Naive wood-turning question.

[chaoticbob]

I don't do much wood turning and when I do it's on a metalwork lathe. I was turning a piece of iroko from an old lab bench tonight with the intention of making a round wooden plinth.:

The brass bar is irrelevant - it's just stuck to the wood with double-sided tape and is there to move the work away from the chuck. The tool isn't that sharp - I am just roughing and the breakout doesn't matter at the moment ,but it will do. How would you guys address this? Do I just need a sharper tool or should I sandwich the work as one does when drilling?
Bob.

 

[Phil Pascoe]

Saw the piece round first.

 

[Paul Hannaby]

Firstly, always make sure your tool is properly sharp. Anything less will result in torn grain and other damage due to the extra pressure you have to put on the tool.

The breakout is caused by pushing the tool off the edge of the piece of wood and has nothing to do with whether the wood is round or not. To prevent the breakout, don't cut off the edge of the wood, cut almost to the edge then cut from the edge inwards.

 

[J-G]

I would make an arbor and clamp the work between two disks - whether they were Brass, Steel or Wood is irrelevant, much more important is your choice of tool - I'm sure I can see a square carbide tipped tool in the toolpost - change that to a simple HSS toolbit. I would use a high rake angle grind, I do hope that you grind your HSS Tooling by hand!

 

[Fergie 307]

As Phil says, get it fairly round to start with. Just making life harder by doing it like that. And carbide tools don't tend to like interrupted cuts, they are quite brittle. Probably not an issue in wood admittedly, but HSS would be much better. For any lathe work, in any material, sharp tools are essential. Hard to see from the picture but inserts can have radiused or pointed tips. Looks as though you have a radiused one, which I should think would pretty much guarantee breakout issues in wood.

 

[clogs]

as above,
thats why most wood turners have a bandsaw.......
be wary if u look at some on youtube.......most start of with stupid shaped peices wood.....
then they cut it back to the round.......it's just mental.....

 

[Democritus]

As everyone else. Do you have a bandsaw? That should be your first point of call. Personally, I would hesitate to turn a square blank of that size on a dedicated Woodturning lathe, let alone on a machine not designed for that purpose.
Anyway, good luck with it.
D.

 

[Phil Pascoe]

Even without a bandsaw it's easy to saw it octagonal.

 

[Richard_C]

Yes. Before I had a small Bandsaw I used a mitre saw to cut the corners off, hexagon, octagon, random-gon,

 

[okeydokey]

As others have said make it more round with a saw - making it round from as is - not a challenge I would take up

 

[Paul Hannaby]

The breakout isn't on the edge of the flat face so cutting it octagonal or round would make no difference.

 

[chaoticbob]

Thanks for replies. I do have a bandsaw and in retrospect it was daft of me not to have cut the piece to some semblance of roundness. I'd have done that if the work was in metal. I guess I was thinking that because wood can be cut much faster than metal on the lathe it would be quicker than changing the bandsaw blade. I'm a lazy b*****d. Wrong, obviously.
I had a lightbulb moment when thinking about how I would do if turning freehand - cut from the edges to the centre, which is essentially what Paul Hannaby suggests. I could do that with either suitable CCGT carbide inserts which are sharp and high rake, or grind an HSS tool.
Maybe someday I'll get a wood turning lathe and learn how to do this stuff properly!
Thanks again, Bob.

 

[Dave Moore]

Thanks for replies. I do have a bandsaw and in retrospect it was daft of me not to have cut the piece to some semblance of roundness. I'd have done that if the work was in metal. I guess I was thinking that because wood can be cut much faster than metal on the lathe it would be quicker than changing the bandsaw blade. I'm a lazy b*****d. Wrong, obviously.
I had a lightbulb moment when thinking about how I would do if turning freehand - cut from the edges to the centre, which is essentially what Paul Hannaby suggests. I could do that with either suitable CCGT carbide inserts which are sharp and high rake, or grind an HSS tool.
Maybe someday I'll get a wood turning lathe and learn how to do this stuff properly!
Thanks again, Bob.

Hi,
you won’t get a decent finish with a carbide tool as they are really working like a scraper, a HSS tool would be much better. As mentioned cut the corners off and when you get nearer the size you want cut in from the edges ensuring you keep the tool well sharpened.Regards,
Dave

 

[chaoticbob]

Hi,
you won’t get a decent finish with a carbide tool as they are really working like a scraper, a HSS tool would be much better. As mentioned cut the corners off and when you get nearer the size you want cut in from the edges ensuring you keep the tool well sharpened.Regards,
Dave

Thanks. I've not got back to it yet but as advised I'll rough out on the bandsaw and find or grind an HSS tool when I do.
As an aside though, there are sharp high +ve rake metalworking inserts designed for non-ferrous metals, eg this chamfer tool:

I know that wood turning carbide inserts exist and wonder if it the same basic technology. Probably a massive subject and I'm in way above my head, but can't help thinking...!
Bob.

