Unequal bevel on Sorby Bowl gouge

[Jacob]

I have just acquired a tool sharpening jig to allow me to produce repeateable sharpening on my tools and have noted something surprising.

When I presented the 1/2” Sorby bowl gouge to the wheel using the jig I found the bevel angle on one of the wings very different from the tip and the other wing - see pics.

I find it surprising given the supposed quality of these tools and wondered if anyone else has encountered similar?

Thanks

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I wouldn't worry about it. Have a go with it, resharpen a few times if it needs it and see what difference it makes if you reshape the edge. It's all part of the curve!
Small wheel means concave bevel, but also the most difficult way to achieve anything in particular. Easily ends up looking like nibbled by rats.
Personally I prefer flattish - achieved on a flat sanding disc.
PS jig obviously no good. Bin the jig.

 

[scooby]

PS jig obviously no good. Bin the jig.

Post no.7

You're not the first to make that mistake.

 

[Jacob]

Post no.7

You're not the first to make that mistake.

Jig is supposed to help the beginner to do things "correctly". If it doesn't, then bin it.

 

[Lazurus]

Sorby 447 jig and an 8" slow grinder, all i have ever used for the past 20 or so years, fast repeatable accurate grinds

 

[scooby]

Jig is supposed to help the beginner to do things "correctly". If it doesn't, then bin it.

He hasn't used the jig yet. The gouge was sent to him like that.

 

[Jacob]

He hasn't used the jig yet. The gouge was sent to him like that.

What about using the jig then?

 

[Inspector]

Do you have any pictures of the gouge from the front looking down the flute? I'm curious if it is symmetrical and what shape it is. Deep U, V or parabolic.

Pete

 

[Limey Lurker]

If the base of the jig is exactly alighned on the centre of the wheel then it should produce the same angle each side but bear in mind, the jig just puts the tool at the correct angle, how much you grind away is down to you, not the jig. If the bevels on each side of the gouge differ, keep grinding until they are the same. The initial differences may be due to how the gouge was sharpened before the jig was used.

As can be seen from your photos, you have ground too much away at the wings and not enough in the centre so the tool has developed a pronounced "beak". That needs to be removed by grinding away at the centre. When you look at the tool from the side, the profile should be a convex curve or at worst, a straight line - never a concave curve.

I can't see how a concave bevel can be avoided when grinding on a wheel's periphery with a jig with a fixed pivot.

 

[scooby]

I can't see how a concave bevel can be avoided when grinding on a wheel's periphery with a jig with a fixed pivot.

I think Paul was referring to cutting edge of the wing is concave (not the bevel, that will always be hollow on a wheel) producing the 'beak'.
The wing edge can be made convex/straight (as Lazarus pictured) but either turning the gouge upside down and running it up and down on the wheel and then use the jig to sharpen on the jig. At about 4 minutes on this video

Or just do it on the jig and grind away the high points.

 

[Phil Pascoe]

I can't see how a concave bevel can be avoided when grinding on a wheel's periphery with a jig with a fixed pivot.

At the club I belonged to they used well worn wheels purposely to get a hollower grind. Several very experienced turners inc. a pro wouldn't use a ProEdge because it gave a flat grind.

 

[Phil Pascoe]

Do you have any pictures of the gouge from the front looking down the flute? I'm curious if it is symmetrical and what shape it is. Deep U, V or parabolic.

Pete

Yes, I wondered if it was symmetrical.

 

[Bob Chapman]

It's my understanding that gouges are ground to approximately the right shape by the manufacturer. They are not exact and they are not sharp. The first thing you should do with a new gouge is grind it to the shape you want and make it sharp. I wouldn't worry too much about its initial shape.

 

[Paul Hannaby]

Turners Retreat is owned by Sorby.
I have never seen one come like that from Sorby so perhaps you were given a return item. I wouldn't get too hung up about how the tip is shaped now. Just regrind it to what you want.
I can't remember ever buying a gouge with a grind on it I wanted - I always shape them to what I want and for the bevel angle I prefer.

