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How can I improve the finish?

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I've recently been turning small bowls-mostly as practice. I am having difficulty with getting a good finish; a result I think of torn grain. I have finished with the lightest of strokes with a scraper, sanded on the lathe to 320; by hand at the offending bits up to 320; used the rotating (Hope System) discs to 600. I finally got fed up and used Microchrystaline Cut N Polish. The finish on most of the bowl is acceptable but I'm not really happy. What can I do to improve (apart from having more patience...)Bowl torn grain.jpg
 

hockenbery

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Are you using a bowl gouge?

Sharp tool, light cuts, bevel riding ( floating over the cut surface)
Cut with longer fibers supporting the cut.
This is cutting down hill with respect to the grain. In your piece the wide part is the bottom of the hill.

You may be interested in a bowl demo I do. Introductory slides, rough turning a green bowl to dry, returning a dried bowl.


E45911AF-C146-4262-AEF0-5196B8C98480.jpeg
 
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Thanks. Yes I started with a bowl gouge both inside and out. The inside I needed a scraper (I used carbide) to reach the bottom and I think I probably used it on the outside also "to finish(!) off". I did cut initially along your blue lines, but I suspect once it was chucked "by the foot", I also did cuts along the red lines. More practice needed!
 
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@hockenbery gave you good advice. No substitute for sharp tools and practice.

Once you’ve finished cutting, sanding is also a skill. A power sander (disc on mandrel in a drill) will make this much easier and quicker. Start with a course grade (80) and don’t change to a finer grade until to no longer see any tool marks. After that, each successive grade is only removing scratches from the last grade of sandpaper. Different woods require sanding to different grades to eliminate sanding scratches.

I’ve found walnut end grain to be the worst, still showing some scratches after 600/800 sometimes. Most American hardwoods are good after 320/400.

After more practice you’ll be starting at 120, then 150, etc. But you’ll learn that a couple seconds at each grit on the way up is faster than skipping grits.

I sand too much, but for reference after many hundreds of bowls I typically start on the outside of a bowl at 150/180, sometimes more, sometimes less. On the inside curve there are days I’m starting all of them at 80, but more and more I can start up a grade or two. I’ve found it’s ALWAYS better to start lower than spend many minutes wasting time by starting at too high of grit. If you start too low, you know it in seconds because all you see are sanding scratches. As with the tool, practice sanding will give you understanding and build this skill.

With all of that said, I still sand too much!
 
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A straight scraper will work okay for sweeping back and forth across the bottom of a bowl. They do not do a good job on the walls because of grain orientation. This can depend or vary a lot according to the piece of wood you are turning too. I prefer a shear scrape for my finish cut. This can be done with a scraper or the wing of a gouge. I did dedicate one video to this. I prefer a sharp gouge for a final cut, then the shear scrape. Look me up on You Tube, most of my videos are about bowl turning.

robo hippy
 
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Learning, improving, becoming skilled with the tools so that finishing is a breeze is surely the goal.
In the mean time though, you’ve done a respectable job with shaping, and you’d like a nice piece, regardless of how you got there.

So, go back to the 80 grit paper and work those areas till ALL of the damaged fibers are gone. Excessive sanding will cause the piece to go out of round. You can lessen the effect by not pushing on the sandpaper. Just like with cutting tools, your sandpaper HAS to be sharp. Once that sharpness is gone, get fresh paper. Also, spend half the time with the lathe running in reverse.
Once the damage has been fixed you can move on through each grit carefully.

600 grit, or higher, on Walnut will produce as fabulous luster, provided all of the previous grits were done properly and thoroughly.

With Walnut, I recommend an oil finish. It’ll darken the darks nicely, and will ‘pop’ the grain.

Good luck, and happy turning!
 
