Scrapers Use on Bowls

[Chris Barnett]

Need help on how to finish a bowl. Have made my 2nd bowl, and each one has had quite rough surface at the end grain portion of the bowl. I have used just a bowl gouge but seem to get just gouge marks in the finished surface the more I try to smooth the surface. I read that scrapers do well at this task, but am really scared to present a piece of steel firmly on the rest to the bowl since it seems to grab and tears out a chunk each time. Seems that if I use a large heavy scraper and it grabs, the bowl could not help but come apart and pieces fly everywhere.

In a previous thread titled Bowls and Gouges, this comment was made...."held at a 45 degree angle". Does this mean at a 45 degree angle down from the rest towards the bowl? If using a negative rake, this would cause the top edge of the skew to contact the work...correct? Otherwise, how is the scraper correctly presented to the work. Should I have the top of the scraper even with the centerline and then present level or down?

I have used a lightweight scraper with a burr on the upper edge, on pens and obtain a surface that does not need sandpaper; the material coming off the wood is a thin, almost smoke like thread. I get into serious trouble when attempting to do the same on a bowl. I have read about as much as I can find on negative rake scrapers, and believe this could solve the problem, but am still concerned with presentation.

[Robert McGowen]

Hold the scraper about 45 degrees from being flat on the rest. In other words, just the bottom corner of the scraper should be on the rest. It works very well and leaves a smooth surface.

[Chris Burgess]

I use my Bowl Gouge as a scraper to clean that up. Before I start I take it to the grinder and hone it to make sure it is sharp. It is hard to explain how I present it to the piece but I hold the handle down at 45 degrees and also hold the tool at a 45 to the piece. I will present the entire flute to the bowl with BOTH sides/edges touching, then I slowly roll the gouge until only the bottom edge is touching and I get very fine whisps of shavings. This is a very light cut. To much pressure and catch-o-rama. I have also used Round nose scrapers for this but find I like using the gouge much better.

[Paul Heely]

Also keep the cutting edge of the scraper above the center line of the bowl and keep the handle of the scraper slightly higher than the cutting edge. This will help prevent catches.

Paul

[Prashun Patel]

I have best luck with scrapers when 'attacking from above'. With a gouge, I set the tool rest slightly below center of the work piece. With the scraper, I set it higher, and the tip is lower than the tool rest by a smidge. For insides of a bowl, curved scrapers work easiest. Use a really light touch. Think 'blending' not 'cutting'. A very sharp tool will allow you to barely touch the surface and remove little shavings. If you're applying pressure INTO the bowl, something's not right.

I also have success using a bowl gouge in a 'shear scrape' mode. I'm not sure I do it right, so please read up on this lest I'm giving you bad or unsafe or incorrect advice. Basically, for the finishing cut, I sometimes rotate the gouge so the flute is completely parallel to the inside of the bowl and you're basically scraping using the bottom, left wing's edge (instead of the area around the nose). I usually pull instead of push thru this kind of cut, and again, it's just a grazing of the surface to blend.

[Chris Barnett]

Perhaps my problem is that I was keeping the cutting edge below the centerline of the work so that if it did grab, the force would raise the handle, increasing the distance of edge to bowl and not pull the tool into the work; this is what I understood from previous information on correct presentation. But if the tool handle was inadvertently lowered, the lever action would push the tool directly into the work. And is this suggestion for a plain scraper edge, or what is called a negative rake edge?

[Prashun Patel]

Others with more experience will comment about all those angles and levers. But I forgot to mention that the other key to scraper success (for me) is to keep the scraper CLOSE to the bowl to prevent catches. If yr using a straight tool rest, then this could mean you have a lot of distance at the middle of the bowl's inside surface. So, you end up being at the highest risk of a catch at the very place that you probably need the most smoothing!

