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Inside Bowl - Final Cut Problem

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modicon

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Morning,

Was wondering if anyone can offer some help with a problem I keep coming up against.

I've done the bowl in the pictures however the the inside rim is giving me a headache as there's a very small step on the edge. I tried using a scraper as shown, result.... huge gouge, tried using the bowl gouge, result... came flying out. I'm pretty sure its the angle horizontal/vertical that's causing this to happen. Have tried various combinations and always the same.

I'll try to sand it down as don't want to wreck the whole thing at this stage but would love to know whats going wrong.

Thanks
 

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ah yes - you never want to use a scraper held flat like that on the side/rim of a bowl (only the bottom where there is more meat). You want to either a) hold it at about 45 degrees to perform a shear cut, or b) use a negative rake scraper.

Check out Brian Havens on youtube. He lots of useful video on such subjects
https://www.youtube.com/user/BHavensWoodworker/videos
 

CHJ

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Scrapers must be presented above the centre line (or the equivalent trailing presentation) on the inside of a bowl so that it does not catch and dig in, above the centre line it gets pushed into space, not deeper into the wood. (conversely below the centre line on the outside)

You should be working from the inside of the bowl towards the edge, not attempting to go in from the edge inwards.
You would be better dressing the top edge face with the bowl gouge from the outside of the bowl towards the inner, ensuring you have maximum bevel support as you go to avoid the problems detailed below.

Trying to true up or dress a bowl edge once the bulk of the support wood is removed is fraught with problems and a high percentage chance of disaster due to the form naturally moving out of round and undamped vibrations.
If possible finish your very top edge and immediate areas as early as possible whilst the bulk of the wood is supporting it.

Having to come back to the top edge at a later time with tools is something you need to avoid if possible.
 

Lazurus

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If I use a scraper in this situation I ensure there is a good sharp burr and I use it freehand without the rest, very light cuts and no chance of a catch as it is not "captured" by the tool rest but will just bounce away. Easier to do than explain.
 

gregmcateer

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Agree with Chas, but bit late for that now.
It may help to support the outside of the rim with your free hand CAREFULLY as you take very gentle cuts inside
 

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Hi,

Thanks for the advice, much appreciated. So I overcame the small step not by sanding as I was planning but by lowering the height off the bowl by about 2mm. Hadnt thought of that yesterday!!! Oops. :roll: #-o

Transatlantic – Quite new to turning so hadn’t ventured into the negative rake scraper territory, mainly because I didn’t understand the use! Will check that out. I’ve tried holding the scraper above centre line but still not having much luck.

CHJ – Good explanation on why to hold above centre line, knew to do that but didn’t know reason, can understand now (my photo didn’t show it very well) also I didn’t know to work from centre outwards. Have been leaving edge till last as didn’t appreciate the support of the wood.

Lazurus – Not sure Id’ be brave enough for that yet but can see what you mean with it being able to bounce away.

Gregmcateer – I’m DEFINELTY not brave enough for that! That’s main problem, the second I put the scraper in, no matter how light I touch the wood it results in a dig.


Thanks to all for taking time to reply. Once this lockdown is out the way I’m going to pay a visit to the local club as looks quite good. Next stop ... axminster, negative scrapers. :lol:
 

CHJ

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modicon":2skibqnf said:
.. Next stop ... axminster, negative scrapers. :lol:
Save your money, an ordinary scraper can be angled to achieve similar results, wait until you have more experience and can appreciate why a negative scraper edge 'might' suit your turning method. (you can always put a negative rake on the top edge of a spare straight scraper.)
 

KimG

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If you grind a negative rake (which is a bevel on both sides much like a Skew chisel) then to make it work well, it must also be very sharp like a Skew as well. I grind an edge on mine till it is as sharp as the grindstone can get it, then very lightly hone the edge on a whetstone to maximize the sharpness, with this I can take wafer thin cuts that leave a fine finish easily sanded to lacquering stage.
 

GarF

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Richard Findley explained this really well in a video clip on instagram recently
 

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