No tear out in bowls

Well, the thread under angle drill failure diverged to the point where I thought it was time to start a new thread. The title of 'No Tear Out' bowls is a claim I have heard from a couple of 'big name' turners, and is some thing that I think does not exist. Given that on standard bowl grain orientation, which is side grain, for 1/4 turn you cut with the grain, then 1/4 against the grain, then 1/4 with, and 1/4 against. The only turnings I have ever seen with no tear out are, in every single example, are all spindle/end grain turnings because with them you can cut totally with the grain. With the claims on bowl turnings, at best you get tear out down to levels where sanding is greatly minimized. When I go up to look at 'no tear out' bowls, you can see little to no tear out, but when you rub your hands over them, you can really feel it. Every single time. Shear scraping, very light cuts, very sharp tools do a good job here. The part I want to bring up in this thread is the fine edge. I prefer to do every thing with tools while the bowl is spinning. There are those who take hand held card scrapers to the pieces after they are done turning and before scraping, like John Jordan, and Prashun. During my process of trying to get things as good as is humanly possible, I have determined that the finer edge leaves a cleaner surface, but trying to find the perfect edge is a challenge because of so many variations. At present, it seems that the burnished burr on scrapers, and/or a 600/1000 grit edge on a gouge leaves the best edge. I am leaning towards the burnished burr on scrapers as having the advantage. What I am trying to figure out is what difference the various metals make, and that includes both the scraper, and the burnishing materials. For metals, that pretty much includes M2, M42, and V10. For burnishing, that includes the steel rods that you find at woodworking stores, carbide rod (Eric Loffstrom uses them), and I have heard of ceramic burnishing rods. I guess we could include honed burrs in here too. Which would include how fine of a grit is used. So, who uses what???

After seeing Eric demo, I made a carbide burnishing tool, and prefer it. I googled carbide rod and found Centennial Carbide in Minnesota, who carry micro grained carbide rod. I bought 100 of them, 3/16 by 1 1/2 inch long. I don't know if they sell 1 or 2 at a time or not. If any one is interested in trying them out, I will sell at cost, $2 each. Not sure if moderators are okay with this part or not, but it is experimental and not for profit... You can PM me, or contact me through my web site.

"If it ain't broke, take it apart and fix it anyway."

robo hippy

I use a carbide rod for all burrs, on either card scrapers or turning scrapers. I have used the shaft of a 1/4 gouge before in a pinch. I bought a couple years ago and gave one away - I'll send a PM for some, thanks.

I also find a finer edge for shear scraping works better. One of my favorite shear scraping tools for the outside of a bowl is a 1/2" spindle gouge with a swept back grind, sharpened on the 1200 grit CBN wheel on the Tormek. Honing with an extra fine (blue) Ez-lap diamond hone seems to help too. I will sometimes use this upside down on outside coves too. I think this one is a bowl gouge but it's the same principle.

Attachment 367873

BTW, I often use hand scrapers while the lathe is turning, inside and out, except in the middle of the bottom. Mostly these are the small, thin and flexible oval shaped hand scrapers. (Just don't do like one poor guy reported some years ago when we were discussing this - held a larger cabinet scraper inside a form and when he dropped it it caught and turned the thing into a food processor...)

Sometimes I use a small flat hand scraper on very thin spindles to handle chatter from difficult wood. The steel on the hand scrapers I have is not very good and they need sharpening a lot. I think the steel in the thick StewMac scrapers is better.

I've done a little "no tear out" on the sides of face turnings but I think a lot depends on the wood itself. Hard, fine grained wood like cocobolo and dogwood are pretty good. (I alway turn dry) Looking at cocobolo with a microscope the pores are full of a resin - I wonder if that helps. The wood is somewhat self-lubricated too. Same with lignum vitae - I've never seen tearout on it. The softer the wood, the worse for me - soft maple, box elder, etc. The exception is eastern red cedar - almost never tears except around knots and such.

I do find a coat or two of thin shellac or lacquer sanding sealer helps minimize tearout on many woods. Where tearout is a problem I often coat, dry, turn, repeat. Again, this is dry wood - I rarely turn green.

I can't comment on the type of steel since I almost always use Thompson (V10). As for the edge on different steels, I think John Lucas is doing some tests on different steels and grinding grits. I took the EdgeOnUp sharpeness tester to him a few weeks ago - maybe he'll get some results less subjective than what we always get.

I do like the 1200 grit CBN Tormek wheel better than the 600 grit. I use it for all my spindle gouges and some bowl gouges. I haven't used it on scrapers yet but I need to. I probably don't do 1/10 as much turning as you do so it may be a while...

JKJ

Quote:

---

Originally Posted by Reed Gray

...
After seeing Eric demo, ....

"If it ain't broke, take it apart and fix it anyway."

robo hippy

---

While I agree with Robo, I'm going to take this subject slightly side-ways :D

If you ever have a chance to see Eric Loffstrom at the lathe, spend a few minutes just watching him move.

The first time I watched Eric I asked him what martial art he had studied. I said this because Eric moves with the best ergonomics of any turner I have ever seen. This type of movement does not come "naturally" but has to be trained in.

