How to deal with tearout?

[Steve Mathews]

Aside from better technique, sharper tool, etc. what can I do to remove tearout? The bowl that I'm working on is most likely Magnolia wood. For some reason I get a significant amount of tearout on the outside but hardly any on the inside. The bowl is almost finished so I can't cut into it much more. I applied a coat of 50/50 shellac thinking it might stabilize the wood fibers. Is there anything that can be done to treat the tearouts and finish the bowl without it being noticed?

[John K Jordan]

Aside from better technique, sharper tool, etc. what can I do to remove tearout? The bowl that I'm working on is most likely Magnolia wood. For some reason I get a significant amount of tearout on the outside but hardly any on the inside. The bowl is almost finished so I can't cut into it much more. I applied a coat of 50/50 shellac thinking it might stabilize the wood fibers. Is there anything that can be done to treat the tearouts and finish the bowl without it being noticed?

You already discounted the two most important things, razor sharp tools and technique. As for technique, the lighter the cut the better - I've heard these referred to as "whisper" cuts. Another thing about technique, experts recommend becoming proficient at spindle turning before starting on turning bowls. Spindle turning is proven to teach the fine tool control that will let you turn anything. The opposite doesn't work the same way.

You already mentioned some shellac sanding sealer to help hold the fibers together. Sometimes I have to use that several times with gentle cuts between coats. Sometimes for terrible wood I resort to soaking with thin CA glue. This will stain the work unless a) it's applied all over, or b) it is wiped on with the grain/figure.

Two ways to take out existing tearout. One is a good negative rake scraper with a good burnished burr. I do this for every piece, tearout or not. The second is scraping with hand scrapers with the lathe off. I scrape in the "downhill" direction. It is amazing not only at removing tearout but for removing divots, humps, and wavy concentric rings left by the turning. A bonus of hand scraping is it eliminates power sanding with rotating disks and generally lets me start with 320 or 400 paper or sometimes even finer.

I used both methods on these two turnings and most other turnings, although there was no tearout on these.

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Some things need smaller hand scrapers.

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If you are left with a small amount of tearount, John Lucas taught me a trick for hiding it that works very well. Take a small piece of coarse sandpaper (I use 220 or 320) and apply a few drops of thin CA glue to the paper. Then wet sand the tearout with CA glue. This creates fine sawdust coated with CA that gets pushed into the little tearout voids and fills them. Since it is using wood directly next to the voids it can leave an invisible repair. Might not be good for massive tearout, I don't know. If I get a perticularly obnoxious piece of wood that tears out regardless of my tool and technique, unless it is something special with sentimental value I tend to throw the wood away and start over with some good wood. Soft, punky wood is like that.

JKJ

[Steve Mathews]

John - Thanks for the ideas on dealing with tearout. I completely forgot about the sanding with CA glue trick. Tried it before and it worked very well. Since I already started using sanding sealer maybe using that with the saw dust will work. The suggestion on using a card scraper was even better as it also tackles another problem I was having with the bowl, humps or wavy rings. Before trying either method I may go back and do some whisper cuts as you call them with a scraping gouge. I don't have a negative rake scraper although maybe a skew gouge will work.

[John K Jordan]

... I don't have a negative rake scraper although maybe a skew gouge will work.

A skew should work on the outside if the curves are not concave anywhere. I make NRS like this and use them for almost everything.

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[John K Jordan]

A skew should work on the outside if the curves are not concave anywhere. I make NRS like this and use them for almost everything.

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These are Thompson steel, ground, the grinding burr removed with a diamond hone, then a cutting burr raised with a burnisher.

JKJ

[Steve Mathews]

A skew should work on the outside if the curves are not concave anywhere. I make NRS like this and use them for almost everything.

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I never used a NGS. It doesn't seem logical that the shape or orientation of the cutting edge would be effective. I also haven't tried the 40/40 grind bowl gouge either so I plan to put both on my shopping list.

[Steve Mathews]

A skew should work on the outside if the curves are not concave anywhere. I make NRS like this and use them for almost everything.

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I never used a NGS. It doesn't seem logical that the shape or orientation of the cutting edge would be effective. I also haven't tried the 40/40 grind bowl gouge either so I plan to put both on my shopping list.

What's the purpose of the T shown in the first photo? Top to differentiate between a normal scraper?

[John K Jordan]

I never used a NGS. It doesn't seem logical that the shape or orientation of the cutting edge would be effective. I also haven't tried the 40/40 grind bowl gouge either so I plan to put both on my shopping list.

What's the purpose of the T shown in the first photo? Top to differentiate between a normal scraper?

BTW, they are NRS (negative rake scrapers) not NGS.

It is logical after you understand the shape and the burr and especially after you used them a while.

