Skew grind angle

[Democritus]

I have three skew chisel, an Axminster, and two Sorby. Both have grind angles of about 15 degrees. I recently got a copy of the late Allan Batty’s ‘Woodturning Notes’, and he recommended grind angles of 55, 40, and 25 degrees, depending on the wood being turned. 55 and 40 suggested for hardwoods, and 25 and 40 for soft. He, himself, used a grind angle of 40, this being able to tackle hard and soft wood.
If this is so, why is 15 degrees recommended by the likes of Sorby.
Sharpening skews is hard enough as it is (at least for me) without this sort of complication making it worse.
Any ideas , clarification?

 

[Phil Pascoe]

15 degrees I would imagine is the measurement from the axis to one side, the other measurements inclusive angles?

 

[scooby]

Alan Batty's angles will be inclusive so 40 would be 20 each side. The same for 55, etc. Most come with 50 inclusive (25 each side), I think Sorby's are 30 inclusive. I reground my Hamlet skew from 50 inclusive to 40 (20 each side) and find it a lot nicer to use.

From what I've read more acute angles are supposed to be harder to use, which contradicts my experience. Having said that, I don't fancy going to 15 each side at the moment.

 

[Phil Pascoe]

I find it easier to control ground unevenly, steeper on the side in contact - the problem being two tools are then needed to work left handed as well as right.

 

[Robbo3]

Production turners, with their years of experience & because they were paid per item, would probably have a tool specially ground for each job. Unlike us amateurs who have one tool for all occasions.

 

[Argus]

Without getting into the bevel, in reality there are two angles involved in a skew chisel on a lathe.

The first is the fixed grind-angle of the chisel, whatever that happens to be.
The second is variable........ the angle at which the long axis of the chisel itself is presented to the work by the turner.

 

[Democritus]

Cheers, guys. If I understand correctly, the skews I have are 30 degrees, I.e. 15 degrees each side? So to get a 40 degree skew, I would have to regrind to 20 degrees each side? Not sure it would be worth the trouble!
Thanks again for your help.
D

 

[scooby]

Yep, 30 degrees will be 15 each side. If you have no difficulty using it at 15, I'd leave it. You might have to sharpen it a bit more often at that angle...I'd still leave it.

Colwin Way has said a few times that his skews are shipped at 50 inclusive (25/25) as its more friendly to beginners. I've not been turning long but I prefer a more acute angle (20 each side). Helps with tighter v cuts as well, I wouldn't mind trying 30 inclusive but I don't feel like reshaping my skew on a whim.

 

[scooby]

If you don't have already, I'd recommend getting a cheap protractor like this https://www.amazon.co.uk/gp/product/B08L6BSK12/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1
The angles will make more sense using that and it'll be useful for other things