Tearout problems - Advice sought

[Thomas Hayman]

Been on something of a bowl binge lately made six in the last week or so and only 8 ever lol.

I've been running into the problem of tearout/finishing as shown in the pictures. I'm self taught so it's likely to be something i'm doing. Tools are sharpened regularly and as sharp as i can get them.

I've included pictures so you can see what i'm doing. Any advice is very gratefully received as this is doing my head in!

 

[ankledeep]

hmmmm...what wood is that????

 

[Robbo3]

The gouge shown in the first pictures is a roughing gouge. Most professionals now refer to this as a spindle roughing gouge to make the point that it should ony be used along the grain & not across it.

As to the tear out, a number of options depending on your competence :

A bowl gouge with a long grind, used at 90° almost like a scraper & taking very gentle cuts.
A scraper tilted on its bottom edge so that it passes across the wood at an acute (less than 90°) angle (sheer scrape).
Apply sanding sealer & allow to dry before taking gentle cuts with a gouge or scraper.
Reverse the wood in the lathe so that it spins in the opposite direction.

HTH

Robbo

 

[Thomas Hayman]

I believe it's monkey puzzle! Not the best of woods but free and good for practising with.

Thanks for the suggestions and advice i'll get to using the other gouge tomorrow and see how i fair!

Cheers

Thomas

 

[boysie39]

When using a scraper make sure that is slightly above center height so that you have the end of the handle raised slightly above the part that is scraping the wood .

 

[CHJ]

When using a scraper make sure that is slightly above center height so that you have the end of the handle raised slightly above the part that is scraping the wood .

Sorry Eugene but I think that is dangerous for a novice without a demonstration that the cutting edge must always be below centre..

Thomas, on an outside of a bowl the cutting edge of a scraper must always be below the centreline for safety, that way any tendency to catch is directed down and away from the piece. Eugene is advocating this by his lifting of the handle but I would advise you to have the rest below centre until you have mastered the technique.

If tool Support is positioned above centre a novice is likely to get the scraper cutting edge above centre line and that is almost guaranteed to cause a catch as the tool has a natural tendency to dig in with the natural rotation.


And please take a serious note of Robbo3 's comment regarding using the spindle roughing gouge on bowl endgrain, the tang construction is not strong enough, should you get a catch you are likely to get a piece of broken steel embedded in you if it fails. A spindle gouge is intended for planing along the grain of spindles not across tough endgrain.

 

[boysie39]

Chj , I stand corrected ,my way of doing it is to have rest just below center so that when tool is presented at 90deg the handle when raised is on or just below center .Maybe I should have qualified that by saying just raise the handle by 1/2 mm or maybe I should not have commented at all ,and left it to thoes that know ,

 

[CHJ]

Nothing wrong with you having the rest where you like Eugene, you are experienced enough to know to tilt the tool so that you are obtaining a 'dragging' or shear cut below the work centre, it's just that as I read your post I had visions of the OP having his rest set above centre and having the scraper bang down hard into it with a catch.

 

[Thomas Hayman]

Thank you *everyone* for your advice. Sharpened the gouges a bit better today and used the right tool for the job and what a differnce it makes! Minimal tearout now, it's like chalk and cheese.

I found out about scrapers the hard way when i first started using it the other year. (homer)

 

[Aled Dafis]

On the topic of scrapers, it wasn't until fairly recently that I started using negative rake scrapers and what a difference they've made! For those of you that aren't familiar with this tool, the negative rake scrapers have a shallow bevel ground on their top face and are used flat on the toolrest with the tool parallel to the floor and cutting dead on the centre of the work.

I had always found scrapers quite difficult to handle accurately due to their tendency to dig in at exactly the wrong time - just one more cut.... but when ground with a negative rake, they can be controlled with the lightest fingertip hold, and produce an surface that means that I can now easily start sanding at 120, and more often than not, 180 grit.

Robert Sorby produce a negative rake scraper, but they can easily be ground on the bench grinder at say 15-20 degrees. Here's a pic of the Sorby for reference.

I use a Crown Heavy duty Bowl scraper for the insides of bowls, and a Straight ground 1 1/4" Scraper (well it's actually ground to a very slight convex curve) for the outsides.

The only negative is that these scrapers are fine finishing tools and the edge does not last very long at all, say 20-30 seconds, but can easily be touched up on a flat platen on the grinder or Proedge.

Have a go, you'll not be disappointed.

