Thread: Thompson 5/8 U gouge - first impressions

All the different cuts..... So many to choose from.

The Michael Mouse cut: He uses a continental style spindle roughing gouge, or as he calls it a broad sweep gouge, with a nose profile like this ), which is about the same as the depth of his flutes. His finish cut is a push cut, with the gouge at about a 60 to 70 degree shear angle, and he DOES NOT RUB THE BEVEL. It is a push cut. I swore that this was not possible, especially on the inside of the bowl because if you came off the bevel, it would catch just like a skew does. Well it didn't catch, and because of the high shear angle gives a very clean cut. You do need to use both hands to push the gouge. As some one who prefers a bevel rubbing cut, I find this totally freaky, but worthy of more study. I don't have the link for his video though.

Mike Mahoney uses a pull cut. Non bevel rubbing, handle dropped. Again, a high shear angle for a clean cut. He uses a 45 degree bevel, and 45 degree sweep. I think he uses more of a push cut on the inside of the bowl. Can't really see how you could do a pull cut on the inside of a bowl.

Stewart Batty uses a bevel rubbing push cut, both inside and outside the bowl, and again the 45 bevel and 45 degree sweep. Can't remember if he grinds a secondary bevel for doing the inside of the bowl or not, even though I took a 3 day workshop with him and his father about 2 years ago.

I used to use the swept back, 45 degree bevel. Now, gradually happening to evolve as I turn more, my grinds are steeper bevels, a more rounded nose, and less sweep. The 45 degree grind is more of a universal grind which will do a lot of things well, especially if the bowl form is more open. As the bowl gets steeper, as in radius is the same as or less than depth (12 inch diameter bowl 6 inches or more deep), it becomes impossible to make the cut from the side through the transition, and across the bottom without having your handle and gouge run into the bowl rim and/or the tool rest. This is where steeper bevel angles come in. Mine are closer to 60 degrees now.

An ongoing experiment.

robo hippy

Here's a link to MM and his finishing cut, the 2nd tool in the vid: click

It does look normal on the outside of the bowl, but when done on the inside, it still gives me shivers even though I know it works. You really can't see it in MM's video, but there is no bevel rub.

robo hippy

He is actually shear scraping with a spindle gouge with a thumbnail grind.

It is my preferred method as well, as I find it easier than a bowl gouge because the cut is not hidden by the upper edge.Attachment 157715

The angle of presentation is easier also than a bowl gouge because it has not got the wings that a bowl gouge has.

Very safe for outside and inside open bowls provided you keep the bevel at right angles to the bowl face and keep the cut in the lower half of the gouge.

, forgive me if I've missed something, but as I said, the 2nd tool he uses in that vid is a (shallow) forged spindle gouge with as far as I can see a straight across cutting edge.

There are other, clearer, vids he's linked to on the AAW forum. I couldn't find them in a cursory search this morning but if you have the time ..

Ern, if you look closely it is sharpened with a thumbnail grind like these:Attachment 157737

,

You touched on one of my personal pet peeves.

The term "shear scraping" baffles me. The cut shown with his broad sweep gouge is a good slicing cut. Scraping to me is the tool flat on the tool rest, and cutting edge at 90 degrees to wood rotation. Can be done with both the gouge and scraper. The "shear scrape" can be done rubbing the bevel or not. The wood fibers cut the same. Some say the difference is bevel rubbing or not. The wood fibers don't know the difference between the tool used or the shear angle of the tool.

Scraping cuts, yes.

Shear cuts, yes.

Shear scrape? Well, maybe a cut with a deep fluted gouge where the nose is at a shear cut angle, and the wings are at a scraping angle. Can not be done with a scraper or broad sweep gouge.

Maybe better defined as roughing cuts (bulk stock removal cuts), shaping cuts (lighter final form shaping cuts), and finish cuts (very fine clean up the tool marks and tear out cuts).

