off the trailing heel can help, honing it so that it doesn't have a sharp edge dragging on your freshly cut wood certainly does.
2) Downward pressure on the toolrest. I wasn't pushing down hard enough to anchor the gouge securely, allowing chatter to start (and once you have it it's really hard to get rid of.)
3) switching to a burnished burr on my scrapers for final shear scraping cuts. The burr off the grinder was way too big and too ragged to make a clean final pass. Honing the edge, then honing the flat on top, raising a burr you can barely feel using a carbide burnisher in one light pass greatly improved the performance of my scraper. (a burnished larger burr also works better and lasts longer when you want a more aggressive cut)

I went from needing to start at 60 grit and spending way too much time (and ending up with lumpy interiors from over-sanding) to starting at 120-150 grit for less than a minute with a power sander to bump off remaining ridges As my technique improves with practice I expect to continue to improve-- sanding a whole bowl down to the bottom of the tearout is really hard vs sanding off small ridges.

 

[Donovan Bailey]

The marks that pester me are those little/fine disgusting concentric circles that end up in the bottom of a bowl that you can't see until sunlight hits the vessel during the finishing process. I can't stand those things...and I have not found a nifty shortcut as a fix.

 

[John Torchick]

Far from an expert here, but it occurred to me- are you moving the tool too fast? I found this to be my situation when turning synthetic materials for pens. I slowed my movement on the blank and the spirals went away. Just a thought.

 

[hockenbery]

The marks that pester me are those little/fine disgusting concentric circles that end up in the bottom of a bowl that you can't see until sunlight hits the vessel during the finishing process. I can't stand those things...and I have not found a nifty shortcut as a fix.

Those are almost always caused by not riding the bevel. When you come off the bevel the tip of the gouge wants to cut deeper. The brain corrects the cut. In the worst cases you get a washboard affect. When you aren’t on bad little lines.

Another cause is lots of transition cuts from many short cuts that are not restarted to cut away the transient line.

also these markers can usually be cleaned up with a round nosed scraper.

 

[robo hippy]

Sounds like most of what you have is tear out. There are many solutions, and more than anything, they depend on the wood. Grinding off at least half of the heel of the gouge is one good starting place for the inside of the bowl, but that is more for tool control. Sharpness is another factor, but a fresh edge for any finish cut. For most of what you cut, a 180 grit sharpening is sufficient. For some softer woods, a 600 grit grind will work best. For some, a shear scrape, and I prefer a burnished burr to the grinder burr. I never use a scraper for the finish cut in a bowl when trying to clean up tear out on the walls of a bowl as it tends to pull the fibers rather than cut. Only exception to this is with very hard woods like sugar maple, and with the burr honed off, and you want angle hair shavings. The negative rake scraper can work, but it is better in harder woods than in softer woods. A standard or NRS works for across the bottom, but once you get into the transition area, it tends to tear. On really bad tear out, some times lubricating the wood with water or oil, then taking very light cuts to remove the wet wood helps. It can take more than one application. When all else fails, the 80 grit gouge works. Make sure to get out all tear out before stepping up to the next grit. Close does not work, check by feeling the wood.

"The bevel should rub the wood, but the wood should not know it." No idea who said that.....

robo hippy

 

[Chuck Marsh]

These are all great suggestions. It is going to take me a couple of days to digest all of this and choose what route to take. I will let you know what works for me.

Chuck Marsh

 

[Keith Tompkins]

I have been turning bowls for about 10 years now and I still cannot eliminate tool marks on the inside of my bowls where the grain is 90 degrees to the bowl (2 places). My tools are nice and sharp. I have tried everything from shear scraping to sanding the heck out of it and I still have tool marks and the surface is rough. Sometimes I get lucky and the inside surface comes out smooth but 75 percent of the time I have tool marks. Also, is there a filler I can apply on the tool marks to make it feel smoother? Would applying sanding sealer before I add my finish help? I would be open to any advice or suggestions. Thanks.

Chuck Marsh

Chuck, without seeing your bowls, it could be the “transition” from the sides to the bottom. If so eliminate the transition and go for a continuous curve.