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I've recently been turning small bowls-mostly as practice. I am having difficulty with getting a good finish; a result I think of torn grain. I have finished with the lightest of strokes with a scraper, sanded on the lathe to 320; by hand at the offending bits up to 320; used the rotating (Hope System) discs to 600. I finally got fed up and used Microchrystaline Cut N Polish. The finish on most of the bowl is acceptable but I'm not really happy. What can I do to improve (apart from having more patience...)View attachment 49520
Hi Michael,
I'm glad you asked your question....many people just start at 80 grit, but I HATE sanding, especially when it's not necessary.
Not many people pay enough attention to grain orientation when turning.
My You Tube channel is filled with resources to explain direction of cuts, supported fibers, the 4 cuts I use, etc. Just type in "torn" in my Channel and numerous videos will come up that cover this topic.
Here's one I picked on sheer scraping with a bowl gouge -
View: https://www.youtube.com/watch?v=BDIvtr7StuA&t=121s

No matter what type of finish you use...it will only accentuate those areas of torn out grain!

@hockenbery Nailed it in his answer as well!

Have Fun!
Lyle
 

odie

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Those who have posted before this have been hitting on best direction of cut, and they are absolutely right that there is a best direction.....and, it has everything to do with supporting fibers below the cut.

Here is a drawing I made up about 25 years ago after watching an early VHS video by John Jordan. It gives a visual example of the best direction of cut, and why one direction is better than the other direction. To this day, this drawing is pinned to the wall behind my lathe! :)

Wood orientation for best cut (2) - Copy.jpg
 
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Scrapers, if not used correctly can actually create more tear out. Shear scraping with a very light cut can give a nice finish. I like to use a negative rake scraper for this - easier to control the shear, at least for me. But I'm still learning too. Cutting in the direction of the grain is also critical. I'm working on a piece now where the grain changes in the middle. I have to cut one way for half and the other for the other half. When shaping while taking a lot of wood off, I prefer a push cut as it yields a nicer finish than a pull cut. Then you can shear with a wing if need be to refine the shape. Yes, sanding sucks!
 

odie

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Shear scraping with a very light cut can give a nice finish. I like to use a negative rake scraper for this - easier to control the shear, at least for me. But I'm still learning too.

It'll be interesting to see what others have to say about this, but I'm finding that negative rake scrapers work best for me with the tool flat to the tool rest. This is working great for shaping the bottoms of bowl interiors. All of my shear scraping for finish cuts, is done with a standard scraper, but with a manually raised bur. Standard scrapers with ground burs, are used for roughing cuts, where the final finish is not the objective, but more removing wood and general shaping.

Even though I'm in my 41st year of turning nothing but bowls, I'm still doing some learning, too! :) This is why this forum has been so important to my continued growth. I have done a lot of testing of other's methods......once in awhile, I adopt some new method, or advice as my own, but the great majority of the time.....I don't! I hope I never get to the point where I can't be open minded about other's methods (and I see a great many experienced turners whom I consider closed-minded about anything new to them), but there does come a time when my own results are the deciding factor about any new experimentation. It is unlikely that anyone who isn't getting good results in their own turnings, will change my mind.....but, it does happen now and then! Even newbies can come up with some fantastic ideas sometimes!

"Critical thinking" is my objective, and hopefully I can keep that in focus.

-----odie-----
 
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Michael, if you find yourself with an end-grain piece (grain runs parallel to bed ways), note that your best, supported cuts will move in the opposite direction of face grain pieces (as shown in Odie’s nice diagram). Here’s a crude, B- drawing showing what I mean:

View attachment 49549
Thanks, I have found when hollowing that a pull cut works best and your diagram reinforces the fibres supporting the cuts.

How often do you sharpen your turning tool?
Right before your last cut?
Several times during the work but probably not just before the last cut-good point, thanks!

Thanks to all your suggestions I have produced a good finish on the outside of a bowl-well dried oak this time. Cutting religiously in the "right" direction with more re-sharpenings,, followed by shear scraping with the bowl gouge produced a much better finish. (Will oak produce a better finish than the walnut?). I followed the sanding suggestions and the result is a big improvement. So now for the interior....

I usually start with a bowl gouge until I can no longer keep the bevel in contact and then change to a scraper. The round carbide one is good for removing wood and I tend to finish using a HSS "teardrop" tip or a regular round nosed scraper.

