Carbide Tool Catches.

[SimonW]

I recently decided to try and turn a bowl from some decent birchwood ply I had lying around, sandwiched with coloured acrylic as a bit of an experiment. I figured I'd need to 'go Carbide' to have a chance of getting through the Acrylic layers, so I took the plunge and bought a round tipped David Lloyd chisel.

Turning the outside was a breeze with the new tool, I had to go slower through the Acrylic layer, but the project started pretty well. The problem came when trying to hollow the blighter out- I knew getting through the Acrylic would be a challenge, but even on the plywood sections I got way too many nasty catches. I'm admittedly fairly new to turning, so maybe I'm just being as tad ambitious with this project. However, I'm pretty sure I followed the basics- Tip on the centre line; chisel flat and at 45 degree's to the piece; turning the tip in case it was getting blunt quickly due to the Acrylic; and as much tool rest support as my over sized rest could muster inside a small bowl ...

I'm reasonably happy with the result (pre finishing), but the process and experience was less than comfortable (heart stopping!) to say the very least.

Has anyone else experienced similar with Carbide? Or maybe I'm just doing something dumb and inexperienced? Also, does anyone have any Valium please?   

[The Bowler Hatted Turner]

Simon in my opinion acrylic turns best with a negative rake scraper, also when cutting plywood the edge is taken off of the chisel very quickly. Sometimes you need to turn (rotate) the chisel slightly so that you do not have a cut which is too aggresive. You don't state how far your tool tip was overhanging the tool rest, that too can have an impact.

[Paul Hannaby]

If you are using a scraper inside a bowl or another hollowing project you want the cutting edge to be above centre. this is because any catch will force the tool down, which effectively pushes the tool out of the wood. Cutting on it below centre will result in big catches because the tool will bury itself farther in the wood when pushed down.

On the outside of a bowl, spindle etc. the opposite applies - use a scraper on or just below centre.

You can also make the cut less agressive and less likely to catch if you rotate the tool anticlockwise so the edge is effectively trailing more. This has the same effect as John's suggestion of using a negative rake scraper.

To compound the problem, the cuts on the outside of a bowl are generally taken from centre to edge because that gives a supported cut in relation to the grain direction. The cuts on the inside are from edge to centre for the same reason. Both these are easily achieved if using a gouge but trying to use a scraper to cut from edge to centre on the inside of a bowl isn't quite so easy so some people end up cutting the wrong way on the inside of the bowl and that leads to problems...

[fuzzyturns]

I've always found that when turning plywood, a lot depends on the quality of it. The only stuff that really gives decent results is the "best quality exterior hardwood ply", and even then you can get voids and cracks. The stuff just isn't made for wood turning, let's face it.

[seventhdevil]

good quality birch ply should have voidless ply's and can be very nice when turned.

Simonw, don't take this the wrong way but the only dumb thing (as you put it) i think you have done is buy a carbide tool in the first place. if you are relatively new t turning then it's my humble opinion that you should do it the old fashioned way and learn to turn properly. a carbide tool does have its place but only on extremely dense tropical timbers like snakewood or lignum. a bowl like this can be turned with a normal bowl gouge.

[APH]

Frankly some of those cranked David Lloyd chisels(sic) are a bad catch waiting to happen, even in really experienced hands.
The cutting edge really ought to be directly supported, not off-axis.

“Carbide” seems to be regarded and promoted as a magic solution by the inexperienced on social media, but really it isn't.
What seems poorly understood is that carbide tools come in three types;
The flat inserts that are really just little scrapers that need less frequent sharpening.
The dished cutters (eg Hope) that actually cut and need, like all cutting tools, to be correctly presented, but need less sharpening.
Normal gouge heads made from Carbide that need less frequent sharpening, but will be awkward to sharpen when needed.

Once you appreciate that 'carbide' isn't a magic bullet for turning, just another material for tools, you then understand that to use carbide tools effectively you still need to know how to work with 'normal' tools first and make the most appropriate choice of tool for the task ahead.

I would also add that Seventhdevil saying “you should do it the old fashioned way and learn to turn properly “ is a good sentiment, but you shouldn't describe learning properly as 'old fashioned' it's just the smart thing to do.

[Derek]

I started with the normal tools and spent time finding the best way to use them. I was then given a set of three carbide tools even though I do use them I still go to my other tools first. I for one don't think these are a good tool to learn or start with and agree with the above coments about learning with normal tools

[SimonW]

Simon in my opinion acrylic turns best with a negative rake scraper, also when cutting plywood the edge is taken off of the chisel very quickly. Sometimes you need to turn (rotate) the chisel slightly so that you do not have a cut which is too aggresive. You don't state how far your tool tip was overhanging the tool rest, that too can have an impact.

Thanks Bowler. I went for the carbide option with this project because I thought I'd be sharpening constantly? The Carbide tip didn't last anywhere near as long as I hoped though. It's good to know a negative rake scraper would be a good choice for Acrylic.

The amount of tool overhang- Too much probably. It definitely felt like an issue at the time. I'm considering getting J or S shaped tool rest bar that should get me closer into the piece.

[SimonW]

If you are using a scraper inside a bowl or another hollowing project you want the cutting edge to be above centre. this is because any catch will force the tool down, which effectively pushes the tool out of the wood. Cutting on it below centre will result in big catches because the tool will bury itself farther in the wood when pushed down.

On the outside of a bowl, spindle etc. the opposite applies - use a scraper on or just below centre.

You can also make the cut less agressive and less likely to catch if you rotate the tool anticlockwise so the edge is effectively trailing more. This has the same effect as John's suggestion of using a negative rake scraper.

