3/8" Gouge Chatter??

[Lawrence Duckworth]

I've been roughing 3" spheres with a 3/4 ``gouge and when I make a final cut with a sharp 3/8" gouge in the direction of the headstock I get a chatter almost every time. Any ideas what i'm doing wrong to get the chatter?... Thanks

[Jerry Lear]

chatter can be caused by left hand putting too much pressure on bevel.Use the left only to hold tool on rest,do not press in

[John K Jordan]

Depending on the grain orientation, cutting "uphill" at certain points might cause chatter.

Jerry makes a good point about bevel pressure. Also, when I encounter unusual problems I sometimes apply a bit more down pressure against the tool rest. Reduce the overhang of course.

Another thing, I've gone to Thompson detail and shallow detail gouges for some things since the cross section of the gouge makes it much sturdier, especially if there is unavoidable overhang. A 1/2" spindle gouge might be better than the 3/8", and the detail gouge better than the usual spindle gouge. (If you look at the gouges on his web site ignore the cover photos but drill down to the descriptions - the detail and shallow detail gouges have a much shallower flute than the photos: 50% for the normal spindle gouge, 33% for the detail gouge, and 20% for the shallow detail gouge. https://thompsonlathetools.com/produ...-detail-gouge/)

Mark StLeger told me he uses a Thompson 1/2" spindle detail gouge more much of his turnings, including his spheres. I've got these on my shelf - in a demo he turns four the same, a corian disk with a groove, and the stack spins like a bearing when you spin the top sphere!

Mark_StLeger_spheres.jpg

JKJ

[Reed Gray]

A couple of solutions already mentioned, and I will add to that. Most people tend to over do the 'rub the bevel' part. If you have much bowl turning experience, especially when turning the outside, you always get a little bounce. Part of the reason is cutting from end grain to side grain, and uphill to down hill. The tools cut differently in different grain patterns. The other is from too much pressure on the bevel and/or having the death grip on your tool in an effort to control that bumping. Clamping down makes it worse, not better.

"The bevel should rub the wood, but the wood should not know it." Unknown

"When holding the sword (tool in our case), hold it as you would a bird. Too tight and you kill it, too loose and it flies away." Old black and white Hollywood movie about Cerano de Bergerac.

I haven't done any spheres in a while, but for finish cuts, I used to use a shear scrape. That was before I had started using NRSs.

robo hippy

[Lawrence Duckworth]

Thanks so much Jerry. You’re probably right I’ll try to loosen up 👍

Again, thanks John. I’m looking at the gouges now and they’re very deep. Makes cents 🤔

[Lawrence Duckworth]

Thanks Reed. Good description. The wood is hickory and looking at it closely the grain….I get it.
The death grip is a good place to start though 😜

[Lawrence Duckworth]

Quick follow up.
Though the flutes are deeper on my tools compared to the ones shown in the Thompson link, I don’t think that plays into it. My final cut with the 3/8 is small and well supported. I took my fat hand off the tool and guided it with my pinky👍

Btw for clarities sake I guess the actual final cut is with a scraper and I hate to use it cuz brings up fibers but I can’t cut without leaving little irregularities 🤷*♂️

[John K Jordan]

Quick follow up.
Though the flutes are deeper on my tools compared to the ones shown in the Thompson link, I don’t think that plays into it. My final cut with the 3/8 is small and well supported. I took my fat hand off the tool and guided it with my pinky👍

Btw for clarities sake I guess the actual final cut is with a scraper and I hate to use it cuz brings up fibers but I can’t cut without leaving little irregularities 🤷*♂️

Sometimes fibers raised from scrapers can be tamed with an application of thin sanding sealer, dried. And a sharp, sharp, sharp scraper! I use hand scrapers a lot for that, off the lathe so I can pay attention to the grain orientation.

[Reed Gray]

Well, if you are using a scraper for the final cut, then I would suggest that you hone the burr off. I saw this done with a piece of sugar/hard maple and it left a glass smooth surface. Not sure how it would work on hickory, which does like to splinter. I would use a shear scrape. I do have one video dedicated to that. With that high shear angle, you get less tear out so a cleaner surface. The cuts are 'whisper' cuts, so VERY light and the little whispies of shavings should float in the air. Can be done with scrapers, or if you are using a gouge, the swept back ones work best. A NRS will also work very well.

robo hippy

[Lawrence Duckworth]

I'm not going to say I've eliminated the chatter completely just yet. On basswood things were pretty smooth but I can still feel a small vibration....
I'll go watch your video.

Thanks

[John Keeton]

Don’t know if it has been mentioned, but sometimes it can simply be a bit of dullness. A slightly dull edge will cut the softer face grain, but not do so well on end grain making the piece get out of round.