I googled and youtubed Negative Rake scrapers. Whenever I use my (regular) scrapers I have the tool rest at, or just above, centre so the tool tip cuts just below the centre line (with the tool handle slightly raised). I understand that creating a micro-bevel with a steel or similar will create a fine finish (albeit blunting quickly). I use the Tormek wet system and sometimes have managed a micro-bevel from that, (probably by accident).

Leaving aside the NRG carbide tips, it seems to me that that the negative rake grind on a HSS tool moves the cutting "edge" part way "down" the thickness of the tool. So the included angle changes from say 0*+ 70* to maybe 20*+55* according to taste. Adding the micro-bevel further changes the angle of contact. Won't the same result be achieved by moving the tool rest slightly higher, thus changing the angle of the whole tool? NRG Scrapers obviously work so I must be missing the point!
 
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I usually start with a bowl gouge until I can no longer keep the bevel in contact and then change to a scraper.
Whenever I use my (regular) scrapers I have the tool rest at, or just above, centre so the tool tip cuts just below the centre line (with the tool handle slightly raised). I understand that creating a micro-bevel with a steel or similar will create a fine finish (albeit blunting quickly). I use the Tormek wet system and sometimes have managed a micro-bevel from that, (probably by accident).

Leaving aside the NRG carbide tips, it seems to me that that the negative rake grind on a HSS tool moves the cutting "edge" part way "down" the thickness of the tool. So the included angle changes from say 0*+ 70* to maybe 20*+55* according to taste. Adding the micro-bevel further changes the angle of contact. Won't the same result be achieved by moving the tool rest slightly higher, thus changing the angle of the whole tool? NRG Scrapers obviously work so I must be missing the point!
You can cut all the way to center of a deep bowl if you switch to a "BOB" or "bottom of bowl" gouge with a steeper bevel angle.

On interior cuts you want the scraper to cut above center.

Changing the tool rest height will not achieve the same result as a negative rake scraper. Grind a round nose steel scraper with a 20* top bevel and an included angle of <90*, and take light cuts with the tool level and slightly above center to see the difference. Honing the bevels and raising the burr with a burnisher will give a finer edge that can be pulled up several times before regrinding.
 
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Thanks, I have found when hollowing that a pull cut works best and your diagram reinforces the fibres supporting the cuts.


Several times during the work but probably not just before the last cut-good point, thanks!

Thanks to all your suggestions I have produced a good finish on the outside of a bowl-well dried oak this time. Cutting religiously in the "right" direction with more re-sharpenings,, followed by shear scraping with the bowl gouge produced a much better finish. (Will oak produce a better finish than the walnut?). I followed the sanding suggestions and the result is a big improvement. So now for the interior....

I usually start with a bowl gouge until I can no longer keep the bevel in contact and then change to a scraper. The round carbide one is good for removing wood and I tend to finish using a HSS "teardrop" tip or a regular round nosed scraper.

I googled and youtubed Negative Rake scrapers. Whenever I use my (regular) scrapers I have the tool rest at, or just above, centre so the tool tip cuts just below the centre line (with the tool handle slightly raised). I understand that creating a micro-bevel with a steel or similar will create a fine finish (albeit blunting quickly). I use the Tormek wet system and sometimes have managed a micro-bevel from that, (probably by accident).

Leaving aside the NRG carbide tips, it seems to me that that the negative rake grind on a HSS tool moves the cutting "edge" part way "down" the thickness of the tool. So the included angle changes from say 0*+ 70* to maybe 20*+55* according to taste. Adding the micro-bevel further changes the angle of contact. Won't the same result be achieved by moving the tool rest slightly higher, thus changing the angle of the whole tool? NRG Scrapers obviously work so I must be missing the point!

NRS for neg rake scraper. Not sure why you use the term microbevel? If you are flipping over a flat scraper and creating a bevel to create an nrs, I suppose one could refer to it as a microbevel if it is thin, say 1/16” or less. Creating a wider bevel makes hand honing a new edge much easier.

Tilting a flat scraper - if you can tilt it down at 20-30 deg through the entire path of the tool, then yes. However, its might near impossible to do so and can actually be a bit dangerous to try. An nrs is just so much easier.

