AWGB Woodturning Forum
General Category => Tool tips & reviews => Topic started by: Bill21 on November 22, 2021, 01:13:51 PM
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I bought a large, and rather expensive round nose scraper some years ago. I resharpened it to negative rake but it doesn’t work as well as a smaller conventional scraper I have. I’m wondering if I should grind it back the way it was. Included angle is under 80°, maybe I should reduce it further. Any ideas?
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Must admit I tried the negative rake and didn't see a lot of differenmce myself. Worls for some though.
Pete
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I must be one of the ones it works for because I've converted almost all my scrapers. Best to remember that even though the cutting edge looks the same either way up the tool cuts better when it is the same way up as it was ground. Also negrake scrapers lose their edge quicker than conventional. One of my grinder wheels has a semi permanent 40* jig attached ready.
Brian
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Must admit I tried the negative rake and didn't see a lot of differenmce myself. Worls for some though.
Pete
This may sound daft... but I think they work better for taller people, or very short people, it is all about angle and vision lines, having watched a bunch of people using them and puzzling over the mixed results I have concluded average height on average lathe height often do at least as well if not better on a standard scraper design.
That is of course the joy of worn out tools, you can try any strange configurations of wing / angles that you have heard about see if it suits you or not.
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I used to use a negative rake scraper when I was turning bone (and many years ago Ivory).It is only recently that I started to use neg rakes on wood. With a traditional scraper you have to be careful to make sure you use a trailing edge but with neg rakes not so much, they are more forgiving than normal scrapers. I have found that they perform better if the top angle is the last one sharpened, I also think you get a finer finish from neg rake . Be gentle with them (and all tools come to that) and you will get better results.
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Must admit I tried the negative rake and didn't see a lot of differenmce myself. Worls for some though.
Pete
This may sound daft... but I think they work better for taller people, or very short people, it is all about angle and vision lines, having watched a bunch of people using them and puzzling over the mixed results I have concluded average height on average lathe height often do at least as well if not better on a standard scraper design.
I am 6'4" (shrunk a bit with age LOL) and afraid that my height doesn't seem to help, maybe I am the odd one one out.
Pete
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Pete perhaps if you stood on a box while wearing high heels it might help!!!
Brian
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I am 6'4" (shrunk a bit with age LOL) and afraid that my height doesn't seem to help, maybe I am the odd one one out.
Pete
That kills that theory :) back to the "some things work for some turners" theory. ;D
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I love the way this forum just occasionally throws up a thread which gets my brain cell excited and leads me to look closer at a subject that I had previously just taken for granted. This thread is a case in point and here are my morning's conclusions.....
My negrake scrapers are ground with twin bevels ,each at 40*. The tools business end looks rather like a blunted skew. This means that the burr, which is going to do the cutting for us, is thrown up at the same angle and is, in fact, forward of the apparent cutting edge so it is almost immaterial what angle you present the tool to the workpiece. It also carries the added advantage that one tool can do the work of two 'handed' shapes, it will cut either left or right according to which bevel was last ground.
A trad scraper, on the other hand, is likely to be ground much closer to a right angle so the burr will face upward. To obtain a similar cut to the horizontally presented negrake the handle will be up amongst the the rafters or the cutting edge well below the works centreline.
So, in Brian's world anyway, the 'big boy/little boy' theory does, in fact, hold water!
Now that's what I call scientific ......
Brian
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Thanks for your thoughts folks. I have a bowl project coming up so I’m going to resharpen the scraper and give it another try. As I mentioned, it was expensive at the time so I want to get my moneys worth!
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I found this interesting.
https://www.sharpeninghandbook.info/WW-Scraper-NRS.html
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I found this interesting.
https://www.sharpeninghandbook.info/WW-Scraper-NRS.html
I am not a regular scraper user, so my method and advise is of limited value, but my method for negative rake is the second one, I knock back the top by 20° then just sharpen the bottom face. I think if I did 2 faces the same it would be upside down 60% of the time.
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Pete perhaps if you stood on a box while wearing high heels it might help!!!
Brian
Or put the box on your head!! ;D ;D ;D
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It never ceases to amaze me how clever some of our members are. I don't have the brain power to workout the whys and wherefores that has happened in this thread. I have always said that I don't do anything clever and it is true. If I find one of my tools is not cutting right I assume it needs sharpening, if it still doen't cut I assume that my technique needs to sharpen up or the tool is ground wrongly in which case example no 2 still applies. It is all about sharpening correctly.
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It never ceases to amaze me how clever some of our members are. I don't have the brain power to workout the whys and wherefores that has happened in this thread. I have always said that I don't do anything clever and it is true. If I find one of my tools is not cutting right I assume it needs sharpening, if it still doen't cut I assume that my technique needs to sharpen up or the tool is ground wrongly in which case example no 2 still applies. It is all about sharpening correctly.
So now you know, if the tool is sharp and the cut still isn't flowing.. you need a box and high heals ;D ;D ;D
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That’s a step too far for me. Tools are probably cheaper than ladies shoes anyway?!
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It never ceases to amaze me how clever some of our members are. I don't have the brain power to workout the whys and wherefores that has happened in this thread. I have always said that I don't do anything clever and it is true. If I find one of my tools is not cutting right I assume it needs sharpening, if it still doen't cut I assume that my technique needs to sharpen up or the tool is ground wrongly in which case example no 2 still applies. It is all about sharpening correctly.
So now you know, if the tool is sharp and the cut still isn't flowing.. you need a box and high heals ;D ;D ;D
Pete you are obviously obsessed by boxes and high heels, is there anything you want to share with us? ;D ;D ;D ;D
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Must admit I tried the negative rake and didn't see a lot of differenmce myself. Worls for some though.
Pete
This may sound daft... but I think they work better for taller people, or very short people, it is all about angle and vision lines, having watched a bunch of people using them and puzzling over the mixed results I have concluded average height on average lathe height often do at least as well if not better on a standard scraper design.
I am 6'4" (shrunk a bit with age LOL) and afraid that my height doesn't seem to help, maybe I am the odd one one out. I am 6'3" and it does not work for me, We may be the two oddmen out!
Pete
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That last bit was from me, and I am 6'3" and cannot make it work for me, which is why we are the two odd menout
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A persons height shouldn’t make any difference provided the lathe is at the correct height? Obviously most products are made for people of average height. If you’re particularly tall the onus is on you to make things fit. Having said that I think OneWay lathes have height adjustment?
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A persons height shouldn’t make any difference provided the lathe is at the correct height? Obviously most products are made for people of average height. If you’re particularly tall the onus is on you to make things fit. Having said that I think OneWay lathes have height adjustment?
Anyone doing demo's or otherwise using a range of lathes needs to be cautious about straying to far from default lathe heights, I raised mine by 4" about 6 months into lockdown 1, sometime after lockdown 2 I had an hour on a friends stock height lathe unfortunately it took 45 minutes to get used to bending that extra 4". Don't think it matters so much if you regularly work at different heights, but I have lowered mine to 2" overstock as current universe means it is an occasional treat to play on someone else's lathe.