[Jim Burr]

Tool presentation depends on the cut desired. A scrap cut must be done with the handle slightly up as taught by Nish, Raffin and Mahoney. If you think about the anatomy of the cutting surface on a scraper, the burr is on the top surface...not on the face. Since the burr is the "cutting surface" it must be presented to the wood. The only way for this to happen is to elevate the handle so the burr is in contact with the wood. If what you want is a shear cut with the scraper, this is done with the tool at a 45 angle to the horizontal plane of the tool rest and the handle in more of a gouge position....like Bill Grumbine teaches...45 and 45. Hope that helps

[Faust M. Ruggiero]

Chris,
I am sure Jim wasn't telling you to hold the handle at 45 degrees down as Grumbine suggests holding a bowl gouge. You want your tool rest a bit high and the handle higher than the cutting edge. When you get a scraper, it is a good idea to grind away the sharp edge that lays on the tool rest when holding the blade at a 45 degree angle to the work. That will help it slide along the tool rest and keep the long edge from making rough spots on the tool rest. The trick is to touch the scraper very lightly to the work and not to allow too much of the scraper's edge to come in contact with the work. Think of it as caressing or stroking the bowl with the scraper. A heavy hand will cause the tool to grab and do a lot of damage. Holding the tool's edge at an angle to the bowl sets up a shear scrape that gives a better surface. Spend a few bucks and buy Richard Raffan's DVD on Bowl turning. He shows how to safely use the scraper. His video will teach you more than all the words we well meaning turners possibly write.
faust

[Chris Barnett]

OK, thanks alot guys. Think I might have an idea of what you are saying, and it's rather similar to my last comment which I was understanding then was wrong; so for a scraper, let me reiterate (understand the suggested use of the bowl gouge as scraper best!).
(1) Hold rear of tool up (45 degrees, too much?) (2) maintain mimimal distance between rest and work surface, (3) approach work at an angle (45 degrees) from the axis of tool travel, if I understand correctly. (3) Keep the cutting edge above the centerline of the bowl? Seems if I do this, any catch would cause the tool to bite into the wood since the radius at the working point would be increasing. Am I understanding that this is what should be done? Seems this is what I was doing when I tore chunks out of the bowl.
I tried to watch scraper use on YouTube but gal doing the demo was constantly, constantly in the way of the camera...really worthless but could have been what I needed to see. Did I mention she did not make a good window! Oh well, YouTube is worth every penny of what we pay for it :). My class on bowl turning was about as useful.

[Prashun Patel]

I think 45 degrees is unnecessary for a scraper. Try it that way, and then try it at a shallower approach. Again, the key is a light touch and a sharp tool. As for catching, in fact if you have your tool tip below the handle, then if you catch, the distance from the catch point to the tool rest will INCREASE as the piece rotates downward- not decrease like with a gouge coming in from underneath). If the dist increases, your scraper tip will fall away from the piece - unless you white knuckle the butt of the handle, which will prevent the scraper from levering safely away.

[Jim Burr]

Chris,
I am sure Jim wasn't telling you to hold the handle at 45 degrees down as Grumbine suggests holding a bowl gouge. You want your tool rest a bit high and the handle higher than the cutting edge. When you get a scraper, it is a good idea to grind away the sharp edge that lays on the tool rest when holding the blade at a 45 degree angle to the work. That will help it slide along the tool rest and keep the long edge from making rough spots on the tool rest. The trick is to touch the scraper very lightly to the work and not to allow too much of the scraper's edge to come in contact with the work. Think of it as caressing or stroking the bowl with the scraper. A heavy hand will cause the tool to grab and do a lot of damage. Holding the tool's edge at an angle to the bowl sets up a shear scrape that gives a better surface. Spend a few bucks and buy Richard Raffan's DVD on Bowl turning. He shows how to safely use the scraper. His video will teach you more than all the words we well meaning turners possibly write.
faust

Respectfully, I'd have to call you on that one Faust. Several scraper shapes...moving away from the norm to say a spear point or a single side are indeed taught that way by professional turning schools. Several video segments by professional/production turners bear this out...so yes...I did mean exactly that. Now is it easy? No it is not, like many other techniques it requires much practice. Some of the best turners I know have yet to get it right and still use the more traditional methods of scraper technique.

[Faust M. Ruggiero]

Thanks for the correction, Jim. I believe Chris was referring to a straight or inside bowl gouge as versus a spear point or Jacobs style scraper. With those in mind, you surely are correct.
faust

[Chris Barnett]

Still have one important question/problem. The handle is held higher than the cutting edge, ok, can do. But if the cutting edge is above the centerline of the work, if a catch occurs, the cutting edge will rotate down with the work, and that point on the work will get closer to the rest, and thus me, and since I am relatively fixed and large, the cutting edge will press into the work, unless, the centerline of the tool passes through, or below, the axis of rotation of the bowl. This would require that the rest be placed higher than is done for a gouge.

