What is the smallest sensible facet for a bevel?

[woodfarmer]

Would like some opinions on how small can a facet be to work effectively as a bevel on a bowl gauge?

Just took delivery of a gouge and somehow it does not seem right. Not sure if it is my lack of knowledge or their misunderstanding.

 

[woodfarmer]

Specifically, how small can facet "A" be?

http://www.peterchild.co.uk/tools/bowlg/anbg.htm

 

[Spindle]

Hi

The smaller you make facet A the easier the gouge will dig in due to the reduced bevel support, it will also be more difficult to keep the bevel contact as it gets smaller. I only grind single bevels on my gouges so have no direct experience of this type of grind but I wouldn't go smaller than about 3mm to start with.

Regards Mick

 

[Rhossydd]

Specifically, how small can facet "A" be?
http://www.peterchild.co.uk/tools/bowlg/anbg.htm

That link has to read carefully; It's not about bowl gouges in general, but only that specific angletip superflute gouge which has a non-standard profile and is only used for final finishing cuts in difficult timber.

Most bowl gouges are ground with a single bevel and that's what you should start with.
Once you know what you're doing there are occasions when grinding some material from the back of the bevel can be helpful to ease access into tight radii (effectively bevel B in the angletip diagram).

 

[Random Orbital Bob]

What sharpening kit have you got Woody?

I agree that you should be grinding single facet bevels only on all your gouges to start off with (spindle and bowl) because they're the easiest to manage and there's plenty other things to worry about for the time being. I would use whatever sharpening jigs you have to create a single facet bevel and then proceed from there. I also grind the heels off my gouges. Just a hair off the bottom as it also helps to avoid catches and helps to smooth transitions.

 

[Richard Findley]

You can use a tiny bevel, or micro bevel - see Jimmy Clewes and you'll see it. Personally, I don't think there is much advantage to such a tiny bevel.

The reason for a shorter bevel is to allow you to cut around a tighter curve with a clean cut. I use a 60 degree bevel then remove the heel until the bevel is reduced in size by about half. I find this <6mm bevel ideal. The advantage of this method is you know the feel of your bevel. With Jimmy's method you have your bevel then produce a tiny micro bevel, but this could be almost any angle so could be a little hit & miss.

Hope this helps

Richard

 

[Mark Hancock]

Hi

The smaller you make facet A the easier the gouge will dig in due to the reduced bevel support, it will also be more difficult to keep the bevel contact as it gets smaller.

Regards Mick

Sorry Mick but if I have understood correctly what you've said here I have to disagree completely. By making the primary bevel (facet A) very small and the secondary bevel much larger makes it more like a convex bevel. With a convex bevel it's actually harder to loose bevel contact so less likely to loose cutting edge support and hence less likely to dig in. Check out Eli Avisera's tool http://www.ashleyilestoolstore.co.uk/index.php?main_page=index&cPath=3_99 with the use of the double and convex bevels. There is also Johannes Michelsen, the hat man, advocates a complete convex bevel; check out the grind on this page http://www.woodhat.com/workshops.asp

Hollow grinding creates a sharp heel to the bevel and as has already been pointed out most of us soften that heel so creating that secondary bevel and this does aid getting round tight curves as well as reducing the chance of bruising the fibres behind the cut. This does of course assume you are sharpening on a round 6" or 8" grinding stone and not using a flat system like the Sorby Pro Edge.

 

[woodfarmer]

My reason for going down this route is when I have made some deep steep sided bowls, I have found it difficult to do the inside bottoms as ATM I can end up with 6 inches or so of gouge sticking out off the rest and cannot run my current 45 degree single facet gouge on the bevel, just not enough room for the shank to clear the rim of the bowl. This is exacerbated by turning natural edged bowls with "wings" flying around looking for fingers to chop off.

I have two strategies in progress to alleviate this, first, I now have the steel to make a better rest and secondly hope that this style of gouge would allow the biggest (bluntest) bevel angle which would give me the most amount of room to get on the bevel when deep inside a bowl.

Flatter bowls are not a problem, especially when they have sloping sides.