Unlike shear scraping with a bowl or spindle gouge, these are held perfectly horizontal and flat on the tool rest. Do NOT raise or lower the handle from horizontal. Do not tilt the scraper. There must be a burr on the edge. As mentioned, some people rely on the burr from the grinder (you can easily feel it with your finger), however that burr is ragged and fragile and doesn't last very long. A burr properly raised with a burnisher is a smooth, razor-sharp cutting edge that lasts much longer.

Negative rake scrapers have a few advantages:
- they are almost impossible to catch.
- they are capable of removing extremely fine shavings.
- used properly there should not be tearout.

The shape shown is my own design. Lots of turners make and sell these but all I've seen are rounded over instead of having a flat on the end. I find the flat perfect for removing tool marks areas on platters that are very shallow curves, even when "turning air" on pieces with wings as in the first photo. The second one is being used on a concave surface.

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Negative rake scrapers will only cut with one side up, the side with the burr. I grind mine so the bevels are equal on both sides (I ground these to 60-deg included angle - anything less than 90-deg should work) then burnish a burr on one side or the other, depending on how I want to use it. I put a "T" on one side to show it is currently the TOP side. I generally have several ground alike, some left and and some right.

Two shown in the earlier photo are burnished one way and one the other. Two are ground from Thompson scraper stock, one I ground from a spare skew chisel.

I also use a number of other NRS in a variety of sizes and grinds. After becoming proficient with these (very easy) I use them on almost every turning. I also use the hand scrapers on nearly every turning.

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A small scraper will leave a glass-like surface on the end grain of fine-grained wood like holly, dogwood, ebony, etc., such as when working on the lid or base of a lidded box.

This is a burnisher, made from a small diameter carbide rod. I use the same burnisher, or another somewhat similar, on hand scrapers I grind from card scrapers.

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The 1/8" thick Stew-Mac scrapers shown at the left in an earlier photo work without a burr.

The hand scrapers are the real trick. I've been preaching them for many years but only in the last few years have people begun to show an interest, often after seeing and feeling the surface I get without sanding.

JKJ

[Mike Nathal]

If I recall correctly Stuart Batty states that NRS may not work that well on soft woods. The only Magnolia I ever turned was quite soft.

[Dave Fritz]

John, it looks like you've sharpened both ends of your scrapers, is that correct? I assume then you use them without handles? Very interesting.

[John K Jordan]

If I recall correctly Stuart Batty states that NRS may not work that well on soft woods. The only Magnolia I ever turned was quite soft.

Although I disagree with some things Stuart says, he is right if he said "may not". I'm glad he didn't say "will not."

I've used them on many soft woods including basswood, yellow poplar, and eastern red cedar, as well as on punky woods when stabilized a bit with lacquer, shellac, or CA glue. Part of the success may depend on the type of burr and the use, of course. With the grinder burr what you get is fixed by the grinder stone and the angle of bevels. A burnished burr can be made to be very delicate or quite aggressive.

From his writings it appears Stuart uses the burr from the grinder: "Negative rake relies on the burr and so the life of the cutting edge is very short and the tool will need to be sharpened a lot. Once the burr has been worn away you must re-sharpen immediately. Life of a negative rake scraper is very short - approx. 15-20 seconds per 3/8 inch wide cutting surface for M2 steel."

The burnished burr can last much longer.

An example in eastern red cedar. With the combination of removing most tool marks with the NRS and smoothing with hand scrapers, the only sandpaper I needed on this piece was 600 grit. (To be clear, this was exceptional, on this type of turning most of the time I start with coarser paper such as 320 or 400.)
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JKJ

[Pat Scott]

Aside from better technique, sharper tool, etc. what can I do to remove tearout? The bowl that I'm working on is most likely Magnolia wood. For some reason I get a significant amount of tearout on the outside but hardly any on the inside. The bowl is almost finished so I can't cut into it much more. I applied a coat of 50/50 shellac thinking it might stabilize the wood fibers. Is there anything that can be done to treat the tearouts and finish the bowl without it being noticed?

If you got tearout on the outside of the bowl why did you finish turning the inside? I would have worked on the outside until all the tearout was gone before going to the inside.

A smaller gouge can help reduce tearout also. Smaller tool = smaller cut. I use a freshly sharpened 3/8" bowl gouge with 45 degree bevel, but if needed I will try a 1/4" bowl gouge with 45 degree bevel. I always try to cut the surface before scraping the surface. You didn't say what RPM you were at, turning up the speed a little can help with tearout too (within safe limits of course). You can also wet the trouble area with water to soften the fibers and then take a light cut. If that doesn't work then try stiffening them. Water is quicker and cheaper and you don't have to worry about it being compatible with whatever your final finish will be.

[John K Jordan]

John, it looks like you've sharpened both ends of your scrapers, is that correct? I assume then you use them without handles? Very interesting.

If by "interesting" you might mean "risky", this could be true! I put protectors on one end when I use the other end. And the three in the picture can certainly be put in a handle - I have handles with set screws and can mount a variety of unhandled tools in a few seconds if needed. (I have more tools without handles than are mounted in permanent handles) One reason for not using a handle on the NRS is it is I find it easier manipulate the tool and make delicate smoothing cuts without the mass of the handle and the need .