 

[jonn]

Thanks. I've not got back to it yet but as advised I'll rough out on the bandsaw and find or grind an HSS tool when I do.
As an aside though, there are sharp high +ve rake metalworking inserts designed for non-ferrous metals, eg this chamfer tool:
View attachment 166263
I know that wood turning carbide inserts exist and wonder if it the same basic technology. Probably a massive subject and I'm in way above my head, but can't help thinking...!
Bob.

Those inserts and the round ones RCGT are excellent for woodturning, both on a metal lathe and a wood lathe. I make my own turning tools for the wood lathe with inserts bought via Aliexpress. Cost me less than £10 equivalent.

 

[niall Y]

Thanks. I've not got back to it yet but as advised I'll rough out on the bandsaw and find or grind an HSS tool when I do.
As an aside though, there are sharp high +ve rake metalworking inserts designed for non-ferrous metals, eg this chamfer tool:
View attachment 166263
I know that wood turning carbide inserts exist and wonder if it the same basic technology. Probably a massive subject and I'm in way above my head, but can't help thinking...!
Bob.

As has been said by @jonn , these type of inserts for non-ferrous metals are really good for turning wood, Your tool shows the cutter presented horizontally, If you are after a good finish on say the outside of a cylinder it is often better to use a "round", or "rounded square cutter", and to cant this at a 45 degree angle.

When I looked for an indexable tool holder for my metal working lathe that would allow me to do this, I couldn't find one, so I have just made one to fit . I'm waiting for some small, 4mm Torx screws, so I can screw the insert on and try it out. I will post a photo in the next few days if you are interested.

 

[chaoticbob]

Thanks for further comments Jonn and Niall.

As has been said by @jonn , these type of inserts for non-ferrous metals are really good for turning wood, Your tool shows the cutter presented horizontally, If you are after a good finish on say the outside of a cylinder it is often better to use a "round", or "rounded square cutter", and to cant this at a 45 degree angle.

When I looked for an indexable tool holder for my metal working lathe that would allow me to do this, I couldn't find one, so I have just made one to fit . I'm waiting for some small, 4mm Torx screws, so I can screw the insert on and try it out. I will post a photo in the next few days if you are interested.

I certainly am interested - I have 6 and 8mm RCGT inserts but obviously the holders present the tools horizontally. I have a milling machine so could make canted holders.
Bob.

 

[Fergie 307]

Thanks. I've not got back to it yet but as advised I'll rough out on the bandsaw and find or grind an HSS tool when I do.
As an aside though, there are sharp high +ve rake metalworking inserts designed for non-ferrous metals, eg this chamfer tool:
View attachment 166263
I know that wood turning carbide inserts exist and wonder if it the same basic technology. Probably a massive subject and I'm in way above my head, but can't help thinking...!
Bob.

I would think the one in the picture would certainly be better than the one you have at the moment.

 

[Fergie 307]

As has been said by @jonn , these type of inserts for non-ferrous metals are really good for turning wood, Your tool shows the cutter presented horizontally, If you are after a good finish on say the outside of a cylinder it is often better to use a "round", or "rounded square cutter", and to cant this at a 45 degree angle.

When I looked for an indexable tool holder for my metal working lathe that would allow me to do this, I couldn't find one, so I have just made one to fit . I'm waiting for some small, 4mm Torx screws, so I can screw the insert on and try it out. I will post a photo in the next few days if you are interested.

Interesting idea, be good to see how it works out.

 

[niall Y]

Following are a couple of pics. One of the cutter and holder I put together and the other of it being used to turn the outside of an African Blackwood tube, fixed to a mandrel on my lathe.

I experimented a bit with trying to get the bevel rubbing against the wood by bringing the top end of the cutter away from the tool-holder. However I found the best position, was half-way between.
It cut the wood really well, but I can't say I was impressed with the finish that I was getting direct from the tool. Part of this is down to the flexing of the carriage on my lathe, and part down to the rack and pinion I have to operate by hand - not smoothly enough I have to add.
I will have to experiment further with a square radius, carbide cutter to try and improve the finish.