As for include angles, yes anything < 90 works. I prefer using the same angle on both top and bottom (30-35 deg for me). The tool use direction is easily reversed depending which way the burr is raised.

As Kevin says, a “BOB” can get you to the bottom center. A BG with a bevel angle > ~ 60 can work - it depends on what angle your BG has. Just for reference, I use a 3 BG’s, depending on the type of cut. All are parabolic flutes - a Batty style 40/40, a Michelson style long wing 60 bevel, and a traditional grind 70 bevel for a BOB. Exact angles are not that important, rather the variation in bevel angle and wing sweep to do different things.
 
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Thanks I was aware of Bob but don't have one

I have a moratorium on new tools so need to use what I have. I have a heavy curved scraper that I could regrind to NRS Though on a Tormec it will probably take a week!

The micro bevel was the result of using a steel on the sharpened edge of a standard scraper. It produced a slightly better finish with than without.

Unfortunately the oak blank I won in the club raffle has a crack that despite CA glue is not going away! Good for (careful) practice though!
 
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I would not use a NRS for shear scraping. The burr on them is gone in seconds with standard scraping cuts. If you have a burnished burr on your NRSs, then that can do a nice shear scrape.

As for BOB tools, if you use a swept back gouge, most of them have about a 60 degree bevel on the nose. That will get you through the transition and across the bottom of most bowls. I don't use the swept back gouges any more. I just prefer the 40/40 for the sides and a BOB tool for the transition and bottom of the bowl. To me, it is a case of the specialized tools work better/easier than the 'one tool does it all' which is what a swept back gouge is to me.

robo hippy
 
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The micro bevel was the result of using a steel on the sharpened edge of a standard scraper. It produced a slightly better finish with than without.
I dont think that is representative of what an nrs will do. There needs to be enough of a bevel such that an upward burr is raised. If you did raise a burr after turning down the existing burr with a steel, you had a flat top with a burnished burr.

I use a Grizzly wetgrinder with tormek jigs/stone grader. Roughen the wheel up with the coarse grader stone, and you can have an 1/8” bevel quick enough.
 
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I for one believe a burr on a scraper is highly overrated. How many times that I have seen a pro tell the audience that you need to raise a burr and that burr is gone in 13 seconds of use. Then he uses it for 3 minutes and later uses it again without sharpening. I have a scraper in a rack next to the lathe that I may pick up and use a dozen more or less times a year, I cannot remember the last time I sharpened it. It still works for exactly what I need it to do. Once it quits working I will sharpen it. That's me your results may vary :)
 
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How often do you sharpen your turning tool?
Right before your last cut?
Sharpening, generally at the final or finishing cuts. But it depends on the wood :) I turn, mainly Aussie hardwoods and some, not all have a ruinous amount of silica in the wood. On these, I have to sharpen long before the finish cuts. The worst i have had was 3–4 cuts on a Thompson 5/8 bowl and back to the grinder it was horrendous, but fabulous colour and grain structure.
 
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As for burr durability, the burr on my Big Ugly tools can last for half a day of heavy roughing. The burr on a D Way or Thompson scraper can last for several bowls. Oh, I sharpen them on 180 grit CBN wheels. The burr on a NRS is gone in seconds, unless you burnish it on, then it lasts a lot longer. With a skew being used as a NRS, there is little metal under the burr to support it which is one reason why it is gone so quickly, same with a burnished burr on a skew. My NRSs are ground 30/60, so 30 degrees for top bevel, and 60 degrees for under bevel. Even the grinder burr lasts longer than the ones on the skew type NRS. I have heard of grinding them up side down for an even sharper/finer burr, and only briefly tried it. Not a noticeable difference to me. I couldn't really notice any difference between the burr left by an 80 grit wheel and the 180 grit wheel. Not sure if there is much difference when using the 320 grit wheel or 600 grit, though I may need to play with them a bit more...

robo hippy
 
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It'll be interesting to see what others have to say about this, but I'm finding that negative rake scrapers work best for me with the tool flat to the tool rest. This is working great for shaping the bottoms of bowl interiors. All of my shear scraping for finish cuts, is done with a standard scraper, but with a manually raised bur. Standard scrapers with ground burs, are used for roughing cuts, where the final finish is not the objective, but more removing wood and general shaping.