It seems safest to me to have the handle higher than the cutting edge, and make the contact below the centerline of the work. I can see that becoming quite difficult when scraping on a curve bowl surface even with a curved rest. On the bottom flat surface on the inside of a bowl, or the side with a bowl scraper seems quite easy, but on the outside curved surface, well, have never seen a concave curve scraper for the outside. I have watched numerous videos, but think I need to see the process in action, close up. Afraid I am getting too tedious about all this and expecting too much help from you guys.
Many thanks.

[Jon Nuckles]

Chris, If you are scraping above the center line of the work and the rest is higher than the nose of the tool, as it should be when you are scraping on the inside of a bowl, if you get a catch the point of the tool will go down and out of the wood. With this configuration, the center of the bowl is farther from the tool rest than where you are cutting. When you are scraping the outside of a piece, keep the tool rest above the nose of the tool and cut below the centerline. Again, in the event of a catch the tool will drop down and out of the cut.

[Prashun Patel]

"the cutting edge will rotate down with the work, and that point on the work will get closer to the rest".

I believe the flaw in yr reasoning is here. The tool rest would actually be above the tip by a smidge.

[Russell Neyman]

Turning is like sailing a boat. You need a basic understanding of what you're doing, but in the end, you need to try different things and pay attention to the results. Then, adjust. Do what works and don't do what doesn't work as well. Try taking smaller "bites" of the endgrain until you find out what works with that particular piece of wood.

[Paul Heely]

Chris, are you trying to scrape the inside or outside of the bowl?



Paul

[Thom Sturgill]

While I have nothing against scrapers and do use one, perhaps a change in the grind of the OPs bowl gouge would be helpful. It sounds like he's getting pressure ridges from the heel of the gouge. Mike Mahoney shows a grind where the heel is cut back to help eliminate that. Add a final sharpening and HONING to the mix and he might find that while scraping does have its place, learning to use a scraper is not as important for most work.

[Scott Hackler]

I use my giant inside bowl scraper on almost every bowl that I have turned. I like the ability of the scaper to create a very smooth inside bowl curvature. I will oftent present the tool to the exact center of the inside and while keeping the tool flat and stationary on the tool rest, rotate the handle away from me. For me, this technique helps smooth out the bottom area where I always struggle to get a real smooth curve.

Now there are a few 100% need to do things in woodturning and raising the toolrest high enough to present a scraper at or above the center line ......while the handle is UP....is a must. Not just for a good cut, but for safety reasons. Below center causes problems because a slight or major catch, of course, will force the scraper down. If you already below center, the wood below the tool is closer to the tool rest and that catch will force the situation into a very BAD second....or third catch within a fraction of a second.

Now raising the cutting surface just above the center line and having the tool already tilted up at the handle will not force the tool into wood closer to the tool rest. Instead, the tool will be immediately in "air" not wood in the event of a catch.

Now technique is everything when presenting a scraper, expecially a large scraper with a large cutting surface. A nice, NEW, burr and a light touch will not only provide a nice surface but help to keep the catches at bay.

The "above center" is used everyday in hollowing setups and most HHS hollowers are small scrapers. Try hollowing below center and you will quickly see how catchy and hard it is to do. Most it to center or slightly above and like magic....it works and will be less catchy.

[Fred Belknap]

I pretty much have to agree with Scott. It seems like using a bowl gouge is kind of traditional, and I do use one a lot but mostly on the outside of a bowl. I use one on the inside till the curvature of the bowl forces the tool to be around 2" from the rest. I then go to a scraper, I have a Henry Taylor round nose 1" wide that I like a lot. When it is sharp it will cut as good as the gouge. I do lower the tool rest below center to cut out the bottom nub. To finish a bowl on the inside I use the same scraper but I use a diamond sharpener and put a small bevel, mayby 10° on the top of the same tool, works for me.