[Lawrence Duckworth]

So I watched Reeds video and a couple others, good stuff! I also saw the importance of a burrrr. I noticed a little hand tool type bur Reed used in one of his videos and would love to know what it was, home made?.. My tools are M42 with 10% cobalt. Do you guys think a rotory file or end mill would be tough enough to make a bur. tool?

thanks John, I have in fact experienced some out of round wobble...

[John K Jordan]

So I watched Reeds video and a couple others, good stuff! I also saw the importance of a burrrr. I noticed a little hand tool type bur Reed used in one of his videos and would love to know what it was, home made?.. My tools are M42 with 10% cobalt. Do you guys think a rotory file or end mill would be tough enough to make a bur. tool?

thanks John, I have in fact experienced some out of round wobble...

I haven't seen the video, but a burr is usually added with a burnishing tool. They are usually carbide but any hard steel will also work in a pinch, for example, the hardened shaft of a HSS too, the smaller diameter the better.

These are some I use. Again, the smaller the diameter the better, i.e., easier to raise a burr:

_scrapers_IMG_7784.jpg

However, if buying one my new favorite is the Arno burnisher - it has a small diameter side and a triangular side, actually an extremely small diameter rounded edge which is more aggressive. This works very well on conventional scrapers, NRS, and cabinet/card hand scrapers.

arno_burnisher.jpg

I usually remove any burr from the grinder with an extra file diamond hone or by stropping, then burnish a burr. The grinder burr is coarse and relatively weak while the burnished burr can be smooth and stronger and last longer. I used to do this with "conventional" lathe scrapers but now I almost always stick to negative rake scrapers like these. NRS are much easier to control, more forgiving in that they are difficult to cause a catch, and I think give a smoother surface. I grind these from 10V steel Thompson Tools.

NRS_IMG_7778.jpg NRS_IMG_7907.jpg

With this grind I can use the end flat or the curve on the inside or outside. I put the burr on the side needed for the piece - with several ground the same I just have left and right-handed versions.

You can also sheer scrape with a gouge with swept back wings. It would be easy to show how this is done but harder to describe. You can probably find pictures somewhere.

After using a scraper on the moving part I generally stop the lathe and even remove the piece and use a hand scraper just before sanding. This usually allows starting with fine sandpaper instead of coarser which can give a better surface.

JKJ

[Lawrence Duckworth]

Geese John, I think my info overload siren is going off


This is the scraper I have.
https://carterandsontoolworks.com/pr...nt=41859860681


I'll snoop around in the barn this morning and see if I can find something I can make a bur tool out of. I didnt realise how important the bur is....or for that matter there was a tool for it.


I like the scraper profiles you have there, especially the left and right hand deal. no idea what the three dagger looking things are...Yikes


wow.. thanks again

[John K Jordan]

...
I like the scraper profiles you have there, especially the left and right hand deal. no idea what the three dagger looking things are...Yikes

Oh, no. Here I go on scrapers again. I can't help myself.

The "dagger" photo is just of the same three scrapers but looking at the sides to see the included angle. I think I use about 60-deg included angle.

Here is one of my three "primary" negative rake scrapers in action, first using the curve and then using the (almost) flat on the end. I've never seen anyone grind them like this but the flat is perfect for smoothing platters, gentle curves, and here, the wings of a small squarish platter. I've had people tell me you can't use a scraper when "turning air" but it's not so.

NRS_curved.jpg NRS_IMG_7515.jpg

A NRS can be any angle less than 90-deg. The first picture shows some smaller ones I use a lot - they will leave end grain on boxes, etc, smooth as glass with good wood. I grind most of my scrapers from Thompson stock, round, rectangular (scraper), skew chisel, and detail gouge. I often sharpen another shape on the other end. Some special use scrapers that don't get so much use are ground from old HSS tools. BTW, I use all these without handles.

NRS_small_thompson.jpg NRS_IMG_7780.jpg NRS_rounded.jpg

As mentioned, I do a lot of final smoothing with hand scrapers, mostly off the lathe, just before sanding:

scraper-shavings-IMG_7864.jpg _scrapers_IMG_7827.jpg

After smoothing on the lathe with the NRS then off they lathe by hand, I can often start sanding with 400 grit, occasionally finer, often by hand. Just say No to power sanding with a rotating disks!

A few of my favorite hand scrapers. I grind cabinet scrapers into various shapes with a belt sander, sharpen at 90-deg on a 600 grit CBN wheel, smooth the flat ground edge with an extra fine diamond hone (also removing any grinding burr), then burnish a smooth burr on both sides for double the use between sharpenings. This method is commonly used by furniture makers to prepare cabinet scrapers. When a burr gets dull, I usually take it off with the diamond hone then raise another one or two before I take it back to the grinder. The two in the upper left are 1/8" thick from StewMac, generally marketed to musical instrument makers.

scrapers_favorite_IMG_7870.jpg

JKJ