However, one nice thing for those who haven't used these scrapers, there is never any force on the tool. I suspect there could be a problem if these were used improperly, i.e., aggressively or not held horizontally or firmly on the rest. I haven't tried that.

For smaller turnings and thin spindles I often hold tools with one hand and sometimes with no handle. It depends on what I'm doing, the tool, and the size and type of wood. I would not recommend this to a beginner or someone with limited experience or prone to distraction. For spindle turning I often use very short handles.

For example, this 5/8" spindle roughing gouge is shown with a handle but most of the time I use it with no handle, again depending on the size of the stock, and situation.

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Like anything else in turning (and woodworking, metalworking, horseback riding, etc), if anyone is feels uncomfortable with something please don't do it!

JKJ

[Reed Gray]

I am wondering why you had more tear out on the outside of the bowl than on the inside. Most of the time, if I am having tear out problems, it is the same on both inside and outside. I would guess that you might be using more of a scraping type cut on the outside, and more of a shear/slicing cut on the inside. I have only turned a couple of pieces of magnolia, co don't really know it...

I generally don't like the NRS for most bowls. Partly because it is still a scraper, and partly because, most of the time I can get a better surface with a shear scrape. I do have one video dedicated to that, on You Tube... Some of the softer woods that tear out when you turn with gouges don't work well with the NRS either. Most of the time the harder woods do better, it just depends.

robo hippy

[Dave Fritz]

John, thanks for the reply. Actually I use some tools without handles myself. I feel I have better control for some smaller, tight work. So the Thompson tools are hardened all the way down? I've heard some tools are only hardened so far down from the tip.

[Dave Mount]

I find that all other things being equal, I get more tearout on the outside of a bowl than the inside from the primary shaping cut using a conventionally presented bowl gouge. I suspect it has to do with using a marginally supported pull cut to shape the outside of the bowl and a well-supported push cut on the inside.

Agree with Reed on a shear scrape using an inverted bowl gouge with the wings ground back as the easiest/most consistent way to removed tearout on the outside of a bowl. It's also the tool already in my hand. If I have tearout on the inside that needs to be addressed, I switch to a 5/8" U flute bowl gouge that is not ground back very far on the wings (my primary shaping gouge is a V flute). Present the tool with the flute fairly closed and the broad curve of the cutting edge gives you a nice shearing cut, and it is simultaneously good for getting a fair curve around the inside "corner" of the bowl.

I know it's kind of "yada yada," but the "sharp tools light cuts" mantra exists for a reason.

Best,

Dave

[John K Jordan]

..So the Thompson tools are hardened all the way down? I've heard some tools are only hardened so far down from the tip.

Doug Thompson said he machines the 10V steel then sends a large batch off for heat treating. I understood the entire tool is treated and my experience with grinding on the end confirms that, at least on those I've tried. I buy round rod from him too with no machining (to make tools) and it's also hardened completely.

In general, the Thompsons are my favorite tools. The 10V steel is excellent and seems to hold an edge longer than Sorby, Crown, and other tools in my stash.

I'm familiar with some tools that are only hardened at the tip. I have a tub of used tools I buy or am given and save them to give to students or starving turners or to regrind into special tools. I test each one with a triangular file. (For those not familiar with this, just try filing a small v-groove on the tool - it it's hardened steel the file will skate on the steel and not cut at all.) Some cheap tools are only hardened for the first inch or so. Once you grind past that you're out of luck. I found some not hardened at all!

JKJ

[Brian Deakin]

I live in the United kingdom and a number of months ago I had a conversation with a Sheffield tool manufacturer

He explained the reason for leaving a small portion of the tool shaft at the handle end unhardened was a safety feature
The rational is if you have a catastrophic event with a tool having a small portion of the shaft unhardened this allows the tool fail and is regarded as a safer option than having the entire length of the tool hardened

[Steve Mathews]

I am wondering why you had more tear out on the outside of the bowl than on the inside. Most of the time, if I am having tear out problems, it is the same on both inside and outside. I would guess that you might be using more of a scraping type cut on the outside, and more of a shear/slicing cut on the inside. I have only turned a couple of pieces of magnolia, co don't really know it...

I generally don't like the NRS for most bowls. Partly because it is still a scraper, and partly because, most of the time I can get a better surface with a shear scrape. I do have one video dedicated to that, on You Tube... Some of the softer woods that tear out when you turn with gouges don't work well with the NRS either. Most of the time the harder woods do better, it just depends.

robo hippy

Thanks Reed for reminding me about your excellent video on shear scraping, one of your best IMO. I watched it a few times more and applied the technique to the bowl. A bowl gouge was used and it helped a lot. The imperfections that I wasn't able to remove were tackled with my usual standby, grunt sanding. I'm almost finished with it now and I have to say this is the largest bowl (13" in diameter) and most difficult thus far.