[Chris Barnett]

Trying to do both, inside on the lower portion, and the outside as well. Have been done then think, it could be smoother, or thinner, then the start over with same ending. Even with one continuous pass to the center, the bottom is not smooth, but have very shallow grooves in the bottom that I am trying to remove (I am on track to solving this,...later). Each attempt to use a scraper has resulted in a catch, that I why I am persevering on this...to learn to use the scraper properly. Just want to make absolutely sure that I have the rest at correct height and the tool approach to the work is correct. I used a modified scraper at a class (with no catches) so intend to grind a relief in the top edge to make the burr somewhere between the top and bottom surface. Seems inherently safe from catches....but if it can be done.....

[Ted Calver]

Chris, do a search for 'negative rake scraper'...might be what you are talking about. I have a couple of scrapers ground this way and they do a good job on cleaning up the bottom of bowls. They do require a burr to be effective and will cause you to do a lot of refreshing on the grinder.

[Jake Helmboldt]

Chris, I'll reiterate the suggestion that you get a copy of Richard Raffan's Turning Wood video. He covers scrapers well.

As others have noted, the key elements are:
handel slightly higher than cutting edge (10-15 degrees or so
cutting edge relative to centerline - inside a bowl higer, outside a bowl, lower. You can't get much of a catch that way. In either case the cutting edge drops away into open space
You can use a scraper flat on the rest, but more for shaping cuts and NOT at the last ~1/3 of the bowl and rim
Shear scraping is when the scraper is on edge at ~45 degrees. That means you roll the handle towards you, lifting the flat scraper onto it edge/corner and lightly pull the edge across the bowl surface in a smooth, continuous motion with a light touch. As someone else called it, you are stroking the surface.
You need a rounded or domed scraper for the inside but can use a variety on the outside

try searching on youtube for "shear scraping"

Here is one on basic scraping, but not the shear cut: http://www.youtube.com/watch?v=H5lTdKpDw8I&feature=relmfu

this shows shear scraping with a Sorby tool. It isn't a traditional scraper, but the cutting edge orientation is still the same. http://www.youtube.com/watch?v=12VNruwwpjI&feature=related

[Wally Dickerman]

Chris, there seems to be some confusion in your questions and in some of the replies. Scraping and shear scraping are not the same. When someone says hold the tool at a 45 deg. angle they are refering to shear scraping. I think that what you want to know and are having a problem with is regular scraping. For sucessful use of the scraper there a few musts...

The tool must be sharp, with a burr.

When turning a bowl that is side grain and not end grain, when scraping on the outside of a bowl, scrape just below center with the handle pointing slightly up. When scraping the inside of a bowl, scrape on or just above center, again with the handle slightly up. (The blade is always pointing slightly down in scraping)

Just as when using a cutting tool, for best results, cut with the grain. With some woods, especially soft woods this can make a huge difference in the surface you get.

On the inside of the bowl, starting at the rim, work your way down to the finished surface an inch or two at a time. Always be cutting toward heavy wood.

Never cut the wood thin in the inside bottom area then try to go back to the rim area. The wood will vibrate and will result in a sure catch, damaging and sometimes breaking the bowl. In beginning bowl classes I always have the students completely finish the first couple of inches of the rim area, including sanding. Then never go back, either inside or outside. Wood vibration is your enemy and will always result in a bad surface or a damaged bowl.

You mention negative rake scrapers. They work best in very hard wood. usually not well in softer wood. To work well they must have a burr. They must be used with a very light touch. The tool should be level. I suggest that you forget neg. rake for the present. They are a special use tool.

[Chris Barnett]

Let me say thanks, again, one more time, and perhaps again later. Using a new round nose from PSI (only $20 to play with) ground a relief on the top edge, which promptly destroyed the beautiful burr that was there, then ground the lower part in reverse to create a burr on the new edge between the upper and lower surfaces. Although I know what a burr is and feels like, I tried it anyway, and the only time I saw any shavings was when the upper edge briefly contacted the work. Have tried three times now to get a burr on the center edge and each time is a failure, I will not despair, for I have at least 4 inches left of grindable tool length remaining :).

I will comment that the contact point was above the work axis of rotation, and the tool rest was above the center by about 1/4 inch (rest post length limited, will weld on length later) and the tool end was lower than the handle (see, your help was not lost on deaf ears). As I said, no burr, thus no scraping, but I think I may have invented the catchless tool grind.....the failure to cut to be resolved later:D. But during the slight cutting with the top edge, control seemed to be much better than previous tries.....I see the light at the end of the tunnel.