 

[Spindle]

Hi Mark

Food for thought but I'll stick to my original statement based on the following:

With this type of grind the supporting bevel is A, B has no supporting influence on the cut

This grind is nothing like a convex bevel where the transition is gradual, there is a defined, (rather large0, step between the two bevels. (I agree your point with regard to maintaining the contact with a convex bevel though but I don't feel it to be relevant in this case).

With regard to the suggestions above to regrind the gouge to a single bevel, I would also advise some forethought.

This gouge's 'feature' is the flute being ground away from the axis of the gouge at the tip, this effectively reduces the inclusive angle of grind between the flute and the bevel over a standard gouge ground to the same bevel angle. As the flute is only ground with this feature at the tip of the gouge, once you've ground past the modified flute you will be left with a standard gouge. The deviation of the flute is also radially ground so as you grind back the gouge the angletip effect becomes proportionally less. I assume there is a premium price attached to this gouge therefore rather than grinding a single bevel onto it and hastening it's demise as an angletip gouge I would restore facet A to a reasonable size, say 4mm, and see how you get on with it.

Regards Mick

 

[Mark Hancock]

My reason for going down this route is when I have made some deep steep sided bowls, I have found it difficult to do the inside bottoms as ATM I can end up with 6 inches or so of gouge sticking out off the rest and cannot run my current 45 degree single facet gouge on the bevel, just not enough room for the shank to clear the rim of the bowl. This is exacerbated by turning natural edged bowls with "wings" flying around looking for fingers to chop off.

I have two strategies in progress to alleviate this, first, I now have the steel to make a better rest and secondly hope that this style of gouge would allow the biggest (bluntest) bevel angle which would give me the most amount of room to get on the bevel when deep inside a bowl.

Flatter bowls are not a problem, especially when they have sloping sides.

It's always good to have more than one bowl gouge so that you can have different grinds for situations like this....I've probably got about 10 1/2" and 3/8 gouges altogether :roll:
I never been a big fan of having the tool rest inside a bowl particularly natural edge ones. My approach has always been to lengthen the tool handle so I have full control when there a large overhang of the tool. IMHO most tool manufacturers put too short a handle on bowl gouges.
Another option I sometimes use with a deep sided form is to switch to using a hollowing tool like the Hamlet Big Brother or Munro. Both can deal with the overhang on the tool rest and the grain orientation towards the bottom of the form is suitable for those tools.

 

[Mark Hancock]

Hi Mark

Food for thought but I'll stick to my original statement based on the following:

With this type of grind the supporting bevel is A, B has no supporting influence on the cut

This grind is nothing like a convex bevel where the transition is gradual, there is a defined, (rather large0, step between the two bevels. (I agree your point with regard to maintaining the contact with a convex bevel though but I don't feel it to be relevant in this case).

With regard to the suggestions above to regrind the gouge to a single bevel, I would also advise some forethought.

This gouge's 'feature' is the flute being ground away from the axis of the gouge at the tip, this effectively reduces the inclusive angle of grind between the flute and the bevel over a standard gouge ground to the same bevel angle. As the flute is only ground with this feature at the tip of the gouge, once you've ground past the modified flute you will be left with a standard gouge. The deviation of the flute is also radially ground so as you grind back the gouge the Superflute effect becomes proportionally less. I assume there is a premium price attached to this gouge therefore rather than grinding a single bevel onto it and hastening it's demise as a Superflute gouge I would restore facet A to a reasonable size, say 4mm, and see how you get on with it.

Regards Mick

Sorry Mick, I've just realised the OP bought that particular gouge, the Angle Tip Superflute. My comments were in relation to gouges where the flute is the same throughout be they a Superflute, Masterflute or Standard. Personally although I see what it's trying to achieve I don't see any advantage to it over 'ordinary' bowl gouges. To me it's just another marketing gimmick. As I've said previously I have a number of gouges with different grinds to suit different situations.

 

[Spindle]

To me it's just another marketing gimmick

Can't disagree with that - I'm with you, similar gouges with different grinds work for me too.

Regards Mick