Turns out Eric is a phys-ed teacher and got his training that way.

Well, I was up in Salem (up north, or down river, never sure which..) to see Nick Stagg demonstrate. His style is very much influenced by Allen and Stuart Batty. He was doing some finish cuts in some ash with scrapers. I asked him what type of cutting edge he had on them and he said 'no burr'. I could feel a tiny burr, so I am guessing he honed off the top side and then the bevel to remove most of the burr. I don't think I have ever tried that method.... More experimenting... So many variations to try...

Eric is really good, and I hope to have him hang out in my booth at the Symposium next summer in Portland.

Ralph and I both have done Tai Chi for years. First day in Tai Chi class, which was some years after I started turning was, 'hmm, this is just like what I do when standing at the lathe...'.

robo hippy

I played around yesterday with some sugar maple, side/bowl grain, and a scraper that had the burr honed off. It did cut okay, but not well. To hone the burr off, I honed the top on a diamond stone, then honed the bevel and top again on my Tormek honing wheel so there was no feelable burr. It did cut fairly cleanly, but very slow, considerably slower than I expected even considering the hardness of the maple. So my question for those that hone off the grinder burrs, do you hone till you can feel no burr like on a skew, or do you hone top, then bevel so there is still a tiny burr???

I did a lot of playing around with burnished burrs, NRS's of a couple of different angles, and shear scraping, with no real 'differences' other than high shear angle gave cleaner cuts than NRS's on side grain...

Oh, burnished burr does a nice bevel rubbing cut as well as shear scrape, and I think I forgot to try grinder burrs from 1000 and 600 grit CBN...

robo hippy

And wait, there is still more....

I got a PM a day or two ago, and accidentally deleted it in the process of emptying my mail box... Anyway, the comment was about sharpening with the wheel or belt (can't remember which) going away from the tool and bevel rather than into it. At pretty much the same time, the same topic came up on the AAW site. The turners got different results, one thought that after the burr wore off, the tool was dull, and the other thought that after the burr wore off, the tool was still very sharp. I do remember Jimmy Clewes preferred an upside down grind on his scrapers for the fine finish cuts as he felt that burr was way sharper. Me, I have no clue.

I have spend a bunch or time on some maple blanks, both highly figured, and one probably sugar maple, and the other a softer maple which is kind of soft from being punky as well as highly figured. Also a piece of myrtle/california bay laurel, and tried every cutting edge I could apply: scraper with burnished burr, scraper with grinder burr, scraper with burr honed off (diamond stone and Tormek) as in really honed off so I couldn't feel any significant burr, negative rake scrapers of different angles both burnished and grinder burrs, V10 from Doug Thompson and M42 HSS from Dave Schweitzer. Don't think I used gouges though.

First impressions are a higher shear angle improves the surface. I can't tell if the smoother finish from a bevel rubbing cut is because the surface is burnished even though I am using the lightest pressure I can (though I need to improve on that), and this is comparing it to a shear scrape with a ) nosed scraper. Visually not much difference, and only a slight difference when rubbing my fingers on it. I am thinking that the honed and burnished burr is the best edge for the cleanest cut compared to any other edge.

I was surprised that with an M2 scraper that was honed on bevel and top side so there was pretty much no burr at all, in flat on the tool rest scraping cut mode, I was able to get a very clean surface on the hard maple. I could feel minimal tear out, but am fairly sure it would come out with 220 easliy. The NRS's that I tried didn't cut as well, both lightly burnished 30/30, and grinder burr 30/30, and same for 70/30 with the same edges.

I am honing the top surface on a 1200 grit DMT stone with honing fluid. The stone is 25 years old, and I would swear it didn't cut at all till I started using lapping/honing fluids. I had a 320 grit stone, and didn't get as keen of an edge.

I need about 10 different profiles in both metals. There are some that say V10 cuts better than M42, and the other way around. I can tell no difference. There are some that say that M2 takes a keener edge. Not that I noticed... For sure, M2 goes dull a LOT faster. So, more experimenting ahead...

robo hippy

Still more.... I had a fairly long chat with Tom Wirsing this morning about burrs and negative rake scrapers. He turns mostly highly figured woods, and the NRS is what he uses as a finish cut on all surfaces. 22 1/2 degrees on both sides... With the highly figured woods, you want to do as little sanding as possible because the wood goes 3D if you do much due to the mixed grains sanding differently. My NRS is 30/30. So, played with some squirrely myrtle. Quite probably I am spending too much time before hitting the grinder to refresh the burr. I seem to be getting almost the same results with a 70 degree bevel scraper with a honed bevel and top/no burr. All of these cuts are 'whisper' cuts. They can remove some marks and minor waves, but not stock. Tom mentioned some thing that I had figures out. With a high angle shear scrape, you have a more vertical cutting edge which is small and tends to leave lines. With a NRS, which is flat on the tool rest, you have a wider cutting edge which makes for way less bumps... I hope to have he, and several other turners in my booth at the AAW Symposium in Portland next summer for some play time....

robo hippy