To compound the problem, the cuts on the outside of a bowl are generally taken from centre to edge because that gives a supported cut in relation to the grain direction. The cuts on the inside are from edge to centre for the same reason. Both these are easily achieved if using a gouge but trying to use a scraper to cut from edge to centre on the inside of a bowl isn't quite so easy so some people end up cutting the wrong way on the inside of the bowl and that leads to problems...

Thanks Paul, that's most helpful. I was probably staying on the centre line rather being just above it, so that's good to know. When you say "rotate the tool anticlockwise', do you mean twist the tool (down the axis of the handle/shaft), and that's with a round carbide tip, while inside the bowl?

[SimonW]

I've always found that when turning plywood, a lot depends on the quality of it. The only stuff that really gives decent results is the "best quality exterior hardwood ply", and even then you can get voids and cracks. The stuff just isn't made for wood turning, let's face it.

I quite like the look of turned ply! So far, it just doesn't like me

[SimonW]

good quality birch ply should have voidless ply's and can be very nice when turned.

Simonw, don't take this the wrong way but the only dumb thing (as you put it) i think you have done is buy a carbide tool in the first place. if you are relatively new t turning then it's my humble opinion that you should do it the old fashioned way and learn to turn properly. a carbide tool does have its place but only on extremely dense tropical timbers like snakewood or lignum. a bowl like this can be turned with a normal bowl gouge.

No offence taken. I am still learning with traditional tools though, not looking for short cuts, just (mistakenly it seems) thought a carbide tip would be the tool for this job.

[SimonW]

Frankly some of those cranked David Lloyd chisels(sic) are a bad catch waiting to happen, even in really experienced hands.
The cutting edge really ought to be directly supported, not off-axis.

“Carbide” seems to be regarded and promoted as a magic solution by the inexperienced on social media, but really it isn't.
What seems poorly understood is that carbide tools come in three types;
The flat inserts that are really just little scrapers that need less frequent sharpening.
The dished cutters (eg Hope) that actually cut and need, like all cutting tools, to be correctly presented, but need less sharpening.
Normal gouge heads made from Carbide that need less frequent sharpening, but will be awkward to sharpen when needed.

Once you appreciate that 'carbide' isn't a magic bullet for turning, just another material for tools, you then understand that to use carbide tools effectively you still need to know how to work with 'normal' tools first and make the most appropriate choice of tool for the task ahead.

I would also add that Seventhdevil saying “you should do it the old fashioned way and learn to turn properly “ is a good sentiment, but you shouldn't describe learning properly as 'old fashioned' it's just the smart thing to do.

Yes I've certainly feel a little misguided by the carbide hype. Having said that, I don't want to give up completely on the tool, I guess I just need more knowledge and experience with it in different applications to get a better feel for it. Thanks for the overview on the types of carbide tools, very helpful .

[Paul Hannaby]

If you are using a scraper inside a bowl or another hollowing project you want the cutting edge to be above centre. this is because any catch will force the tool down, which effectively pushes the tool out of the wood. Cutting on it below centre will result in big catches because the tool will bury itself farther in the wood when pushed down.

On the outside of a bowl, spindle etc. the opposite applies - use a scraper on or just below centre.

You can also make the cut less agressive and less likely to catch if you rotate the tool anticlockwise so the edge is effectively trailing more. This has the same effect as John's suggestion of using a negative rake scraper.

To compound the problem, the cuts on the outside of a bowl are generally taken from centre to edge because that gives a supported cut in relation to the grain direction. The cuts on the inside are from edge to centre for the same reason. Both these are easily achieved if using a gouge but trying to use a scraper to cut from edge to centre on the inside of a bowl isn't quite so easy so some people end up cutting the wrong way on the inside of the bowl and that leads to problems...

Thanks Paul, that's most helpful. I was probably staying on the centre line rather being just above it, so that's good to know. When you say "rotate the tool anticlockwise', do you mean twist the tool (down the axis of the handle/shaft), and that's with a round carbide tip, while inside the bowl?

Yes that's twisting the handle. It would apply to any scraper used for hollowing.

[edbanger]

Hi SimonW

We have all got our own ways of doing things, but reading the comments here no one as pointed out the the real problem.

My guess is that your upper frame is to stiff and your holding on to the tool to hard which means your applying to much pressure on the cutter. In turn causes you to get a catch which by nature means that your hold on to the tool even harder and this increases the problem.

If you have not done so, take a lesson with someone who understands what they are doing. There really is not the need to start spending money on this or that shape of tool rest it's all about the tool control.

All the best

Ed

[SimonW]

Hi SimonW

We have all got our own ways of doing things, but reading the comments here no one as pointed out the the real problem.

My guess is that your upper frame is to stiff and your holding on to the tool to hard which means your applying to much pressure on the cutter. In turn causes you to get a catch which by nature means that your hold on to the tool even harder and this increases the problem.

If you have not done so, take a lesson with someone who understands what they are doing. There really is not the need to start spending money on this or that shape of tool rest it's all about the tool control.

All the best

Ed

Thanks Ed. There was certainly times during that project that I had to remind myself to relax my grip when things got a bit lively. But the only way I actually managed to complete it was by taking really light cuts (but still got catches).

My tool rest is quite deep (vertically), so it stops me getting much tool support deeper into a bowl with a narrow rim. (I don't normally have this kind of issues with a normal bowl gouge or scraper in a wider rimmed bowl)

Lessons wise I've taken a few, and I will take more, and I've been doing reasonably OK turning beech, oak and a few other species. But this project had me feeling like an absolute beginner again!