Even though I'm in my 41st year of turning nothing but bowls, I'm still doing some learning, too! :) This is why this forum has been so important to my continued growth. I have done a lot of testing of other's methods......once in awhile, I adopt some new method, or advice as my own, but the great majority of the time.....I don't! I hope I never get to the point where I can't be open minded about other's methods (and I see a great many experienced turners whom I consider closed-minded about anything new to them), but there does come a time when my own results are the deciding factor about any new experimentation. It is unlikely that anyone who isn't getting good results in their own turnings, will change my mind.....but, it does happen now and then! Even newbies can come up with some fantastic ideas sometimes!

"Critical thinking" is my objective, and hopefully I can keep that in focus.

-----odie-----
Odie, There is no question you know more about turning than I do, so I'm sure I'm not telling you anything you don't already know and, for that matter, others will say also.. For the outside of bowls, sheer scraping always results in the best finish. For the inside, I haven't yet come close to perfecting my technique, but I do you NR scrapers, both flat on the tool rest and angled slightly. I have also used NR carbide cutters with some success on some pieces, again both flat on the tool rest and angled slightly. I am still in the process of investigating other methods but, for now these work best when I don't get the inside smooth with my bowl gouge.

Again, I'm sure I'm just repeating what you already know.
 

odie

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Odie, There is no question you know more about turning than I do, so I'm sure I'm not telling you anything you don't already know and, for that matter, others will say also.. For the outside of bowls, sheer scraping always results in the best finish. For the inside, I haven't yet come close to perfecting my technique, but I do you NR scrapers, both flat on the tool rest and angled slightly. I have also used NR carbide cutters with some success on some pieces, again both flat on the tool rest and angled slightly. I am still in the process of investigating other methods but, for now these work best when I don't get the inside smooth with my bowl gouge.

Again, I'm sure I'm just repeating what you already know.

Hi Randy......As with most experienced turners, I know what works for me.....and I recognize that others feel the same about their own methods. The difference is I speak for myself only, and speak only within the realm of my own experiences. Others are free to disregard whatever I say in my posts, specifically because of that. IMHO, I believe a few other experienced turners, feel they can apply their knowledge outside of the scope of their own sphere of knowledge to a more generic, or generalized blanket statement about woodturning. (Sometimes, I feel this attitude is directly related to my beliefs about "herd think", and how it actually stifles creative thinking outside of the box.)

-----odie-----
 
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hockenbery

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For the outside of bowls, sheer scraping always results in the best finish

There are few absolutes in woodturning. I shear scrape when it improves the surface - close to “always”

With very soft wood and some punky woods shear scraping makes the surface worse.

Willow is one example of a wood where scraping pulls the fibers out destroying a clean gouge cut surface.
 

odie

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Those who have posted before this have been hitting on best direction of cut, and they are absolutely right that there is a best direction.....and, it has everything to do with supporting fibers below the cut.

Here is a drawing I made up about 25 years ago after watching an early VHS video by John Jordan. It gives a visual example of the best direction of cut, and why one direction is better than the other direction. To this day, this drawing is pinned to the wall behind my lathe! :)

View attachment 49539
Just a quick note about this grain orientation drawing of mine.....

The drawing is accurate, but only for common straight grained pieces of wood that are frequently used by turners. However, there are exceptions to this.....among them are burls, curly grain, quilted grain, and any wood with an intense swirly grain pattern. Many of these exceptions make little to no difference which direction the cut is directed, because there will be spots where the most difficult of grain orientation will be the case.....no matter from what direction you approach it.

In these cases, the only solution is to refine one's techniques to get a very clean cut without tearout, even though grain orientation opposes a successful outcome. It can be done, but not without sharp tools, a lot of practice, self-evaluation and personal adjustments.

-----odie-----

1674891510235.png
 
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