Maybe this is a topic for another thread.

robo hippy

Good point RH.

I define it thus: A cut is when the bevel is rubbing. A scraping action is when the tool has no bevel support no matter what tool is used.

That is what I find so confusing, and I don't need any help being confused. Whether the bevel is rubbing or not makes almost no difference in how the steel cuts. The angle of the cutting edge relative to the spin of the wood (shear/angled vs scrape/flat/perpendicular) makes a huge difference.

robo hippy

Originally Posted by robo hippy

The term "shear scraping" ......

Maybe this is a topic for another thread.

Agreed, it was covered extensively here.
.

Heh heh.

, thanks.

robo hippy, actually for the tip of the tool to penetrate (to cut at all), there's a tiny part of the bevel just from the tip back that is in fact supporting the tool. So you have the shaving coming into the flute pushing the tip down, and the small length of bevel helping to keep the tip up. A balance of forces.

When folk talk about the bevel rubbing I guess they mean more than a smidgen from the cutting edge, and I also guess that this rubbing is pushing the fibres down and is burnishing the wood (which is what has said about the action of a skew in spindle turning if memory serves).

Sorry if this is trying to teach you to suck eggs.

Back to the Thompson 5/8 U gouge ...

Just used it to shape the outside of a bowl of Euro Ash and it worked very nicely.

The 60* bevel angle (flute to bevel included) means that compared to the more common 45* bevel more of the pounding goes to the tool rest and less to the hands.

The wide arc at the edge means that lots can be hogged out and the tool readily rolled to get more of a shear angle for cleaner cutting. It did that to about 3/4s up the side from the base and from there a 3/8 Superflute finished the job.

It's quite like my old 17mm P&N Supagouge but the flute curve is more regular running up the walls.

So as a bowl rougher, partic with the high Vanadium content to resist sand and other crap that might be in the bark, on this bit of wood at least it performed very well.

This role has been played by the Thompson 5/8 V gouge so far and I've progressively been grinding more off the tip to get a wider cutting arc, but can easily see the two swapping roles. However, I'll continue with it as is in order to determine more clearly the hollowing advantages.

Meantime, I'll need to determine the settings for the Tormek gouge jig cos the edge needs a lick on the grinder now. Diamond wheel and BGM first, then the big T.

Originally Posted by robo hippy

I used to use the swept back, 45 degree bevel......

Mine are closer to 60 degrees now.

I settled on 60 deg for all of my bowl gouges a few years back and haven't felt any need to vary from that, but my roughing and spindle gouges are all over the place.

RH, I understand that you put a secondary bevel on the heel of your bowl gouges. If so, that must come into the consideration of which primary bevel angle you settle on?
.

I do grind off the back of the bevel on my gouges. Main effect is that when turning the inside of a bowl, the bevel will rub closer to the cutting edge. Not a problem on the outside (convex shape) of the bowl, but more of a problem on the inside (concave shape). Stewart Batty explained that if you are rubbing the heel of the bevel on the inside of a bowl, it does 2 things. One, it can bruise the wood because it is a rather sharp edge. Two, it actually pushes the gouge into the cut, which is part of why you can some times see concentric rings on the inside of the bowl. Ever notice how much easier it is to turn the outside of the bowl than it is to turn the inside? It isn't all due to just being able to see the outside shape/form better than you can see the inside. I don't grind a second bevel, but round it over by rolling and raising and lowering the handle so it is rounded.

Again the bevel rubbing/not bevel rubbing. By definition, cut = bevel rubbing. Scrape = no bevel rubbing. So, if my scraper is flat on the tool rest, then it is a shear scrape? If my scraper is at a 45 degree angle, it is a shear scrape? If my gouge is on its side, no bevel rub, pull cut it is a shear scrape? If my gouge handle is dropped and flutes rolled over, and no bevel rub it is a shear scrape? My rock hard Irish head just can't seem to get around this as there are 3 different cuts here to me.

robo hippy