Ellsworth Grind Grabby?

[Paul39]

I have been using a Crown 1/2 inch bowl gouge with a moderate swept back grind for a couple of years. I'm quite comfortable with it and seldom have a catch.

I recently got a used Thompson 1/2 inch bowl gouge with a very swept back grind. It was reasonably sharp, so I honed it with some 400 grit sandpaper and was happily hollowing a bowl.

The rim was undercut with a gentle curve and I started at the rim, slicing down the inside, marveling how clean a cut I was making. The tip caught, flung the bowl out of the chuck and gave me a good rap on the knuckles.

Made a nice spiral trench on the inside and broke half the spigot off for good measure.

So, is the long finger nail grind more volatile than a blunter swept back grind?

[TTIT]

Can only speak for my experience and I've never had a catch with the long grind yet - I consider my Superflutes with the long grind just about catch-proof - but then I'm not an aggressive turner as I like to finish every piece I start. :shrug:

On a recent turning weekend with Guilio Marcolongo, Guilio showed me how to manage the area inside a form that runs parallel with the ways a bit better than I had been and I found it to be borderline catching but still controllable. All comes down to technique no matter how it's ground I reckon.

[RETIRED]

When running down the inside of a bowl with long swept back wings you have to rotate the chisel a little to maintain the cut in the right place i.e. on the bottom wing otherwise the top wing can engage and the gouge loses tool rest support.

This is more prevalent when using the chisel horizontal with the tool rest high which seems to be the norm these days.

I wonder if the mini lathes are to blame for this?:shrug:

[tea lady]

Is it a "v" or "u" shape? Maybe it is a slightly different profile that you are not use to! :shrug:

[robo hippy]

Like said, roll it onto its side a bit, rolling the flutes away from the wood you are cutting. This keeps the cutting part of the gouge directly over the tool rest. If you have the flutes straight up, you risk getting the wing caught.

robo hippy

[tea lady]

The rim was undercut with a gentle curve and I started at the rim, slicing down the inside, marveling how clean a cut I was making. The tip caught, flung the bowl out of the chuck and gave me a good rap on the knuckles.

Made a nice spiral trench on the inside and broke half the spigot off for good measure.

So, is the long finger nail grind more volatile than a blunter swept back grind?:think: Don't you kinda need to come"up" the form in an undercut rim? :hmm: You are going against the grain there a bit. The differant wing profile probably doesn't allow the bevel to rub like your old chisel did! :shrug: If you were doing this cut no probs before something differant must be happening.

:pi: So you were cutting down the curve with the wings? :hmm: The longer wings are too long to fit the curve allowing the tip to touch? :shrug: Shorter wings on an inside curve might be better! :cool:

[Tim the Timber Turner]

I do my undercut rims with a pointy nose scraper.

Refered to by some as a skew chisel.

Cheers

Tim:U

[rsser]

If the bowl was thin for that cut wood flex can do that too if the bevel wasn't rubbing.

[rsser]

As said, to add, gouge horizontal or close to it poses challenges of its own, grind aside. My lathe doesn't have a huge swing and when I mount a cast Woodfast style tool rest into what I think is the over-generous banjo post mount, the tool is not far off horizontal when getting to the bowl centre (without swinging the rest closer cos I too am impatient).

See the pic.

What's also clear in the pic is that whopping knot which unusually does not appear on the outside of this 4" deep bowl and barely provided a heads-up on the flat top of the blank.

So I was having at it during hollowing and wondering is wrong with my gouge, technique, rest position and the alignment of the moon and stars. 'til I stopped the lathe and took a look.

To back up, diagnosis of a catch is the critical step. Try and reproduce it next time around just turning the workpiece by hand.

When I take ski lessons and do a faceplant, the teacher takes me back up the slope to analyse the tracks and what when wrong. The evidence can't be denied hoomilating though the whole experience is :(

HTH.

[Paul39]

Thanks for all the comments.

The shape of the Thompson is very close to the rounded bottom V shape on the Crown.

I set my varigrind jig to the profile that was on the Thompson gouge when I got it and sharpened.

I had a go at a dry piece of walnut and made a shallow bowl.

I have been using the blunter ground Crown gouge rolled over with the open top facing the direction of cut, almost parallel to the bed and getting OK results.

With the Thompson I used a more up angle and the slicing off of long strings makes a better finish. I soon found that the tool must be right down on the rest and the bevel rubbing and bring the tool down to cut.

I can see why people like the grind, lots of material removed, and very smooth finish. You need to be paying attention, because when the tool begins to cut, you are off to the races.

I think the more swept back grind is more unforgiving. The pointier tip digs in deeper and makes a more violent catch.

I had a careful look at the bowl that precipitated this thread. It is a cedar root with many knots and hard and soft places along with several long bark inclusions.

I think the wing hit something and bumped the nose into the bottom with the tool off the rest. The bowl was not badly damaged, and as I was roughing, I still have lots of timber left to remove.

Tea Lady, I have been going uphill and down hill on the sides of bowls with the Crown, a couple of round nosed home made bedan tools - 3/8 & 3/4 in. wide, and scrapers. I sometimes hollow with the bedans.

The scrapers are used right off the grinder with a bit of burr very lightly for 15 to 30 seconds, then resharpened. The final scrape before sanding is done with the scraper sharpened, top honed flat on 400 grit on a flat surface and very lightly skimming the timber.

My favorite scraper is made from a high speed steel planer blade, no handle yet. 12 inches long, 2 1/2 inches wide and 3/8 inch thick. It weighs about 2 pounds. No bouncing around, no kicking back over bumpy surfaces.

I bought 4 for $15 at an auction. Obviously I was the only turner there. I was prepared to pay $50 - $60 for the lot.

Two photos of the scraper, one of a mushroom that was done entirely with the Thompson except for the spigot, which was done with an accursed skew for the first cut through the bark, and finished with a parting tool made from a screw driver.

The mushroom is "right off the tool", no scraper, no sanding. Since seeing Mrs. Blackie's mushroom, I have been obsessed with making them.

[Paul39]

I love it!

It works like an accursed skew without the accursed part. It takes some practice to control it.

I use it for bowls, tool handles, long skinny weed pots, and mushrooms. The long nose is nice for under cutting the caps of the mushrooms.

I use it cutting uphill, downhill, rolled over on either side, and almost upside down.

I can use it to cut 95% of a spigot or recess with a final touch up with a notched scraper.

Happy New Year to all.

[NeilS]

I love it!



Glad to hear that you have got to appreciate the versatility of that grind and flute profile. I reckon you will will want to have at least one like that from now on.




I set my varigrind jig to the profile that was on the Thompson gouge when I got it and sharpened.



Good move. I found the profile on Doug's V gouges as received just about perfect for my purposes. Not surprising that they work so well the way they come given that Doug is a turner himself and also his close collaboration with many top turners to produce their signature gouges.