I now need to search the creation of burrs ....slight brain cloud....for a moment thought of Arron :D so shame on me. No rocket science, and have done dozens of times, on tools, chisels and knives, but for some reason, it fails to happen. Maybe, it is something about the .....$20 :o.

All my friends out there, have a safe holiday.

[Chris Barnett]

Ground the negative rake back to standard edge and it works fine, and better than the thicker, unwieldy Sorbys; tool produces just thin ribbon shavings and cleans up the grooves great; holding just above centerline with rest just above center of bowls. Have given up on negative rake experiment for now.

[Reed Gray]

Sorry to have missed this one, I was on vacation.

Scrapers: NEVER use a scraper flat on the tool rest for finish cuts for a bowl, especially if the bowl has been hollowed out. A scraping cut, with the cutting edge 90 degrees to the rotation of the wood puts more stress on the wood, and tends to pull the fiber out before it actually cuts. It makes a super roughing cut for heavy stock removal. If you try to use a scraping cut for finish cuts, it will start the bowl walls oscillating or flexing, there will be some screeching and howling sounds, then at best you get skipping dig in marks in your bowl, and at worst, your bowl explodes. You 'can' get away with it with a smaller bowl but never on larger bowls. It will always leave a rougher surface than a shear type cut.

A shear cut with a scraper, works very well as a finish cut. This is a cut with the scraper up on its edge at about a 45 degree angle or even higher. The advantage here is the 'shear' angle. Think of it like a speed bump in the parking lot. If you hit it straight on, you get a big bump (scraping cut). If you hit it at a 45 degree angle, you still get a bump, but it is much more gentle (shear cut). It actually is better at getting under the fiber and slicing it before you pull it out (tear out). Considering that gouges and scrapers are made from the same steel, and sharpened on the same grinders and hones, you should be able to get the same finished surface, if you know how to use the tools. There is no cut that you can do with the small tear dropped type scraper tips that you can not do with a standard scraper.

For finish shear cuts with a scraper, on the inside of a bowl, I pull it towards the rim. This is a very gentle cut, and I stabilize the rim with my left hand on the outside edge. ROUND OVER THE RIMS BEFORE DOING THIS AS A SQUARE/SHARP EDGE WILL SLICE YOU TO THE BONE BEFORE YOU CAN SAY SHEAR SCRAPE! Hand pressure = tool pressure. It will take a couple of passes to remove tool marks, you can not get it all done in one pass. Work down in stages from the rim to the bottom, blending in start and stop points. Wood will move no matter how dry it is. Part of this is because of how the tools cut through end grain and side grain. Also because the wood 'adjusts' to having stock removed. Pretty much the same thing on the outside of the bowl, except if you haven't hollowed out the inside, you will not get wall vibration. I use pull cuts with the scraper on the outside of the bowl as well, and pull them from base to the rim.

Another safety point here is to work on the lower half of the scraper, which is the part that is resting on the tool rest. If you work above the center line of the tool, the tool is not balanced, and it can catch and rotate down into your tool rest, slam, bang, explosion, broken tool rest, etc. This is where dropping the handle slightly helps. You can not use the upper half/above center line part of the tool.

Negative rake scrapers don't work well here. It is still a scraping cut. They do better on really hard woods. They also do better on end grain bowls and forms. Standard scraper cuts work well on end grain for finish cuts as well, but I have found I get better cuts with a shear angle rather than with a scraping angle.

For handle holding angles, always keep it at least level, and preferably angled a bit down. Ever play with a ceiling fan? I am not recommending you do this, but some times I just have to. If you point your finger into/opposite the direction the fan spins, you can get severely jammed fingers. If you point your finger with the way the blades spin, it ticks, and bends out of the way, kind of like putting playing cards on your bicycle wheels with cloths pins. If you angle the handle down slightly, you are pointing away from the spin, and the cutting edge will fall out of the wood rather than dig in deeper. On the outside of the bowl, I work at center height or slightly below, and on the inside, I work at center height or slightly above.

robo hippy