SRG on Bowls, Wrong/Right

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CHJ

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Lightweeder":261escoj said:
....Can anyone explain to me why the tang on the SRG is so weak when it's the tool we use for the roughest work ?
LW, the SRG is intended for use on SPINDLES, that is with the grain of the wood running parallel to the lathe bed axis, the diameter of the spindle is relatively immaterial.

The main point being that the strength of the wood fibres are at their weakest when stripped from the 'log' in this orientation, resulting in much lighter loads on the tool.

If you try to use the SRG on wood that is presenting End Grain then you will be subjecting the tool to perhaps a factor of 5-10 times the shock load. Beware of significant Knots.

Think in terms as the difference in cutting action needed to split a log down its length and then trying to cut it in half by chopping across its diameter with the same little axe.
Or sharpening a pencil as opposed to cutting it in half with a stanley knife.

Although attacking a log with bark on may visually appear to present a heavy duty load on the tool, as long as there are no major knots to navigate it is in fact presenting its weakest facet to a well supported cutting tool.
 

Paul Hannaby

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Hi Robo,
I would agree that most tools can catch if not used correctly but not all of them present the risk of breakage and potential injury in the same way as the SRG.

I would also disagree with the statement in your video that turning the SRG on its side will prevent it from trying to rotate. The tool is more or less a semicircular section so when presented to a near vertical surface, as in the case of the finishing cut you demonstrate, the horizontal distance between the point of the cut and the contact point on the toolrest is the same no matter how you rotate the tool because it is just a semicircle. It is this distance from the support point that makes it unstable in the cut and for that reason, an inexperienced user might run in to trouble.

What you choose to do in the privacy of your own workshop is up to you but don't you think it would be safer not to suggest that people use the spindle roughing gouge on a bowl? People get sued for a lot less, do you want to take that chance?

I have first hand experience of just how much force can be generated when you get a catch on a bowl. In my early woodturning days I managed to break a circular section gouge. Fortunately I was left with the shaft in one hand and the handle in my other hand and no injury but it could easily have been much worse. This was a tool from a quality supplier too. I wouldn't like to think how much worse this might have been if I had been using a SRG with a wider cut that would generate even more force.
 

chipmunk

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I hesitate to get involved in this dismembering of RoboHippy....

I should start by saying that he did start it himself by poking his SRG into the lion's mouth with somewhat gay abandon ;-)

...but to be fair to him, he does talk in the video about noting the point at which the tool is cutting and its relationship to the support of the toolrest. If we all made sure that the cutting point was directly above the support point at all times, then catches would be a thing of the past wouldn't they?

So, I'm not sure he quite deserves quite the grubbing he is getting and certainly doesn't deserve turners the world over queueing up to sue him for encouraging them to harm themselves with SRG's on bowls. After all most of us are good enough at harming ourselves without encouragement ;-)

Many have spoken about catches they have had. I believe that it's precisely those close shaves, most of which are probably as a result of catches of one form or another, that teach us respect for the tools and equipment around us. Nothing concentrates the mind more while turning than the thought of what might happen if an edge catches. We probably all need those catches to happen to us for us to learn the need for support under the cutting edge.

Some on the other hand may see RoboHippy's video and think about the cutting point always needing to be supported and avoid any catches at all.

It's unfortunate that the most likely people to use a SRG on a bowl are those novices who haven't quite worked out the difference between the various turning gouges. After all most lathe manuals come with pretty rudimentary turning instructions and in a photocopied manual one gouge looks very similar to another.

Here's hoping I haven't stuffed another SRG into the lion's mouth ;-)
Jon
 

Jonzjob

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I hope that i'm not taking anyone to bits Jon?

I have used an SRG on the outside of bowls since I first started and at that stage the wood is supported between the chuck/faceplate and the tailstock. Normally to get the worst off and the rest is moved in to be as close to the work as possible. I have never even thought of using it on the inside I have to admit. I would be too afraid of getting that catch with such a big cutting edge.

I have watched your video Robo and it is very impressive, but not for me thank you.. You appear to be a better turner than I.
 

robo hippy

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I haven't minded the comments at all. I would like to see all turners be able to avoid catches. That is the point of showing what I did in the video. Showing the relationship between the part of the tool that is cutting and the part that is on the tool rest is the best way I have found to emphasize that point. I do not think that point is taught properly in most situations, at least not to the point where the student/newbie understands. The SRG (I believe that adding the Spindle part to the name is fairly recent, as in the last few years, rather than an ages old name) gouge is not my go to tool for finish cuts, but I have found it handy at times, especially for softer punky wood or some wood that is more tear out prone than others.

robo hippy
 
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