Cheers
Aled

 

[Mark Hancock]

On the topic of scrapers, it wasn't until fairly recently that I started using negative rake scrapers and what a difference they've made! For those of you that aren't familiar with this tool, the negative rake scrapers have a shallow bevel ground on their top face and are used flat on the toolrest with the tool parallel to the floor and cutting dead on the centre of the work.

I had always found scrapers quite difficult to handle accurately due to their tendency to dig in at exactly the wrong time - just one more cut.... but when ground with a negative rake, they can be controlled with the lightest fingertip hold, and produce an surface that means that I can now easily start sanding at 120, and more often than not, 180 grit.

Robert Sorby produce a negative rake scraper, but they can easily be ground on the bench grinder at say 15-20 degrees. Here's a pic of the Sorby for reference.

I use a Crown Heavy duty Bowl scraper for the insides of bowls, and a Straight ground 1 1/4" Scraper (well it's actually ground to a very slight convex curve) for the outsides.

The only negative is that these scrapers are fine finishing tools and the edge does not last very long at all, say 20-30 seconds, but can easily be touched up on a flat platen on the grinder or Proedge.

Have a go, you'll not be disappointed.

Cheers
Aled

It must be my simple mind but it always make me when I read about grinding a negative rake on scrapers. For years I had no idea what people were talking about and never bothered about it. But because of the amount of teaching I do I thought I better find out and found that basically grinding a negative rake on a scraper is the same as presenting the scarper in a trailing manner as Chas has described. Both methods have an angle less than 90 degrees between the work and the tool ie a negative rake. So back to my simple mind - why go to the trouble of grinding a neagtive rake on a scraper when the same is achieved by raising the handle to trail the cutting edge

Aled,
The other thing that caught my attention was your comment that negative rake scrapers is a fine finishing tool. I would consider any scraper as a fine finishing tool and as such needs constantly sharpening. Having said that I seem to recall Del Stubbs turning entire bowls with scrapers only so maybe...................... #-o

Mark :lol:

 

[Aled Dafis]

On the topic of scrapers, it wasn't until fairly recently that I started using negative rake scrapers and what a difference they've made! For those of you that aren't familiar with this tool, the negative rake scrapers have a shallow bevel ground on their top face and are used flat on the toolrest with the tool parallel to the floor and cutting dead on the centre of the work.

I had always found scrapers quite difficult to handle accurately due to their tendency to dig in at exactly the wrong time - just one more cut.... but when ground with a negative rake, they can be controlled with the lightest fingertip hold, and produce an surface that means that I can now easily start sanding at 120, and more often than not, 180 grit.

Robert Sorby produce a negative rake scraper, but they can easily be ground on the bench grinder at say 15-20 degrees. Here's a pic of the Sorby for reference.

I use a Crown Heavy duty Bowl scraper for the insides of bowls, and a Straight ground 1 1/4" Scraper (well it's actually ground to a very slight convex curve) for the outsides.

The only negative is that these scrapers are fine finishing tools and the edge does not last very long at all, say 20-30 seconds, but can easily be touched up on a flat platen on the grinder or Proedge.

Have a go, you'll not be disappointed.

Cheers
Aled

It must be my simple mind but it always make me when I read about grinding a negative rake on scrapers. For years I had no idea what people were talking about and never bothered about it. But because of the amount of teaching I do I thought I better find out and found that basically grinding a negative rake on a scraper is the same as presenting the scarper in a trailing manner as Chas has described. Both methods have an angle less than 90 degrees between the work and the tool ie a negative rake. So back to my simple mind - why go to the trouble of grinding a neagtive rake on a scraper when the same is achieved by raising the handle to trail the cutting edge

Aled,
The other thing that caught my attention was your comment that negative rake scrapers is a fine finishing tool. I would consider any scraper as a fine finishing tool and as such needs constantly sharpening. Having said that I seem to recall Del Stubbs turning entire bowls with scrapers only so maybe...................... #-o

Mark :lol:

I agree Mark that using a trailing angle presents the tool in a similar manner to the wood, but I've never managed the same control nor the same quality of finish from using a standard scraper in the trailing position. I still haven't got my mind around exactly what happens at the edge and how the two grinds behave differently, but in my experience at least, they give very different turning experiences.

Yes, I also see scrapers as finishing tools, but there are so many would be turners out there that were taught to turn bowls at school with nothing more than a couple of scrapers, and bearing in mind that this thread was started by a relative beginner I thought it wise to bring this to his attention.

Cheers
Aled