 

[Limey Lurker]

I think Paul was referring to cutting edge of the wing is concave (not the bevel, that will always be hollow on a wheel) producing the 'beak'.
The wing edge can be made convex/straight (as Lazarus pictured) but either turning the gouge upside down and running it up and down on the wheel and then use the jig to sharpen on the jig. At about 4 minutes on this video

Or just do it on the jig and grind away the high points.

Now I understand! Thank you!

 

[Fergie 307]

I wouldn't worry about it. Have a go with it, resharpen a few times if it needs it and see what difference it makes if you reshape the edge. It's all part of the curve!
Small wheel means concave bevel, but also the most difficult way to achieve anything in particular. Easily ends up looking like nibbled by rats.
Personally I prefer flattish - achieved on a flat sanding disc.
PS jig obviously no good. Bin the jig.

I bought a Parkside disc sander, just basically a motor with a disc on the end. Designed to take 125mm sanding discs. Thing that attracted me was it is variable speed. Modified to take diamond lapping discs I now use it for sharpening all my metal lathe tools, best 25 quid I've spent in a long time. One thing to bear in mind if you use a flat wheel is that the disc is travelling a lot faster across the tool at the edge than in the centre. If the tool is wide this can lead to you taking more off one side than the other, particularly if you are doing it freehand.

 

[Kerrowman]

Gee I wasn’t aware of all the new posts while I’ve been away sorting this tool.

Anyway I sent my 1/2” bowl gouge back to Turners-Retreat and they decided to regrind it instead of replacing the tool. I’m happy with that and in one of the pics you can see the very nice shape that it should have been in the first place.

However, when in future I come to resharpen this I will meet the same thing that I observed before which is that the wings don’t lie flat on the wheel when using my jig and the toe bevel has been set flush with the wheel (see pics). This presumably means that they use some other system of sharpening (by practiced hand?) that results in the profile I have received. So as suggested I will reshape when I next need to sharpen.

When I do come to sharpen then I will have to regrind the wings in particular so that subsequent resharpening will match the way my jig works. It seems that lots of people use a jig like the one I acquired but maybe it’s best for tools with ‘simple’ bevels and not the sweptback bowl gouge. I notice that even my new 3/4” bowl gouge has a straightforward bevel the same all round.

That’s all fine in principle, but there is still one question that as yet no one has answered, including the company where I bought the tool from.

At the moment the bevel is nice and straight and not concave but using a sharpening wheel will tend to produce a concave shape on the bevel due simply to the curvature of the wheel, as one of the replies here mentioned. I How can one avoid this while still obtaining a straight or even convex bevel with a consistent grind along the bevel’s length?

The only way I can think of is to use a sanding belt instead, which is flat at the grinding point but, in my case, I can’t rotate the tool fully due to the casing next to the belt as shown in the picture.

Thoughts welcomed.

Julian

 

[RichardG]

Now you have the perfect grind use this to “calibrate“ your jig. You have a couple of adjustments so see if you can get close without the grinder running. Pull out the bottom slide and then extend/withdraw the gouge in the holder to match the tip angle and then see how the wings are. If it‘s better then keep going otherwise move things in the opposite direction. You won’t replicate exactly but probably get closer than you are.

 

[Kerrowman]

Thanks for suggestions. I wasn’t aware that changing the projection of the gouge from the holder made much difference but will happily give it a go. Is there a sharpening setup that uses a flat belt sander to avoid the concave bevel?

 

[Inspector]

Why avoid the concave bevel. Turners have used gouges sharpened with 6", 8" & 10" and worn wheels from them forever and never had an issue with the concave bevel. Get a scrap or chunk of firewood mounted and start playing. You'll see it works just fine.

Pete

 

[Kerrowman]

Someone on this thread said to avoid a concave bevel.